Glossary of technical terms for the use of metallurgical engineers Terms starting with alphabet ‘F’
Glossary of technical terms for the use of metallurgical engineers
Terms starting with alphabet ‘F’
F1 score – It is a metric in machine learning which measures a model’s accuracy by calculating the harmonic mean of precision and recall, providing a balanced performance measure (0 to 1 or 0 % to 100 %). It is important for imbalanced datasets where false positives and false negatives carry different costs.
Fabric – It is a material made of woven fibers or filaments. It is a planar textile which is also known as cloth.
Fabric belts – These are multi-ply, flexible bands used to transport heavy, abrasive, and hot materials. They consist of a carcass composed of woven synthetic fabrics (typically polyester for warp and polyamide for weft) encapsulated within, and coated with, specialized rubber compounds. These belts are specifically designed to provide high impact resistance, high tensile strength, and low elongation for conveying applications.
Fabricate – It means to work a material into a finished state by machining, forming, or joining.
Fabricated component – It is a custom-engineered, specialized part created by shaping, cutting, welding, and assembling raw or semi-finished materials (such as metal, plastic, or composites) into a finished, ready-to-assemble state. These components are necessary in engineering, construction, and manufacturing to build larger systems.
Fabricated frame scaffold – It is also called tubular welded frame scaffold. It is a modular, supported scaffolding system consisting of pre-manufactured steel or aluminum end frames, integral posts, horizontal bearers, and diagonal braces. Designed for rapid assembly, it provides a stable, high-load capacity platform for construction, maintenance, and repair work.
Fabricated pipe – It refers to a pipe produced by fabrication process which involves cutting, bevelling (end preparation), welding, fitting, and sometimes bending or applying protective coatings to metallic components. It also refers to a network of piping components (tees, elbows, flanges, reducers), which has been custom-assembled from raw pipes and fittings, typically within a controlled workshop or shop environment, to meet specific project design requirements. Unlike standard manufactured piping, fabricated pipes are frequently assembled into pipe spools, sub-assemblies which are cut, bent, and welded together, before being transported to a construction site for final installation.
Fabricated scaffold – It is a modular, pre-engineered, and pre-manufactured temporary structure used in construction, featuring welded frames with integral posts, bearers, and intermediate members. Designed for rapid assembly, it provides secured elevated platforms for workers, supporting their own weight plus a high load-bearing capacity, frequently made of steel or aluminum.
Fabricated structure – It refers to a metallic assembly constructed by cutting, bending, and joining (welding, bolting, or riveting) standardized metal parts, such as plates, beams, and bars, rather than creating the entire structure from a single cast or forged piece. Fabricated structures are typically created in a controlled shop environment (a fabrication shop) based on engineering specifications and then transported to a site for final assembly.
Fabricated valve – It is a valve in which the body is neither cast nor forged but rather is formed from plate or pipe welded together.
Fabricating – It is the manufacture of products from moulded parts, rods, tubes, sheeting, extrusions, or other form by appropriate operations, such as punching, cutting, drilling, and tapping. Fabrication includes fastening parts together or to other parts by mechanical devices, adhesives, heat sealing, welding, or other means.
Fabricating nano-fibres – It is the process of producing fibres with diameters less than 1 micro-metres (typically 100 nano-meters to 500 nano-meters), characterized by high surface-area-to-volume ratios and exceptional porosity. It involves advanced techniques, mainly electros-pinning, to draw polymers, ceramics, or composites into ultra-fine filaments for applications in filtration, and energy storage.
Fabricating technology – It is the process of creating metal structures, components, or machinery by cutting, bending, forming, and assembling raw or semi-finished materials. It transforms raw materials into finished products through specialized techniques, such as welding and machining, frequently guided by CAD (computer-aided design) / CNC (computer numerical control) technology to ensure precision, customization, and structural integrity.
Fabrication – Metal fabrication is the creation of metal structures by cutting, bending and assembling processes. It is a value-added process involving the creation of machines, parts, and structures from different raw materials. Common techniques include cutting (laser, plasma), bending, welding, machining, forming, stamping, and punching.
Fabrication aids – These are temporary, non-permanent components or devices, such as scaffolding, braces, lifting lugs, or jigs, used during manufacturing and assembly to support, position, or align structural elements. These are necessary for ensuring stability and precision, but are typically removed after the permanent structure is completed and inspected.
Fabrication approach – It is a structured strategy for constructing components or structures from raw materials using processes like cutting, bending, welding, and assembling. It defines the sequence of operations, tools, and techniques needed to transform raw materials into finished parts based on engineering specifications.
Fabrication method – It is a systematic process used to construct finished parts, structures, or components from raw materials, mainly metals, through cutting, bending, forming, and assembling. These methods, such as welding, CNC (computer numerical control) machining, and stamping, convert materials like sheet metal or metal bars into precise shapes as per the engineering designs.
Fabrication parts – These refer to components or parts which are created through the process of fabrication, which involves cutting, shaping, and assembling raw materials to create a final product. These parts can be made from different materials such as metal, plastic, wood, or composite materials. Fabrication parts are commonly used in industries such as manufacturing, construction, and more, where custom or specialized components are needed. Examples of fabrication parts include brackets, frames, enclosures, panels, and structural components.
Fabrication sequence – It is the chronological, step-by-step order of operations used to transform raw materials into finished parts or assemblies. It includes design, cutting, bending, machining, and welding, specifically structured to optimize production efficiency, minimize structural distortion, and ensure material traceability from raw stock to final assembly. It defines the precise sequence, such as cutting, then bending, then welding, to prevent interference between the tool and the part.
Fabrication stages – The core stages of fabrication typically follow a sequence of design, cutting, forming (bending / rolling), assembly (welding), and finishing, producing items for sectors like construction and automotive.
Fabrication technique – It is a specialized process used to transform raw materials (typically metals, plastics, or composites) into finished components or structures. These techniques involve cutting, forming, welding, and assembling, designed to achieve precise shapes and functional needs for industrial applications.
Fabrication time – It is the total duration needed to manufacture a component or assembly, spanning from initial material preparation to final production. It covers cutting, bending, assembly, and welding, and is heavily influenced by design complexity, material type, and structural needs. It is the time taken to produce a finished, deliverable product (frequently measured from raw material availability). This typically includes setup time, actual machining / forming, assembly, and inspection.
Fabrication tolerance – It is the allowable variation or deviation from a specified, nominal dimension of a manufactured part, defining the acceptable limit between upper and lower measurements. It ensures components fit together (functionality) and allows for inter-changeability while accounting for unavoidable manufacturing limitations and inaccuracies. Fabrication tolerance is the total permissible amount a specific dimension (length, diameter, angle) can vary, represented as a +/- value off a nominal dimension. It ensures components fit together properly (e.g., a shaft in a hole) without causing premature failure or assembly issues.
Fabrication yard – It is a specialized industrial facility designed for the manufacturing, assembly, and testing of large-scale engineering structures, particularly for oil and gas, renewable energy, and ship-building sectors. It functions as a hybrid site combining manufacturing work-shops, assembly bays, and, crucially, specialized facilities for loading out massive structures to offshore or remote sites.
Fabricator – Fabricator is a producer of intermediate products that does not also produce primary metal. For example, a reinforcement bar fabricator processes the material to the specifications of a particular construction project.
Fabric attributes – These refer to the specific characteristics of fabrics which is to be considered in the design of technical textiles, including aspects such as fabric type, construction, and performance features essential for their intended applications.
Fabric conveyor belt – It is a type of conveyor belt where the core of the belt, known as the carcass, is made from layers of woven fabric, typically polyester, nylon, or cotton. These fabric layers are then coated with rubber or synthetic materials for protection and to improve its properties like strength, flexibility, and resistance to wear and tear.
Fabric damage – It is defined as any physical, chemical, or structural alteration to a textile material which degrades its performance, strength, or appearance, making it unfit for its intended purpose. This includes manufacturing defects (e.g., holes, snagging) and operational wear (e.g., abrasion, pilling).
Fabric density – It refers to the tightness of a fabric’s structure, quantified by the number of warp threads (ends) and weft threads (picks) per unit length (e.g., ends / picks per centimeter). It defines the internal construction, directly affecting durability, weight, opacity, and air permeability.
Fabric drape – It is the objective measurement of how a textile deforms and hangs under its own weight, typically forming 3D folds. It is an important functional characteristic determined by bending rigidity, shear stiffness, and fabric density. Key metrics include the drape coefficient, the percentage of the projected shadow area relative to the original fabric area, used to determine how fabric contours to shapes. It is the ability of a fabric to fold and conform to a three-dimensional surface, defined as the extent of deformation under gravitational force.
Fabric fill face – It is that side of the woven fabric where the highest number of the yarns are perpendicular to the selvage.
Fabric filter – It is an air pollution control device which removes dry particulates from industrial gas streams by passing them through a woven or felted fabric medium. It collects dust on the surface, forming a filtering cake. With efficiencies above 99 %, it is a leading technology for fine particle capture, frequently used in industries like cement, power, and mining.
Fabric filter baghouses – These are highly efficient (above 99 % efficiency) industrial air pollution control devices designed to remove particulate matter from gas streams. They work by passing dust-laden air through large woven or non-woven fabric bags (baghouse filters), trapping particles on the surface to form a ‘filter cake’ which further improves filtration before cleaning.
Fabric handle – It is the subjective, sensory evaluation of a fabric’s physical, tactile properties, such as stiffness, softness, smoothness, and flexibility, when touched. It is a characteristic which affects the quality of fabrics, encompassing the evaluation of surface and mechanical properties, including bending, compression, shear, and tensile properties.
Fabric layer – It involves designing, assembling, and treating single or multiple textile layers to improve functional properties like thermal insulation, moisture management, and durability. It utilizes techniques like layering, coating, or laminating to create specialized structures, which manage heat, moisture, or structural strength.
Fabric mechanical properties – These properties define how fabric materials respond to external forces, such as tension, compression, bending, and shear, measured through resistance, deformation, and recovery. These properties are important for determining a fabric’s durability, handling, and suitability for applications, frequently analyzed in low-stress, real-world conditions.
Fabric, non-woven – It is a planar textile structure produced by loosely compressing together fibres, yarns, rovings, and so on, with or without a scrim cloth carrier. It is accomplished by mechanical, chemical, thermal, or solvent means, and combinations thereof.
Fabric prepreg batch – It consists of prepreg containing fabric from one fabric batch, impregnated with one batch of resin in one continuous operation.
Fabric warp face – It is that side of the woven fabric where the highest number of the yarns are parallel to the selvage.
Fabric, woven – It is a material (normally a planar structure) constructed by interlacing yarns, fibres, or filaments to form such fabric patterns as plain, harness satin, or leno weaves.
Fabry-Perot fibre – It is a high-sensitivity optical sensor or resonator formed by two parallel reflective surfaces (mirrors) separated by a small cavity along an optical fibre. It acts as an interferometer to detect small changes in optical path length caused by physical, chemical, or biological parameters.
Fabry-Perot interferometer – It is a reflective optical device composed of two mirrors separated by a cavity, which is highly sensitive to changes in the optical path length and is used in applications such as gas detection. It can be categorized into intrinsic and extrinsic types based on the arrangement of the light-carrying medium.
Fabry-Perot sensor – it is an optical device which measures physical parameters (such as pressure, strain, or temperature) by detecting changes in light interference caused by altering the distance between two parallel, partially reflective mirrors. It uses a small, high-sensitivity cavity to analyze light wavelength shifts. It consists of two parallel reflecting surfaces (mirrors) defining an optical cavity (also known as an etalon).
Fabry-Perot spectrometer – It is a high-resolution optical instrument which analyzes light spectra by utilizing multiple-beam interference. It consists of two parallel, highly reflective mirrors (an ‘etalon’) which create a cavity where light reflects multiple times, causing constructive interference only for specific resonant wavelengths, which are then transmitted.
Facade – It is the vertical face of a building envelope, such as the exterior wall, which is important in sustainable design and energy performance because of its substantial impact on energy loss. It can be categorized into opaque façades, which offer better insulation, and glazed façades, which provide more daylight access but can increase energy demands for heating and cooling.
Facade engineering – It is the art and science of resolving aesthetic, environmental and structural issues to achieve the effective enclosure of buildings.
Facade module – It is a standardized, prefabricated exterior building component, typically panel-based, such as curtain walls or cladding, designed for efficient assembly and high-performance, frequently serving as a non-load-bearing, protective, and aesthetic envelope. It acts as a filter against environmental elements while controlling thermal, acoustic, and fire performance.
Facade solution – It is the design, analysis, and execution of a building’s outer envelope (curtain wall, rainscreen, glazing, etc.) to optimize environmental, structural, and aesthetic performance. It acts as a specialized barrier regulating thermal efficiency, structural integrity, moisture control, and occupant comfort.
Face – In a lathe tool, it is the surface against which the chips bear as they are formed. In mining, it is the end of a drift, cross-cut or stope in which work is taking place.
Face-centered – It consists of having atoms or groups of atoms separated by translations of (i)1/2, 1/2, 0, (ii) 1/2, 0, 1/2 and (iii) 0, 1/2, 1/2 from a similar atom or group of atoms. The number of atoms in a face-centered cell is to be a multiple of 4.
Face centred cubic (fcc) – It is a type of atomic arrangement and is relatively ‘tightly packed (atomic packing factor = 0.74). Face centred cubic is formally defined as a cubic lattice with the face positions fully equivalent to each of the eight corners. A Face centred cubic unit cell contains atoms at all the corners of the crystal lattice and at the centre of all the faces of the cube. The atom present at the face-centered is shared between 2 adjacent unit cells and only 1/2 of each atom belongs to an individual cell.
Face-centered cubic (fcc) crystal structure – It is a unit cell arrangement where atoms are located at all eight corners of a cube and in the centre of all six faces. It has a high atomic packing factor of 74 %, 12 nearest neighbours (coordination number), and normally shows high ductility and toughness.
Face-centered cubic (fcc) materials – These are metals with a crystal structure consisting of a cubic unit cell with atoms at each corner and one in the centre of all six faces. Known for high ductility and toughness, face-centered cubic structures have 4 atoms per unit cell, 12 nearest neighbours, and a 74% packing factor. Common examples include aluminum, copper, and gold.
Face (crystal) – It is an idiomorphic plane surface on a crystal.
Face milling – It is a machining process which creates flat, planar surfaces on a work-piece by using a rotating cutter, known as a face mill, with its axis perpendicular to the surface. It typically uses replaceable carbide inserts for high-efficiency, shallow, and wide material removal, frequently serving as a main operation to establish a reference datum.
Faceplate – It is a circular, slotted metal plate fastened to a lathe spindle, used for clamping irregularly shaped or large work-pieces which cannot be held by a conventional chuck. It features radial slots and T-slots to secure components using bolts, allowing for precise turning, boring, and machining operations.
Face pressure – It is the face load divided by the contacting area of the sealing lip. The face load is the sum of the pneumatic or hydraulic force and the spring force. For lip seals and packings, the face load also includes the interference load.
Face reinforcement – It is the weld reinforcement at the side of the joint from which welding has been done.
Face seal – It is a device which prevents the leakage of fluids along rotating shafts. Sealing is accomplished by a stationary primary-seal ring bearing against the face of a mating ring mounted on a shaft. Axial pressure maintains the contact between seal ring and mating ring.
Face-to-face, valve – It is the overall dimension from the inlet face to the outlet face of the valve (one end to the other). This dimension is governed by the standards, to ensure that such valves are mutually interchangeable regardless of the manufacturer.
Face-type cutters – These are the cutters which can be mounted directly on and driven from the machine spindle nose.
Face width – It is the measurement across the outer face of the pulley on the conveyor belt, demands periodic checks for alignment and wear to ensure optimal performance.
Facilitate comprehension – It refers to the process of ensuring that information is conveyed in a language and manner which is understandable to the audience, hence enabling effective communication and informed consent.
Facilitated self-assessment – It is a structured process where employees critically evaluate their own learning, technical skills, or work products against established criteria, supported by a facilitator. (such as an instructor, AI (artificial intelligence) tool, or mentor, to ensure accuracy, honesty, and alignment with professional standards. It moves beyond simple grading to become a focused on identifying strengths, weaknesses, and areas for improvement.
Facilitated self-assessment methodology – It is a structured approach where individuals or teams evaluate their own performance, processes, or competencies, guided by a facilitator or a systematic framework to ensure objectivity, accuracy, and actionable results. This methodology is heavily used in engineering education, software development, and quality management to improve learning outcomes, improve team performance, and foster continuous improvement.
Facilitated transport membranes – These are defined as membranes designed to improve the permeability and selectivity for gases, such as carbon di-oxide (CO2), through reversible reactions with reactive carriers embedded in the membrane matrix, improving gas diffusion beyond the solution-diffusion mechanism. They are available in several configurations, including support liquid membranes, ion-exchange membranes, and fixed-site-carrier membranes.
Facilitator – Facilitator is a neutral, process-oriented expert who guides a group of engineers, designers, or stakeholders through structured activities to solve complex technical problems, align on decisions, and improve collaboration. Unlike a technical leader or project manager, the facilitator focuses on how the team works together, rather than what technical solution is ultimately chosen. They are ‘guides on the side’ who enable the team to find their own solutions, rather than providing the answers themselves.
Facility – It consists of land, buildings, and other structures, their functional systems and equipment, and other fixed systems and equipment installed therein, including site development features outside the plant, such as landscaping, roads, walks, and parking areas, outside lighting and communication systems, central utility plants, utilities supply and distribution systems, and other physical plant features. Facility consists of the equipment, structure, system, process, or activity which fulfills a specific purpose.
Facing – In machining, it consists of generating a surface on a rotating work-piece by the traverse of a tool perpendicular to the axis of rotation. In foundry practice, it is a material which is applied in a wet or dry condition to the face of a mould or core for improving the surface of the casting. For abrasion resistance, the preferred term is hard-facing which is the application of a hard, wear-resistant material to the surface of a component by welding, spraying, or allied welding processes for reducing wear or loss of material by abrasion, impact, erosion, galling, and cavitation. In case of pipe fittings, facing is the finishing of the contact surface of flanged fittings.
Facings – These are skins and doublers in any lay-up. Facings is also the outermost layer or composite component of a sandwich construction, normally thin and of high density, which resists most of the edgewise loads and flatwise bending moments, It is synonymous with face, skin, and face sheet.
Facing sand – It is a specialized, high-quality, fine-grained sand mixture (typically silica sand, clay, and carbonaceous additives) used in casting to directly line the surface of a pattern. It forms the mold cavity’s inner layer to provide high refractoriness, superior strength, and excellent surface finish, while preventing molten metal from burning into the mould. It is applied directly against the pattern, typically in a layer having thickness of 20 millimeters to 30 millimeters. It possesses high refractoriness (withstands heat) and high strength.
Factor – It refers to a specific, frequently numerical or physical parameter which influences the behaviour, processing, properties, or performance of a metal or alloy. These factors help quantify complex physical phenomena like atomic structure, mechanical deformation, corrosion resistance, or manufacturing processes.
Factor analysis – It is a statistical method for reducing a set of variables to a smaller number of factors or basic components in a scale or instrument being analyzed. Two main forms are exploratory factor analysis (EFA) and confirmatory factor analysis (CFA).
Factor analysis of information risk – It is a quantitative risk framework that decomposes risk into measurable factors threat frequency, vulnerability, and loss magnitude, to calculate the probability and financial impact of security events. It standardizes risk assessment, enabling organizations to prioritize investments by analyzing the root causes of risk, rather than relying on qualitative, subjective, or high / medium / low ratings.
Factor design – It refers to a reliability-based approach which incorporates partial safety factors to ensure a uniform level of reliability across structural components, allowing for the adjustment of nominal values to achieve target reliability in design equations.
Factored shear force – It is the total shear force acting on a component (such as a beam, bolt, or connection) multiplied by specific safety factors (load factors) to ensure the component can safely withstand maximum expected loads. It represents the worst-case scenario for shear, the tangential forces trying to ‘cut’ or slide a material along a plane, as part of a ‘load and resistance factor design’ (LRFD) philosophy.
Factorial design – It refers to a method where multiple factors (independent variables) are manipulated or observed simultaneously to study their effects and interactions on a dependent variable. This approach allows people to evaluate the main effects of each factor and any interaction effects between them, providing more comprehensive information than studying one factor at a time. Factorial designs involve two or more factors, each with multiple levels (discrete values or conditions).
Factorial moments – These are integral characteristics of correlations within a system of particles, calculated from inclusive q-particle differential cross sections. They provide a measure of all correlations among particles, while cumulants represent genuine q-particle correlations which cannot be decomposed into lower-order correlations.
Factor interaction – It occurs when the effect of one input factor (independent variable) on a response (dependent variable) changes depending on the level of another factor. It indicates that factors do not act independently, and their combined effect is non-additive, rneeding analysis of their combined influence.
Factorization algorithm – It is a procedure used to decompose a complex mathematical object (like a large integer, a polynomial, or a matrix) into a product of simpler components called factors. The goal is to transform a problem into a simpler form that is easier to analyze or solve.
Factor measurement – It normally refers to quantifying a dimensionless ratio (like power or safety) to evaluate performance or reliability. Key examples include the ‘power factor’ (PF = real power/apparent power), which quantifies electrical efficiency from 0–1, and the Q-factor (quality factor), measuring resonator efficiency based on energy storage against dissipation.
Factor of safety – It is the ratio of the material strength to the computed stress. The factor of safety can vary from around 1.3, where component performance is well known and material properties show little variability, to 3 or 4 for an untried material or where stresses or environment are uncertain.
Factory – It is an industrial facility, frequently a complex consisting of several buildings filled with machinery, where workers manufacture items or operate machines which process input raw materials into products and by-products.
Factory acceptance test – It is a quality assurance process conducted at the supplier’s facility before equipment shipment to verify it meets design specifications, functional needs, and safety standards. It involves testing systems, such as control panels and machinery, through simulation or operation, witnessed by stakeholders to validate performance and minimize site installation issues.
Factory automation – It is the use of integrated control systems , such as PLCs (programmable logic controllers), and computers, to manage machinery and industrial processes, reducing human intervention to increase production speed, efficiency, and safety. It involves automating tasks ranging from single operations to complete, end-to-end manufacturing lines.
Factory gate – It represents the physical boundary of a production facility where finished goods are assessed, finalized, or shipped. It acts as the boundary for ‘cradle-to-gate’ life cycle assessments (LCA), covering raw material extraction to product exit, excluding distribution and end-of-life.
Factory process – It involves designing, implementing, and optimizing the methods used to transform raw materials into finished products. It defines the specific technical steps, tools, and sequences (machinery or manual labour) needed to increase product value. This ensures efficiency, safety, and quality through layout design and operational control.
Fading – In wireless communication and signal processing, it is defined as the variation of signal attenuation (strength) and phase over time, geographical position, or radio frequency. It refers to the fluctuation of the amplitude or phase of a signal as it travels through a propagation medium. Fading is normally characterized as a random process frequently caused by multipath propagation, environmental obstructions (shadowing), or atmospheric conditions.
Fading channel – It is a communication link where the received signal’s amplitude and phase fluctuate over time, frequency, or space because of multipath propagation, reflection, scattering, or diffraction. It is modeled statistically to describe small-scale effects, such as Doppler spread and delay spread, which cause signal attenuation and distortion.
Fading distribution – It is a statistical model which characterizes the rapid, random fluctuations in the received signal level (amplitude or power) over time, space, or frequency. These fluctuations are mainly caused by multipath propagation, where a signal takes multiple paths to reach the receiver, leading to constructive or destructive interference.
Fading effect – It is the phenomenon whereby the effectiveness of inoculation diminishes as the time between inoculation and casting increases.
Fail action – It is a term used to describe the desired failure position of a control valve. It can be fail-closed, fail-open, or fail-in-place. With a spring-return actuator fail-in-place action normally needs the use of a lock-up valve.
Fail-closed – It is a condition wherein the valve closure member moves to a closed position when the actuating energy source fails.
Failed blade – It is a component, such as in turbines, which can no longer perform its needed function because of the structural damage, deformation, or fracture, frequently resulting from operational stresses, material defects, or environmental factors. Common failure modes include fatigue (high cycle / low cycle), creep, erosion, corrosion, and vibration-induced cracking.
Failed component – It is a part which cannot perform its intended function, resulting in total failure, degraded performance, or inability to meet operational requirements. It occurs when a component breaks, wears out, or fails to meet specifications because of the design flaws, manufacturing defects, or improper usage.
Failed sample – It is a component, material, or system which has ceased to perform its intended function, fallen outside of acceptable performance specifications, or undergone permanent structural degradation. Defining a ‘failure’ is important for reliability testing, and it is normally quantified by specific criteria rather than just total breakage.
Failed state – It is a state of inoperability resulting from material imperfections, design errors, or service abuse. Common causes include overloading, cyclic loading (fatigue), chemical degradation (corrosion), improper material selection, and high-temperature deterioration. Failed state is reached through mechanisms like fracture, corrosion, or deformation, often caused by fatigue, wear, or stress exceeding material limits.
Failed tank – It refers to the structural or functional breakdown of a container, preventing it from storing contents safely. Catastrophic failures occur from overstress, corrosion, improper maintenance, overfilling, or pressure issues, causing leaks, collapses, or ruptures.
Failed tube – It refers to a structural component, typically in boilers or heat exchangers, which has lost its integrity through phenomena such as ruptures, cracking, thinning, or overheating. These failures lead to leaks or complete separation, often caused by fatigue, creep, corrosion, or erosion.
Failing infrastructure – It refers to the deterioration, over-capacitation, or functional degradation of important physical systems, such as bridges, roads, and utilities, which no longer meet safety or service demands. It results from deferred maintenance, aging, or design flaws, frequently causing episodic disruptions or catastrophic, systemic failure.
Fail-open – It is a condition wherein the valve closure member moves to an open position when the actuating energy source fails.
Fail-safe – It is a design feature or practice ensuring that if a system, component, or process fails, it defaults to a safe state, causing minimal or no harm to people, property, or the environment. It prioritizes preventing catastrophic outcomes over maintaining operation, ensuring safety remains intact even when failure occurs. It is a characteristic of a valve and its actuator, which upon loss of actuating energy supply, causes a valve closure member to be fully closed, fully open, or remain in the last position, whichever position is defined as necessary to protect the process and equipment. Action can involve the use of auxiliary controls connected to the actuator.
Fail-safe approach – It is a design philosophy ensuring that if a system, component, or process fails, it defaults to a safe, stable, or inoperative state rather than creating danger. It focuses on mitigating consequences rather than just preventing failure, ensuring no harm to people, equipment, or the environment.
Fail-safe design – It is a design which seeks to ensure that a failure is not going to affect the product or change it to a state in which injury or damage occurs.
Fail-safe structure – It is designed to maintain overall integrity and prevent catastrophic failure even if a primary component breaks, cracks, or fails. It ensures that structural failure is localized and not immediate, allowing time for detection and repair through redundancy and alternative load paths.
Fail-safe valve – In a face-safe valve, when there is a failure in the pipeline system, the actuated valve is designed to automatically either open or close the valve.
Fail-secure – It is a design principle where a system defaults to a locked, restricted, or safe state upon power loss or failure, preventing unauthorized access or data loss. It prioritizes security over accessibility, ensuring assets remain protected when control systems fail.
Fail-soft – It is a design approach ensuring a system continues operating in a degraded or reduced capacity rather than shutting down completely when components fail. It prioritizes essential functions by selectively terminating nonessential processes, allowing for graceful degradation.
Fail to known state – It is a design principle where, upon a failure or disruption, a system automatically transitions to a pre-determined, safe condition rather than an unpredictable or hazardous one. It prevents injury, property damage, and unauthorized access, maintaining confidentiality, integrity, or availability.
Failover – It is a process which automatically switches to a redundant or standby component (server, network, database) when the main system fails. It is an important component of high availability (HA) and disaster recovery, designed to eliminate or reduce service downtime and ensure operational continuity.
Failure – It is a general term which is used to imply that a part in service (i) has become completely inoperable, (ii) is still operable but incapable of satisfactorily performing its intended function, or (iii) has deteriorated seriously, to the point that it has become unreliable or unsafe for continued use. The term failure is also normally applied to the manufacturing processes which produce products that do not meet specifications.
Failure analysis – It is a process of collecting and analyzing data and it is carried out to determine the causes or factors that have led to the undesired loss of functionality or failures of equipment components and assemblies, or structures. It is a multi-level process that includes physical investigation. The normal scope of a failure analysis is to find the failure mechanism and the most probable cause of the failure. The term failure mechanism is normally described as the metallurgical, chemical, mechanical, or tribological process leading to a particular failure mode.
Failure behaviour – It defines how a structure, material, or system breaks down, deforms, or ceases to fulfill its intended function under stress. It involves understanding material responses, such as ductile yielding (deformation) or brittle fracture (snapping), to predict and prevent catastrophic failure, ensuring safety and reliability.
Failure condition – It is the effect on a system, its performance, or its surroundings caused by one or more failures, often classified by severity (e.g., minor, major, hazardous, catastrophic). It defines how a system behaves when it fails to perform its intended function, considering operating conditions.
Failure condition effect – It is the immediate consequence, impact, or outcome of a system, component, or product failure, as experienced by the user or on the system’s operational capability. It defines how the failure compromises functionality, safety, or performance, ranging from minor inconveniences to catastrophic failures (e.g., loss of equipment, fatalities)
Failure costs – These are the costs incurred when a customer is or going to be dissatisfied. In such case the organization pays the price in the form of damaged reputation, rework, waste, legal penalties, special charges or loss of pride. The cost of failure is always huge and bringing back the things to normal conditions need a herculean task involving substantial cost at each step.
Failure criterion – It is a mathematical formula or model which predicts when a material or structural component ceases to perform its intended function under applied loads. It defines the boundary between safe, elastic behaviour and failure, which can be defined as yielding (ductile), fracturing (brittle), or buckling. It is used to predict failure in design, ensuring safety by determining the needed material strength under complex stress states.
Failure criteria in sheet metal forming – These are metallurgical and mechanical limits defining when a material ceases to deform successfully, normally marked by localized necking or fracture. Key criteria include the ‘forming limit diagram / forming limiting curve (FLD / FLC), which maps major / minor s strains, and ductile fracture criteria that predict cracking based on stress-strain history.
Failure distribution – It is a mathematical model which describes how failures occur over time. It represents the probability of failure within a given time interval, frequently using a ‘probability density function’ (PDF) or a ‘cumulative distribution function’ (CDF). These functions help to understand the likelihood of failure at different points in a product’s or system’s lifespan.
Failure effect – It is the consequence of a specific failure mode on the operation, function, or status of a system, component, or process. It describes how the failure is experienced, such as reduced performance, system shutdown, safety hazards, or environmental damage, and is used in FMEA (failure mode and effects analysis) to assess risk severity.
Failure frequency – It is the number of failures an item or system experiences over a specific period, or per unit of time / operating cycle, normally expressed as failures per hour or year. It measures component reliability, dictating maintenance schedules, risk assessments, and system downtime, frequently representing the average rate of failures in a population.
Failure initiation – It is the microscopic or macroscopic onset of damage, such as crack formation, plastic deformation, or void nucleation, where a material begins to lose its intended functionality. It occurs when local stresses exceed material strength, typically starting at flaws, inclusions, or stress concentrations, even if the nominal load is low.
Failure locus – It is the boundary in stress, strain, or load space defining the limit between safe operation and material failure. It acts as a failure envelope, representing combinations of loading (e.g., tension, shear) which cause damage or fracture. It is normally used in structural integrity assessment.
Failure mechanisms – These are the physical, chemical, or mechanical processes of material degradation (such as corrosion, fatigue, creep, or wear) which lead to a component losing its function. These processes occur over time and are driven by factors like stress, heat, or environmental interactions, resulting in failure modes like cracking or breaking.
Failure mode – It is the specific manner or observed way in which a component, subsystem, or system fails to meet its intended function. It describes how a failure occurs, such as breaking, leaking, seizing, or short-circuiting, rather than why it failed (the cause). It is the observable symptom of a failure. Failure modes are categorized by how they affect system safety, functionality, and structural integrity. Common examples are structural failure (rupture), leakage, improper function, binding / jamming, or electrical faults (short / open).
Failure mode analysis – It is defined as a bottom-up, inductive analytical approach which identifies and assesses the impacts of different failure types on system operation, ultimately providing insights for improving system reliability and safety.
Failure mode and effect analysis (FMEA) – It is a systematic, detailed method of analysis of the malfunctions or defects which can be produced in the components of an engineering system. The analysis examines each potential failure mode to assess the reliability of the system elements and to ascertain the consequences of the failure upon the entire system. It is a ‘bottom up’ hazard identification technique. It considers the individual elements of a system, determines how each element can fail, and explores the effects of each such element failure on the operation of the system as a whole. This technique can also be used to quantify the failure rate of the total system by counting the contribution of each individual element.
Failure mode, effect, and criticality analysis (FMECA) – It is an extension of failure mode and effect analysis in which the criticality of each assembly is examined and the components and assemblies to which special attention are required to be given are identified.
Failure mode, effect and diagnostic analysis (FMEDA) – It is a systematic, quantitative, bottom-up reliability analysis method used to evaluate how components fail, the effects of those failures, and the effectiveness of diagnostic mechanisms. It extends traditional FMEA (failure mode and effect analysis) by including component failure rates and diagnostic coverage to predict safe /unsafe failure fractions, important for functional safety in metallurgy, automotive, and automation industries.
Failure model – It is a systematic framework, frequently mathematical or conceptual, used to predict the conditions under which a metal component ceases to perform its intended function. It relates external loading (stress), environmental factors (temperature, corrosion), and material properties (micro-structure) to determine the likelihood and method of failure.
Failure path – It is also known as a fracture path or crack trajectory. It refers to the specific route a crack takes through a metallic material as it breaks under stress. It is the physical, observable trajectory of a fracture surface, providing a map of the failure initiation site and the sequence of material separation. Analyzing of the failure path is an important part of metallurgical failure analysis, as it reveals the interaction between applied stresses, the material’s microstructure, and any environmental influences.
Failure plane – It is a distinct surface within a material along which separation, fracture, or shearing occurs when the material can no longer support applied loads. It represents the path of least resistance or the critical area subjected to the highest damaging stress, which can be predicted using failure theories. The failure plane is not always the weakest structural point, but the plane on which the difference between the shear stress and shear strength is minimum. It is typically inclined to the loading direction. In ductile materials under tensile tests, this frequently forms a 45-degree angle to the axis (maximum shear stress), leading to a ‘cup-and-cone’ shape.
Failure probability (Pf) – It is defined as the statistical likelihood, a value between 0 and 1, which a metal component ceases to perform its intended function under specified operating conditions and within a given time-frame. It is a quantitative measure of risk, frequently used to determine the reliability of components subjected to loads, fatigue, or environmental degradation (like corrosion). It is the proportion or fraction of components in a population expected to fail by a certain time (t), frequently expressed as a cumulative distribution function F(t).
Failure process – It is a sequence of events involving faults, errors, and failures, where a fault causes an error in a system, and an error can lead to a failure which deviates the delivered service from the correct operation as specified in functional or security needs.
Failure propagation – It is the progressive growth of a microscopic flaw, crack, or damage into a macroscopic fracture under loading. This process involves the expansion of failure mechanisms, such as ductile void coalescence, transgranular cracking, or intergranular fracturing, until the remaining cross-section cannot support the load, causing final structural failure.
Failure rate – It is also known as the hazard rate. It is a measure of how frequently something (a device, system, or component) fails, typically expressed as failures per unit of time (e.g., failures per hour, or failures per million hours). It indicates the likelihood of failure at a specific point in time, given that the item has survived up to that point.
Failure rate data – It refers to the quantified frequency with which metal components, assemblies, or materials fail under specified operating conditions, typically expressed as a number of failures per unit of time or distance (e.g., failures per million hours, failures per year, or failures per kilometer). It is a foundational metric in reliability engineering, metallurgical failure analysis, and maintenance planning, helping to determine the probability of failure over an asset’s lifespan.
Failure rating – It refers to the quantitative or qualitative assessment of the reliability, frequency, or severity of failure modes in metal components or structures. It is frequently used to rank the risk of component failure based on probability and consequences, such as in risk-based maintenance programmes.
Failure reporting analysis and corrective action system – It is a closed-loop process for capturing failure data, analyzing it, and verifying that corrective actions are effective. Unlike a single-event investigation, failure reporting analysis and corrective action system (FRACAS) operates continuously across all assets and failure events. It feeds data into reliability programs and enables trend analysis across similar asset populations, making it one of the most powerful long-term failure analysis frameworks.
Failure response – It is a structured notification which informs a user or system that a request failed to meet expected outcomes. It includes the error type, detailed explanation, and a unique identifier to help pinpoint and resolve the issue.
Failure scenario – It is a predefined, documented sequence of events, conditions, and system states leading to a specific failure mode (e.g., breakdown, component loss). It simulates potential issues, central processing unit (CPU)-intensive, network-intensive, or human error, to test system resilience, identify vulnerabilities, and improve reliability. It is a detailed description of how a system or component fails, including the preconditions, causes, and resulting behaviour. They are used in testing to proactively identify weak points before they cause real-world outages.
Failure strain – It is also called strain-to-failure. It is the quantity of deformation (elongation or strain) a material experiences at the moment it fractures, breaks, or loses structural integrity. It measures a material’s ductility, defining the maximum strain it can withstand before failure occurs, typically expressed as a dimensionless ratio or percentage.
Failure stress – It is the specific level of stress at which a material breaks, fractures, or ceases to function as intended under load. It represents the material’s strength limit, frequently defined by the maximum stress on a stress-strain curve or the point of rupture. Failure can involve yielding, buckling, or cracking.
Failure surface – It is the boundary in stress space separating stable states from failure, or a physical rupture surface in geo-technical / mechanical applications. It represents the critical stress condition, where material yields, breaks, or slips, distinguishing between safe (elastic) and failure (plastic / rupture) regions.
Failure theories – These are engineering models used to predict the conditions under which a solid material, subjected to complex loading, is going to fail, either by yielding (permanent deformation) or fracturing. These theories help determine safe design limits for components by comparing multi-axial stress states to allowable tensile / shear strengths determined by simple tests.
Failure zone – It is a region where material, structural, or geological components have lost integrity or strength, resulting in damage, deformation, or fracture. It is defined in engineering as the area where stress exceeds capacity, and in geology as a zone of crushed, faulted rock.
Fairing – It is a member or structure, the main function of which is to stream-line the flow of a fluid by producing a smooth outline and to reduce drag.
Fairly uniform distribution – It refers to an even or consistent spatial arrangement of constituents, such as alloy elements, second-phase particles, precipitates, or pores, within the metal matrix. It represents a high-quality micro-structure where these particles or inclusions are neither clustered (segregated) nor completely absent in large areas, leading to homogeneous mechanical properties throughout the material.
Fair practice – It refers to the consistent application of ethical, transparent, and equitable principles across all phases of projects, from design and data management to construction and career development. It focuses on ensuring safety, honesty, and accountability, while avoiding conflicts of interest and discriminatory behaviours.
FAIR principles – These are a set of guiding precepts designed to improve the infrastructure supporting the reuse of digital assets, ensuring they are findable, accessible, interoperable, and reusable. These principles aim to optimize data reuse by both humans and machines, addressing the need for automated discovery and processing in data-intensive engineering environments.
Falcon concentrators – These are enhanced gravity separators (EGS) consisting of a fast-spinning bowl. The bowl is fed from its bottom and uses centrifugal force to drain the slurry in a thin flowing film at its wall. The Falcon concentrator is basically a combination of a sluice and a continuously operating centrifuge. It is capable of operating at a high speed of rotation and hence gravity force enables fine particles of different specific gravity to be separated. The shape of the spinning bowl is such that as the feed slurry moves up the bowl the heavier particles react more than the lighter particles to the forces acting upon them. This results in migration of the heavier particles within the slurry stream to the surface in contact with the bowl, while the lighter particles tend to move to the top of the slurry with the water. Separation then takes place by removal of the lower (higher specific gravity) portion of the slurry through a collection lip / slot, the flow through which is regulated by a number of orifices which open and close in a controlled manner, removing the concentrate from the main stream, which discharges to tailings.
Fall accident – It is normally defined as an unintended event where a person unintentionally comes to rest on the ground, floor, or a lower level, frequently resulting from a loss of balance or support. In industrial settings, these incidents are categorized into two main types namely (i) falls from height which occurs when a worker falls from elevated platforms, scaffolding, ladders, or structural steel, normally defined as a drop from two meters or higher and (ii) same level falls (slips / tips) which occurs when a person trips over objects or slips on contaminants (e.g., oil, sand, or debris) on the ground.
Fall arrest – It is a form of fall protection which safely stops a worker after a fall has already begun, preventing them from hitting the ground or a lower level. It is used as a last resort, relying on personal protective equipment (PPE), typically a full-body harness, lanyard, and anchor, to reduce impact forces on the body.
Fall arrest protection – It is a type of fall protection designed to safely stop a worker after a fall has begun, preventing them from hitting a lower level or the ground. It is an active system, typically using a full-body harness, connector, and anchor, designed to absorb energy and reduce impact forces on the body during a fall.
Fall detection – It is the process of identifying when a fall has occurred, frequently utilizing wearable sensing technology such as accelerometers and gyroscopes to monitor movement patterns and thresholds. This technology aims to improve safety, particularly for aging individuals, by recognizing falls and potentially predicting to implement preventative measures.
Fall from height – It is an incident where a person falls from an elevated position to a lower level, or into an opening / gap, with the potential to cause personal injury. Common examples include falling from ladders, scaffolding, or roofs.
Fall hazard – It is a condition, equipment, or workplace situation which can cause a person to lose balance, lose bodily support, and fall to a lower level, resulting in injury or death. Common examples include unprotected leading edges, open floor holes, unguarded scaffolding, and unstable / slippery walking surfaces, frequently categorized in work-places as risks when working at heights of 1.2 meter or more.
Falling film evaporation – It is a process in which liquid is distributed on a heating surface, forming a thin film which is heated, causing part of the liquid to evaporate and remove heat from the surface. This process can occur on different surfaces, including plates and tubes, both vertically and horizontally.
Falling object hazard – It means any item, tools, materials, or debris, which can fall from a higher level to a lower level, posing a risk of injury or fatality to people below. It includes both static objects (unsecured items) and dynamic objects (dropped during work). Key causes include elevated work, inadequate securement, and lack of protective barriers like toe boards.
Falling rate period – It is the phase where the rate of moisture removal decreases as the material dries. It begins after the critical moisture content is reached, meaning surface moisture is gone and the drying speed is controlled by internal diffusion and capillary movement. Unlike the constant rate period, the drying speed drops as the remaining moisture is harder to remove.
Falling weight deflectometer – It is a non-destructive testing (NDT) device used to evaluate the structural capacity of road, highway, and airport pavements. It measures surface deformation under a simulated dynamic, impulsive traffic load to analyze structural integrity and material stiffness (modulus). A falling weight deflectometer (FWD) consists of a trailer-mounted weight which is dropped onto a loading plate, producing a load impulse that mimics the stress of a moving heavy vehicle. Sensors (geo-phones) placed at specific intervals measure the deflection basin (vertical deflection) caused by the impulse. The data is used to calculate the elastic moduli (stiffness) of pavement layers (asphalt, concrete, granular base), determine load-carrying capacity, and predict remaining service life.
Falling weight test – It is also called drop-weight test. It is an impact test where a specific mass is dropped from a measured height onto a metal sample to evaluate its resistance to impact loading, fracture toughness, and brittle crack propagation. It simulates high-speed, real-world shock loading to determine material durability. It is mainly used to determine the ‘nil-ductility t transition temperature (NDTT) of steels, which is important for identifying the temperature at which materials change from ductile to brittle.
Fall of Ground (FOG) – In mining, it is the unplanned or uncontrolled detachment of rock or material from the roof, sidewalls, or face of underground workings. These failures are substantial safety hazards, frequently categorized into gravity-induced rockfalls or dynamic movements like rock-bursts, posing major risks of injury and structural damage.
Fall prevention and restraint – These are proactive safety strategies designed to stop a worker from falling while working at heights. Fall prevention (or passive protection) eliminates the hazard, such as installing guardrails, while fall restraint (or travel restraint) uses a harness and fixed-length lanyard to prevent the worker from ever reaching an unprotected edge.
Fall protection – It refers to safety measures, equipment, and protocols used to prevent workers from falling from heights or to safely stop them if a fall occurs. It includes passive systems like guardrails and active systems like harnesses, needed when working at heights typically over 1.2 meter to 2 meters to prevent serious injury or death.
False accept rate – It is also called false acceptance rate. It is a key performance metric which measures the probability that a system incorrectly authorizes an unauthorized user. It represents the percentage of invalid inputs which are wrongly accepted as valid matches.
False alarm – It is an alarm signal transmitted when no genuine alarm condition exists. It is an incorrect or unintended alert triggered by a security, safety, or monitoring system when no real threat, hazard, or emergency condition exists. These activations occur because of malfunctions, environmental interference (e.g., dust, insects), improper installation, or user error, reducing system reliability and wasting resources.
False alarm rate – It is the frequency at which a system incorrectly signals a detection (false positive) when no valid target or event exists. It is an important performance metric defined as the number of false alarms per unit of time, per detection opportunity, or as a probability of noise exceeding a set threshold.
False bottom – It is an insert put in either member of a die set to increase the strength and improve the life of the die.
False brinelling -It is the damage to a solid bearing surface characterized by indentations not caused by plastic deformation resulting from overload, but thought to be because of other causes such as fretting corrosion. It is also the local spots appearing when the protective film on a metal is broken continually by repeated impacts, normally in the presence of corrosive agents. The appearance is normally similar to that produced by brinelling but corrosion products are normally visible. It can result from fretting corrosion. This term is to be avoided when a more precise description is possible. False brinelling (race fretting) can be distinguished from true brinelling since in false brinelling, surface material is removed so that original finishing marks are removed. The borders of a false brinell mark are sharply defined, whereas a dent caused by a rolling element does not have sharp edges and the finishing marks are visible in the bottom of the dent.
False cheek – It is a temporary or intermediate flask section used during the sand moulding process, specifically designed to facilitate the moulding of complex shapes which have undercuts. It allows a complex, three-part moulding scenario to be produced using what is basically a standard two-part mould structure (cope and drag). It is used when the parting line of a pattern cannot be made in a single flat plane, needing an intermediate section to manage the undercut area. It is considered a part of the casting nomenclature which helps in removing the pattern without damaging the mould.
False discovery rate – It is a statistical measure used in multiple hypothesis testing. It represents the expected proportion of false positive results (incorrectly rejected null hypotheses) among all the results declared as significant. Essentially, it quantifies the rate at which you might be wrong when claiming a finding is real in a set of tests.
False echo – It is a misleading signal return (reflection) displayed on a system, caused by reflections off objects other than the intended target, side-lobes, or multiple reflections. It appears as a real target but is inaccurate in distance, bearing, or presence, frequently causing confusion or mis-measurement.
False negative – It is a ‘type II error’ where a test, monitoring system, or algorithm fails to detect a present fault, hazard, or condition, erroneously reporting a ‘negative’ or safe result. It occurs when an actual positive event is missed, leading to a failure in detecting real threats, such as a, missed defect, failed sensor alert, or false security clearance.
False positive reduction – It refers to the process of decreasing the number of incorrect positive identifications (false alarms) made by a detection system, e.g., computer-aided detection (CADe), intrusion detection systems, or sensors, without substantially reducing the system’s sensitivity or true detection rate. This is achieved by analyzing the features of flagged candidates and applying classification algorithms or rules to distinguish true positives from false ones.
False precision – It occurs when numerical data are presented in a manner which implies better precision than is justified. Since precision is a limit to accuracy, this frequently leads to over-confidence in the accuracy, which is named precision bias.
False rejection – It is type I error in automated inspection systems. It is the incorrect denial of access or improper rejection of a legitimate user or valid component. It measures system usability rather than security, with high rates causing user frustration or operational inefficiencies.
Fan bearing – It is a critical mechanical component which supports the fan shaft, enabling rotation while reducing friction and limiting motion to specific axes (radial or axial). It ensures efficient, stable operation by bearing the load of the rotating impeller, with common types including sleeve, ball, fluid dynamic, and magnetic bearings.
Fan blade – It is an aerodynamically shaped component mounted on a rotating hub, designed to convert rotational energy into airflow by creating pressure differentials. Engineered with specific curvature, pitch, and profile, frequently airfoils, fan blades move air axially or radially through lifting surfaces to maximize efficiency, minimize noise, and manage pressure.
Fan coil – It is a heat exchanger which utilizes hot or chilled water to condition air within a space, allowing it to operate in either heating or cooling mode based on the central system’s operation.
Fan coil unit – It is a simple HVAC (heating, ventilation, and air conditioning) device consisting of a heating or cooling coil and a fan, used to condition air in individual residential or commercial spaces. It works by drawing air from the room, passing it over a coil connected to a central chilled / hot water system, and blowing the conditioned air back into the space. Fan coil units contain a fan, a heat exchanger (coil), a filter to clean the air, and a thermostat to control fan speed and temperature. They normally do not supply fresh air from outside. Instead, they recirculate the existing air in a room.
Fan discharge – It refers to the outlet of a fan where the pressurized air or gas exits. It represents the high-pressure side of the blower system, tasked with delivering air into ductwork or the atmosphere, frequently classified by direction, angle, and rotation (e.g., top horizontal, bottom vertical) to match specific system requirements.
Fan impeller – It is the rotating component of a fan or blower, consisting of a hub with mounted blades, which transfers kinetic energy from a motor to the air or gas. It increases air velocity and pressure by drawing air into the centre and forcing it outward, typically through a spiral-shaped housing, acting as the core mechanism for moving fluids efficiently.
Fan inlet – It is the entry point for air into a fan system, specifically designed to guide the airflow into the impeller (or wheel) with minimal pressure loss and turbulence. Proper design includes, frequently with an inlet cone or bell to ensure uniform, swirl-free flow, preventing system effects which decrease efficiency.
Fan motor– It is an electro-mechanical device designed to convert electrical energy (alternating current or direct current) into rotational mechanical energy to drive an impeller or blades. It provides the necessary torque to move air for cooling, ventilation, or HVAC (heating, ventilation, and air conditioning) applications. Key components include a stator, rotor, shaft, and bearings, frequently designed for high-efficiency, continuous operation.
Fanning equation – It is a method for calculating pressure drop in fluid flow, utilizing the fanning friction factor, which is one fourth the value of the Darcy friction factor. It accounts for different flow types (laminar and turbulent) and incorporates parameters such as fluid density, average velocity, channel length, and diameter.
Fanning friction factor – It is a dimensionless factor used in conjunction with the Reynolds number to estimate the pressure drop in a fluid flowing in a pipe or conduit. It is evaluated to determine the pressure drop at a given flow rate and geometry, allowing for meaningful comparisons between cases. It is one fourth the value of the Darcy friction factor and is used in calculations related to pressure drop in fluid flow, differing for laminar and turbulent flow conditions.
Fan performance curves – Fan performance is typically defined by a plot of developed pressure and power needed over a range of fan-generated air flow. Understanding this relationship is necessary for designing, sourcing, and operating a fan system and is the key to optimum fan selection.
Fan pressure – It is the total energy (or pressure difference) a fan adds to an air stream to move it through a system, overcoming resistance. It is defined by the difference between the ‘total pressure at the outlet’ and the ‘total pressure at the inlet’ (Pt-outlet – Pt-inlet), typically measured in pascals (Pa) or milli-meters of water gauge (mm, WGS.
Fans – Fans are normally identified as machines with relatively low pressure rises which move air, gases, or vapours by means of rotating blades or impellers and change the rotating mechanical energy into pressure or work on the gas or vapour. The result of this work on the fluid is in the form of pressure energy or velocity energy, or some combination of both. Fans are widely used in industrial and commercial applications. Fans are critical for process support and human health from shop ventilation to material handling to boiler applications. There are two primary types of fans namely (i) centrifugal fans, and (ii) axial fans. These types are characterized by the path of the airflow through the fan. Centrifugal fans use a rotating impeller to move the air stream. As the air moves from the impeller hub to the blade tips, it gains kinetic energy. This kinetic energy is then converted to a static pressure increase as the air slows before entering the discharge. Axial fans move the air stream along the axis of the fan. Fan and blower selection depends on the volume flow rate, pressure, type of material handled, space limitations, and efficiency. Fan efficiencies differ from design to design and also by types.
Fans, industrial – Industrial fans are machines, whose primary function is to provide a large flow of air or gas to various processes. This is achieved by rotating a number of blades, connected to a hub and shaft, and driven by a motor or turbine. The flow rates of these fans range from around 5.7 cubic meter perm minute to 57,000 cubic meter per minute. A blower is another name for a fan which operates where the resistance to the flow is primarily on the downstream side of the fan.
Fan suction – It is the low-pressure (negative pressure) area created at the inlet of a fan, where it draws air or gases into the rotor / impeller. It acts as an intake to move gas against a system’s resistance, frequently measured as static pressure (millimeters of water gauge) to overcome air resistance.
Fan systems – These are necessary to keep manufacturing processes working. A fan system consists of a fan, an electric motor, a drive system, ducts or piping, flow control devices, and air conditioning equipment (filters, cooling coils, and heat exchangers, etc.).
Fan tone noise – It is a type of periodic, humming aerodynamic sound produced by fans, characterized by discrete, high-amplitude spikes in the sound spectrum at specific frequencies. Primarily driven by ‘blade passing frequencies’ (BPF) and their harmonics, this noise results from the interaction between rotating blade wakes and stationary components.
FAQ – It is abbreviation of frequently asked questions.
Farad – It is the SI (The International System of Units) unit of capacitance.
Faradaic process – It is an electro-chemical reaction occurring at an electrode-electrolyte interface (such as in electrolysis or electroplating) where electrons are transferred across the interface, causing oxidation or reduction reactions. These processes are directly proportional to the quantity of charge transferred, following Faraday’s law of electrolysis. Faradaic processes involve the transfer of charged particles (electrons or ions) across the electrode surface, causing a continuous current to flow, unlike non-Faradaic processes which only store charge.
Faradaic reaction – It refers to an electro-chemical oxidation or reduction reaction which occurs at the surface of an electrode, involving the direct transfer of charge (electrons) across the electrode-electrolyte interface. These reactions are the fundamental mechanism for producing or refining metals in electro-chemical cells (e.g., electro-refining, electro-winning, electro-plating).
Faraday constant (F) – It is a unit of electric charge widely used in electro-chemistry equal to the negative of the molar charge (electric charge per mole) of electrons. It is equal to approximately 96,500 coulombs per mole.
Faraday–Lenz law – It is one of Maxwell’s equations, describing the relation between a changing magnetic field and production of an electro-motive force.
Faraday shield – It is a solid conductive shield around a volume, which blocks electromagnetic fields.
Faraday constant (F) – It is a unit of electric charge widely used in electro–chemistry equal to the negative of the molar charge (electric charge per mole) of electrons. It is equal to approximately 96,500 coulombs per mole.
Faraday rotator – It is a magneto-optic device which rotates the polarization plane of light passing through a transparent material using an external magnetic field. Engineered for non-reciprocal rotation, it rotates light by a specific angle (e.g., 45-degree) in the same direction, regardless of propagation direction, important for creating optical isolators.
Faraday’s constant (F) – It is the total electric charge carried by one mole of electrons (or elementary charges), approximately 96,485 C/mol. In electro-chemistry, it connects macroscopic charge (Q) and time to microscopic material changes, enabling calculations of electrolytically deposited mass, battery capacity, and Faraday efficiency.
Faraday’s law – It says that the quantity of any substance dissolved or deposited in electrolysis is proportional to the total electric charge passed. It also says that the quantities of different substances dissolved or deposited by the passage of the same electric charge are proportional to their equivalent weights.
Faraday’s laws of electrolysis – These are foundational engineering principles relating electric charge to chemical changes. They state that the mass (m) of a substance altered at an electrode is proportional to the total electric charge (Q) passed, where ‘m = ZQ’ (Z = electrochemical equivalent). First law states that the mass of a substance (m) produced, deposited, or dissolved at an electrode is directly proportional to the quantity of electricity (Q = I x t) passed through the electrolyte. Here ‘I’ is the current and ’t’ is the time. Second law states that when the same quantity of electricity passes through different electrolytes, the masses of different substances produced at the electrodes are proportional to their equivalent weights (atomic weight / valence).
Faraday’s law of induction – It is the relation between a changing magnetic field and the resulting voltage produced in a closed path.
Faradic efficiency – It is a metric which measures the effectiveness of electrical current in driving the desired electro-chemical reaction, specifically quantifying the efficiency with which electrical energy is converted into the chemical energy of produced hydrogen and oxygen gases during processes like seawater electrolysis. It is calculated by comparing the actual volume of produced gas to the theoretical volume, based on Faraday’s second law.
Far field approximation – It is a simplification method used in analyzing wave propagation, where distances from a source to an observer are large enough that certain terms in the wave equation can be neglected, allowing for a Taylor series expansion to approximate the propagation distance.
Far-field sound – It is the region far from a source where sound pressure waves act as spherical waves spreading outwards (approximating plane waves) and acoustic particle velocity is in phase with pressure. It begins approximately one wavelength away, where sound pressure level decreases by 6 dB (decibels) for each doubling of distance.
Far-infrared laser – It is a light source emitting coherent radiation between roughly 30 micro-meters and 1,000 micro-meters (0.1 tera-hertz to 10 tera-hertz), bridging the infrared and micro-wave spectra. These devices, frequently utilizing optically pumped molecular gases or quantum cascade structures, are engineered for high-resolution imaging, spectroscopy, and plasma diagnostics.
Far-infrared radiation – It is the infrared radiation in the wave-length range of 30 micrometers to 300 micro-meters.
Fast axis – It is the orientation within a birefringent material, such as a waveplate, fibre, or crystal, along which light polarized parallel to it experiences the lowest refractive index and consequently travels the fastest. It is one of the two orthogonal principal axes (fast and slow) which dictate how polarization states are manipulated.
Fast breeder – It is a reactor type which is driven by the use of fast neutrons and which exploits the ‘plutonium economy’ fuel cycle by utilizing natural / depleted uranium after an initial fuel charge of plutonium. The fast neutrons (as opposed to the thermal neutrons used in conventional pressurized water reactor, PWR and boiling water reactor, BWR designs) react with the uranium-238 (U-238) to produce plutonium-239 (Pu-239).
Fast carbonation – It is also frequently referred to as accelerated carbonation or early age carbonation. It is a controlled, rapid chemical process in which carbon di-oxide (CO2) reacts with freshly cast, unhardened cement-based materials, or alkaline industrial wastes, to produce stable calcium carbonates (CaCO3) within hours rather than years. Unlike natural, slow carbonation, which occurs over decades and can lead to rebar corrosion, fast carbonation is used as a curing technique to improve early-age strength, reduce porosity, and permanently sequester carbon di-oxide.
Fastener – It is a hardware device which mechanically joins or affixes two or more objects together. Fastener can be easily installed and removed with hand tool or power tool. Common fasteners include screws, bolts, nuts and rivets. In general, fasteners are used to create non-permanent joints, i.e., joints which can be removed or dismantled without damaging the joining components. Steel fasteners are normally made of stainless steel, carbon steel, or alloy steel.
Fastener forming operations – These are manufacturing processes which create fasteners (bolts, screws, rivets, nuts) by reshaping metal stock, typically wire or rod, using mechanical force, without cutting or removing material (chipless manufacturing). This process is largely based on plastic deformation, where compressive forces are applied to make the metal flow into a specific die cavity shape, frequently at room temperature (cold forging) or sometimes under heat (hot forging).
Fastener head – It is the top part of a bolt or screw used to drive, tighten, or hold the fastener using a tool. It acts as the bearing surface which compresses the jointed components, ensuring mechanical stability and proper load distribution. Key engineering functions include head shape, drive style, and bearing surface design, which dictate the tightening torque and assembly clearance.
Fastener hole – It is a specially designed opening, including simple, threaded, counter-bored, or counter-sunk types, created to accommodate screws, bolts, or rivets, enabling the joining of two or more components. These holes facilitate assembly, maintain structural integrity, or provide flush surfaces for fastener heads.
Fastener plate – It is a metal plate which is integral to mechanical belt fastening systems, needing regular inspections for secure attachment and wear resistance.
Fastening device – It is a hardware component used to mechanically join or affix two or more objects together securely. These are frequently standardized parts, such as bolts, screws, nuts, washers, and rivets, designed to create non-permanent joints which allow for disassembly, or permanent joints which need high structural integrity.
Fastening technique – It is a method used to mechanically join, secure, or assemble two or more components together, either permanently (e.g., riveting) or non-permanently (e.g., bolting). It utilizes specialized fasteners, such as screws, nuts, bolts, or clips, to create strong, reliable connections designed to withstand specific mechanical stresses, environmental conditions, and load requirements. Purpose of fastening is to connect parts, ensure structural integrity, and frequently allow for assembly / disassembly (non-permanent) or rigid, sealed joining (permanent).
Fastest crack – It is the catastrophic advancement of a crack through a structure at speeds frequently approaching the characteristic wave speeds of the material. These cracks typically grow at speeds of 500 meters per second –1,500 meters per second for several common materials, driven by high energy levels which cause the crack to run, frequently creating brittle, catastrophic failure.
Fast Fourier transform – It is an efficient algorithm used to compute the ‘discrete Fourier transform’ (DFT) of a sequence, or its inverse. Its main value is enabling the rapid conversion of a signal from its original time or space domain into a frequency domain representation and vice versa, which drastically reduces computational complexity and makes real-time signal analysis practical. The fast Fourier transform (FFT) is not a distinct transform itself but rather a computationally optimized implementation of the ‘discrete Fourier transform’ (DFT).
Fast fracture – It is also called rapid fracture. It is the sudden, unstable, and high-speed propagation of a crack, leading to catastrophic failure. It occurs when a pre-existing flaw reaches a critical size under applied load, normally without substantial plastic deformation, and is frequently associated with brittle materials or low temperatures.
Fast logic – It refers to high-speed digital logic devices, families, or design methodologies characterized by extremely rapid response times, typically with edge rates in the 1 nano-second per volt region. It is used in applications needing high performance, such as high-speed telecommunications, data processing, and supercomputing.
FASTMET process – It is a coal-based process of ironmaking. It enables the conversion of metallic oxides from either iron ore fines or steel plant metallurgical waste, into metalized iron. FASTMET is a unique process uses a rotary hearth furnace (RHF) to reduce agglomerates containing coal with a high reduction ratio and high productivity. The FASTMET process converts iron ore pellet feed, iron ore fines and / or steel plant metallurgical waste into direct reduced iron (DRI) using pulverized non-coking coal as a reductant. The end product DRI can be either hot briquetted to produce hot briquetted iron (HBI), or discharged as hot DRI into transfer containers, or cooled if cold DRI is needed.
FASTMELT process – It is the FASTMET process with the addition of an ‘electric iron melting furnace’ (EIF) to produce liquid iron or hot metal.
Fast-moving goods – These are products which are sold quickly, at a relatively low cost, and have a high turnover rate. From an operational perspective, these goods are characterized by high-volume manufacturing, short shelf-lives, and the need for rapid, efficient distribution systems. These products are sold quickly and replenished frequently, making inventory turnover velocity a key metric.
Fast multipole method (FMM) – It is a numerical algorithm designed to compute long-range interactions in N-body systems, reducing computational complexity from O(N-square) to O(N) or O(N logN). By hierarchically grouping particles and approximating far-field interactions using expansions, Fast multipole method enables efficient solutions for large-scale problems, including computational electro-magnetics, molecular dynamics, and boundary element methods (BEM).
Fastness properties – These properties define a material’s resistance to colour change or transfer when exposed to environmental factors like light, washing, or abrasion. Measured on a 1 to 5 scale (5 = excellent, 1 = poor), high fastness ensures durability by minimizing fading (colour loss) and bleeding (staining adjacent materials).
Fast neutron – It is a neutron which has not been slowed down (or ‘moderated’) by a moderator material, typically water or graphite. The slower neutrons are referred to as thermal neutrons, meaning they have the sort of energy associated with ‘normal’ levels of heat.
Fast-neutron reactor – It is a nuclear reactor which sustains a fission chain reaction using high-energy, ‘fast’ neutrons (above 1 million electron volts, MeV average) without a neutron moderator. These reactors efficiently use Pu-239 (plutonium-239) fuel to breed more fissile material from U-238 (uranium-238), enabling a closed fuel cycle, reduced waste, and high-temperature operation using liquid metal coolants.
Fast prototyping – It is defined as an investment in hardware design which allows design ideas to be rapidly built and tested for defects, facilitating quick deployment to customers for feedback. It encompasses several techniques, including advancements in 3D printing and prototype machine shops, enabling rapid development across different engineering disciplines.
Fast pyrolysis – It is a high-temperature process which rapidly decomposes biomass (within seconds) at 400 deg C to 600 deg C in the absence of oxygen to maximize liquid bio-oil production, typically yielding up to 80 % dry feed. Key technical criteria include high heating rates (above 100 deg C per second), small particle sizes (below milli-meters), and rapid vapour quenching.
Fast reactor – It is a nuclear engineering design which utilizes high-energy (‘fast’) neutrons directly from fission to sustain a chain reaction without a moderator. Operating with higher energy neutrons (above 0.1 million electron volts, MeV), these reactors maximize fuel efficiency by breeding more fuel than they consume and can utilize uranium-238, reducing waste.
Fast scheduling – It refers to techniques aimed at minimizing task completion time (latency) or reducing overall project duration. In computing, this involves algorithms like ‘shortest job first’ (SJF) to quickly clear tasks.
Fast subsystem – It is a component of a dynamic model characterized by rapid dynamics, where the variables evolve quickly compared to slow dynamics, frequently analyzed using a two-time scale method to simplify the behavior of the system.
Fast time scale – It refers to a modeling or data analysis approach focusing on rapid, short-duration events, frequently where the time-scale factor is less than one or changes occur within milliseconds. It captures rapid dynamics, such as fast-acting system failures, typically modeled as variations of order. .
Fast tracking – It is a schedule compression technique or duration compression technique in which the duration of a critical path is shortened by performing sections of some critical path activities concurrently instead of consecutively.
Fast transform – It refers to efficient computational methods for performing multidimensional transforms, which reduce complexity by breaking larger transforms into smaller separable transforms, as exemplified by the Cooley-Tukey and Winograd algorithms for discrete Fourier transforms (DFT). These methods leverage the separability of unitary matrices to optimize calculations, thereby requiring fewer multiplications and summations.
Fast wave – It is a wave whose phase velocity (the speed at which the wave’s phase propagates) is higher than the speed of light in a vacuum or, in other contexts, higher than the speed of light in a given medium or a designated velocity. This contrasts with ‘slow waves’ where the phase velocity is less than this reference speed. Fast waves are frequently associated with specific types of wave propagation, such as leaky wave antennas or in the context of certain microwave and RF (radio frequency) vacuum electronic devices.
Fast wavelet transform algorithm – It is an efficient mathematical method for converting a signal from the time (or spatial) domain into a sequence of coefficients in the wavelet domain. Essentially, it provides a fast way to compute the discrete wavelet transform (DWT). The main purpose of the fast wavelet transform (FWT) is to analyze nonstationary signals or data where frequency content changes over time. Unlike the ‘fast Fourier transform’ (FFT), which provides global frequency information, the fast wavelet transform offers simultaneous localization in both time and frequency domains by using small, finite ‘wavelets’ instead of continuous sine waves as its basis functions.
Fat – It is an organic ester, the product of a reaction between a fatty acid and glycerol. Fat can be of animal or vegetable materials or can be made synthetically.
Fatal injury – It is industrial accident resulting in a fatal injury to either the organization’s employees, contractor’s employee undertaking work for the organization or other persons where these result from an industrial accident arising from the organization’s activities. Death is to be certified by a medical professional. Fatality does not include fatalities involving voluntary social activities even if they are sponsored by the organization.
Fatal occupational injury – It is the occupational accident or injury leading to the death of a worker.
Fatality – It is the death resulting from an accident.
Fatality frequency rate – It is calculated on the number of fatalities per million-man hours.
Fatigue – It is the phenomenon leading to fracture under repeated or fluctuating stresses having a maximum value less than the ultimate tensile strength of the material. Fatigue failure normally occurs at loads which applied statically produces little perceptible effect. Fatigue fractures are progressive, beginning as minute cracks which grow under the action of the fluctuating stress.
Fatigue analysis – It is a method used to predict the life of a component subjected to repetitive (cyclic) loading, ensuring it does not fail prematurely because of the accumulated damage. It calculates how many cycles a material can withstand before crack initiation and propagation lead to fracture, even if stress levels remain below the material’s yield strength.
Fatigue assessment – It consists of fatigue resistance verification of a component subjected to a number of design / operating cycles.
Fatigue behaviour – It is the process of progressive, localized, and permanent structural damage in materials subjected to cyclic or fluctuating stresses, frequently leading to crack initiation, propagation, and ultimate failure at stress levels below the yield strength. It is a time-dependent failure mode important in engineering design to prevent sudden fracture in components subjected to repeated loading.
Fatigue crack growth – It is the progressive extension of a crack in a material under cyclic or fluctuating load conditions. It is an important aspect of fracture mechanics, where a pre-existing flaw grows with each load cycle, normally quantified as the crack growth rate (da/dN), the change in crack length (a) per number of cycles (N).
Fatigue crack growth rate (da/dN) – It is the rate of crack extension caused by constant-amplitude fatigue loading, expressed in terms of crack extension per cycle of load application, and plotted logarithmically against the stress-intensity factor range, ‘K’.
Fatigue cracking – It is the progressive, localized, and permanent structural damage which occurs when a metal is subjected to cyclic or fluctuating stresses. These cracks initiate and propagate at stress levels often below the material’s yield strength, leading to sudden failure. Fatigue cracking is a three-stage process involving crack initiation, crack propagation, and final fracture.
Fatigue crack nucleation – It is the initial stage of material failure where cyclic loading causes localized plastic deformation, resulting in the formation of microscopic cracks, normally at free surfaces or stress concentrators. It involves the creation of persistent slip bands (PSBs) and surface roughness (extrusions / intrusions) which grow into cracks, typically occurring at grain boundaries or inclusions.
Fatigue crack propagation – It is the progressive, sub-critical growth of a crack in a material subjected to cyclic or fluctuating loading, occurring even when stresses are below the yield strength. It is the stage following crack initiation where the crack tip advances per cycle, eventually leading to structural failure when the crack reaches critical length.
Fatigue crack propagation rate – It is the speed at which a crack increases in length (a) per loading cycle (N), defined as the derivative da/dN. This value represents the incremental crack growth per cycle and is important for predicting the remaining life of materials subjected to cyclic stress, typically growing faster as the crack length or stress intensity range (delta K) increases.
Fatigue cracks – When the material is subjected to fatigue stress (cyclically applied stress), fatigue cracks can develop and grow and this eventually leads to failure. Fatigue cracks can happen even if the magnitude of the stress is smaller than the ultimate strength of the material. Fatigue cracks normally originate at the surface but in some cases can also initiate below the surface. Fatigue cracks initiate at location with high stresses such as discontinuities (hole, notch, scratch, sharp corner, porosity, crack, or inclusions etc.) and can also initiate at surfaces having rough surface finish or due to the presence of tensile residual stresses.
Fatigue crack threshold – It is a function of a number of variables, including the material, the test conditions, the R-ratio, and the environment.
Fatigue curve – It is a graph representing the relationship between the applied cyclic stress amplitude (S) and the number of cycles to failure (N) for a material. It is used to predict the fatigue life and endurance of materials. The y-axis shows the stress amplitude (S), and the x-axis represents the number of cycles to failure (N), typically plotted on a logarithmic scale.
Fatigue cycle – It is the single, repeated application of a stress or strain fluctuation (loading and unloading) on a material, which, over several repetitions, causes cumulative damage, crack initiation, and eventual structural failure at stress levels below the material’s yield strength. The fatigue cycle includes a maximum load, a minimum load, and the resulting stress amplitude.
Fatigue damage – It refers to the cumulative deterioration of a material because of the repeated cyclic loading, leading to the initiation and propagation of cracks, ultimately resulting in fracture at stress levels below the material’s yield or ultimate strength.
Fatigue data – It defines how metals weaken and fail under repeated, fluctuating stress, frequently occurring at loads below their maximum tensile strength. It comprises fatigue life (cycles to failure), fatigue strength (stress for a specific life), and fatigue limit (infinite life stress), normally represented through S-N (stress-number of cycles) curves. Key components of fatigue data are fatigue limit (endurance limit), fatigue strength, S-N curve (Wohler curve), low cycle fatigue, and high cycle fatigue.
Fatigue damage parameters – These are quantitative metrics, such as stress amplitude, strain amplitude, and cycle count, used to define the cumulative deterioration of a metal under cyclic loading. These parameters describe the initiation and propagation of microcracks, typically analyzed through S-N curves, critical-plane methods, or energy-based models (e.g., Smith-Watson-Topper, SWT), to predict the remaining fatigue life of materials.
Fatigue damage accumulation – It is the progressive, incremental deterioration of a material’s integrity caused by repeated loading and unloading cycles (fatigue), ultimately leading to failure at stress levels below its yield strength. It is a cumulative process where minor defects grow into cracks, frequently modeled linearly (e.g., Miner’s rule) or non-linearly.
Fatigue damage assessment – It is the process of evaluating structural components subjected to cyclic loading to determine the accumulation of deterioration, predict fatigue life, and identify failure risks before they occur. It involves calculating stress / strain states (using tools like finite element analysis simulation) to determine when cumulative damage exceeds allowable limits.
Fatigue damage parameter – It is a continuum-based, measurable quantity which quantifies the material degradation (e.g., crack initiation, strain energy, or softening) caused by cyclic loading. It acts as a bridge between experimental fatigue data and the prediction of fatigue life, frequently incorporating factors like strain / stress ranges, mean stress effects, and material properties.
Fatigue damage process – It is the initiation and propagation of damage in materials, characterized by mechanisms such as fibre breakage, matrix cracking, interface debonding, and delamination, which are influenced by material properties, loading conditions, and service environments.
Fatigue deformation – It is the progressive, localized, and irreversible microstructural change in a material subjected to cyclic loading. It involves cumulative, irreversible microplastic deformation, such as slip bands and dislocation accumulation, even when stresses are below the yield strength. This process typically leads to crack initiation and failure.
Fatigue design – It is an engineering process which ensures structures and mechanical components withstand fluctuating, cyclic stresses over their intended lifespan without failing. It focuses on predicting crack initiation and growth under repetitive loading (e.g., vibrations, pressure fluctuations) to prevent premature, catastrophic failure below the material’s yield strength.
Fatigue design criteria – These refer to the methods used for predicting the fatigue life of structures, particularly welded structures, by relating design stress to the number of cycles characterizing failure, typically represented through S-N curves. These criteria take into account the unique stress states in welded zones where conventional methods does not apply.
Fatigue ductility coefficient – It is a material property representing the true strain corresponding to fracture in one strain reversal (N = 0.5 cycles) in low-cycle fatigue, frequently approximated by the monotonic tensile ductility (true fracture strain). It is the fatigue analog to the fatigue strength coefficient and is a key parameter in the Coffin-Manson relationship.
Fatigue effects – These refer to the degradation of electrical properties observed in piezoelectric materials during electrical cycling, influenced by factors such as measurement conditions and the material’s structure.
Fatigue failure – It is the failure which occurs when a sample undergoing fatigue completely fractures into two parts or has softened or been otherwise considerably reduced in stiffness by thermal heating or cracking.
Fatigue growth – It is the progressive, cycle-dependent extension of a crack in a material under fluctuating or cyclic loading, typically occurring at stress levels below the material’s yield strength. It is the second stage of fatigue failure (propagation), where small flaws grow incrementally (measured as da/dN, or length per cycle) until reaching a critical size causing final overload fracture.
Fatigue life (N) – It is (i) the number of cycles of stress or strain of a specified character which a given sample sustains before failure of a specified nature occurs, (ii) the number of cycles of deformation needed to bring about failure of a test sample under a given set of oscillating conditions (stresses or strains).
Fatigue life calculation – It is the quantitative estimation of the number of loading cycles (Nf) a metal component can withstand before a localized, progressive, and permanent structural change culminates in cracks or complete fracture. It is an important analysis since fatigue failure frequently occurs below the yield strength and without warning, causing roughly 80 % to 90 % of all metallic engineering failures. The process involves identifying the relationship between applied cyclic stresses / strains and the metallurgical damage accumulation, frequently using material-specific curves and empirical equations to predict when the material is going to fail.
Fatigue life distribution – It is the statistical representation of the variation in the number of cycles (Nf) needed to cause failure in seemingly identical components under identical cyclic loading conditions. Since fatigue is a stochastic process driven by microscopic inhomogeneities (like inclusions, voids, or surface imperfections), identical parts do not fail at the exact same time, the fatigue life distribution describes this scatter.
Fatigue life for ‘p’ % survival – It is an estimate of the fatigue life which ‘p’ % of the population is going to attain or exceed at a given stress level. The observed value of the median fatigue life estimates the fatigue life for 50 % survival. Fatigue life for ‘p’ % survival values, where ‘p’ is any number, such as 95, 90, etc., can also be estimated from the individual fatigue life values.
Fatigue life prediction – It is the process of estimating the number of load cycles (Nf) a metal component can withstand before failure under cyclic loading. It involves analyzing stress / strain levels, material properties, and damage accumulation (crack initiation and propagation) to ensure structural integrity and prevent unexpected brittle failure. It determines the longevity of materials subjected to fluctuating stress (e.g., vibration, rotation) which are lower than the ultimate tensile strength.
Fatigue lifetime – It is the total number of loading cycles (Nf) a metal component sustains before failing under cyclic or fluctuating stress. It represents the sum of cycles needed to initiate a microcrack (Ni) and the cycles needed for that crack to propagate (Np) until final fracture. It is the measure of durability, frequently expressed as ‘Nf = Ni + Np’.
Fatigue limit – It is the maximum stress which presumably leads to fatigue fracture in a specified number of stress cycles. The value of the maximum stress and the stress ratio also is to be stated.
Fatigue limit for ‘p’ % survival – It is the limiting value of fatigue strength for ‘p’ % survival as the number of stress cycles becomes very large. ‘p’ cam be any number, such as 95, 90, etc.
Fatigue load – It is the repetitive, cyclic application of stress or force on a material or structural component over time, frequently causing failure at levels well below its ultimate strength. These variable, repeated loads, such as bending, torsion, or pressure, initiate and propagate cracks, leading to premature fracture after several cycles. Fatigue loading is a critical factor in engineering design.
Fatigue loading condition – It is a condition where materials experience failure because of the fluctuating or cyclic stresses (tension / compression) well below their yield strength, resulting in progressive damage. It is characterized by repeated loading / unloading, leading to crack initiation, propagation, and final fracture.
Fatigue model – It is a mathematical framework used in engineering to predict material degradation and structural failure caused by repeated, cyclic loading. These models correlate stress, strain, and energy variables to estimate fatigue life (number of cycles to failure) by analyzing crack initiation and growth stages, frequently employing methods like Palmgren-Miner linear damage rule.
Fatigue modeling – It is the formulation of mathematical relations and computational frameworks which correlate material deformation, such as stress, strain, or energy, to fatigue life. It is a fundamental process used to predict the degradation, crack initiation, and propagation in materials and structures subjected to cyclic or fluctuating loads, which frequently result in failure at stress levels below the material’s yield strength.
Fatigue notch factor (Kf) – It is the ratio of the fatigue strength of an unnotched sample to the fatigue strength of a notched sample of the same material and condition. Both the strengths are determined at the same number of stress cycles.
Fatigue notch sensitivity (q) -It is an estimate of the effect of a notch or hole of a given size and shape on the fatigue properties of a material, measured by ‘q = (Kf -1)/(Kt -1)’, where ‘Kf’ is the fatigue notch factor and ‘Kt’ is the stress-concentration factor. A material is said to be fully notch sensitive if ‘q’ approaches a value of 1, it is not notch sensitive if the ratio approaches 0.
Fatigue performance – It is a material’s or component’s ability to withstand repeated loading and unloading cycles (cyclic stress) without experiencing failure. It measures longevity under dynamic conditions, where stress levels are frequently below the yield strength, and is important for preventing premature fractures in structures.
Fatigue process – It can be roughly divided into four stages namely cyclic hardening / softening, crack nucleation, crack propagation, and overload (fracture). In flaw-free materials a considerable fraction of the total life-time is spent before the first detectable micro-cracks appear. At low amplitudes the nucleation stage can occupy the majority of the lifetime. At high amplitudes nucleation is normally accomplished within a small fraction of the fatigue life. Another fraction of the lifetime is needed for propagation of the micro-structurally small cracks (cracks small compared to micro-structural size scales) to reach the size of the physically small cracks (i.e., cracks of the size 0.5 millimeter to 1 millimeter). Again, this fraction can be quite high at low amplitudes. Propagation of physically small cracks and macro-cracks can be quantitatively described by means of fracture mechanics. On the other hand, there is no normally accepted quantitative description of the nucleation process, and there is no widely applicable description of the propagation of microstructurally small cracks. Hence, any numerical analysis of these stages in the fatigue process is to be preceded by deeper understanding of the physical mechanisms.
Fatigue properties – These properties define a material’s resistance to, and life under, repeated or fluctuating (cyclic) loading, which causes failure at stress levels well below its static yield strength. These properties are important in predicting component longevity against cracking initiated by fatigue, which is estimated to cause 90 % of metallic service failures.
Fatigue ratio – It is the ratio of fatigue strength to tensile strength. Mean stress and alternating stress is to be stated.
Fatigue reliability – It is defined as the probability which a structural component or system performs its intended function without failing because of the cyclic, cumulative degradation over a specific lifetime. It is a probabilistic approach accounting for uncertainties in material strength, loads, and environmental factors, calculating the probability that fatigue damage remains within acceptable limits.
Fatigue resistance – It refers to the ability of a material to withstand repeated cycles of stress or strain without experiencing failure. This property is crucial in applications where materials are subjected to fluctuating loads over time, such as in automotive, aerospace, and industrial machinery components.
Fatigue response – It refers to the material’s reaction and progressive degradation when subjected to cyclic or fluctuating loads. It is a process of localized, permanent structural damage which frequently leads to failure at stress levels considerably below the material’s yield strength.
Fatigue safe-life – It is a design approach ensuring a component survives a designated number of loading cycles without failure by limiting operating stresses below a threshold where fatigue cracks form. It relies on S-N curves (stress-life) to establish a finite, safe lifespan, frequently using large safety factors.
Fatigue slip bands – These are localized, persistent bands of intense dislocation motion (slip) on a metal’s surface, formed by cyclic stress. They represent accumulated, irreversible damage where atomic planes slide over one another, creating surface roughening, intrusions, and extrusions which eventually nucleate fatigue cracks,
Fatigue strength – It is the maximum cyclical stress which a material can withstand for a given number of cycles before failure occurs.
Fatigue strength at ‘N’ cycles (SN) – It is a hypothetical value of stress for failure at exactly ‘N’ cycles as determined from an S-N curve. The value of ‘SN’ hence determined is subject to the same conditions as those which apply to the S-N curve. The value of ‘SN’ which is normally found in the literature is the hypothetical value of maximum stress, ‘Smax’, minimum stress ‘Smin’, or stress amplitude, ‘Sa’, at which 50 % of the samples of a given sample can survive ‘N’ stress cycles in which the mean stress Sm = 0. This is also known as the median fatigue strength at ‘N’ cycles.
Fatigue strength coefficient – It is a material property parameter representing the stress intercept at one reversal (2Nf = 1) on a log-log plot of stress amplitude versus reversals to failure. It is an important component in the Coffin-Manson relationship for low-cycle fatigue, determining the elastic portion of strain-life curves. It represents the true stress at which a material fails after a very small number of load reversals (frequently approximated as the first quarter-cycle), acting as a ‘strength coefficient’ in fatigue.
Fatigue strength diagram – It is commonly known as an S-N curve or Wohler curve, is a graph used in metallurgy to plot alternating stress (S) against the number of cycles to failure (N) for a material. It defines the relationship between cyclic stress magnitude and fatigue life, showing that lower stress allows higher cycle life, important for assessing fatigue resistance.
Fatigue strength exponent – It is denoted by the symbol ‘b’. It is a material property which represents the slope of the fatigue strength against fatigue life curve when plotted on a log-log scale, specifically within the high-cycle fatigue regime. It is a key parameter in the Basquin equation for fatigue life prediction, which models the relationship between alternating stress and the number of cycles to failure.
Fatigue strength for ‘p’ % survival at ‘N’ cycles – It is an estimate of the stress level at which ‘p’ % of the population is going to survive ‘N’ number of cycles. ’p’ can be any number, such as 95, 90, etc. The estimates of the fatigue strengths for ‘p’ % survival values are derived from particular points of the fatigue-life distribution since there is no test procedure by which a frequency distribution of fatigue strengths at ‘N’ cycles can be directly observed.
Fatigue-strength reduction factor – It is the ratio of the fatigue strength of a member or sample with no stress concentration to the fatigue strength with stress concentration. This factor has no meaning unless the stress range and the shape, size, and material of the member or sample are stated.
Fatigue stress – It refers to the fluctuating, cyclic, or alternating loads applied to a material over time, which, despite being significantly below the material’s yield strength, cause cumulative, localized plastic deformation and progressive crack growth. It represents a ‘wear and tear’ process leading to sudden brittle-like failure.
Fatigue stress concentration factor (Kf) – It is the ratio of the fatigue strength of a notch-free (unnotched) sample to the fatigue strength of a notched sample. It represents the increase in localized fatigue stress compared to the nominal stress, with typically being lower than the theoretical static stress concentration factor (Kt). It accounts for how notches, holes, or discontinuities raise the stress at a specific location, leading to cracks, especially under cyclic loading.
Fatigue striation – It is a micro-scale fatigue fracture feature sometimes observed which indicates the position of the crack front after each succeeding cycle of stress. The distance between striations indicates the advance of the crack front during one stress cycle, and a line normal to the striation indicates the direction of local crack propagation. It is not to be confused with beach marks, which are much larger (macroscopic) and form differently. It is also not to be confused with other similarly appearing micro-scale features, such as a stretch zone at the tip of a pre-existing crack-like imperfection, a Wallner line, and so on. Fatigue striation is the parallel lines frequently observed in electron microscope fractographs or fatigue fracture surfaces. The lines are transverse to the direction of local crack propagation. The distance between successive lines represents the advance of the crack front during the one cycle of stress variation. In glasses, fatigue striation is a fracture-surface marking consisting of the separation of the advancing crack front into separate fracture planes. It is also known as coarse hackle, step fracture, or lance. Striations can also be called shark’s teeth or whiskers.
Fatigue test – It is a method for determining the range of alternating (fluctuating) stresses a material can withstand without failing.
Fatigue testing – It is a specialized, cyclic mechanical testing process which evaluates a material’s durability, lifespan, and crack growth behavior by subjecting it to repeated, fluctuating stress, well below its static yield strength, until failure. It determines important performance parameters like fatigue life, fatigue strength, and the resistance of metals to long-term cyclic loading.
Fatigue threshold (delta Kth) – It is the critical stress intensity factor range below which fatigue cracks in a material do not propagate. It represents the boundary where cyclic loading, such as in mechanical parts, fails to cause crack growth, typically defined at 10 million cycles or 100 million cycles without failure.
Fatigue wear – It is the removal of particles detached by fatigue arising from cyclic stress variations. It is also the wear of a solid surface caused by fracture arising from material fatigue. Fatigue wear is essential in periodically loaded dies and tools, such as rolls. In loaded tools, the surface is in compression and shear stresses are generated below the surface. Repeated loading causes generation of micro cracks, usually below the surface, at a point of weakness, such as an inclusion or second phase particle. On subsequent loading and unloading, the micro crack propagates and voids coalesce. When the crack reaches a critical size, it changes direction to emerge the surface and a flat sheet-like particle is detached. This is also known as delamination wear or if the particle is relatively large it is known as spalling. When normal loading is combined with sliding, the location of maximum shear stress moves towards the surface and fatigue cracks may then originate from surface defects.
Fats, oils, and grease – These refer to organic polar compounds derived from animal or vegetable sources, alongside hydrocarbons, which are insoluble in water. Fats, oils, and grease (FOG) solidify in sewers, reducing pipe capacity and cause blockages. These consist of mainly triglycerides (triacylglycerols) composed of fatty acids and glycerol, forming solid deposits when cooled. These are less dense than water (10 % to 15 % less), causing it to float, harden, and bond with other materials, causing roughly 30 % to 40% of sewer clogs. Engineering controls include grease interceptors (GIs), grease traps, and separators that use baffles to create non-turbulent flow, allowing fats, oils, and grease to rise and separate from wastewater. Fats, oils, and grease can react with calcium ions (Ca2+) in sewer systems to form hard soap deposits, leading to substantial blockages
Fatty acid – It is an organic acid of aliphatic structure originally derived from fats and fatty oils.
Fatty acid methyl esters – These are compounds formed by the transesterification of fats (vegetable oils / animal fats) with methanol, acting as the main component of bio-diesel. They are valuable not just as fuel, but as eco-friendly, bio-degradable lubricants, corrosion inhibitors, and cleaning agents for metal surfaces. While free fatty acids are acidic and corrosive, fatty acid methyl esters (FAMEs) are less corrosive, protecting metal surfaces in engines and industrial infrastructure. These can act as superior lubricity agents, reducing wear in metal processing and engine parts (e.g., in castor oil derivatives). These are used in cleaning, degreasing, and metalworking fluids because of their low toxicity, high flash point, and renewability. These are typically produced through base-catalyzed trans-esterification, where fats are reacted with methanol, frequently chosen over raw oils for improved stability and lower viscosity.
Fatty acid profile – It is defined as the composition of different fatty acids present in a sample, which can be determined using techniques such as gas chromatography.
Fatty oil – It is a fat (glycerol ester) which is liquid at room temperature.
Fault – It is an abnormal condition, defect, or flaw in a system, component, or material which causes it to operate incorrectly, fail to perform its intended function, or produce unintended results. It is the underlying cause of a failure or deviation from expected performance. It is also a break in the earth’s crust which is caused by tectonic forces which have moved the rock on one side with respect to the other.
Fault candidate – It is typically a structural defect or microstructural feature within a material which is identified as a potential initiator or site for failure (such as cracking, fatigue, or fracture) under service conditions. In the context of alloy design and metallurgical research, this term is frequently associated with stacking faults (planar imperfections in the atomic arrangement) that affect plastic deformation and damage mechanisms.
Fault detection – It is defined as the process of identifying, in real-time or through data analysis, abnormal conditions or malfunctions in equipment (such as furnaces, rolling mills, or conveyors) and production processes. It serves as a binary decision-making tool to differentiate between normal and abnormal operations by recognizing deviations from expected performance thresholds, typically before those issues escalate into costly component failures or major production downtime.
Fault detection and diagnostics – It involves the use of sensors, data analytics, and modeling to continuously monitor metallurgical processes (such as smelting, casting, or rolling) to detect deviations from normal operation and identify the root cause of these malfunctions to ensure product quality and prevent costly equipment failure.
Fault diagnostics – It refers to the systematic process of identifying, locating, and determining the root cause of abnormal conditions, malfunctions, or material failures in metal components or metallurgical production processes. It is a critical component of maintenance and quality control, designed to distinguish between normal operating behavior and failure modes, such as cracking, corrosion, or casting defects, before they cause severe damage, downtime, or safety hazards.
Faulted loop – It is a planar, two-dimensional dislocation loop, typically a Frank loop, which encloses a region of stacking fault on close-packed planes (e.g., {111} in face-centered cubic metals). These sessile defects, formed by point defect agglomeration (vacancies / interstitials) in irradiation or quenched metals, are characterized by high-energy stacking faults.
Fault, electrical – It is a short circuit, open circuit, or other disruption of a power system.
Fault energy – It refers to the energy associated with the formation of defects in materials, such as antiphase boundaries and stacking faults, which can be influenced by alloying elements and is related to macroscopic parameters like yield stress and work-hardening coefficient.
Fault exception – It is an event which occurs when an error, such as a divide by zero operation. It is detected during program execution, triggering a specific handler to manage the error and potentially trace it back to the source of the fault.
Fault exclusion – In safety engineering, it is frequently applied to metallurgical and mechanical components. It is the elimination from consideration of a specific, identified failure mode within the safety-related parts of a control system (SRP/CS). This, basically, is a decision by designers to rule out certain types of dangerous faults, such as the breaking of a bolt or the fracture of a metallic part, since they are deemed highly improbable because of the quality of material, design, and operating conditions.
Fault hazard analysis – It is a qualitative analysis of design hazards other than malfunctions. Failure mode effect analysis, failure mode effect and criticality analysis, and fault tree analysis consider only malfunctions.
Fault impedance – It is defined as the total resistance to electrical flow at the location of a malfunction. It is an important parameter influencing the magnitude of fault current and voltage, typically expressed in ohms. It characterizes the severity of a fault (e.g., short circuit) and is used to distinguish between ‘bolted’ faults (near-zero impedance) and high-impedance faults (HIFs).
Fault management – It refers to the systematic process of detecting, diagnosing, and resolving abnormal operating conditions in machinery, processes, or material quality to ensure safe, stable production and prevent failures. It involves the use of advanced modeling and data-driven methods, such as neural networks, to analyze high-dimensional, non-linear, and time-varying data from production lines, frequently targeting bearing failures, which are a major cause of industrial downtime.
Fault model – It is a representation or simulation of physical, metallurgical, or mechanical defects which can occur during the production, processing, or service life of a metal component. These models are used to predict the consequences of defects (such as cracks, voids, or corrosion) on structural integrity, enabling failure analysis and enabling the development of predictive maintenance techniques. Metallurgical fault models frequently focus on the microstructure and material properties, rather than just geometric shapes, and are frequently used in failure analysis (cracks, corrosion, or contamination), process monitoring (detecting abnormal working conditions in smelting or manufacturing), and mechanical signaling (analyzing stress-strain behaviour).
Fault modes – These refer to specific types of failures or faults which occur at a component or sub-assembly level, which can be identified and evaluated through methodologies such as ‘failure mode and effects analysis’ (FMEA).
Fault plane – It refers to the specific crystallographic plane where a disruption occurs in the normal stacking sequence of atomic planes within a crystal lattice. These faults are planar defects (2D defects) which separate regions of crystal that have slipped or are stacked incorrectly, often acting as barriers to dislocation motion.
Fault tolerance – It is the property which allows a system (computer, machine, or network) to continue operating properly, without interruption or with minimal degradation, in the event of hardware or software failures. It is achieved through redundancy, error detection, and automatic recovery mechanisms, ensuring reliability in critical systems.
Fault-tolerant control – It refers to automated systems designed to maintain safe, operational stability during component failures (like sensor or actuator malfunctions) in furnaces, casting machines, or rolling mills. It allows the process to continue or shut down safely, avoiding costly production stops, damage, or accidents.
Fault tree – It is the analysis of an event in a top-down manner. The event is analyzed by breaking it down at each successive stage to identify what equipment and operator actions, if failed, would lead to the postulated outcome. The fault tree starts with the top event, as defined within the event tree analysis, and at each stage identifies combinations of precursor event(s) using logical operators such as ‘AND’ and ‘OR’.
Fault tree analysis – It is an analysis method which provides a systematic description of the combinations of possible occurrences in a system which can result in failure. It is a graphical representation of the Boolean (a data type which has one of two possible values normally denoted true and false) logic which relates to the output (top) event. It is a graphical method for analyzing how a top event (normally a hazardous event) can be caused by lower-level events combined by logical operators (most frequently ‘AND’ and ‘OR’ gates). The method is useful for identifying single points of failure or limited redundancy in complex systems, and can be used for system reliability and availability calculations.
Fault tree diagram – It is a top-down, deductive logic diagram used to identify the root causes of an undesired metallurgical failure (e.g., fatigue, fracture, corrosion). It maps pathways from a major failure event back to basic events, such as raw material impurities, improper heat treatment, or processing errors, using logical AND/OR gates to analyze risk.
Faulty cell – It normally refers to a unit of material, component, or energy storage device which fails to perform its intended function reliably because of the defects in structure, composition, or manufacturing.
Faulty design – It refers to errors in the engineering, planning, or material selection phase of a component’s development which lead to operational failures. Unlike manufacturing defects, which imply a deviation from a, correct design, faulty design implies that the blueprint itself is inadequate for the intended service conditions, frequently resulting in systemic failures across an entire product line.
Faulty operation – It refers to an abnormal condition or the failure of a system, component, or process to function within its designated performance specifications, safe operating limits, or designed intent. This can occur during system operation due to internal defects, design deficiencies, or external factors, and can be either permanent (hard fault) or transient / sporadic (soft fault).
Fax – It is the facsimile, the transmission of paper images by radio or by wire.
Fayalite (2FeO.SiO2 or Fe2SiO4) – It is an iron-silicate mineral belonging to the olivine group which plays an important role in extractive metallurgy, particularly as the primary phase in copper and nickel smelting slags. It is formed when iron oxides (FeO) react with silica (SiO2) at high temperatures, typically around 1,177 deg C to 1,205 deg C, to create a low-melting, liquid slag, frequently referred to as ‘acidic’ or ‘silica-rich’ slag.
Fayalite slag – It is a ferrous silicate by-product (2FeO.SiO2 or Fe2SiO4) produced during the smelting and refining of non-ferrous metals, notably copper and nickel. It acts as a liquid flux which removes impurities, specifically iron, from ores. It is characterized by high iron content, low viscosity, and glassy, dark, or granular appearances.
Faying surface – It is the mating surface of a member which is in contact with or in close proximity to another member to which it is to be joined.
fcc crystal – It is a cubic crystal structure characterized by its face-centered arrangement of atoms, where the reciprocal lattice shows body-centered cubic (bcc) symmetry. The primitive cell of the fcc structure has a volume which can be mathematically described using specific primitive vectors.
fcc material – It is a metal characterized by a crystal structure featuring atoms located at the eight corners of a cube and in the centre of all six faces.
fcc metals – These are metallic elements which show a face-centred cubic crystal (fcc) structure, characterized by high ductility, toughness, and the ability to retain these properties at absolute zero. They include metals such as aluminum, nickel, and copper, which are normally used in several applications.
fcc phase – It refers to the face-centered cubic (fcc) structure observed in certain alloys, such as Fe-Ag (iron-silver) alloys, which can exist alongside other phases, including bcc (body-centered cubic), depending on factors like substrate temperature and composition.
fcc structure – It is defined as a cubic unit cell which contains one atom at each corner and one atom at the centre of each face, with atoms touching along the diagonals of the cube faces. This structure shows characteristics such as high ductility, toughness, and resistance to crack propagation, making it common among certain metallic elements.
FeAl-based alloys – These are iron aluminides which are inter-metallic compounds of iron and aluminum (typically FeAl or Fe3Al phases) which combine low cost and low density with exceptional oxidation, corrosion, and wear resistance. These materials are classified as “’materials of the future’ for high-temperature and aggressive environments, frequently used in power plants, furnaces, and chemical industries.
FeAl inter-metallic – It is an ordered intermetallic compound within the iron-aluminum (Fe-Al) binary system, characterized by a 50 / 50 atomic ratio (equi-atomic composition) of iron and aluminum. It is recognized as a high-temperature structural material belonging to the iron aluminides family, which acts as a bridge between conventional metals and technical ceramics.
Fe3Al inter-metallic – It is a type of iron aluminide intermetallic compound, comprising roughly 75 atomic percent iron (Fe) and 25 atomic percent aluminum (Al). It is recognized as an ordered structural inter-metallic, meaning its atoms occupy specific positions in the crystal lattice rather than being randomly distributed. Fe3Al is considered a ‘material of the future’ for high-temperature and corrosive environments due to its excellent combination of properties, including low density, high strength-to-weight ratio, and outstanding resistance to oxidation and sulphurization.
Feasible criterion space – It is (often referred to as the feasible region, solution space, or operating envelope) is defined as the set of all possible processing parameters, compositions, or design variables that satisfy all imposed constraints—such as economic, metallurgical, physical, and environmental limitations, to produce a material with desired properties. It represents the allowed operational area where a metallurgical process (e.g., smelting, heat treatment, alloy design) can produce a viable, high-quality product without exceeding the technical, safety, or economical limits.
Feasible design – It is a solution which satisfies all defined requirements, constraints, and functional goals. It is a practical, workable, and compliant design which meets technical, financial, and operational standards, as determined by a feasibility study before full-scale development. The design is to adhere to all constraints, including budget, safety, physical, and regulatory requirements.
Feasible direction method – It is an iterative, gradient-based numerical optimization technique used to solve constrained problems, aiming to improve an objective function (e.g., reduce cost / weight) while keeping design variables within allowable limits (satisfying inequalities). It starts at a feasible point and moves along a direction which reduces the objective function without violating active constraints.
Feasible location – It refers to a site for establishing metallurgical facilities (such as smelters, refineries, or processing plants) where operations are technically possible, economically viable, and legally permitted. Such a location is determined by a comprehensive feasibility study which hat considers factors such as proximity to raw materials, energy supply, labour, infrastructure, and environmental regulations.
Feasible solution – It is a design, plan, or decision which satisfies all identified constraints, limitations, and requirements of a problem. It is a valid, workable option within the permissible ‘feasible region’ (the set of all possible solutions), but it is not necessarily the most optimal or cost-effective choice.
Feasible state – It refers to identifying a set of operating conditions, design parameters, or system configurations which satisfy all defined constraints (linear, non-linear, equality, or inequality). In the context of system design, a feasible design is a point within a designated region which satisfies all requirements, making it workable for its intended function.
Feasibility report – It is a report which evaluates a set of proposed project paths or solutions to determine if they are viable. Persons who prepare the feasibility report evaluate the feasibility of different solutions and then chooses their recommendation for the best solution.
Feasibility mineral resource – Feasibility mineral resource is that part of measured mineral resource, which after feasibility study has been found to be economically not mineable.
Feasibility study – It is a comprehensive technical and economic assessment of the practicality of a project or system. A feasibility study aims to objectively and rationally uncover the strengths and weaknesses of a proposed venture, opportunities and threats present in the natural environment, the resources needed to carry through, and ultimately the prospects for success. In its simplest terms, the two criteria to judge feasibility are cost needed and value to be attained. A well-designed feasibility study is to provide a historical background of the project, a description of the product or service, accounting statements, details of the operations and management, marketing research and policies, financial data, and regulatory requirements. Normally, feasibility studies precede technical development and project implementation. A feasibility study evaluates the project’s potential for success. Hence I is perceived objectivity is an important factor in the credibility of the study for potential investors and lending institutions. It is hence to be conducted with an objective, unbiased approach to provide information upon which decisions can be based.
Feasible path – It is a sequence of actions or state transitions which can actually be executed while satisfying all imposed constraints. It is a trajectory linking a start point to a goal point which respects physical, geometric, or logical rules.
Feather burr – It is a very fine or thin burr.
Feather edge – It is same as feather burr except that feather edge can also refer to the ends of a lead-in or lead-out thread, which is a very thin machined ridge. It is sometimes called a wire edge or whisker-type burr.
Feature band – It refers to a subset of specific, highly informative spectral bands extracted from high-dimensional spectral data (such as hyperspectral imaging) which correlate strongly with a target variable. These bands are chosen for their predictive power in modelling, classification, or identification tasks, allowing researchers to remove redundant or irrelevant bands while keeping the most relevant spectral information.
Feature density – It is a measure of the quantity, concentration, or compactness of specific features within a defined area, volume, or dataset. It is normally defined as the number of features per unit area or volume. Depending on the context, it can refer to physical surface textures, computer vision image analysis, or data analysis.
Feature extraction – It is a dimensionality reduction process which transforms raw, complex data (images, text, audio) into a simplified, numerical set of actionable features. It improves machine learning model accuracy and speed by focusing on relevant information while reducing noise and computational complexity, frequently creating new, more meaningful attributes.
Feature extraction network – It is a specialized neural network component (frequently a ‘convolutional neural network’, or ‘backbone’) designed to automatically identify, transform, and reduce raw input data into high-level, meaningful feature representations. It acts as an encoder, extracting structural information (edges, textures, or semantic patterns) for tasks like classification or localization while ignoring noise.
Feature propagation – It is an inference process in graph machine learning which spreads node features across the graph topology to aggregate information from neighbours. It is used to generate informative node representations by allowing nodes to exchange information based on graph structure.
Features – In computer modeling, these are higher level constructs (other than points, curves, and surfaces) which allow designers to work more naturally with geometries such as slots, through holes, and bosses etc. Form features such as these allow designers to add relatively complex yet common shapes without having to apply Boolean (a data type which has one of two possible values normally denoted true and false) operations on blocks and other shapes.
Feature sequence – It normally refers to a data structure that explicitly attaches information, such as structural, functional, or descriptive properties, to specific, ordered regions within a larger sequence, normally used in machine learning, and data engineering.
Feature space – It is a multi-dimensional vector space where each axis corresponds to a specific feature (variable) of a dataset, and every data point is represented as a coordinate within it. It is the fundamental space for machine learning algorithms, mapping data points (e.g., pixels, objects) into a mathematical structure used for analysis, classification, and clustering based on proximity.
Fe content – It is the iron content. It refers to the proportion or percentage of iron (Fe) present within a material, such as ores, alloys, or waste by-products (e.g., slag). It dictates the quality, value, and processing route for ironmaking, steel production, and, if undesired, indicates impurity levels in non-ferrous alloys.
Fed-batch mode of reaction – It basically involves the supply of substrate in batches in the reactor, whereas the product is removed only once after the completion of the reaction cycle. This reaction basically ensures that there is no saturation or substrate inhibition.
Fed-batch operation – It refers to a process in which one or more reactants are added continuously during the operation, allowing for controlled reaction conditions and product formation.
Fed induction motor – It refers to a type of induction motor which is supplied with dual excitation, allowing for direct regulation of torque and air-gap flux, which improves its performance characteristics.
Fed induction motor drive – It is a motor control system which uses a power electronic converter (inverter) to supply variable-frequency, variable-voltage AC (alternating current) power to an induction motor. It enables precise speed and torque control by modulating the input electrical parameters, typically using a ‘voltage source inverter’ (VSI) to drive a squirrel cage induction motor.
Fed inverter – It is also called a ‘current-fed inverter (CFI) or ‘current source inverter (CSI). It is a power electronic converter which receives a constant, stiff DC (direct current) current at its input and converts it into an alternating current (AC) output. Unlike voltage-fed inverters, the current source inverter (CSI) controls the output current rather than the voltage, making it robust and suitable for high-power, AC (alternating current) motor drives and industrial heating, frequently needing a large series inductor for current regulation.
Fed motor – It refers to an electric motor powered and controlled by a specific power electronics device rather than directly by the electrical grid. This setup allows for variable speed, improved torque control, and improved efficiency by supplying precise voltage / frequency, normmally used in industrial drives.
Feed – It is the rate at which a cutting tool or grinding wheel advances along or into the surface of a work-piece, the direction of advance depending on the type of operation involved.
FEED – This acronym means ‘front-end engineering design’. FEED is the process by which early design and planning of a project is undertaken. The outcomes of front-end engineering design normally provide information for project execution and assist with gaining more certainty on price models and commercial terms for the project.
Feedability – It is the ability of a grease to flow to the suction of a pump.
Feed aqueous solution – It is a homogeneous mixture where water acts as the solvent, specifically used as the initial input (feed) to a process, such as chemical reaction, extraction, or separation. It consists of solid, liquid, or gaseous solutes dissolved in water, denoted by the symbol (aq). It contains water (solvent) and dissolved components (solutes).
Feed attachments for long work-pieces – These refer to specialized lathe or machining centre components designed to support, guide, and advance heavy or elongated materials, typically 10 times to 12 times their diameter, to prevent bending, vibration, and damage during rotation. These attachments are important for maintaining dimensional accuracy, surface finish, and safety when dealing with long stock.
Feed-back – It is a system which samples part of its output and adds that to its input; feed-back can be either positive or negative, aiding or opposing the initial input signal.
Feed-back amplifier – It is an amplifier which feeds back a small sample of its output to its input, for improving the linearity.
Feed-back analysis – It is the systematic process of collecting, categorizing, and interpreting customer feed-back, from surveys, reviews, and social media, to transform raw data into actionable insights. It identifies trends, sentiments, and pain points to drive data-driven decisions which improve products, services, and customer satisfaction.
Feed-back bits – It is a quantifiable unit of information transmitted back from a receiver to a transmitter to maintain specific rate performance or, in digital systems, to enable, modulate, or modify the system’s input based on its output. It serves as a control mechanism in closed-loop systems to minimize error or optimize output.
Feed-back branch – It is a circuit connection or pathway which links the output of a system back to its input, allowing part of the signal to influence the system’s behaviour. It is used to modify performance, frequently stabilizing systems (negative feed-back) or amplifying output (positive feed-back). Feed-back branch defines the physical connection (e.g., resistors, wires) in systems like differentiators or amplifiers.
Feed-back capacitor – It is a component placed within the feed-back loop of an electronic circuit (typically an operational amplifier) to control high-frequency behaviour. It connects the output back to the input, allowing designers to stabilize amplifiers, filter out unwanted noise, manage bandwidth, and prevent unwanted oscillations. A feed-back capacitor prevents self-excited oscillations by providing phase lead compensation, correcting phase shifts at high frequencies.
Feed-back channel – It is a structured pathway, method, or medium, such as surveys, hotlines, or meetings, used by customers or employees to communicate input, experiences, or concerns to an organization. It is important for gathering insights to improve products, services, and employee engagement. Feed-back channels facilitate the flow of information to allow organizations to address concerns and enhance satisfaction.
Feed-back circuit – It is an electronic system which takes a portion of the output signal and feeds it back to the input, allowing the circuit to monitor, compare, and adjust its output. Used heavily in operational amplifiers and audio systems, these circuits improve stability, reduce distortion, and control gain.
Feed-back coefficient – It quantifies how a nuclear reactor’s reactivity (r) changes in response to alterations in operating parameters, such as fuel temperature, moderator density, or void fraction. Defined as dr/dx (where ‘x’ is the parameter), it is important for reactor safety, with negative coefficients normally desired to ensure stability by reducing power when temperatures rise.
Feed-back control – It is a control mechanism which uses information from measurements to manipulate a variable to achieve the desired result. In feed-back control, the variable being controlled is measured and compared with a target value. This difference between the actual and desired value is called the error. Feed-back control manipulates an input to the system to minimize this error.
Feed-back controller – It is a mechanism that maintains a system’s variable near a desired setpoint by measuring the output, comparing it to the target, and adjusting inputs to minimize error. It enables closed-loop control by using negative feed-back to counteract disturbances and stabilize system dynamics, frequently applied in automated processes. The controller calculates the error (the difference between setpoint and actual output).
Feed-back control system – It is a configuration which maintains a prescribed relationship between the output and the reference input by comparing them and using the difference to generate a control action.
Feed-back delay – It is the time lag between taking an action and receiving information about its consequences. It is the duration between an input (or stimulus) and the subsequent output (or feed-back). This gap can hinder decision-making in dynamic systems, diminish learning efficiency, or cause instability. In management and control systems, it is the delay between acting and observing results, frequently leading to instability or overshooting targets.
Feed-back design methodology – It is an iterative, data-driven approach which integrates performance data from manufacturing, casting, or processing stages back into the initial material design and simulation phases to improve efficiency, material properties, and process control. It bridges the gap between physical metallurgy (micro-structure / properties) and process engineering, frequently utilizing simulation-based design, data-driven modeling (machine learning), and experimental validation to optimize parameters like composition and micro-structure
Feed-back equation – It defines how the overall gain (Af) of a system is modified by feeding back a portion of the output signal to the input, expressed as ‘Af = A/(1 + AB)’ (for negative feed-back) or ‘Af = A /(1 – AB)’ (for positive feed-back), where ‘A’ is the open-loop gain and ‘B’ is the feed-back fraction.
Feed-back factor – It is the ratio of the feed-back voltage (Vf) to the output voltage (Vo) in a feed-back amplifier, represented as ‘B = Vf/Vo’. It quantifies the quantity of feed-back applied to the input signal, influencing the overall gain of the amplifier.
Feed-back gain – It is frequently denoted as ‘B’ or ‘H’. It is the fraction of an amplifier’s output signal which is fed back to the input side, defined as the ratio of feed-back voltage (Vf) to output voltage (Vo), or ‘B = Vf/Vo’. It determines how much of the output affects the overall system gain, ‘Af = A/(1 + AB)’.
Feed-back linearization – It is a nonlinear control design approach that transforms a nonlinear system into an equivalent linear system through a change of variables (state transformation) and a suitable control input (feed-back). Unlike approximation methods (e.g., Jacobian linearization), this approach uses algebra to exactly cancel non-linearities, allowing standard linear control techniques like pole placement to be applied.
Feed-back loop – It is the signal path from the output back to the input to correct for any variation between the output levels from the set level. In other words, the output of a process is being continually monitored, the error between the set point and the output parameter is determined, and a correction signal is then sent back to one of the process inputs to correct for changes in the measured output parameter.
Feed-back matrix – It is a 2×2, four-quadrant tool used to categorize, analyze, and act upon feed-back based on its positivity / negativity and whether it has been expected or unexpected. It helps individuals and teams overcome emotional responses, reduce defensiveness, and identify actionable insights to improve performance or products. The matrix normally plots positivity / negativity (y-axis) against expectancy (x-axis), creating four distinct quadrants for analysis namely (i) positive / expected (celebration), (ii) positive / unexpected (hidden strength), (iii) negative / expected (actionable improvements), and (iv) negative / unexpected (blind spot).
Feed-back network – It is a system configuration where a portion of the output signal is fed back to the input, creating a closed-loop system which influences its own behaviour, stability, and performance. Unlike feed-forward networks (where information flows in only one direction), feed-back networks allow signals to travel in both directions, enabling the system to adapt or adjust based on its previous outputs.
Feed-back overhead – It refers to the additional data or resources needed to transmit channel state information (CSI) from the receiver to the transmitter. This overhead enables better link adaptation and optimization but consumes capacity, frequently mitigated by techniques like CSI (channel state information) compression to reduce resource usage.
Feed-back path – It is the mechanism or circuit component configuration which routes a portion of a system’s output back to its input, enabling it to function as part of a closed loop. This path compares the actual output to the desired input to improve performance, regulate behaviour, or amplify signals.
Feed-back pin – It is an input pin on a power management integrated circuit (like regulators or converters) used to monitor and regulate the output voltage. By comparing the voltage at this pin against an internal reference, the IC (integrated circuit) adjusts its duty cycle or operating point to maintain a stable, desired output. Feed-back pin acts as the inverting input to an internal error amplifier, typically holding the voltage at a fixed level when the loop is in regulation
Feed-back principle – It is the process of returning a portion of a system’s output signal to its input to control, regulate, or stabilize its performance. By comparing actual output with desired results, it allows systems to ‘learn from errors’ and adjust accordingly, fostering stability or modification. It operates in a loop (Input -> System -> Output -> Measurement -> Comparison -> Correction -> Input). Negative feed-back (stabilization) is the feed-back signal which opposes the input, reducing errors to stabilize the system and improve performance. Positive feed-back (amplification) is the feed-back signal which reinforces the input, amplifying signals and promoting rapid change or oscillations. Feed-back principle is used in engineering (e.g., cruise control), electronics (e.g., amplifiers), and communication.
Feed-back problem – It involves the failure or inefficiency in the transmission, reception, or utilization of evaluative information, hindering improvement or correction in systems, communication, or performance. Key challenges include power dynamics, lack of actionable details, and improper implementation of feedback cycles.
Feed-back resistor – It is a passive electronic component placed between the output and input of an amplifier (typically an operational amplifier) to feed a portion of the output signal back to the input. It controls gain, increases stability, and improves linearity by regulating the signal flow, fundamentally setting the operating characteristics of the circuit.
Feed-back scheme – It is a control strategy where a portion of an output signal (voltage or current) is sampled and returned to the input to modify the system’s behaviour. By comparing the actual output with a desired reference input, the scheme creates a closed-loop system which acts to reduce errors, improve stability, and improve performance (such as linearity, band-width, and gain stabilization).
Feed-back sensor – It is an electrical device which monitors a system’s output (such as position, velocity, temperature, or pressure) and converts it into a measurable electrical signal. This signal is returned to the controller to close the control loop, enabling real-time adjustments, improved accuracy, and automatic error correction.
Feed-back signal – It is a portion of a circuit’s output (voltage or current) which is returned to the input to control, modify, or stabilize the system’s performance. This signal creates a closed-loop system, allowing the input to compare the actual output against a desired value.
Feed-back stabilization – It is a process which uses a closed-loop system to modify the behaviour of an inherently unstable or poorly performing system to achieve a stable, desired output. It operates by measuring the output of a system and feeding a portion of it back to the input, typically in a negative (subtractive) manner to correct errors and eliminate fluctuations.
Feed-back term – It refers to a correction excitation signal which modifies a system’s output based on the departure of the output from a desired level, necessary for achieving stability and error reduction in control systems.
Feed-back vector – It is frequently part of a multi-variable or ‘vector’ feed-back loop. It is a set of signals representing multiple output characteristics (such as voltage, current, or motor speed) returned to the input to be compared against reference signals. It represents a system’s multi-variable control approach, where multiple feed-back loops are analyzed together rather than as a single, openable loop.
Feed-block – It is a device which shapes and combines multiple polymers into a well-defined stack for delivery to a flat die, and it can be categorized into fixed geometry feed-blocks, and variable geometry feed-blocks, which can be adjusted during operation.
Feed check valve – It is a safety-critical, non-return valve mounted on a boiler which allows water to enter from the pump while preventing high-pressure backflow. It acts as a one-way directional control, automatically sealing if pump pressure fails. Common materials include cast steel, stainless steel, bronze, gunmetal, or forged steel for high-pressure durability. It ensures high-pressure water flows only from the feed pump to the boiler, preventing reverse flow which can cause boiler pressure drop or damage the pump. It is installed on the boiler shell slightly below the normal working water level.
Feed coal – It is the raw or processed coal precisely controlled and delivered from a storage bunker to a pulverizer or furnace by a coal feeder, which regulates the flow to meet steam generation demands. It acts as the main fuel source for power plant boilers and is typically ranked as sub-bituminous or bituminous. It ensures a continuous, regulated supply of fuel to a combustion chamber to produce electricity. These coals frequently consist of varied mineralogy, including pyrite, quartz, and clays. Depending on quality, the coal can undergo washing to remove ash and impurities before it is fed into the plant. Typically, this includes thermal grade coal, which can be easily pulverized.
Feeder – It is a device which is mounted at the outlet of storage units such as bins, bunkers, silos or hoppers and which are used to control and meter the flow of bulk materials from the storage unit to meet the specified discharge flow rate. When the feeder stops, material flow ceases and when the feeder is turned on, there is a close correlation between its speed of operation and the rate of discharge of the bulk material.
Feeder belt – It is also known as a belt feeder. It is a type of belt conveyor designed for controlled material flow, frequently used to extract material from a hopper or storage area and regulate its feed onto another conveyor, screen, or crusher. It is a short belt conveyor with adjustable speed to manage the flow rate of materials.
Feeder connector – It is a specialized, high-capacity electrical fitting designed to connect a feeder cable, a conductor carrying bulk electrical power from a source (like a sub-station or main panel) to a distribution point (like a sub-panel, transformer, or branch circuit device). These connectors ensure a secure, low-loss, and electrically safe connection, frequently handling high currents or high frequencies.
Feeder conveyor – It is a conveyor responsible for transferring materials onto a main conveyor, necessitating periodic checks for proper feeding and alignment.
Feeder – It is also called feeder head. In foundry practice, it is a riser which is a reservoir of molten metal connected to a casting to provide additional metal to the casting, needed as the result of shrinkage before and during solidification.
Feeder plate – It is frequently referred to as a plate feeder or reciprocating plate feeder. It is a mechanical device used to feed bulk material, such as ore, coal, or stone, at a fixed, uniform rate from a hopper, bin, or storage area to downstream equipment like conveyors, crushers, or screens. It is a heavy-duty, reciprocating tray-type feeder which uses a back-and-forth movement to move materials toward a discharge end. Driven by a motor and a crank or hydraulic cylinder, the plate moves forward, and on the back-stroke, material is discharged. It consists of a rigid, fabricated steel plate, frequently with strengthening ribs underneath to manage high impact from large, heavy materials. The plate is typically supported by rollers, allowing it to slide back and forth in guide rails.
Feed flow rate – It is the volume (e.g., litre per hour or cubic-meter per hour) or mass (e.g., kilo-grams per hour) of material (liquid, gas, or solid) introduced into a system, reactor, or machine per unit of time. It is an important operational parameter controlled to optimize residence time, processing capacity, and product quality in chemical, manufacturing, and separation processes.
Feed forward – A feed forward is an element or pathway within a control system which passes a controlling signal from a source in its external environment to a load elsewhere in its external environment. This is frequently a command signal from an external operator.
Feed-forward control – It is a control system which adjusts the controlled variable based on a model of the process and measurements of disturbances, instead of feed-back from measurement of the process. It is also called anticipative control. It is a control mechanism which predicts the effects of measured disturbances and takes corrective action to achieve the desired result.
Feed-forward control system – It is a proactive control method that measures incoming disturbances or input changes before they affect the output, using a mathematical model to calculate and apply corrective action preemptively. Unlike feed-back, it operates in an open-loop fashion regarding the output, offering faster responses to known disruptions.
Feed-forward design methodology – It refers to a proactive, model-driven approach which utilizes anticipated information regarding process disturbances or material inputs to adjust manufacturing parameters before those disturbances affect the final product quality. Unlike reactive feedback systems which correct errors after they occur, this methodology focuses on predicting the impact of variations (e.g., in raw materials, furnace temperature, or additive manufacturing build speed) to maintain consistent micro-structure and mechanical properties.
Feed-forward neural network – It is the simplest form of artificial neural network where data moves in a single direction, forward, from input to output layers, with no loops or feedback. Engineered as a layered structure (input, hidden, output), it uses weighted connections, biases, and activation functions to model complex, nonlinear relationships, normally trained through back-propagation to minimize error.
Feed-forward path – It is a component in a control system which processes a command signal and directs it to the power converter, improving the command response without forming a feed-back loop, hence maintaining system stability. Unlike feed-back control, which is reactive, the feed-forward path acts proactively by using a model of the process to predict and counteract disturbances before they affect the system’s output.
Feed gas flow – It is the volumetric or mass rate at which raw material gas is supplied into a processing unit (such as a catalyst bed, or reactor) per unit of time. It determines the system’s efficiency, production capacity, and conversion rate by defining both the composition and velocity of the input material. It defines the quantity (e.g., kilograms per hour) and the chemical composition of the input gas.
Feed gas temperature – It is the temperature of the gaseous mixture as it enters a processing unit or vessel (e.g., reactors). It is a critical operational parameter, frequently managed to prevent hydrocarbon condensation, ensure optimal absorption in treatment processes, or protect against high-temperature degradation, with temperatures reaching up to 55 deg C in specific applications.
Feed grade – It is the average concentration or quality of valuable metal / mineral content within the ore delivered to a processing plant. It is an important key performance indicator (KPI) calculated as the total metal content divided by the total mass of ore fed, directly impacting recovery rates, operating costs, and profitability.
Feed head – It is also known as a riser or feeder. It is a reservoir of molten metal built into a casting mould to prevent shrinkage defects. As molten metal solidifies, it contracts (shrinks). The feed head provides a supply of liquid metal to fill these shrinkage cavities, ensuring the casting remains solid and sound. Feed head is positioned above or beside the main casting cavity, frequently connected through a passage (gate). It is designed to stay molten longer than the casting itself. This allows it to ‘feed’ the casting with liquid metal until the entire piece has solidified.
Feed heating – it is also called feed-water heating. It is the process of preheating the water (feed-water) before it enters a boiler, steam generator, or furnace to improve thermal efficiency and reduce thermal stress. It is a core component of the regenerative Rankine cycle used in thermal power plants, where heat from extracted steam is recovered rather than lost in the condenser.
Feed hopper – It is a container which is used for holding the powder prior to compacting in a press.
Feed-in – It is being or belonging to something which feeds material (as into a machine) or to the process of feeding in this way. A feed-in device connects the main source of power to the subsidiary outlets.
Feeding – It refers to the process of supplying additional molten metal to a casting during solidification to compensate for volume contraction (shrinkage). As liquid metal cools and passes into a solid state, it shrinks, which can create voids, porosity, or cavities if not compensated for. Feeding ensures that these shrinkage cavities form in a designated, removable ’feeder head’ or ‘riser’ rather than inside the casting, hence ensuring casting soundness. Feeding is also conveying metal stock or work-pieces to a location for use or processing, such as wire to a consumable electrode, strip to a die, or work-pieces to an assembler.
Feeding distance – It is the maximum distance over which a riser (or feeder) can supply molten metal to a solidifying casting section to prevent internal shrinkage porosity. It determines how far a single riser can effectively reach and is an important parameter for establishing how many risers are necessary for a casting. Feeding distance (FD) is typically measured from the edge of the riser to the furthest point in the casting section which it is required to feed.
Feeding zone – It is a designated area or functional, localized space where sustenance, materials, or energy is added or accumulated. It normally refers to a specific, controlled section in a process, such as a cycling feed-zone for refueling, an industrial area for material entry in manufacturing.
Feed inlet – It is the designated entry point, nozzle, or opening through which raw materials, such as ore, concentrate, fuel (coal / coke), flux, or molten metal, are introduced into a metallurgical reactor or processing vessel. Its main purpose is to ensure the uniform distribution of materials, maintain feeding capacity during operations, and prevent blockages. It is designed to distribute material evenly across the reactor, which is particularly crucial in large fluidized bed reactors to maintain consistent processing.
Feed-in tariff – It is a premium rate paid to distributed generators to encourage alternative energy sources.
Feed line – In the context of technology, it refers to a transmission line or cable which carries radio frequency (RF) signals between components in a communication system, such as an antenna and transmitter or receiver. Feed lines are made of specialized cables. Each feed line has its own characteristic impedance which is to be matched with that of the antenna to transfer the radio frequency power efficiently.
Feed lines – These are linear marks on a machined or ground surface which are spaced at intervals equal to the feed per revolution or per stroke.
Feed material – It is also called feedstock. It is the raw ore, concentrate, scrap metal, or chemical compound introduced into a furnace, reactor, or processing unit for extraction, refining, or fabrication. It represents the initial input material, such as iron ore pellets, copper concentrate, or metal powders, intended for treatment to create a valuable metal product. It is the raw material input in metallurgical processes, including mineral processing, smelting, and refining. Feed material can be raw ore, concentrated minerals (middlings), recycled scrap, or metal powders (rods / powders for additive manufacturing). It is frequently characterized by its chemical composition, grade, particle size distribution, and moisture content, which affect the efficiency of the metallurgical process. The quality of the feed material determines the efficiency, energy consumption, and environmental impact of the processing.
Feed mixture – It is the combined, pre-processed raw material, comprising ore, concentrates, fluxes, and fuels, which is introduced into a metallurgical furnace or processing unit for extraction or refining. The feed mixture is tailored to specific compositional needs to ensure efficient smelting, roasting, or chemical reactions.
Feed pad – It is also known as a feeding pad. It is a type of riser / riser pad. It is a localized, thickened section of a casting designed to facilitate the flow of molten metal, helping to ensure that the casting remains solid and free from defects, such as shrinkage porosity. It acts as a reservoir of molten metal, supplying material to the thickest, last-to-solidify sections of the cast part.
Feed phase – It refers to the raw material or concentrated ore (the ‘feed’) which is introduced into a furnace or reactor for processing, such as smelting, roasting, or refining. Feed phase is the input material (solid, particulate, or liquid) which enters the processing vessel and is subjected to chemical and physical changes to recover valuable metals. The feed phase typically consists of ore concentrates (e.g., copper, nickel sulfides), fluxes (like silica or limestone), and fuel (e.g., coal or anthracite).
Feed rate – It is the velocity at which the cutter is fed, i.e., advanced against the work-piece. It is expressed in units of distance per revolution for turning and boring (typically in millimeters per revolution).
Feed rate control – It is the precise regulation of the speed at which a cutting tool advances into or along a work-piece (e.g., millimeters per minute or millimeters per revolution), or the rate at which raw materials / powder are fed into a processing unit. It directly manages material removal rates, chip thickness, surface finish, and tool life.
Feed roller – It is a hardened, cylindrical component designed to transport, guide, and meter raw material (such as sheet metal, coils, or slabs) into a processing machine, such as a rolling mill, punch press, or casting machine. These rollers ensure consistent material feeding to maintain precision and productivity.
Feed shoe – It is the part of the powder feed system which delivers the powder into the die cavity.
Feed slurry – It is a fluid mixture of finely divided solid particles (such as crushed ore, coal, or concentrate) suspended in a liquid, very frequently water. This mixture is specifically prepared or conditioned for introduction into a subsequent processing unit, such as a grinding mill, flotation cell, leaching vessel, or filter. It typically consists of insoluble mineral particles and a carrier liquid (water). It acts as a main method for transporting solids and a medium for unit operations such as separation, classification, and chemical treatment.
Feed solid concentration – It refers to the proportion of solid particles (ore / mineral) suspended in a liquid, typically water, within a slurry feed stream. It is normally expressed as a percentage of solids by weight or volume, indicating how dense the feed is before it enters a processing unit like a flotation cell or thickener. It is normally expressed as the percentage of solids in a pulp or slurry.
Feed-stock – It is the raw material which goes into a process or plant as input to be converted into a product.
Feed-stock availability – It defines the quantity, accessibility, and consistency of raw materials needed to supply industrial manufacturing processes, specifically energy or chemical production. It encompasses the sourcing of raw materials, including logistical, economic, and logistical factors determining if materials can be gathered and delivered, frequently dictating the total output of finished products.
Feed-stock material – It is a raw or processed material supplied to an industrial machine, or chemical process to be converted into finished products, energy, or fuel. It represents the fundamental, frequently bulk, input needed for production.
Feed-stock powder – It is the raw material used in additive manufacturing (3D printing), powder metallurgy, and thermal spraying, consisting of specialized metal, ceramic, or polymer particles. Its important properties, particle size distribution, shape, flowability, and density. directly influence the micro-structure, porosity, and performance of the final manufactured component.
Feed-stock production – It involves preparing inputs to ensure quality and consistency for manufacturing processes.
Feed-stock variability – It refers to the inconsistency in the physical and chemical properties of raw materials used in industrial processes. It encompasses fluctuations in moisture, composition, and particle size, affecting production efficiency, consistency, and conversion rates.
Feed system for gaseous fuels – Gaseous fuels are relatively easy to transport and handle. Any pressure difference causes gas to flow, and most gaseous fuels mix easily with air. Since on-site storage of gaseous fuel is typically not feasible, boilers are to be connected to a fuel source through a gas pipeline. Flow of gaseous fuels to a boiler can be precisely controlled using a variety of control systems. These systems normally include automatic valves which meter through gas flow through a burner and into the boiler based on steam or hot water demand.
Feed system for liquid fuels – Like gaseous fuels, liquid fuels are also relatively easy to transport and handle by using pumps and piping networks which link the boiler to a fuel supply such as a fuel oil storage tank. For promoting complete combustion, liquid fuels are to be atomized to allow thorough mixing with combustion air. Atomization by air, steam, or pressure produces tiny droplets which burn more like gas than liquid. Control of boilers which burns liquid fuels can also be accomplished using a variety of control systems which meter fuel flow.
Feed system for solid fuels – Solid fuels are much more difficult to handle than gaseous and liquid fuels. Preparing the fuel for combustion is normally necessary and can involve techniques such as crushing and / or pulverizing. Before combustion can occur, the individual fuels particles are to be transported from a storage area to the boiler. Mechanical devices such as conveyors, augers, hoppers, slide gates, vibrators, and blowers are frequently used for this purpose. The method selected depends primarily on the size of the individual fuel particles and the properties and characteristics of the fuel. Stokers are commonly used to feed solid fuel particles such as crushed coal, wood chips, and various forms of biomass into boilers.
Feed temperature – It refers to the temperature of raw materials, ores, concentrates, scrap, or charge materials, at the exact moment they enter a furnace, reactor, or smelting process. Controlling this parameter is important for optimizing energy consumption, reaction kinetics, and product quality. The feed temperature dictates the quantity of energy (fuel or electricity) needed to reach the needed reaction temperature. A higher feed temperature reduces the energy needed to melt or react the material.
Feed-through – It is an electrical conductor or connector which passes a signal or power through a sealed barrier, such as a chassis, circuit board, or vacuum chamber wall. It enables communication between internal components and the outside environment while maintaining environmental integrity (hermetic seal), preventing leaks.
Feed-through terminal block – It is also called feed-block. It is a modular, insulated component designed to connect two or more wires together, enabling a secure, organized, and reliable electrical connection, particularly within control panels and industrial automation.
Feed valve – It is an important boiler mounting which regulates the flow of feedwater into a boiler while preventing the backflow of steam or water from the boiler to the feed pump. It is necessary for maintaining safe pressure levels and protecting equipment during pump failure or shutdowns.
Feed velocity – It is the velocity at which the rolling stock enters the rolling mill. It is expressed in units of distance per minute (typically in metres per minute).
Feed water – It is the water which is used to remove heat from a reactor and produce (‘feed’) steam to drive the turbine generators. In case of a boiler in a power plant, feed water is the water supplied to the boiler which is converted into steam.
Feed-water heater – The purpose of feedwater heater is to preheat the feedwater with the heat energy of the spent steam. This improves the boiler efficiency. Heaters are shell and tube heat exchangers with the feedwater on the tube side (inside) and steam on the shell side (outside). The heater closest to the boiler receives the hottest steam. The condensed steam is recovered in the heater drains and pumped forward to the heater immediately upstream, where its heat value is combined with that of the steam for that heater. Ultimately the condensate is returned to the condensate storage tank or condenser hotwell.
Feed water tank – It is a storage vessel in boiler systems which collects, heats, and treats makeup water and condensate before it enters the boiler. It stabilizes water supply, mitigates thermal shock by preheating water, and removes dissolved gases like oxygen (O2) and carbon di-oxide (CO2) to prevent corrosion and metallurgical degradation of downstream equipment.
Feed zone – It is the initial area in an extrusion screw (typically for plastics / polymer processing) or a furnace (like a blast furnace) where raw solid material is introduced, transported, and pre-compressed. In casting, it refers to the area fed by a riser. It is necessary for ensuring consistent material flow into the machine.
Feldspathic ceramic – It is a type of translucent, glass-matrix ceramic material mainly composed of feldspar (KAlSi3O8 or NaAlSi3O8), quartz (SiO2), and kaolin. It is recognized as a pioneer, high-fusion porcelain frequently used for veneering metal-ceramic frameworks. It consists of a predominantly amorphous (vitreous/glassy) matrix with one or more crystalline phases, most commonly leucite (KAlSi2O6).
Feldspathoids – These are frequently shortened to ‘foids’. These are a group of alkali alumino-silicate rock-forming minerals which are chemically similar to feldspars but contain considerably less silica (SiO2). These are characterized by their inability to coexist with quartz (free silica) since they react with it to form feldspars. These are tectosilicates (framework silicates) of sodium, potassium, or calcium.
Feldspar – It is a group of common rock-forming minerals which includes microcline, orthoclase, plagioclase and others. It is a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the plagioclase (sodium-calcium) feldspars and the alkali (potassium-sodium) feldspars. Feldspars crystallize from magma as both intrusive and extrusive igneous rocks and are also present in several types of metamorphic rock. Rock formed almost entirely of calcic plagioclase feldspar is known as anorthosite. Feldspars are also found in several types of sedimentary rocks.
Fellgett advantage – It is also known as the multiplex advantage. It is a principle in spectroscopy, widely used in analytical metallurgy and materials characterization, which refers to the improved signal-to-noise ratio (SNR) got by collecting all spectral frequencies simultaneously rather than sequentially.
Felsic – It refers to igneous rocks and magma enriched in light-colored silicate minerals (quartz, feldspathoids and feldspar), featuring silica, lower density, and high viscosity. These light-coloured rocks (e.g., granite, rhyolite) constitute continental crust. They are typically less dense, frequently pink / white, and form plutonic or volcanic structures. It is the term which is used to describe light-coloured rocks containing feldspar, feldspathoids and silica.
Felt – It is a fibrous material which is made up of interlocked fibres by mechanical or chemical action, moisture, or heat. It is made from fibres such as asbestos, cotton, glass, and so forth.
Felt washers – These are ring-shaped components made from compressed wool or synthetic fibres, engineered for sealing, cushioning, lubrication, and vibration damping in mechanical and metallurgical applications. They are normally used in industrial machinery, automotive engines, and metalworking to provide a flexible seal that prevents contaminant entry and retains oil lubrication.
Female fasteners – It refers to the component with internal threads which receive and mate with a corresponding ‘male’ component, typically a screw or bolt. Essentially, the female component is the one with the hole or recess that accepts the protruding part of the male component. Example of female fasteners is ‘nut’.
Female slip fit – In these pipe fittings there are no threads. They slip fit into a slightly smaller diameter sleeve.
Female threaded – These pipe fittings have interior threads. They are either screwed on the outside of pipe end of a smaller diameter with external threading or they receive male threaded pipe fittings.
FE model – It is also called finite element model. It is a computational, numerical representation of a metal component, microstructure, or manufacturing process designed to simulate and analyze its behaviour under specific thermal, mechanical, or chemical conditions. It is a core tool in ‘finite element analysis’ (FEA), used to predict stress, strain, deformation, heat transfer, and microstructural evolution (such as phase transformations) during processes like casting, welding, and forming.
Femto-second (fs) – It is a unit of time in the International System of Units (SI) equal to 10 to the power -15 or 1 /1,000, 000,000,000,000 of a second, i.e., one quadrillionth, or one millionth of one billionth, of a second.
Femto-second (fs) laser – It is an ultra-fast, high-precision tool which emits optical pulses lasting on the order of a femto-second (1 fs = one millionth of one billionth of a second). These lasers act as a ‘cold’ ablation source, delivering extremely high instantaneous peak power while keeping the heat-affected zone (HAZ) negligible or non-existent.
Femtosecond (fs) laser ablation – It is a high-precision, non-thermal machining process using ultrashort (roughly one quadrillionth seconds) laser pulses to instantly vaporize metal surfaces. Because the pulse duration is shorter than electron-phonon relaxation times, energy is deposited before heat can transfer to the surrounding lattice, resulting in cold, burr-free, and high-precision cutting or texturing with a minimal heat-affected zone (HAZ).
Femto-second (fs) laser pulse – It is an ultrafast light pulse lasting between a few femto-seconds and hundreds of femto-seconds ((1 fs = one millionth of one billionth of a second), normally utilized for high-precision, cold-ablation material processing. These pulses enable high-intensity energy delivery with minimal thermal damage or heat-affected zones (HAZ).
Femto-second (fs) pulse – It is an ultrafast laser pulse lasting between a few femto-seconds and hundreds of femto-seconds (1 fs = one millionth of one billionth of a second), utilized in precision manufacturing and material processing to enable ‘cold etching’. Since the pulse duration is shorter than the time needed for energy transfer from electrons to the atomic lattice (electron-phonon coupling time, typically a few pico-seconds), these pulses deliver extreme energy densities with minimal heat diffusion into the surrounding material.
Fender piles – These are sheet piles which are used to protect water front structures from impact of ships and vessels.
Fenton’s reaction – It is a powerful ‘advanced oxidation process’ (AOP) which utilizes a mixture of hydrogen peroxide (H2O2) and a ferrous iron catalyst (Fe2+) to generate highly reactive hydroxyl radicals (OH-). These radicals non-selectively oxidize persistent organic contaminants into smaller inorganic compounds, such as water and carbon di-oxide (CO2).
Fe-olivine – It is also called iron-olivine. It refers to fayalite (Fe2SiO4), the iron-rich end-member of the olivine solid solution series [(Mg,Fe)2SiO4]. It is a nesosilicate mineral characterized by its olive-green to brownish-black colour, high density, and ortho-rhombic crystal structure, frequently utilized in high-temperature industrial processes. In industrial, pyro-metallurgical contexts, olivine, particularly magnesium-rich (Mg-rich) varieties used as flux and refractory material, acts as a substitute for dolomite to bind impurities and form slag in ironmaking.
Ferberite – It is a black, monoclinic mineral composed of iron (II) tungstate (FeWO4). It is defined as the iron-rich end member of the wolframite solid solution series (the other end member being manganese-rich hubnerite). It is a significant primary ore of tungsten (W), which is necessary for producing high-hardness alloys, cutting tools, and electronics because of its high melting point.
Fermi energy – It is the highest energy level occupied by electrons in a solid (such as a metal) at absolute zero temperature (0 K). It acts as a sharp boundary, a ‘Fermi Sea’ top, where all electron states below it, are filled and those above, are empty. It is a fundamental parameter for understanding electrical / thermal conductivity and electron behaviour. Fermi energy is technically defined at 0 K but changes minimally with increased temperature.
Fermi wave-length – It is the de Broglie wavelength of electrons at the Fermi energy level in a solid. It represents the characteristic spatial extent of electron wave-functions at the highest occupied energy state at absolute zero temperature, important for defining quantum-based transport in semi-conductors and metals.
Ferric chloride (FeCl3) – It is an inorganic iron salt used as a strong acidic coagulant for water treatment and a potent oxidizer for etching copper in electronics. It acts by neutralizing charges to bind suspended solids and corroding metal surfaces, appearing as a dark brown, hygroscopic solid.
Ferric nitride (gamma prime Fe4N) – It refers to binary compounds of iron and nitrogen, normally formed during the nitriding process, which is a thermo-chemical heat treatment used to harden the surface of metals. Nitriding introduces atomic nitrogen into the surface of alloy steel at temperatures below 538 deg C (normally around 500 deg C to 550 deg C), resulting in a hard, wear-resistant ‘white layer’ composed of nitrides. Ferric nitride is a hard, stable compound which forms in the white layer.
Ferric oxide (Fe2O3) – It is also called iron (III) oxide. It is a reddish-brown inorganic compound and one of the main oxides of iron. It occurs naturally as hematite, a major source of iron for steel production. It is used in smelting processes, pigment production, and magnetic materials. It has a +3-oxidation state and is typically formed by the oxidation of iron.
Ferric salt – It is an inorganic compound containing iron in its +3-oxidation state (Fe3+), normally utilized for its oxidizing and leaching capabilities in processing metal ores, refining metals, and surface treatments. Unlike ferrous salts (Fe2+), which are normally pale green, ferric salts are typically yellow, orange, or reddish-brown and act as effective electron acceptors in chemical reactions.
Ferric sulphate [Fe2(SO4)3] – It is a yellowish, water-soluble inorganic salt used mainly as a strong oxidizing agent and in metal pickling (surface cleaning). It is highly effective for cleaning metals, removing rust, and in hydro-metallurgical processes to leach or extract metal values from ores, frequently manufactured by oxidizing ferrous sulphate.
Ferri-magnetic material – It is a material which macroscopically has properties similar to those of a ferro-magnetic material but that microscopically also resembles an anti-ferro-magnetic material in that some of the elementary magnetic moments are aligned antiparallel. If the moments are of different magnitudes, the material can still have a large resultant magnetization. It is also a material in which unequal magnetic moments are lined up anti-parallel to each other. Permeabilities are of the same order of magnitude as those of ferro-magnetic materials, but are lower than they are to be if all atomic moments are parallel and in the same direction. Under ordinary conditions the magnetic characteristics of ferri-magnetic materials are quite similar to those of ferro-magnetic material.
Ferrimagnetism – It is a type of magnetic ordering found in certain materials, mainly metallic oxides like ferrites, where atomic or ionic magnetic moments align in opposite (anti-parallel) directions, but are unequal in magnitude. This imbalance results in an incomplete cancellation of the moments, producing a net spontaneous magnetization. Ferrimagnets are considered a special, uncompensated case of anti-ferromagnetism, yet they behave like weak ferromagnets by possessing a permanent magnetic field in the absence of an external field.
Ferrite – It is a solid solution of one or more elements in body-centered cubic crystal structure. It is a solid solution of carbon in iron, stable at room temperature, holding very low carbon (maximum 0.022% at 723 deg C), making it almost pure iron. Unless otherwise designated (for example, as chromium ferrite), the solute is normally assumed to be carbon. On some equilibrium diagrams, there are two ferrite regions separated by an austenite area. The lower area is alpha ferrite, while the upper area is delta ferrite. If there is no designation, ferrite is assumed. Ferrite is also an essentially carbon-free solid solution in which iron is the solvent and which is characterized by a body-centered cubic crystal structure. Fully ferritic steels are only obtained when the carbon content is quite low. The most obvious micro-structural features in such metals are the ferrite grain boundaries.
Ferrite, allotriomorphic – It is a phase of steel which nucleates at austenite grain boundaries during slow cooling, taking on an irregular shape that conforms to the prior austenite boundary rather than reflecting its own internal crystal symmetry. It is a reconstructive, diffusion-controlled transformation which involves little to no invariant-plane strain shape change, mainly resulting in volume changes.
Ferrite banding – It is parallel bands of free ferrite aligned in the direction of working. Sometimes it is referred to as ferrite streaks.
Ferrite (ceramic) – It is a class of ferrimagnetic, electrically insulating, ceramic compounds derived from iron oxide (Fe2O3 or Fe3O4) blended with one or more metallic elements (such as barium, manganese, nickel, or zinc). They are manufactured through powder metallurgy (sintering) and are widely used in electronic components because of their high magnetic permeability and high electrical resistivity. Ferrites show ferrimagnetism, meaning they are attracted by magnets and can be magnetized, but their internal magnetic moments are anti-parallel and unequal, resulting in a net magnetic field which is normally weaker than pure ferromagnetic metals.
Ferrite core – It is a magnetic core for an inductor made from a metal oxide compound.
Ferrite formation – It is the process where austenite (gamma-iron, fcc) transforms into ferrite (alpha-iron, bcc) upon cooling, typically between 912 deg C and 723 deg C in iron-carbon alloys. It is a diffusional transformation, frequently forming on austenite grain boundaries, which increases material ductility and magnetic permeability while decreasing hardness.
Ferrite grains -These are the individual, microscopic crystals of body-centered cubic (bcc) alpha-iron which form the structural matrix of low-carbon steel, characterized by a soft, ductile, and magnetic nature. Appearing as light, polygonal (equiaxed) shapes under a microscope, they typically nucleate at austenite grain boundaries during cooling, and their size considerably affects steel strength.
Ferrite grain size – It refers to the average diameter or size of alpha-iron (alpha-Fe) crystals in steel, typically forming at austenite grain boundaries during cooling. It is a critical microstructural parameter which dictates mechanical strength (Hall-Petch relationship) and toughness, with smaller grain sizes producing stronger, tougher steel.
Ferrite, idiomorphic – It is faceted shapes, frequently intragranular. Idiomorphic ferrite nucleates on inclusions within austenite grains during slow cooling. Nitriding is a thermo-chemical process which diffuses nitrogen into the surface of ferritic steel, typically between 350 deg C to 590 deg C, increasing surface hardness without altering the underlying ferrite structure.
Ferrite interface – It refers to the boundary between the ferrite phase (alpha-iron, body-centered cubic) and another phase, very frequently austenite (gamma-iron, face-centered cubic) during solid-state transformations in steels. The migration, mobility, and structure of this boundary (e.g., alpha / gamma interface) are important in determining final micro-structures, grain size, and mechanical properties.
Ferrite magnet – It is a magnet made of a mixture of ferric oxide and a strong basic oxide, e.g., NaFeO2 (sodium ferrate). The oxides are used as compacted powders for rectifiers or permanent magnets or as powder on memory or record tapes.
Ferrite matrix – It is a continuous microstructural phase in steel or iron composed of alpha-iron (alpha-Fe) with a body-centered cubic (bcc) crystal structure, serving as the soft, ductile matrix for other phases like cementite or pearlite. It is characterized by high ductility, high magnetic permeability, low strength, and low carbon solubility.
Ferrite number – It is an arbitrary, standardized value designating the ferrite content of an austenitic stainless steel weld metal. This value directly replaces percent ferrite or volume percent ferrite and is determined by the magnetic test.
Ferrite-pearlite banding – It is inhomogeneous distribution of ferrite and pearlite aligned in filaments or plates parallel to the direction of working.
Ferrite-pearlite steels – These are normal carbon steels characterized by a two-phase microstructure consisting of soft, ductile ferrite (alpha-Fe) and lamellar pearlite (alternating layers of ferrite and hard cementite, Fe3C). Formed during slow cooling, they balance high ductility with moderate strength, typical of structural steels.
Ferrite phase transformation – It is the temperature-activated process where austenite (gamma-iron, fcc) transforms into ferrite (alpha-iron, bcc) upon cooling. This solid-state transformation, frequently happening during slow cooling or annealing, is a diffusion-controlled process which reduces carbon solubility and forms a soft, ductile, ferritic micro-structure.
Ferrite plates – These plates refer to plate-shaped (or lath-shaped) micro-structure constituents which form during the solid-state decomposition of austenite, specifically through displacive transformation mechanisms. These plates typically contribute to high strength and toughness in steels because of their fine-scale, frequently sub-micrometer, structure.
Ferrite stabilizer – It is an alloying element which, when added to iron, increases the region of the phase diagram in which ferrite is the stable phase. The strongest ferrite stabilizers are silicon, chromium, and molybdenum.
Ferrite streaks – It is parallel bands of free ferrite aligned in the direction of working.
Ferrite transformation – It is the phase change where austenitic iron (face-centered cubic, fcc) transforms into ferritic iron (body-centered cubic, bcc) upon cooling below the A3 temperature (around 912 deg C). It is a diffusion-controlled, solid-state transformation, producing soft, ductile, and magnetic bcc (body-centered cubic) ferrite, frequently nucleating at austenite grain boundaries.
Ferrite, Widmanstatten – It is a characteristic, wedge-shaped microstructure which forms in steels during intermediate cooling rates, growing in plates from austenite grain boundaries. It is a displacive transformation, meaning it involves an invariant-plane strain (shape deformation) of the austenite, but also needs the diffusion of carbon (interstitial atoms) to occur, distinguishing it from diffusion-less transformations like martensite.
Ferritic bainitic (FB) steels – Ferritic bainitic steels are sometimes called ‘stretch flangeable’ (SF) or ’high hole expansion’ (HHE) steels because of their improved edge stretch capability. Ferritic bainitic steels have a micro-structure of fine ferrite and bainite. Strengthening is obtained by both grain refinement and the second phase hardening with bainite. Ferritic bainitic steels are available as hot-rolled products. The primary advantage of ferritic bainitic steels over high strength low alloy steels and dual face steels is the improved stretchability of sheared edges as measured by the hole expansion test. Compared to high strength low alloy steels with the same level of strength, ferritic bainitic steels also have a higher strain hardening exponent and increased total elongation. Because of their good weldability, ferritic bainitic steels are considered for tailored blank applications. These steels are characterized by both good crash performances and good fatigue properties.
Ferritic grain size – It is the grain size of the ferritic matrix of a steel.
Ferritic malleable – It is a cast iron made by prolonged annealing of white iron in which decarburization, graphitization, or both take place to eliminate some or all of the cementite. The graphite is in the form of temper carbon. If decarburization is the predominant reaction, the product shows a light fracture surface, hence white-heart malleable. Otherwise, the fracture surface is dark, hence black-heart malleable. Ferritic malleable has a predominantly ferritic matrix.
Ferritic-martensitic steels – These are a class of high-chromium (typically 9 % to 12 % chromium) stainless steels which combine ductile ferritic (body-centered cubic) and hard martensitic (body-centered tetragonal) phases, providing a balance of high strength, creep resistance, and radiation resistance. These steels offer superior resistance to swelling under irradiation, higher thermal conductivity, and lower thermal expansion compared to other steels. They are designed for high-temperature structural applications, such as nuclear reactor components and turbine blades.
Ferritic matrix – It is a microstructure composed mainly of alpha-iron (body-centered cubic, bcc) which acts as the continuous phase surrounding other constituents, such as pearlite or cementite. Characterized by high ductility, softness, and magnetic properties, this Fe-C (iron-carbon) solid solution is stable at room temperature.
Ferritic nitro-carburizing processes – These are those thermochemical treatments which involve the diffusional addition of both nitrogen and carbon to the surface of ferrous materials at temperatures completely within the ferrite phase field. The primary object of such treatments is normally to improve the anti-scuffing characteristics of ferrous engineering components by producing a ‘compound layer’ on the surface which has good tribological properties. In addition, the fatigue characteristics of the material can be considerably improved, particularly when nitrogen is retained in solid solution in the ‘diffusion zone’ beneath the compound layer. This is normally achieved by quenching into oil or water from the treatment temperature, normally 570 deg C. A wide range of engineering components, such as rocker-arm spacers, textile machinery gears, pump cylinder blocks and jet nozzles are being treated for wear resistance, while components such as crankshafts and drive shafts are being treated for improved fatigue properties. Ferritic nitrocarburizing treatments have been successfully applied to majority of the ferrous materials, including wrought and sintered plain carbon and alloy steels, stainless steels, and cast irons. However, the most marked Improvement in both anti-scuffing and fatigue properties, relative to untreated material, is found with plain low-carbon steels.
Ferritic rolling of ultra-low carbon (ULC) steels – It is a hot rolling process where the final rolling passes are performed in the ferritic (body-centered cubic iron) phase, rather than the austenitic (face-centered cubic iron) phase as in conventional rolling. This technique offers several advantages, including reduced energy consumption, decreased oxide scale formation, and improved formability of the steel.
Ferritic stainless-steels – These steels with body centered cubic crystal structures are a family of utility stainless steels which offer considerable better atmospheric corrosion resistance than carbon steels, as well as having good ductility, formability and impact resistance. Ferritic grades, containing only chromium and possibly other elements such as molybdenum, titanium, aluminum, and niobium etc., are well known as cost savings materials since majority of them have no expensive nickel additions. Also, the chromium content can be optimized ranging from 10.5 % to 29 % taking into account a very wide range of applications. The ferritic stainless steels are ferro-magnetic. They can have good ductility and formability, but high-temperature strengths are relatively poor compared to the austenitic grades. Toughness can be somewhat limited at low temperatures and in heavy sections.
Ferritic steel – It is a type of steel which is composed of less than 0.1 % carbon. It is magnetic and not capable of hardening through heating and quenching.
Ferritizing anneal – It is a treatment given as-cast gray or ductile (nodular) iron to produce an essentially ferritic matrix. For the term to be meaningful, the final micro-structure desired or the time-temperature cycle used is to be specified.
Ferro-alloys – Ferroalloys are a group of materials which are alloys of iron that contain a high percentage of one or more non-ferrous metals as alloying elements. These alloys are used for the addition of these other elements into liquid metal. They are normally used as addition agents. More than 85 % of ferroalloys produced are used primarily in the manufacture of steel.
Ferro-alloy smelting – It is a high-temperature pyro-metallurgical process used to produce alloys of iron with elements like manganese, silicon, or chromium. It involves reducing metal oxides using carbon, aluminium, or silicon, mainly in electric arc furnaces / submerged arc furnace to create additives necessary for refining steel, improving strength and corrosion resistance.
Ferro-aluminum – It is a ferro-alloy composed of iron and aluminum with the content of the aluminum ranging from 30 % to 75 %. It is primarily used as a deoxidation agent for steel, as well as for moulding in combination with scrap copper and carbon steel. Ferro-aluminum as ferro-aluminum thermite (FAT) is an agent, which when ignited and mixed, can give off super extreme quantities of heat. Although this reactant is stable at room temperature, it burns through an extremely intense exothermic reaction.
Ferroan enstatite – It is an iron-bearing variety of the mineral enstatite, with a chemical formula of around (Mg,Fe)SiO3. It belongs to the orthopyroxene group, forming a solid-solution series between pure enstatite (Mg2Si2O6) and ferrosilite (Fe2Si2O6), frequently representing mid-range members normally referred to as hypersthene. It is frequently found as a crystalline phase in slags or refined materials.
Ferro-boron – It is a noble ferro-alloy which is mainly used as an additive in steelmaking to increase the hardenability, creep resistance and hot workability since steels alloyed with boron are oxidation resistant up to 900 deg C. The raw materials needed to produce ferro-boron are boric oxides and boric acid. Carbon (charcoal) and aluminum or magnesium is used as a reducing agent. The alloys can be produced by carbo-thermic or metallo-thermic reduction processes.
Ferro-chrome – Ferro-chrome is an alloy of chromium and iron containing between 45 % and 70 % of chromium. It also contains varying amounts of iron, carbon and other alloying elements. Ferro chrome with chrome content below 56 % is known as ‘charge chrome’. Ferro chrome is the major alloying element in the production of stainless steel. The use of ferro chrome depends widely on the carbon content. Ferro chrome can hence be classified as (i) high carbon ferro chrome with 4 % to 12 % C, (ii) medium carbon ferro chrome with 0.5 % to 4 % C, and low carbon ferro chrome with 0.1 % to 0.5 % C.
Ferro-chromium (Fe-Cr) – It is a ferro-alloy composed of chromium (50 % Cr to 70 % Cr) and iron (Fe), mainly used to introduce chromium into stainless steel to improve corrosion resistance, hardness, and durability. It is produced by the carbo-thermic reduction of chromite ore (FeO.Cr2O3) in submerged electric arc furnaces.
Ferro-electric – It is a crystalline material which shows spontaneous electrical polarization, hysteresis, and piezoelectric properties.
Ferro-electric ceramics – These are specialized poly-crystalline dielectric materials possessing spontaneous electric polarization which can be reversed or reoriented by an applied external electric field. These are characterized by high permittivity, piezo-electric / pyro-electric properties, and perovskite crystal structures. Below their Curie temperature, they show hysteresis, retaining polarization even after field removal.
Ferro-electric crystals – These are non-metallic, dielectric crystalline materials possessing spontaneous, reversible electric polarization. These crystals are defined by non-centrosymmetric structures which show electrical polarization hysteresis (similar to ferro-magnetism) below a specific Curie temperature (Tc), making them necessary for piezoelectric sensors and ferro-electric random-access memory (FeRAM).
Ferro-electric effect – It is the phenomenon whereby certain crystals can show a spontaneous dipole moment (which is called ferro-electric by analogy with ferro-magnetism showing a permanent magnetic moment). Ferro-electric crystals frequently show several Curie points, domain structures, and hysteresis, much as do ferro-magnetic crystals.
Ferro-electricity – It is the property of materials which spontaneously maintain an electrical polarization, as a ferro-magnetic material maintains magnetic polarization.
Ferro-electric polymers – These are a specialized class of crystalline or semi-crystalline polar polymers which show spontaneous electric polarization (an internal electric alignment) which can be reversed, or switched, by an external electric field. Unlike ferro-electric ceramics, these materials are light, flexible, easy to process, and show high dielectric strength, making them ideal for modern electronic applications such as sensors, actuators, and nonvolatile memory.
Ferro-graph – It is an instrument which is used to determine the size distribution of wear particles in lubricating oils of mechanical systems. The technique relies on the debris being capable of being attracted to a magnet.
Ferro-magnet – It is a material (typically iron, cobalt, or nickel) characterized by strong, spontaneous magnetization, high permeability, and magnetic hysteresis below a critical Curie temperature. These materials are classified by their ability to form permanent magnets because of the aligned atomic magnetic moments within structural domains which persist after an external magnetic field is removed.
Ferro-magnetic – It is the ability to become highly magnetic and have the ability to retain a permanent magnetic moment. The elementary magnetic dipoles inside the domain are all oriented in a direction parallel to each other.
Ferro-magnetic material – It is a material which in general shows the phenomena of hysteresis and saturation, and whose permeability is dependent on the magnetizing force. Microscopically, the elementary magnets are aligned parallel in volumes called domains. The unmagnetized condition of a ferro-magnetic material results from the overall neutralization of the magnetization of the domains to produce zero external magnetization.
Ferro-magnetic resonance – It is the magnetic resonance of a ferro-magnetic material.
Ferro-magnetism – It is a property shown by certain metals, alloys, and compounds of the transition (iron group), rare-earth, and actinide elements in which, below a certain temperature termed the Curie temperature, the atomic magnetic moments tend to line up in a common direction. Ferro-magnetism is characterized by the strong attraction of one magnetized body for another. Ferro-magnetism is a physical phenomenon (long-range ordering), in which certain materials like iron strongly attract each other. It is one of the common phenomena which are responsible for magnetism in the magnets. One of the vital requirements of ferro-magnetic material is that ions and atoms are to possess permanent magnetic moments. Some ions and atoms consist of the permanent magnetic moment which can be considered as a dipole that comprises a north pole separated from a south pole. Ferro-magnetism is caused in ferromagnets and the ferromagnets need to have net angular momentum which is got either through the orbital component of the spin component. In electro-magnetism, permeability is the measure of magnetization which a material obtains in response to an applied magnetic field.
Ferro-manganese (Fe-Mn) – It is a bulk ferroalloy of great importance, mainly in the steel and stainless-steel industries. Initially employed as a deoxidizing and desulphurizing agent, ferro manganese is mostly being used today for improving the hardness and wear resistance of steels. Ferro manganese is produced as three types of products namely (i) high carbon ferro manganese, (ii) medium carbon ferro manganese, and (iii) low carbon ferro manganese. High carbon ferro manganese has manganese in the range of 72 % to 82 %, carbon in the range of 6 % to 8 % and silicon in the range of around 1.5 %. Medium carbon ferro manganese has manganese in the range of 74 % to 82 %, carbon in the range of 1 % to 3 % and silicon in the range of around 1.5 %. Low carbon ferro manganese has manganese in the range of 80 % to 85 %, carbon in the range of 0.1 % to 0.7 % and silicon in the range of 1 % to 2 %.
Ferro-molybdenum (Fe-Mo) – It is an important noble ferro alloy. It is used in the production of different alloy steels. Commercial grade ferro-molybdenum contains between 60 % and 70 %. Ferro-molybdenum is a molybdenum based ferro-alloy, produced by alumino / silico thermic reduction from technical grade molybdenum trioxide (MoO3) or in induction / electric arc furnaces from molybdenum containing scraps.
Ferro-nickel (Fe-Ni) – It is a noble ferro-alloy. It is used for alloying in the production of stainless and construction steels. It is produced in reduction furnaces from nickel concentrates. It can contain up to 97.6 % nickel and be with high / low iron content.
Ferro-niobium – It is a niobium based ferro-alloy. It contains niobium in range of 60 % to 70 %. It is used as alloying additive in heat resistant and stainless steels to improve their corrosion resistance, plasticity and welding properties. It is also used for preventing the inter-crystalline corrosion of stainless chrome nickel steel. Its addition to construction steels prevents welded joint from corrosion. It is also used for micro-alloying in high strength low alloy steels. It is used in specialty alloyed steels. Vacuum grade ferro-niobium is used for super alloys additions in turbine blade applications in jet engines and land-based turbines, inconel family of alloys, and super alloys for the aerospace industry. The raw materials needed to produce ferro-niobium are ores and concentrates which contain niobium and iron oxide. Basic raw material for producing ferro niobium is pyrochlore ore. From this ore niobium penta-oxide (Nb2O5) is produced. Niobium penta-oxide is mixed with iron oxide and aluminum and is then reduced by alumino-thermic reaction to produce ferro-niobium.
Ferro-phosphorus – It is a ferro-alloy composed of iron and phosphorus (typically 23 % phosphorus to 32 % phosphorus), created mainly as a by-product of elemental phosphorus production or in steel manufacturing. Used in metallurgy as an additive, it boosts wear resistance, improves fluidity in molten iron for castings, acts as a deoxidizer, It mainly consists of iron phosphides, such as Fe2P and Fe3P.
Ferro-resonance – It is a complex, non-linear resonance phenomenon in electrical circuits which involves capacitance (such as in long cables) and iron-core, saturable inductance (such as in transformers or reactors). It is characterized by chaotic or sub-harmonic oscillations which can create extreme over-voltages and over-currents, leading to substantial damage to electrical components. Ferro-resonance is a rare type of resonance occurring in power systems where a non-linear inductance interacts with system capacitance, causing the circuit to jump between multiple, unpredictable stable states. It is normally initiated by transient disturbances, such as single-phase switching, fuse blowing, or transformer energization / de-energization. It frequently occurs in medium-voltage, lightly loaded, or unloaded systems, especially when a transformer is fed through a long underground cable.
Ferro-silicon (Fe-Si) – Ferro-silicon contains 65 % to 90 % of silicon and minor amounts of iron, aluminum and carbon. Ferro-silicon increases the strength of steel and is therefore used in those steels which are needed for producing wire cords for tyres and ball bearings. Ferro-silicon is also used for deoxidation during steel making. The other major applications of ferro-silicon are in electrical steels used for transformers and dynamos, alloy steels for tools and automobile valves, and in iron castings.
Ferrosilite – It is a silicate mineral which serves as the iron-rich end member of the ortho-pyroxene solid solution series, with the ideal chemical formula FeSiO3 (or Fe2Si2O6). It is a pyroxene group mineral which typically forms greenish-black to brownish-black grains or crystals, normally found in metamorphic rocks (granulites) and iron-rich slags.
Ferrostatic pressure (P) – it refers to the hydrostatic pressure exerted by a column of molten metal (specifically liquid steel in continuous casting) on the surrounding solidifying shell. This pressure is directly proportional to the height (or head) of the liquid metal, the density of the liquid metal, and gravity. It is calculated as P = d x g x h, where ‘d’ is the density of the liquid steel, ‘g’ is acceleration because of the gravity, and ‘h’ is the ferrostatic head (vertical height of the liquid).
Ferro-titanium – It is produced in two grades containing titanium in the range of 25 % to 35 % and 65 % to 75 %. This alloy is used for production of construction and stainless steels, and welding electrodes. Ferro-titanium when added to steel, increases yield strength of steel and reduces its cracking tendency. In the production of stainless steel with a high chrome and nickel content, it is used to bond the sulphur. Ferro-titanium is manufactured from various raw materials such as titanium scrap, ilemenite sand, rutile and titanium sponge. It is produced either from primary or secondary raw materials. The primary raw materials are minerals that contain titanium oxide, such as ilmenite. The reduction is normally carried out by the metallo-thermic process since the carbo-thermic reduction produces a ferro-alloy which contains too much carbon and hence not of much use in steel making. The production takes place as a batch process in a refractory lined crucible or in an electric furnace, depending on the process variation.
Ferro-tungsten – It is a tungsten based ferro-alloy which is used for the production of special steels. It is produced from different raw materials which contain tungsten oxides, e.g. wolframite, scheelite and hubnerite. The reduction of these minerals is done either by carbo-thermic or metallo-thermic reduction as well as by a combination of both. The tungsten trioxide in these ores is reduced by silicon and / or aluminum. Ferro tungsten contains 75 % to 85 % tungsten. Fe-W has a steel grey appearance and a fine-grained structure consisting of FeW and Fe2W.
Ferrous – This term is used for metallic materials in which the main component is iron.
Ferrous alloys – These are metallic materials composed mainly of iron (Fe), frequently alloyed with carbon (C) and other elements (such as manganese, chromium, or nickel) to improve properties like strength, hardness, and durability. They are magnetic, normally prone to rust, and constitute the foundation of structural engineering.
Ferrous ammonium sulphate – Its chemical d formula is Fe(NH4)2(SO4)2.6H2O. It is also known as Mohr’s salt. It is a stable, light-green crystalline inorganic compound used as a reducing agent and iron source. It is mainly used in iron plating baths, brass colouring, and as a standard in redox (reduction-oxidation) titrations to analyze metal solutions.
Ferrous chloride (FeCl2) – It is a greenish, water-soluble inorganic compound, iron (II) chloride. It is generated when hydrochloric acid removes rust or iron oxide from steel surfaces. It is used in metal finishing and electroplating, particularly to assist in depositing iron coatings, a mordant in dyeing, a precursor for synthesizing other iron-based compounds or refining metals, and as a reducing agent in metallurgical processes requiring reduction reactions.
Ferrous metals – These are alloys consisting mainly of iron (Fe) combined with carbon and other elements. These metals are characterized by high tensile strength, durability, and magnetic properties, making them necessary for construction, automotive, and industrial machinery. Majority of ferrous metals are susceptible to corrosion, with key exceptions being stainless steel.
Ferrous oxide (FeO) – It is also known as iron (II) oxide or wustite in its mineral form. It is a black-coloured inorganic compound composed of iron in the +2-oxidation state and oxygen. It is one of the key iron oxides, alongside hematite (Fe2O3) and magnetite (Fe3O4), which plays a critical role in the extraction of iron from its ore and the production of steel. It contains ferrous ions (Fe2+) and oxide ions (O2-), frequently appearing as a black powder. It has a cubic, rock salt (NaCl) structure, where iron atoms are octahedrally coordinated by oxygen atoms. While theoretically FeO, it is frequently non-stoichiometric and iron-deficient, with compositions ranging from Fe0.84O to Fe0.95O. It is stable at high temperatures (above 575 deg C), but can break down (disproportionate) into iron metal and Fe3O4 at lower temperatures. It is a basic oxide, easily soluble in acids, and is highly reactive, tending to oxidize to Fe2O3 when exposed to air.
Ferrous powder – it is also called iron powder. It is a versatile, fine-grained material consisting of metallic iron particles, typically less than 500 micro-meters (or 1 millimeter) in size, with high purity (frequently above 98 %). It is widely used in powder metallurgy for sintering, welding, magnetic applications, and chemical processes due to its magnetic properties, strength, and durability.
Ferrous powder metallurgy – It is a highly developed, chipless manufacturing process which converts iron and steel powders into precise, solid components. It involves mixing or blending iron-based powders, compacting them in dies to a specific shape, and sintering (heating) them below the melting point to create high-strength components, frequently with controlled porosity. It mainly uses iron and steel powders, frequently alloyed with elements like copper, nickel, or carbon to achieve desired engineering properties.
Ferrous scrap – It is also referred to as, iron and steel scrap, or simply scrap comes from end-of-life products (old or obsolete scrap) as well as scrap generated from the manufacturing process (new, prime or prompt scrap). It is metal that contains iron. Iron and steel scrap can be processed and re-melted repeatedly to form new products. Due to the value of metal in the ferrous scrap, it is recycled or reused wherever it is possible. In fact, ferrous scrap is being recycled long before current awareness of environmental concerns started. Ferrous scrap is generated during the production of iron and steel, fabrication or manufacture of iron and steel products, or when the product made of iron and steel reaches its end of life. Because of the high value of the metal, the ferrous scrap is largely being recovered.
Ferrous scrap recycling – It consists of collection, sorting, shredding and / or sizing, and final melting at the steel plants.
Ferrous slag – It is a by-product of iron and steel production, formed by combining limestone, dolomite, and other fluxes with impurities (gangue) from iron ore during smelting. Mainly composed of calcium, magnesium, and aluminum silicates, this molten material is separated from the metal to create a durable, non-metallic by-product used mainly as construction aggregate or in cement production.
Ferrous sulphate (FeSO4) – It is an inorganic salt, normally known as green vitriol, iron vitriol, or copperas, which appears as blue-green crystals in its hydrated form (FeSO.7H2O). It is a versatile compound used mainly as a cost-effective water treatment coagulant, fertilizer additive, and in manufacturing pigments. It serves in reducing chromium VI in cement, producing iron oxide, and in sewage treatment. It is used as a raw material for iron compounds, for pickling steel, and as a reducing agent in specialized chemical processes.
Ferro-vanadium – It is vanadium based ferro-alloy which is used for the modification of the micro-structure of steel and for increasing the tensile strength, hardness, and high temperature strength. It is used in the high-speed steels. Vanadium content in ferro-vanadium ranges from 35 % to 80 %. Ferro-vanadium is produced by a carbo-thermic or a metallo-thermic (alumino thermic) reduction of vanadium oxides, assisted by the presence of iron. Since carbon is used in a carbo-thermic reduction, the carbon content of the ferro-alloy is normally high. Hence the process cannot be used if there is a requirement for low carbon content. Low carbon ferro-vanadium is normally produced by an alumino thermic reduction.
Ferroxyl test – It is a highly sensitive, non-destructive chemical surface test used in metallurgy to detect the presence of free iron (embedded iron or iron oxide) on the surface of stainless steels, nickel-rich alloys, and chromium-plated materials. It is specifically designed to verify the effectiveness of cleaning, pickling, and passivation processes by identifying iron contamination (from tools, dust, or welding) which, if left behind, destroys the passive layer and cause pitting corrosion.
Fertilizer – It is a substance, natural or synthetic, which is added to soil or plant tissues to provide essential nutrients for plant growth and development. Fertilizers can be organic (like manure or compost) or inorganic (synthetic compounds). The primary goal of fertilization is to improve soil fertility and improve crop yields.
Fe solution – It is also called iron solution. It refers to a solid solution where iron (Fe) acts as the solvent, hosting solute atoms (such as carbon, nickel, chromium, or manganese) within its crystalline lattice structure. It is a homogeneous, solid-state mixture which maintains a single crystal structure. This is mainly divided into solid solutions of carbon in iron, forming the key phases of steel and cast iron.
Festoon cable – It is a type of flexible cable which is designed to be used in a festoon system, which is a track-based system used to provide power and / or control signals to moving machinery. These cables are typically flat or round, and they are supported by a track or bar system which allows them to move along with the machinery.
Festoon system – It is a method of supporting and supplying power or other media (like air or fluids) to moving machinery, frequently used in industrial settings such as overhead cranes. It utilizes a series of trolleys or carriers which run along a track, supporting and guiding cables or hoses as the machinery moves. This system ensures that the moving equipment receives the necessary power, control signals, or other media without the cables dangling or becoming entangled. A festoon system typically includes a track (C-rail, I-beam, etc.), trolleys or carriers which move along the track, and the cables or hoses themselves. The trolleys suspend the cables, allowing them to move with the machinery while keeping them organized and protected. Common applications include overhead cranes, monorail hoists, machine tools, plating lines, and other machinery which moves along a defined path.
Fe system – It is also called iron system. It refers to iron (Fe, atomic number 26) as the main base metal combined with other elements, very frequently carbon, to create different ferrous alloys like steel and cast iron. It is the foundational system in physical metallurgy, focusing on the phase transformations, microstructure, and properties of iron-based materials during melting, casting, and heat treatment.
FET bio-sensor – It is a type of biosensor which utilizes an ion-sensitive field-effect transistor (FET), where an ion-sensitive membrane replaces the metal gate, allowing for the detection of bio-molecules through changes in charge distribution and conductance in the semiconductor material upon binding of charged molecules.
Fettle – It is a British term meaning the process of removing all runners and risers and cleaning off adhering sand from the casting. It also refers to the removal of slag from the inside of the cupola and to repair the bed of an open-hearth furnace.
Fettling – It is the important process of finishing and cleaning metal castings, forgings, or galvanized steel to remove excess material. It involves removing risers, gates, fins, and rough edges using methods like grinding, chipping, or shot blasting to create a smooth, functional component. It also refers to lining furnace hearths.
Fettling mixes – These are also granular refractory materials, with function similar to gunning mixes, but are applied by shoveling into the furnace needing patching.
Few-layer graphene – It refers to a form of graphene consisting of multiple layers of carbon atoms, which presents different properties and potential applications compared to monolayer graphene, particularly in molecular separation and composite film formation.
Fibering – It is also called mechanical fibering. It is the elongation and alignment of internal boundaries, second phases, and inclusions in particular directions corresponding to the direction of metal flow during deformation processing. It refers to the alignment of grains, microstructural features, and inclusions along the direction of mechanical working (such as rolling, forging, or drawing). This process results in an elongated, fibrous microstructure, which leads to anisotropic properties, meaning the material’s strength and toughness differ depending on the direction of testing.
Fibre – It is the characteristic of wrought metal which indicates directional properties and is revealed by etching of a longitudinal section or is manifested by the fibrous or woody appearance of a fracture. It is caused mainly by extension of the constituents of the metal, both metallic and non-metallic, in the direction of working during rolling, extrusion, or other solid-state processes, or by crystallographic alignment of the matrix phase itself. It is also the pattern of preferred orientation of metal crystals after a given deformation process, normally wire-drawing. In composites, fibre is a general term used to refer to filamentary materials. Frequently, fibre is used synonymously with filament. It is a general term for a filament with a finite length that is at least 100 times its diameter, which is typically 0.1 millimeter to 0.13 millimeter. In majority of the cases, it is prepared by drawing from a molten bath, spinning, or deposition on a substrate. A whisker, on the other hand, is a short, single- crystal fibre or filament made from a wide variety of materials, with diameters ranging from 1 micro-meter to 25 micro-meter and aspect ratios (a measure of length) between 100 and 15,000. Fibres can be continuous or specific short lengths (discontinuous), normally no less than 3.2 milli-meters.
Fibre alignment – It refers to the deliberate orientation of reinforcing fibres (such as steel, carbon, or glass) along a specific, designed axis within a matrix material (like metal, cement, or polymer). Unlike random fibre distribution, where reinforcement is chaotic, aligned fibres are normally oriented parallel to the direction of anticipated tensile stress to maximize structural efficiency, improve strength, and optimize the material’s anisotropy.
Fibre arms – These refer to the components of sensors, such as the reference fibre and measurement fibre in the SOFO (Surveillance d’Ouvrages par Fibres Optiques, which translates to ‘structural monitoring using optical fibres’) sensor, where the reference fibre is loosely placed for mechanical protection and the measurement fibre is tightly stretched to sense changes in distance between anchor pieces.
Fibre array – It is called fibre-optic array It is a high-precision, rigid assembly that aligns multiple optical fibres (or fibre ribbons) in a specific one-dimensional (1D) linear row or two-dimensional (2D) matrix on a substrate. It is typically formed at the end of a fibre bundle and used as an interface for coupling light between fibres and other optical components like photonic integrated circuits (PICs), arrayed waveguide gratings (AWGs), and laser arrays.
Fibre attenuation – It is also known as fibre loss or transmission loss. It is defined as the reduction in optical power (intensity of the light signal) since it propagates through an optical fibre. It represents the loss of signal strength over distance and is a critical parameter limiting the maximum transmission distance and data rate of optical communication systems.
Fibre attenuation coefficient (a) – It is a measure of optical signal power loss per unit length, typically expressed in decibels per kilometer (dB/kilometer). It represents the rate at which signal strength decays because of the scattering, material absorption, and bending losses. The coefficient is calculated by formula’ ‘a = 10/L x log10 (Pin / Pout)’, where ‘L’ is length, ‘Pin’ is input power, and ‘Pout’ is output power.
Fibre axis – It is the preferred orientation direction of heavily deformed grains in a poly-crystalline material, typically aligned with the direction of maximum strain during processing like wire drawing or rolling. It defines an axis of axial symmetry where grains are elongated, leading to anisotropic mechanical properties.
Fibre-board – It is a type of engineered panel product manufactured from lignocellulosic fibres (typically wood, but also other plant fibres) which are combined with synthetic resins, binders, or natural lignin and compressed under high heat and pressure. It is classified based on density and production method into low-density fibre-board (LDF), medium-density fibre-board (MDF), and high-density fibre-board (HDF).
Fibre bonding – It refers to the methods used to connect fibres together (fibre-to-fibre) or to a matrix (fibre-to-matrix) to form a cohesive, structurally sound material, such as fibre-reinforced metal composites or specialized engineering mats. The bonding mechanism creates a unified structure designed to improve mechanical properties, like tensile strength and stiffness, by creating a strong interfacial bond which allows load to be transferred efficiently.
Fibre Bragg grating – It is a type of distributed Bragg reflector constructed in a short segment of optical fibre which reflects particular wave-lengths of light and transmits all others. It is created by producing a periodic variation in the refractive index of the fibre core, acting as an optical filter or sensor. Fibre Bragg gratings are used as highly sensitive, quasi-distributed sensors. They measure strain, temperature, pressure, and vibrations by detecting shifts in the Bragg wave-length caused by deformation of the optical fibre’s micro-structure.
Fibre Bragg grating sensor – It is an optical fibre-based, wave-length-encoded, passive sensor which measures strain, temperature, and pressure by detecting shifts in reflected light, created by a periodic refractive index structure in the fibre core. These lightweight sensors are immune to electro-magnetic interference and are widely used in structural health monitoring for industrial applications.
Fibre break – It refers to the failure or fracture of individual reinforcing filaments (fibres) when they are subjected to stresses, such as tension, shear, or impact, which exceed their tensile strength. This breakage is an important, frequently sudden, damage mechanism where fibres, typically brittle in nature, split or shatter into two or more segments, causing a reduction in load-bearing capacity and contributing to the overall failure of the composite.
Fibre breakage – It is also called fibre fracture. It is defined as the failure, snapping, or rupture of individual reinforcement fibres (such as carbon, glass, or steel) within a matrix material. This phenomenon occurs when the tensile or shear stresses acting on the fibre exceed its ultimate tensile strength, leading to the loss of load-bearing capacity and a reduction in the overall structural integrity of the material.
Fibre bundle model – It is a theoretical, statistical framework used to investigate the fracture, failure, and constitutive behaviour of disordered, heterogeneous materials (such as composites, alloys, or fibre-reinforced metals) under mechanical loading. It models a material as a collection of ‘N’ parallel elements (fibres) with stochastically distributed breaking strengths, typically clamped between two rigid platforms.
Fibre cable – It is a thin and lightweight medium which uses light, typically infrared, to transmit information, offering advantages such as very low attenuation, high bandwidth, and immunity to electro-magnetic interference. It is encapsulated in protective jackets and provides electrical isolation, making it secure against signal tapping.
Fibre channel – It is a high-speed networking technology, mainly used for storage area networks (SANs) in enterprise data centres to connect servers to shared storage devices. It is designed to provide high-performance, low-latency, and lossless delivery of raw block data. Fibre channel is a layered, serial data transfer protocol designed to handle high-throughput work-loads, such as mission-critical data-bases and virtualized environments.
Fibre characterization techniques – These techniques refer to a comprehensive suite of analytical methods used to quantify the structural, physical, chemical, and mechanical properties of individual fibres or fibre bundles. These techniques are important for assessing the quality, performance, and interaction of reinforcing fibres (such as carbon, ceramic, or metallic fibres) within a composite matrix. These characterization methods allow for the analysis of the fibre, the matrix, and the interface between them.
Fibre cladding – It is the outer layer of glass or plastic which surrounds the core of an optical fibre, possessing a lower refractive index to confine light within the core through total internal reflection. It typically has a standard diameter of 125 micro-meter, providing mechanical strength and protecting the core while enabling efficient light transmission.
Fibre cladding by conform extrusion – It is a continuous, solid-state cladding process used to apply a metallic sheath (cladding) directly onto a central core (such as electrical conductors or steel wires) using rotary extrusion technology. It utilizes frictional heat and pressure, rather than melting, to form a metallurgical bond between the cladding material (e.g., aluminum or copper) and the core.
Fibre coating – It is the application of a thin protective or functional layer onto the surface of reinforcing fibres (such as carbon, silicon carbide, or alumina) before they are incorporated into a matrix material to form a composite. These coatings are typically applied using advanced techniques like chemical vapour deposition (CVD), physical vapour deposition (PVD), or slurry coating, with a thickness usually less than 1 micro-meter.
Fibre cohesion – It is the inter-fibre attraction and resistance to separation, driven by surface friction, crimp, and morphology. It represents the ability of fibres to cling together, forming a coherent structure, which is important for managing fibre movement in composite preforms or reinforcing material.
Fibre component – It refers to a reinforcing, high-aspect-ratio material, either inorganic (metallic, ceramic) or carbon-based, embedded within a matrix to improve the mechanical properties of a composite material. In fibre-reinforced metal matrix composites (MMCs), these fibres act as the main load-bearing constituent, providing superior stiffness, strength, and fatigue resistance compared to the base metal alone.
Fibre composite materials – These are materials composed of high-strength fibres embedded within a continuous matrix phase. They combine distinctive constituents to improve mechanical properties like strength, stiffness, and weight-to-strength ratios. The fibres provide strength, while the matrix binds and protects them.
Fibre content – It is the quantity of fibre present in a composite. This is normally expressed as a percentage volume fraction or weight fraction of the composite.
Fibre core – It normally refers to a specialized, frequently non-metallic or composite, central component of a structural element, such as in wire ropes or fibre-reinforced metals. Fibre core is also the inside part of the fibre. It can be made of plastic, glass, fused silica, sapphire, or in some cases, a liquid. Normally, the fibre core is surrounded by a layer of material which has lower index of refraction than the core and is referred to as the ‘cladding’.
Fibre count – It is the number of fibres per unit width of ply present in a specified section of a composite.
Fibre coupler – It is also called a fused fibre coupler. It is a passive optical device which splits or combines light signals between two or more optical fibres by fusing them together, allowing evanescent wave coupling, or the transfer of light between cores. In the context of manufacturing, they are created by heating and stretching two or more fibres, modifying their structure to allow mode interaction.
Fibre cut – It typically refers to a metallurgical defect where the internal, elongated grain structure (fibre structure) of a forged or rolled metal part is severed or interrupted, frequently because of improper machining or forging, leading to reduced structural integrity.
Fibre damage – It refers to the irreversible deterioration of the physical, chemical, or mechanical properties of reinforcement fibres. This damage, caused by processing or service conditions, results in reduced load-bearing capacity of the fibres and, hence, a decline in the overall structural integrity of the metal composite.
Fibre degradation – It refers to the process where the structural integrity, mechanical strength, or chemical stability of reinforcing fibres (such as glass, carbon, aramid, or metal fibres) deteriorates because of the environmental, thermal, or mechanical factors. This process results in a reduction of the tensile strength, elasticity, and load-bearing capacity of the fibers, which directly reduces the performance of the overall composite material.
Fibre density – It refers to the quantity of fibre reinforcement present per unit volume or mass of the composite. Fiber density is not only an important quality control parameter in fibre manufacture but also needed for determination of the void content of the fibrous composite. It can also be used as a distinguishing parameter to identify a fibre.
Fibre diameter – It defines the thickness of thin metal filaments or fibres, typically ranging from 1 micrometer to 80 micrometers. It represents the straight-line distance across the centre of a fibre’s cross-section, frequently measured by ‘scanning electron microscopy’ (SEM) for precision. This metric determines material strength, flexibility, and conductivity, with smaller diameters normally increasing the flexibility and surface area of metal fibres.
Fibre direction – It refers to the alignment or orientation of reinforcement fibres (such as carbon or glass) within a composite matrix, determining the direction of maximum strength and stiffness. It is normally characterized as unidirectional, bidirectional, or random, and can be defined by angles relative to a reference axis. It is the orientation or alignment of the longitudinal axis of the fibre with respect to a stated reference axis.
Fibre directional coupler – It is an optical component which splits or combines light signals between two or more fibres by bringing their cores close enough for their evanescent fields to overlap. By fusing and stretching two parallel optical fibres (frequently called a biconical taper coupler), optical power is transferred between them, typically used for splitting, tapping, or multiplexing, and frequently fabricated by melting / fusing silica fibres.
Fibre dispersion – It refers to the distribution, spacing, and layout of reinforcing fibres within a host matrix material (such as a metal matrix composite, MMC). Good fibre dispersion implies that the fibres are separated from each other and individually surrounded by the matrix, avoiding clumping or agglomeration.
Fibre element – It normally refers to a slender, high-aspect-ratio reinforcing component (metallic or ceramic) used to improve the mechanical properties of a composite material, typically within a metal matrix composite (MMC). Fibres are long, thin strands, filaments, or whiskers with a high length-to-diameter ratio (aspect ratio above 100).
Fibre end – It refers to the termination point or tip of a high-strength, thin strand of metal (like steel, aluminum, or copper) embedded within a matrix.
Fibre end surface – It is also called fibre end-face. It is the polished or cleaved tip of an optical fibre, acting as the interface where light enters or exits the waveguide. It refers specifically to the exposed cross-section of the core and cladding. The quality of this surface, measured by its topography, cleanliness, and geometry (e.g., flat or domed), is important for reducing signal losses, reflections, and damage, particularly in high-power laser applications.
Fibre engineering – It refers to the design, production, and application of high-strength, thin filaments (fibres) to reinforce a base material (matrix), creating composite materials with improved mechanical properties. This frequently involves the creation of metal matrix composites (MMCs), where continuous or discontinuous fibres (such as boron, silicon carbide, or tungsten) are embedded within a metallic matrix (such as aluminum, titanium, or copper) to increase specific strength, stiffness, fatigue resistance, and high-temperature performance.
Fibre entanglement – It refers to the mechanical interlocking, intertwining, or weaving together of metal fibres (such as steel wool or chopped metal wires) to form a 3D network, frequently characterized by low density and high porosity. It is a structural architecture where individual metallic fibres are randomly oriented and linked together through friction, forming a stable ‘mat-like’ network, which can subsequently be bonded through sintering or adhesive bonding.
Fibre facet – It is the end face or terminal surface of an optical fibre. It is the cross-sectional surface where light enters or exits the fibre, frequently polished, cleaved, or treated with micro-structures (such as moth-eye structures) to improve optical transmission and reduce damage.
Fibre failure – It is the rupture, fragmentation, or degradation of reinforcing fibres within a material (frequently metal matrix or fibre-reinforced composites), occurring when stress, strain, or localized loading exceeds the fibre’s ultimate strength. It is a highly destructive failure mode, frequently resulting from tensile, compressive, or shearing loads which lead to fibre breakage, matrix cracking, or fibre pull-out.
Fibre failure modes – These are the specific physical mechanisms, such as splitting, fracturing, or peeling, by which fibre tows lose integrity under tensile, compressive, or shear loads. These modes define how reinforcing fibres (like carbon or glass) break under stress, leading to structural failure. Main modes include fibre tensile fracture, buckling or shear kinking under compression, fibre pull-out (de-bonding from the matrix), and fibre-matrix interfacial delamination, frequently caused by overloading or fatigue.
Fibre fineness – It refers to the linear density (mass per unit length) or diameter of reinforcement fibres (e.g., carbon, metal, or ceramic) used in composite materials. It defines the thinness, normally measured in decitex, impacting fibre surface area, reinforcement efficiency, and composite mechanical properties. It is most accurately defined as the linear density, sometimes referred to as ‘titre’ or ‘count’, which relates to the weight per unit length, or by the cross-sectional diameter, normally in micro-meters.
Fibre fracture – It refers to the breakage of individual, aligned reinforcing fibres (e.g., carbon, glass, silicon carbide) within a composite material when the stress or strain acting along the fibre axis exceeds the fibre’s ultimate strength. It is an important damage mechanism, particularly in fibre-reinforced metal-matrix composites (MMCs) and fibre-metal laminates, where it frequently indicates the initiation of catastrophic failure.
Fibre fragmentation – It refers to the process where a reinforcement fibre, such as silicon carbide (SiC) or carbon, embedded in a matrix (frequently a ductile metal or polymer) breaks into increasingly smaller segments under tensile loading. This process is used in testing (single-fibre fragmentation tests) to evaluate the interfacial shear strength between the fibre and the matrix.
Fibre friction – It is defined as the force which opposes the relative motion (or tendency toward motion) between two contacting surfaces, specifically where at least one of those surfaces is a fibrous material. It is a surface phenomenon important for maintaining the cohesion of fibre assemblies, such as in composite preforms, and for controlling fibre flow during processing. It is determined by the surface characteristics of the fibres (roughness, scale structure, crimp) rather than their bulk properties. Similar to classical friction, it consists of static friction (force needed to initiate motion) and kinetic friction (force needed to maintain motion), with static friction typically being higher.
Fibre-glass – It is an individual filament made by drawing molten glass. A continuous filament is a glass fibre of great or indefinite length. A staple fibre is a glass fibre of relatively short length, normally less than 430 millimeters, the length related to the forming or spinning process used.
Fibre-glass filter – It is frequently called a fibre-glass mesh filter or casting filter. It is a high-temperature resistant, inorganic non-metallic filter material, woven from fine, alkali-free glass fibres, used in the foundry industry to remove impurities (such as slag and non-metallic inclusions) from molten metals like aluminum, iron, and steel. These filters are positioned within the casting gating system, frequently in the ladle, sprue, or flow channel, to improve the purity, mechanical properties, and surface finish of the final casting, while increasing the overall yield by reducing casting defects.
Fibre-glass reinforcement – It is the major material which is used to reinforce plastic. It is available as mat, roving, fabric, and so forth. It is incorporated into both thermosets and thermoplastics.
Fibre grating – It is a type of diffraction grating formed by creating a periodic modulation of the refractive index in the core of an optical fibre. It functions as an inline optical filter or mirror, reflecting a specific narrow range of wavelengths (the Bragg wavelength) while transmitting others. In metallurgy and structural health monitoring, fibre gratings, particularly fibre Bragg gratings (FBGs), are utilized as high-precision sensors for real-time monitoring of strain, temperature, and corrosion in metallic structures and materials.
Fibre grating structure – It is a periodic modification or perturbation of the refractive index in the core of an optical fibre. This structure is created by inducing changes in the photosensitive material of the core, frequently through ultra-violet (UV) irradiation, creating a periodic variation (diffraction grating) which can improve sensitivity or filter specific light wave-lengths.
Fibre grease – It is a type of grease having a pronounced fibrous structure.
Fibre Identification – It refers to the systematic process of determining the specific composition, structure, and type of metallic, mineral, or synthetic fibres. This process involves utilizing different analytical, chemical, and physical techniques to distinguish between types such as metal filaments, mineral fibres (e.g., asbestos, glass), or synthetic fibres used in composites.
Fibre input – It refers to the individual optical fibres which connect to a receiver in a fibre-optic network, allowing for the transmission of signals. In configurations with redundant fibre inputs, each fibre is routed to its own receiver to improve reliability and maintain signal quality in the event of a failure or degradation of one path.
Fibre intersection – It refers to the localized contact point where two or more individual reinforcing fibres (e.g., steel, carbon, ceramic, or metal fibres) cross or connect within a fibrous network or matrix. These intersections are important load-transfer points which define the mechanical properties, such as stiffness and tensile strength, of the resulting composite or sintered material.
Fibre laser – It is a type of solid-state laser where the active gain medium is an optical fibre doped with rare-earth elements (such as ytterbium, erbium, or neodymium). Fibre lasers are renowned for generating a high-quality, high-power beam which is delivered through a flexible fibre, making them ideal for high-speed, precise cutting, welding, and marking of metals.
Fibre laser system – It is a type of solid-state laser where the active gain medium is an optical fibre doped with rare-earth elements (such as ytterbium, erbium, or neodymium). These systems are used to generate, amplify, and deliver a high-intensity, coherent laser beam, typically in the near-infrared wavelength region (around 1.06 micrometers to 1.08 micrometers), to cut, weld, mark, or clean metals.
Fibre length – It is the measurement of the physical length of reinforcement fibres (such as carbon, glass, or ceramic) within a matrix, which directly determines the material’s strength, load-transfer capacity, and failure modes.
Fibre level – It refers to the preferred, axially aligned orientation of heavily deformed grains or micro-structure within a metallic material, normally created through mechanical processing like rolling, drawing, or extrusion.
Fibre link – It is defined as a communication pathway which utilizes optical fibres to transmit data, and can include components such as amplifiers to compensate for signal loss over long distances, as exemplified by a multi-span fibre link emulated with a recirculation loop.
Fibre loading – It refers to the proportion or quantity of fibre reinforcement (such as carbon, glass, or metal fibres) incorporated into a matrix material (polymer, metal, or ceramic) to create a composite. It is typically expressed as a percentage of the total weight or volume of the composite, and it is an important factor in determining the resulting material’s mechanical properties.
Fibre loss – It refers to the degradation or reduction of fibre-reinforced metal matrix composites (MMCs) because of the different degradation mechanisms, mainly oxidation and chemical interaction with the matrix, especially at high temperatures. This loss leads to a reduction in the content, structural integrity, and reinforcing effectiveness of the fibres within the metal matrix. It is also the exponential reduction of optical power during transmission through a fibre, mainly caused by material absorption and Rayleigh scattering. It is quantified by the attenuation constant, which varies with factors such as impurities in the core medium and the optical wave-length.
Fibre mat – It is a non-woven, porous assembly of interconnected fibres, which can be inorganic, ceramic, or metallic, arranged in a random 2D pattern, typically used to provide high thermal insulation, filtration, or structural reinforcement. Unlike woven fabrics, fibre mats feature randomly oriented fibres held together by van der Waals forces, friction, a binding agent, or mechanical interlocking (needle punching). In high-temperature metallurgical processes, these mats are frequently ‘matrix-free’ or inorganic, allowing for infiltration by liquid metal or resin.
Fibre metal laminates – These are high-performance hybrid structural materials composed of alternating, bonded thin layers of metal (typically aluminum) and fibre-reinforced polymer composite materials. They combine metallic properties like ductility and impact resistance with composite advantages like high fatigue resistance and low weight.
Fibre mechanical properties – These properties define how fibrous materials resist applied forces (tension, bending, torsion), characterized by tensile strength, modulus of elasticity (stiffness), elasticity, elongation, and tenacity (strength per unit density). These properties determine durability, flexibility, and load-bearing capacity in composites and textile applications. Key mechanical properties of fibres are tensile strength / tenacity, Young’s modulus / stiffness, elongation / elasticity, flexural rigidity / bending and abrasion resistance.
Fibre metallurgy – It is the technology of producing solid bodies from fibres or chopped filaments, with or without a metal matrix. The fibres can consist of such non-metals as graphite or aluminum oxide, or of such metals as tungsten or boron.
Fibre migration – It refers to the relative movement or displacement of reinforcement fibres from their initial positions within a metal matrix or textile assembly during processing. This phenomenon is important in metal-matrix composites (MMCs) when reinforcement fibres move during infiltration, forging, or solidification, directly impacting the final properties of the component.
Fibre mode – It refers to a specific type of preferred orientation of grains in a material. This texture occurs when grains become heavily deformed and align themselves along the direction of maximum strain, normally developed during manufacturing processes such as wire drawing, extrusion, or rolling. Fibre mode is the preferential alignment of elongated grain structures along the axis of processing (e.g., drawing direction). It occurs mainly in heavily cold-worked materials, particularly in wire-drawing or rolling, where the metal experiences significant stretching. It shows axisymmetrical grain orientation (axial symmetry). The fibre mode strongly affects the mechanical properties of the material, making the material’s strength or ductility direction-dependent (anisotropic).
Fibre non-linearity – It is an optical phenomenon where the refractive index of an optical fibre core changes based on light intensity, deviating from linear behaviour. Mainly caused by the Kerr effect at high power levels, it creates phenomena like self-phase modulation and Raman scattering, which are critical in telecom and specialized fibre lasers.
Fibre-optic cable – It is a transmission medium which uses infra-red energy or light to transmit information down a long thin transparent filament such as glass.
Fibre optic communication – It is a communication infrastructure which utilizes optical fibres to provide reliable data transmission with strict ‘quality of service’ and nearly unlimited bandwidth, while being highly immune to electro-magnetic interferences.
Fibre optic components – These are essential elements used in optical systems to facilitate the transmission of light signals, frequently for data, sensing, or imaging, by acting as wave-guides, typically consisting of a core, cladding, and protective coating. While mainly made of dielectrics (glass or plastic), the metallurgy of these components involves specialized doped silica and metals used for structural reinforcement, coating, or specialized sensing applications.
Fibre optic networks – These are high-capacity communication systems which transmit data as light pulses through thin, flexible strands of pure glass (silica) or plastic. They serve as the backbone of modern telecommunications, offering considerably higher bandwidth, faster speeds, and longer transmission distances compared to traditional copper cables, while being immune to electro-magnetic interference.
Fibre optic probe – It is a specialized, ruggedized sensor consisting of one or more optical fibres housed in a protective, frequently metallic, casing. It acts as an optical interface to transmit light to and from a metallurgical sample or process, such as molten metal, high-temperature furnaces, or plasma arc processes, to analyze its physical or chemical properties in real-time. These probes are frequently used for in situ measurements in harsh environments where traditional electrical sensors fail, offering high immunity to electro-magnetic interference.
Fibre optic sensors – These are devices using optical fibres to measure physical parameters like temperature, strain, and pressure in real-time, frequently acting as the sensing medium themselves. In high-temperature or electro-magnetically noisy environments, they provide accurate, distributed monitoring, important for processes like welding, furnace control, and casting.
Fibre optics technology – It uses thin, flexible strands of high-purity glass or plastic to transmit data as light signals through total internal reflection. These fibres, frequently thinner than a human hair, consist of a core and cladding with different refractive indices, providing high-speed communication and immunity to electro-magnetic interference.
Fibre orientation – It refers to the precise alignment, direction, and spatial distribution of reinforcing fibres (such as carbon or glass) within a matrix. It defines the orientation of fibre axes, acting as an important, frequently anisotropic, factor controlling mechanical strength, stiffness, and structural performance.
Fibre orientation distribution – It describes the statistical arrangement (angles and directions) of fibres within a material, impacting structural anisotropy and mechanical strength. It defines the probability density function, showing how many fibres align with specific directions (e.g., flow direction) against being randomly dispersed. Fibre orientation distribution tracks the orientation of short or long fibres, typically quantified by the probability of a fibre being oriented within a certain solid angle on a unit sphere.
Fibre output – It refers to the transmission of light, signals, or energy out of the terminal end of an optical fibre (a thin, flexible filament of glass or plastic).
Fibre parameters – These are the quantitative characteristics defining the dimensions, distribution, and orientation of fibrous reinforcing elements within a matrix (such as metal, polymer, or concrete). These parameters are important for predicting the mechanical properties, such as tensile strength, fracture toughness, and creep resistance, of the resulting composite material. Core fibre parameters are fibre length, fibre diameter, aspect ratio, fibre volume fraction, orientation parameter, fibre distribution, and interphase thickness.
Fibre pattern – It consists of visible fibres on the surface of laminates or moulding. It is the thread size and weave of glass cloth.
Fibre placement – It is the continuous process for fabricating composite shapes with complex contours and / or cutouts by means of a device which lays pre-impregnated fibres (in tow form) onto a non-uniform mandrel or tool. It differs from filament winding in several ways. There is no limit on fibre angles. Compaction takes place on-line through heat, pressure, or both, and fibres can be added and dropped as necessary. The process produces more complex shapes and permits a faster put-down rate than filament winding.
Fibre-preform – It is a pre-shaped, engineered assembly of dry fibre layers (such as carbon, glass, or aramid) which acts as the structural skeleton for a fibre-reinforced composite component. It is designed to be placed into a mould and infused with a resin (liquid injection moulding) to create a net-shape or near-net-shape finished part.
Fibre-reinforced composite – It is a composite building material which consists of three components namely the fibres as the discontinuous or dispersed phase, the matrix as the continuous phase, and the fine inter-phase region, also known as the interface. The term is generic for composite materials and applies to metal and non-metal reinforcements. The metallic component can be made by powder metallurgy techniques.
Fibre reinforced concretes – In recent years, a great deal of interest has been shown in fibre reinforced concrete, and today there is much ongoing research on the subject. The fibres used are made from steel, plastics, glass, and other materials. Different experiments have shown that the addition of such fibres in convenient quantities (normally up to about 1 % or 2 % by volume) to conventional concretes can appreciably improve their characteristics. The compressive strengths of fibre reinforced concretes are not significantly greater than they would be if the same mixes were used without the fibres. The resulting concretes, however, are substantially tougher and have greater resistance to cracking and higher impact resistance. The use of fibres has increased the versatility of concrete by reducing its brittleness. It is to be noted that a reinforcement bar provides reinforcing only in the direction of the bar, while randomly distributed fibres provide additional strength in all directions.
Fibre-reinforced material – It refers to a high-performance composite consisting of high-strength fibres (e.g., carbon, boron, silicon carbide) embedded within a metal matrix (e.g., aluminum, titanium, copper). It improves structural strength, stiffness, and heat resistance, with the matrix protecting fibres and transferring stress.
Fibre reinforced plastic – It is a composite material composed of a high-strength, fibrous reinforcement (such as glass, carbon, or aramid) embedded within a polymer matrix (u-normally epoxy, polyester, or vinyl ester). The fibres provide strength and stiffness, while the resin acts as a binder and protective matrix. Fibre reinforced plastic consists of high-performance fibres, frequently glass, carbon, or aramid, which provide structural strength.
Fibre-reinforced polymer composites – These are advanced materials consisting of high-strength fibres (reinforcement) embedded in a tough polymer resin (matrix). They are designed to deliver superior strength-to-weight ratios, high stiffness, and corrosion resistance compared to conventional metals like steel or aluminum
Fibre-reinforced polymers – These are composite materials made by combining a polymer matrix with high-strength fibres. The fibres, frequently glass, carbon, or aramid, provide strength and stiffness, while the polymer matrix binds the fibres and transfers loads. This combination results in a material with a high strength-to-weight ratio, making fibre-reinforced polymers suitable for a wide range of application. The matrix is the continuous phase which holds the fibres together and transfers loads between them. Common matrix materials include epoxy, polyester, and vinylester resins.
Fibre reinforcement – It is a composite material technique which involves incorporating high-strength, high-modulus filaments (fibres) into a ductile metal, polymer, or ceramic matrix to improve the overall mechanical properties, such as tensile strength, stiffness, wear resistance, and fatigue life. The reinforcement acts as the main load-bearing constituent, while the matrix binds the fibres together, protects them from environmental damage, and transfers stress between them.
Fibre ring laser – It is a type of fibre laser where the optical cavity is arranged in a closed-loop (ring) configuration, rather than a linear Fabry-Perot cavity. It is a high-power, high-beam-quality tool used for precision applications, frequently using rare-earth-doped fibres (such as ytterbium) to achieve superior cutting, welding, and marking capabilities on metals and alloys.
Fibre ropes – These ropes are made from a range of materials in a wide variety of constructions for a great diversity of uses, from the purely decorative to demanding engineering. fibre ropes are split into two categories namely (i) natural fibre rope such as manila, sisal, jute and cotton etc. and (ii) synthetic or man-made fibre rope such as polyester, polypropylene and nylon etc. Each type has its own range of characteristics and benefits but also some drawbacks.
Fibre rupture – It refers to the failure of reinforcing fibres, typically ceramic or carbon, when they break under tensile load within a matrix, frequently at weak points or defects. It is a critical, frequently irreversible, damage mechanism in fibre-reinforced composites which leads to load redistribution, matrix cracking, and total component failure.
Fibre section – It refers to the cross-sectional shape and dimension of a fiber, typically a metallic filament or whisker, which has been heavily deformed (e.g., through wire drawing or rolling) to have a long axis, frequently with a length-to-diameter ratio exceeding 1,000. This term is also used in structural modeling to define how a cross-section is discretized into smaller, manageable fibres. for nonlinear analysis, where each fibre is assigned specific, non-linear stress-strain properties.
Fibre segment – It refers to a distinct, finite portion of a fibre located between two successive contact points or failure locations within a fibrous network or matrix (such as in fibre-reinforced metal matrix composites or steel fibre reinforced concrete). Fibre segments are identified as the length of fibre (or individual unit) which lies between two intersections with other fibres or between failure points caused by applied load.
Fibre show– It consists of strands or bundles of fibres which are not covered by plastic and which are at or above the surface of a composite.
Fibre size – It typically refers to the diameter, width, or thickness of the reinforcing fibres (such as carbon, glass, or metal fibres) used in fibre-reinforced metal matrix composites (MMCs). It is an important parameter influencing the reinforcement efficiency, stiffness, and overall mechanical strength of the resulting material. Fibre size is the average width or diameter of an individual fibre, normally measured in micro-meters or through linear density. In the case of non-circular cross-sections, it is frequently treated as the minor axis of an equivalent ellipsoid.
Fibre slippage – It refers to a failure mechanism in fibre-reinforced composite materials or reinforced structures where the reinforcing fibres (such as carbon, glass, or steel) slide relative to the surrounding matrix or each other rather than breaking.
Fibre span – It refers to the distance over which optical signals are transmitted in fibre optic networks, with typical span lengths ranging from 50 kilo-meters to 100 kilo-meters in terrestrial and submarine applications. Shorter fibre spans can improve the optical signal-to-noise ratio (OSNR) after transmission.
Fibre splitting – It refers to a failure mechanism in fibre-reinforced composite materials or specific metallic alloys, where the material develops long, longitudinal cracks parallel to the axis of reinforcement or rolling direction. It is a form of fracture where the material separates between fibres or along metallurgical grains. It frequently occurs due to excessive hoop stress (circumferential stress) exceeding the material’s strength, radial cracking, or shear stress in notched samples.
Fibre strain – It refers to the deformation or change in length experienced by a material line element (a fibre) along its axis within a component, normally in response to applied mechanical loads like tension, compression, or bending. It is typically the ratio of the change in length (dL) to the original length (L) of that fibre, frequently denoted by the Greek letter ‘epsilon’.
Fibre strength – It refers to the maximum tensile force or stress an individual fibre can withstand before breaking or undergoing catastrophic failure, frequently influenced by surface defects and flaw distribution. It is a critical metric for determining the durability and structural reinforcement capability of composite materials (e.g., metal matrix composites).
Fibre strength distribution – It refers to the statistical representation of how failure stress varies along a fibre because of random manufacturing defects. It is typically modeled using Weibull statistics, which show that stronger fibres are rarer and smaller samples or shorter lengths tend to be stronger than longer ones.
Fibre stress – It is the local stress through a small area (a point or line) on a section where the stress is not uniform, as in a beam under a bending load.
Fibre surface – It refers to the outer boundary, morphology, and micro-structure of a reinforcing fibre (metallic, ceramic, or carbon) which determines its interaction with the surrounding matrix in a composite material. This interface is important for bonding, as it governs how stress is transferred between the fibres and the matrix.
Fibre switch – It is also called fibre optic switch. It is a programmable optical device which selectively routes, blocks, or switches optical signals from one or more input fibres to one or more output. Unlike traditional electronic switches, it manages light signals directly without converting them into electrical signals first, ensuring low signal degradation and high speed.
Fibre system – It refers to the engineered incorporation of high-strength, slender, and flexible filaments (fibres) into a matrix material, normally metals, polymers, or ceramics, to improve its mechanical, physical, and thermal properties. Fibre systems are a subclass of composite materials designed to improve performance metrics such as tensile strength, stiffness, fatigue resistance, and crack management.
Fibre tenacity – It is a measure of a fibre’s tensile strength, defined as the breaking force divided by its linear density (mass per unit length). It represents the maximum stress a fibre can withstand before breaking, typically measured in grams per denier or centinewtons per tex. It is the specific strength of a fibre, frequently used since measuring the exact cross-sectional area of irregular fibers is difficult.
Fibre texture – It is a texture characterized by having only one preferred crystallographic direction.
Fibre transfer – It refers to the movement of fibres from one surface to another, occurring through direct contact (primary transfer) or subsequent indirect contact (secondary transfer). This process can result in substantial quantities of fibres being transferred, with the quantity decreasing with each successive transfer.
Fibre treatment – It refers to the processes applied to fibres after their formation, which can include drawing, twisting, texturing, coating, and thermal or chemical treatments, aimed at improving their properties, prolonging their life-span, and reducing environmental impact.
Fibre type – It refers to the classification of fibres used in cementitious composites, which can include steel, natural, polymeric, glass, and carbon fibres. These fibres affect the mechanical properties of the composites, with low strength fibres improving ductility and high strength fibres improving overall strength.
Fibre volume fraction (Vf) – It is the ratio of the volume of fibres to the total volume of a composite material to determine strength and stiffness (Vf = Vfibre/Vcomposite). It represents the proportion of load-bearing fibre against matrix, normally ranging from 30 % to 65 % in composites. It is an important parameter in micro-mechanical analysis to determine elasticity, strength, and expansion coefficients.
Fibre wash – It is the splaying out of woven or non-woven fibres from the normal reinforcement direction. Fibres are carried along with bleeding resin during cure.
Fibrous fracture – It is a gray and amorphous fracture which results when a metal is sufficiently ductile for the crystals to elongate before fracture occurs. When a fibrous fracture is got in an impact test, it can be regarded as definite evidence of toughness of the metal.
Fibrous material – It refers to a structural form composed of elongated, fine metallic filaments or fibres. These structures, created through drawing, melt spinning, or deposition, show exceptional high-strength-to-weight ratios, high-temperature resistance, and improved electrical conductivity, frequently used for structural, filtration, or reinforcing applications.
Fibrous nano-materials – These are 1D (one-dimensional) nano-structures, such as nano-tubes, nano-wires, or nano-fibres, which possess a fibre-like, high-aspect-ratio morphology, where the diameter of the fibre is typically less than 100 nano-meters. These materials are characterized by their thread-like structure (long length compared to diameter) and are intentionally engineered to show superior mechanical strength, electrical conductivity, or magnetic properties compared to their bulk metallic or ceramic counter-parts.
Fibrous scaffolds – These are porous structures fabricated from electro-spun nano-scale to micro-scale fibres, created by dissolving a polymer in an organic solvent and applying a high force electric field. They are frequently fabricated through electro-spinning polymers.
Fibrous structure – In forgings, it is a structure revealed as laminations, not necessarily detrimental, on an etched section or as a ropy appearance on a fracture. It is not to be confused with silky or ductile fracture of a clean metal. In wrought iron, it is a structure consisting of slag fibres embedded in ferrite. In rolled steel plate stock, it is a uniform, fine-grained structure on a fractured surface, free of laminations or shale-type discontinuities.
Fibrous tearing – It is a type of ductile failure characterized by a rough, dull, or fibrous appearance on the fracture surface. It occurs when a material undergoes substantial plastic deformation, leading to the nucleation, growth, and coalescence of internal microscopic voids or cavities.
Fickian diffusion – It refers to the process where the diffusive flux of a substance moves from areas of high concentration to areas of low concentration, with a magnitude proportional to the concentration gradient. This behaviour is described by Fick’s first law, which applies under the assumption of a steady state in an isotropic medium.
Fickian diffusion curve – It represents the concentration profile or mass transfer over time which obeys Fick’s laws, where flux is directly proportional to the concentration gradient. It typically shows a smooth, parabolic-like approach to equilibrium (saturation), indicating a constant diffusion coefficient.
Fickian model – It is a theoretical framework based on Fick’s laws of diffusion which describes the transport of atoms, molecules, or solutes within a material (solid, liquid, or gas) as a process driven by a concentration gradient. It is the fundamental model used to predict the redistribution of alloying elements, impurities, or dopants, assuming that the flux of atoms moves from areas of high concentration to low concentration, with a magnitude proportional to the concentration gradient.
Fick’s first law – It states that the steady-state diffusion flux (J) of atoms, the rate of mass transfer through a unit area, is directly proportional to the concentration gradient (dc/dx), moving from high to low concentration. The formula is J = -D dc/dx, where ‘D’ is the diffusivity (diffusion coefficient).
Fick’s law – It refers to two fundamental laws of diffusion which describe how diffusive flux is related to concentration gradients. The first law states that the diffusive flux is proportional to the negative gradient of concentration, while the second law provides a spatial-temporal relationship for diffusion based on changes in concentration over time.
Fick’s laws of diffusion – These laws define that the net movement of particles from high to low concentration is driven by a concentration gradient. First law describes steady-state flux, while the second law governs non-steady state, time-dependent concentration changes. In crystal structures, diffusion occurs through interstitial or vacancy (substitutional) mechanisms, where atoms jump between lattice sites, a process highly dependent on temperature.
Fick’s second law – It predicts how diffusion causes the concentration of a solute to change over time (non-steady-stat). It states that the rate of concentration change is proportional to the curvature of the concentration gradient, expressed as dC/dt = D (d-square C/dx-square), (assuming a constant diffusion coefficient D). It applies to non-steady-state diffusion, such as carburizing steel or alloy homogenization, where the concentration gradient changes. It models diffusion where the concentration profile changes with time, meaning the diffusion flux varies with position.
Fictitious configuration – It is a theoretical, undamaged state of a material used to quantify damage and plastic deformation. It represents the deformed geometry of a material without the effects of damage (such as micro-voids or micro-cracks) which have developed during deformation.
Fictitious domain methods – These are numerical simulation techniques used to analyze physical problems, such as heat transfer, stress analysis, or fluid-structure interactions, by embedding a complex-shaped physical domain (e.g., a non-spherical particle or casting part) into a simpler, larger computational domain (e.g., a rectangular box). This approach eliminates the need for body-conforming meshes, allowing simulations to run on simpler, fixed structured grids, which drastically reduces computational costs associated with mesh generation, particularly for moving boundaries or evolving geometries.
Fictitious load – It is an artificial, theoretical force applied to a mathematical model, typically finite element analysis (FEA), to simulate complex material behaviours, such as crack growth or crack closure, without requiring a fully non-linear, computationally intensive simulation. It is frequently used in combination with the ‘fictitious material concept’ (FMC), which allows engineers to treat ductile materials as fictitious brittle materials for simpler fracture analysis.
Fictitious material concept – It is a theoretical approach in fracture mechanics used to predict the load-bearing capacity and fracture toughness of ductile materials with notches or cracks. It acts as a converter which simplifies complex, non-linear elastic-plastic behaviour into a fictitious, linear elastic, brittle material model, allowing for easier, faster predictions of ultimate strength without needing complex, time-consuming nonlinear finite element analyses.
Fictitious node – It refers to a numerical point located outside the physical boundary of the material domain. These nodes are used to enforce boundary conditions, such as heat flux or symmetry, in scenarios where the physical boundary does not align directly with the mesh grid, frequently in fictitious domain methods or immersed boundary methods.
Fictitious play – It is a learning process in which players in a game adjust their strategies based on the observed actions of their opponents, ultimately converging towards Nash equilibria. It can be characterized in both continuous-time and discrete-time frameworks, with the continuous-time variant being referred to as continuous-time fictitious play.
Fidelity – It is the degree to which an instrument indicates the measure variable without dynamic error.
Fidelity measurement – It is the degree to which a system, model, or instrument reproduces an input signal or replicates real-world phenomena accurately without dynamic error. It quantifies how well the output resembles the input or true value, frequently measuring the absence of distortions, noise, or deviations, important in simulation, and data analysis.
Fiducials – These are precisely located, artificial reference points or marks on a component, such as a PCB (printed circuit board) or machinery, used by imaging systems to determine position, alignment, and orientation. They act as reference markers (frequently copper dots, crosses, or circles) for high-accuracy alignment during automated manufacturing, assembly, and 3D computer vision processes.
Field – It is a physical quantity (scalar, vector, or tensor) which assigns a specific value to every point in space and time, representing how a physical property, such as force or temperature, is distributed. It represents a region where forces like electromagnetism or gravity act on objects.
Field amplitude – It is the maximum displacement, magnitude, or strength of a wave (mechanical, electro-magnetic, or signal) measured from its equilibrium or reference position. It indicates the wave’s peak intensity, energy level, or signal strength and is typically positive, representing the distance from the baseline to the highest crest.
Field angle – It is the angle between the two directions (on opposite sides of the beam axis) where the light intensity drops to 10 % of the maximum intensity. It represents the total angular spread of a light source, including the main beam and peripheral ‘spill light’.
Field assessment – It is a practical, on-site evaluation of real-world conditions, equipment, or structures to gather data, verify performance, and identify deficiencies. It bridges design with reality, frequently involving inspections, testing (e.g., structural, geo-technical), and data gathering to ensure compliance with standards or to analyze failures.
Field assisted sintering technique – It is frequently called ‘spark plasma sintering’ (SPS). It is a rapid, pressure-assisted powder process which uses low-voltage, high-current direct current (DC) to heat conducting tools (normally graphite) and samples through Joule heating. It enables near-theoretical density in metals, ceramics, and composites within minutes, frequently resulting in reduced grain growth.
Field assumption – It is a foundational, frequently simplified, premise taken for granted to make complex modeling or analysis possible when exact data is missing or calculations are too complex. These, such as assuming rigid bodies or ignoring, are necessary, provisional simplifications which are to be validated later. Field assumptions provide structure to unknown variables, enabling project progress in early stages (e.g., assuming a specific material is homogeneous and isotropic).
Field boundary – It refers to setting precise limits, conditions, or physical edges for computational modeling (computational fluid dynamics, CFD / finite element analysis, FEA) or geographical mapping. It involves defining, for instance, wall surfaces and flow conditions in simulations or outlining, using satellite imaging, plot perimeters (e.g., hedge, fence).
Field boundary conditions – These are the specific, known values (Dirichlet), derivatives / fluxes (Neumann), or combinations (Robin) prescribed at the boundaries of a numerical model’s computational domain to simulate physical constraints. They are necessary to solve partial differential equations (PDEs) for CFD (computational fluid dynamics), electro magnetics, and structural analysis.
Fieldbus – It is a digital, serial, two-way communications system which interconnects measurement and control devices such as sensors, actuators and controllers. Additional intelligence can be embedded in field devices which can allow calibration and diagnostics and decentralized control. A fieldbus is a member of a family of industrial digital communication networks used for real-time distributed control. Fieldbus profiles are standardized by the International Electrotechnical Commission as IEC 61784/61158.
Field circuit – It is the electrical pathway providing excitation current (direct current) to the field windings of an electric machine, such as a generator, motor, or alternator, to create a magnetic field. It is responsible for establishing the magnetic flux necessary for conversion between electrical and mechanical energy.
Field classification – It is the visual and manual identification of materials (like soil or rock) conducted on-site to assess engineering properties such as texture, structure, and consistency. It provides a rapid ‘word picture’ for engineering logs, assisting with design, construction, and planning decisions without immediate laboratory testing. The purpose of the field classification is to quickly determine material behaviour (e.g., strength, permeability) and identify soil constituents which impact construction.
Field coefficient – It is a numerical, frequently dimensionless, constant which quantifies a specific property or relationship within a physical system, such as field transmission / reflection in electromagnetics or force interactions in fluid dynamics. It characterizes how a field, like an electromagnetic wave or pressure field, interacts with materials, boundaries, or structures.
Field coil – It is an electro-magnet used to generate a magnetic field in an electro-magnetic machine, typically a rotating electrical machine such as a motor or generator. It consists of a coil of wire through which a current flows.
Field computation – It is frequently referred to as computational electromagnetics (CEM) or field modeling. It is the numerical analysis and simulation of physical fields (such as electric, magnetic, or thermal fields) interacting with objects and the environment. It involves using computer programmes to solve partial differential equations (PDEs) or integral equations, such as Maxwell’s equations, to compute field distributions and their interactions.
Field core – It is a cylindrical sample of material, typically rock, soil, or asphalt, extracted from a structure or geological formation for laboratory analysis to determine its physical properties, such as porosity, permeability, strength, and age. These samples, frequently obtained using specialized drilling tools, provide ‘ground truth’ for calibrating field data (e.g., logging) and assessing material integrity.
Field curvature – It is also called Petzval field curvature. It is an optical aberration where a lens focuses a flat object onto a curved surface rather than a flat image plane. It causes an image to be sharp in the center but blurry at the edges, or vice-versa, since the sensor cannot align with the curved focal plane.
Field development – It is the structured, multi-disciplinary process of planning, designing, and executing the infrastructure required to extract hydrocarbons (oil / gas) from a reservoir after discovery. It bridges exploration and production, involving ‘front-end engineering design’ (FEED) to optimize well location, drilling, and processing facilities.
Field development option – It is the critical ‘front-end engineering design’ (FEED) phase where multiple technical concepts for producing oil or gas are generated, evaluated, and refined into a single, optimized, and financially viable development plan. It bridges appraisal and project execution to minimize risk and maximize NPV (net present value).
Field development plan – It is a comprehensive, multi-disciplinary document outlining the optimal technical and economic strategy to extract hydro-carbons from a reservoir. It bridges exploration and production, defining well requirements, surface facilities, infrastructure, and financial forecasts. It is important for securing project approval (final investment decision, FID) and maximizing returns through detailed studies.
Field devices – These are equipments which are connected to the field side on the integrated circuits. Types of field devices include remote thermal units (RTUs), programmable logic controller (PLCs), actuators, sensors, HMIs, and associated communications.
Field effect transistor – It is a transistor which relies on modulation of conductivity of a channel instead of injection of minority carriers as does a bipolar transistor.
Field emission – It is also called field electron emission. It is a quantum mechanical process where electrons are emitted from a solid surface (normally metal or semiconductor) into a vacuum, induced by a strong external electric field, typically at low or room temperature. It is distinct from thermionic emission since it does not need high temperatures to excite electrons.
Field emission gun – It is a high-performance electron source used in electron microscopy which produces an electron beam by applying a strong electrostatic field to a sharply pointed emitter, normally made of single-crystal tungsten. Unlike conventional thermionic guns which use high heat to release electrons, field emission gun (FEG) allows electrons to tunnel through the potential barrier at the tip, frequently referred to as ‘cold-cathode’ or auto-electronic emission, which provides superior brightness, a smaller beam diameter, and higher coherence.
Field-emission microscopy – It is an image-forming analytical technique in which a strong electro-static field causes emission of electrons from a sharply rounded point or from a sample which has been placed on that point. The electrons are accelerated to a phosphorescent screen, or photographic film, producing a visible picture of the variation of emission over the specimen surface.
Field emission scanning electron microscope – It is a high-resolution imaging tool which uses a field emission gun (FEG) to produce narrow, high-energy electron beams, resulting in superior surface topography images of materials at the nanoscale. It enables ultra-high-resolution imaging (frequently below 1 nano-meter) of conductive and insulating surfaces.
Field emission scanning electron microscopy – It is a high-resolution imaging technique which uses a field emission gun (FEG) to emit electrons, creating detailed, nano-meter scale images of surface morphology. Engineered for superior imaging compared to conventional scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM) operates under high vacuum to produce bright, focused electron beams, enabling 3D imaging, precise particle size analysis, and elemental characterization at low voltages.
Field enhancement – It is a phenomenon where electric or electro-magnetic fields are concentrated and amplified locally, creating ‘hot-spots’, because of the sharp geometries, plasmonic resonances, or dielectric contrasts. It is widely used to lower threshold voltages for electron emission and boost light-matter interactions at the nano-scale. It is defined as the ratio of the localized maximum electric field to the average applied electric field (field enhancement factor, FEF).
Field enhancement factor (B) – It is a dimensionless parameter defined as the ratio of the local electric field (Eloc) at a specific location (normally a sharp tip or protrusion) to the average macroscopic applied field (Emacro), expressed as ‘B = Eloc/Emacro. It quantifies how much a structure amplifies an external electric field, critical for field emission and vacuum electronics.
Field estimation – It is the process of predicting project quantities, costs, and time-frames before construction or development begins. It entails calculating materials, labour, and equipment needed, frequently using drawings, specifications, and historical data to ensure project feasibility, budget alignment, and to prepare for tenders. Field estimation determines the total cost of a project, assess material requirements for procurement, and establish a construction schedule.
Field evaluation – It is an on-site, real-world assessment of equipment, products, or systems to verify safety, performance, and compliance with standards. It involves on-site inspection and testing of uncertified, customized, or prototype products at their final installation site, providing an alternative to laboratory certification.
Field expansion – It typically refers to thermal expansion, where materials increase in volume, area, or linear dimensions because of the temperature rises. It is defined by a material’s coefficient of expansion, affecting structural integrity, and requires careful calculation of stress in constrained components. Field expansion also refers to the use of optical devices, such as prisms and mirrors, to increase peripheral field awareness in individuals with visual field loss, thereby aiding in efficient scanning and improving navigation safety.
Field factor – It is a specialized coefficient, frequently used in electrostatics (e.g., field ion microscopy), which modifies the relationship between voltage and the electric field strength at a sample’s surface, heavily dependent on the geometry and shank angle of a tip. It represents the ratio of the maximum electric field to the average field, with a value of 1 indicating no enhancement.
Field failure analysis – It investigates failures which at occur in operating environments rather than in controlled test conditions. It is used when a component fails in service and the failure is to be analyzed in context, incorporating actual operating conditions, load cycles, and environmental factors.
Field flattener – It is an optical lens, frequently a plano-concave lens, placed near the curved focal surface (image plane) of an imaging system, such as a telescope or microscope. Its function is to correct field curvature, ensuring that images are sharp and in focus across the entire flat detector surface, rather than only in the centre.
Field flow fractionation – It is an elution-based separation technique for macro-molecules and particles (1 nano-meter to 100 micro-meters) which uses an external field (e.g., flow, gravity, centrifugal) applied perpendicularly to a laminar flow in an open channel. It separates based on physico-chemical properties (diffusion, mass, density) without a stationary phase, reducing sample degradation.
Field flux – It is the measure of the total field (electric or magnetic) passing through a given surface, representing the intensity and flow of the field. It is defined as the surface integral of the normal component of the field, where maximum flux occurs when the surface is perpendicular to field lines.
Field gradient – It refers to the variation of the magnetic field with spatial position, typically described in three principal directions (Gx, Gy, Gz), which is generated by a set of gradient coils. This variation causes nuclei at different positions to experience slightly different magnetic fields, leading to distinct precessional frequencies which can be used to allocate spatial information for image reconstruction. Field gradient is the spatial variation or rate of change of a field, normally magnetic or electric, across a specific location. It represents the gradient of a potential, defining the direction of fastest increase and the rate of change. Gradient coils generate these variations.
Field image – It refers to the design, optimization, and processing of ‘light field’ (LF) images, high-dimensional data that records not only the intensity of light but also the direction of rays in free space. Unlike conventional 2D imaging, this approach focuses on capturing 4D data (two spatial dimensions x, y and two angular dimensions u, v) to enable post-acquisition manipulation, such as digital refocusing, depth estimation, and 3D scene reconstruction.
Field instruments – These are devices used in industrial automation and process control to measure, monitor, and control different process variables like pressure, temperature, flow, and level within a plant or industrial site away from control rooms. They are essential for gathering real-time data, enabling operators to maintain control and optimize processes. These instruments are physically located in the ‘field’, meaning they are directly connected to the process being controlled. Field instruments are made very sturdy and can withstand the harshest environments.
Field intensity – For electric fields (E), it is a vector quantity defined as the force (F) exerted per unit charge (q) on a stationary test charge placed at a specific point in that field. It represents the strength and direction of the electric field, measured in newtons per coulomb (N/C) or volts per meter (V/m).
Field investigation – It is the process of physically surveying, sampling, and testing soil, rock, and groundwater at a construction site to assess its geotechnical and environmental properties. It is important for determining safe, cost-effective foundation designs, preventing failures, and mitigating risks related to subsurface conditions, such as landslides or groundwater contamination.
Field ion microscopy (FIM) – It is an analytical technique in which atoms are ionized by an electric field near a sharp specimen tip, the field then forces the ions to a fluorescent screen, which shows an enlarged image of the tip, and individual atoms are made visible. It can be used to resolve the individual atoms on the surface of a solid. It can also be used to study the three-dimensional structure of a material since successive atom layers can be ionized and removed from the surface by field evaporation. The ions removed from the surface by field evaporation can be analyzed chemically by coupling to the microscope a time-of-flight mass spectrometer of single-particle sensitivity, known as an atom probe (AP). The range of applications of the field ion microscopy / atom probe technique has extended rapidly, and virtually all metals and semi-conductors can now be studied. Whenever atomic-scale information on the structure or composition of a material is necessary, this approach is required to be considered.
Field ionization – It is the ionization of gaseous atoms and molecules by an intense electric field, frequently at the surface of a solid.
Field maintenance – It refers to on-site, remote servicing of assets, including installation, preventive maintenance, repair, and modification, conducted away from the manufacturer’s or organization’s base. It involves troubleshooting equipment at the site of operation to maximize reliability and ensure functional restoration.
Field measurement – It is the process of acquiring direct, on-site data, such as dimensions, structural positions, or environmental conditions, at a construction or project site. It ensures design accuracy, validates theoretical models, and supports safe construction by comparing planned specifications with actual site conditions.
Field method – It refers to the procedures, instrumental techniques, and practices used to measure, collect data, and observe materials or phenomena in their natural, ‘in-sit’ environment rather than in a controlled laboratory setting. These methods are important for verifying structural performance, assessing environmental conditions, and monitoring systems in real-world scenarios.
Field model – It is a computational framework which defines and calculates continuous physical quantities, such as temperature, velocity, or material phase, across a domain, typically using partial differential equations. These models, like phase-field models, are necessary for simulating micro-structure evolution or material behaviour without tracking explicit interface boundaries.
Field monitoring data – It involves the systematic planning, collection, processing, and management of on-site measurements and observations. This data, frequently gathered through automated sensors or manual inspection (e.g., in civil, environmental, or manufacturing engineering), is crucial for evaluating real-world structural, environmental, or operational performance.
Field of view – It is the total diameter or area of a sample, such as a metal micro-structure, visible at any given time through an objective lens or on a screen. It is inversely proportional to magnification: higher magnification yields a smaller, more detailed field of view (FOV), while lower magnification shows a wider area.
Field operations – These refer to on-site tasks, installation, maintenance, and repair activities performed outside a central office or plant. These activities ensure technical, safe, and efficient project execution, involving field-based technicians, engineers, and crews who manage equipment, collect data, or deliver services at specific project locations.
Field-oriented control – It is also called vector control. It is a high-performance alternating current (AC) motor control technique which drives sinusoidal currents by decoupling stator current into two orthogonal components: magnetic flux and torque. By converting 3-phase AC (alternating current) motor currents into a DC (direct current)-like rotating reference frame (direct-quadrature frame, dq-frame) using Clarke and Park transformations, field-oriented control (FOC) provides precise, independent control of torque and flux, similar to a direct current motor. It is a control strategy for variable frequency drives which models the magnetic field of the motor to control it.
Field performance – It means performance of a device / equipment in its actual use.
Field-programmable gate array – It is an integrated circuit (IC) which can be programmed or reconfigured by a designer or end-user after manufacturing. In engineering, this reprogrammability provides a unique balance of custom hardware performance and design flexibility, distinguishing it from fixed-function chips like ‘application-specific integrated circuits’ (ASICs) or general-purpose processors.
Field-programmable gate array technology – It refers to a programmable and reconfigurable hardware device which allows the implementation of digital systems by programming the physical hardware itself, enabling the creation of different hardware components and functions using a hardware description language (HDL). Field-programmable gate arrays can be used for a range of applications, including prototyping and acceleration of specific functions within digital systems.
Field pulse – It is pulsed electric field (PEF). It is a non-thermal, high-voltage electrical treatment applied in short bursts (nano-seconds to milli-seconds) to induce electroporation in cell membranes. It is characterized by high amplitude, typically 100–300 volts per centimeters to 300 kilo-volts per centi-meter, creating intense power across the cell to improve membrane permeability.
Field separation – It is frequently referred to as force field or field-flow separation. It is a technique which uses an external force field, such as centrifugal, electric, magnetic, or thermal fields, acting perpendicular to a laminar flow stream to separate components of a mixture. Unlike methods which rely on phase changes (like distillation) or stationary phases (like chromatography), field separation acts directly on particles, macro-molecules, or colloidal particles based on their physical and chemical properties, causing them to move at different velocities.
Field separator – It is a specialized device, such as a pressure vessel or cyclone, designed to divide combined streams, typically oil, gas, and water, into individual components using gravity, density differences, or centrifugal force. These are important for processing, transportation, and equipment protection in several industries.
Field serviceable – An equipment is field serviceable when normal repair or replacement of operating parts can be accomplished in the field without returning to the manufacturer.
Field site – It is the physical location where construction, installation, maintenance, or surveying activities take place, directly where infrastructure is being built or equipment is operated. It is the ‘field’ where engineering designs and blueprints are translated into physical reality.
Field strength – It defines the magnitude of an electric or magnetic field vector, representing the intensity of force exerted on a unit charge or magnetic pole at a specific point. It quantifies how energy, such as radio waves, is transmitted or how magnetic materials are magnetized, measured respectively in volts per meter or amperes per meter.
Field studies – These studies involve gathering data in a natural setting rather than a controlled environment like a laboratory. They are a type of qualitative studies which that uses observation and interaction in real-world situations to understand phenomena as they occur naturally. A field survey, specifically, is a method within field studies which involves systematically gathering information through direct observation, interaction, and measurement in a specific location or area
Field survey – It is involves systematically gathering information through direct observation, interaction, and measurement in a specific location or area. It refers to the systematic investigation and study of rocks, minerals, and geological structures in their natural setting, frequently involving mapping, data collection, and analysis. It involves direct observation and measurement of geological features in the field, as opposed to laboratory-based studies.
Field test result – It is the data, metrics, or performance observations got by testing a product, material, or system in its actual, uncontrolled operating environment rather than a laboratory. These results validate real-world reliability, identify unexpected failures, and confirm design specifications.
Field tests – These are analytical tests which are normally carried out outside the laboratory, i.e., in the field. These tests refer refers to the process of testing and evaluating an application in real-world conditions outside of the controlled development environment. Field testing plays a key role since it allows the product to be evaluated in actual user settings. It uncovers performance issues, usability challenges, and compatibility gaps that controlled tests can miss. This helps make sure the product is reliable, user-friendly, and ready to handle different situations before it is launched.
Field uniformity – It refers to the spatial consistency of a field’s magnitude and direction (e.g., electro-magnetic, thermal, or fluid) within a specified volume or area. A uniform field maintains constant properties (strength and direction) across that space, ensuring consistent performance, such as uniform heating, illumination, or EMC (electro-magnetic compatibility) testing.
Field vane shear test – It is an in-situ geo-technical method used to directly measure the in-place undrained shear strength of soft to medium-stiff, saturated cohesive soils (clays). It is highly valued for its speed, portability, and ability to determine shear strength in undisturbed, natural states.
Field weakening region – it is the operational range of an electric motor above its base speed, where the motor speed is increased beyond rated capacity by reducing the magnetic field. It operates at constant power, where voltage remains at the inverter limit, while torque decreases and speed increases.
Field winding – It is the insulated current-carrying coils on a field magnet which produce the magnetic field needed to excite a generator or motor.
FIFO – It means ‘first in first out’. It is an inventory method which assumes the first goods produced / purchased are the first goods sold. It is an asset management and valuation method in which older inventory is moved out before new inventory comes in. The first goods to be sold are the first goods produced / purchased.
Figure of merit – It is a quantity used to characterize the performance of a device, system, or method relative to its alternatives, frequently used to assess the utility of particular materials or devices for specific applications.
Filament – It is a small, thin wire with two bigger wires holding it up in an incandescent light bulb. The filament is the part of the light bulb which produces light. Filaments are made of tungsten. Whenever an electric current goes through the filament, the filament glows. It is also known as the electron emitting element in a vacuum tube. To make the bulb produce more light, the filament is normally made of coils of fine wire, also known as the coiled coil. In case of composites, filament is the smallest unit of a fibrous material. It consists of the basic units formed during drawing and spinning, which are gathered into strands of fibre for use in composites. Filaments normally are of extreme length and very small diameter, normally less than 25 micrometers. Normally, filaments are not used individually. Some textile filaments can function as a yarn when they are of sufficient strength and flexibility.
Filamentary composite – It is a major form of advanced composite in which the fibre constituent consists of continuous filaments. Specifically, a filamentary composite is a laminate comprised of a number of laminae, each of which consists of a non-woven, parallel, uniaxial, planar array of filaments (or filament yarns) embedded in the selected matrix material. Individual laminae are directionally oriented and combined into specific multi-axial laminates for application to specific envelopes of strength and stiffness requirements.
Filamentary shrinkage – It is a fine network of shrinkage cavities, occasionally found in steel castings, which produces a radiographic image resembling lace.
Filament diameter – In 3D printing (fused deposition modeling, FDM / fused filament fabrication, FFF). It is the cross-sectional width of the thermoplastic material, typically standardized to 1.75 milli-meters or 2.85 milli-meters. It is a critical specification determined during extrusion and cooling, where consistency determines extrusion pressure, material flow, and overall part structural integrity.
Filament fibre -It is a continuous, long-strand fibre measured in meters or kilometers, rather than millimeters. These fibres are produced through extrusion (polymers) or reeling (silk), offering high strength and smooth texture, unlike short ‘staple’ fibers. They are either used singly (mono-filament) or gathered into bundles (multi-filament).
Filament lamp – It is an incandescent light source which produces visible radiation by heating a thin, coiled wire, normally tungsten, to high temperatures using electrical resistance (Joule heating). Typically enclosed in a vacuum or inert gas, it works on AC (alternating current) / DC (direct current), emitting a warm light but converting most energy to heat rather than light.
Filament source – it is a specialized component, frequently a thin tungsten wire, which produces electrons through thermionic emission or emits light / heat when energized by electric current, acting as a high-resistance cathode in vacuum tubes, lamps, or vapour deposition systems. It enables precise thermal control for applications like material coating, heating, or lighting.
Filament winding – It is a process for fabricating a reinforced plastic or composite structure in which continuous reinforcements (filament, wire, yarn, tape, and the like), either previously impregnated with a matrix material or impregnated during the winding, are placed over a rotating and removable form or mandrel in a prescribed way to meet certain stress conditions. Normally, the shape is a surface of revolution and may or may not include end closures. When the needed number of layers is applied, the wound form is cred and the mandrel is removed.
Filament-wound composite pressure vessel – It is a high-performance, light-weight pressure vessel constructed by winding resin-impregnated fibre strands (carbon fibre, fibre-glass, or Kevlar) onto a rotating mandrel or liner in a controlled helical or hoop pattern. Engineered for maximum strength-to-weight efficiency, they are normally used for high-pressure storage (e.g., hydrogen, oxygen) in several industries.
Filament, wrapping – It refers to a continuous filament strand which is wound around a core strand without receiving true twist, and can serve as matrix-forming filaments or fine yarns in composite materials, contributing to the structural integrity and protection of reinforcing fibres during processing.
Filar eyepiece – It is an eyepiece having in its focal plane a fiducial line which can be moved using a calibrated micrometer screw. It is useful for accurate determination of linear dimensions. It is also termed filar micrometer.
File – It is a hardened high-carbon steel, multi-point hand-cutting tool used to shape, size, smooth, or remove material from workpieces. Files remove material through abrasion, typically for precision work in fitting, workshop, or fabrication processes. Key types include flat, round, half-round, square, and triangular, categorized by length, shape, and cut. In computer, file is a digital unit of storage which contains information, such as documents, images, or application code, saved on a computer system. Files are stored on persistent storage devices like hard drives, allowing users to store and retrieve data. They are managed by the operating system and identified by a unique file-name.
File-button – It refers to a GUI (graphical user interface) element in CAD (computer aided design) or simulation software used to manage data, such as opening, saving, or creating new projects.
File extension – It is a suffix (normally 3-4 characters) added to a file-name, separated by a dot, indicating the file format and the application needed to open it. It identifies the data structure, allowing operating systems to associate files with specific CAD (computer aided design), analysis, or document software.
File hardness – It is the hardness as determined by the use of a steel file of standardized hardness on the assumption that a material that cannot be cut with the file is as hard as, or harder than, the file. Files covering a range of hardnesses can be used. The most common are files heat treated to around 67 HRC (Rockwell C hardness) to 70 HRC.
File menu – It is the main GUI (graphical user interface) component for managing project data, acting as a central hub for file operations. It enables creating, opening, saving, closing, importing, and exporting files / projects, ensuring proper data lifecycle management. It normally holds commands like New, Open, Save, Save As, and Print.
File pointer – It is a reference within an open file which indicates the position for the next read or write operation, moving forward by the appropriate number of bytes with each request. It can be repositioned using specific procedures to access different parts of the file.
File register – It is frequently referred to as a register file. It is an array of addressable, high-speed storage registers located within the central processing unit (CPU) or functional unit of a computer, acting as the top of the memory hierarchy. It stores temporary variables, operands, and intermediate results for immediate use by the ‘arithmetic logic unit’ (ALU).
Filiform corrosion – It is the corrosion which occurs under some coatings in the form of randomly distributed thread-like filaments.
Filing – It is a manual or mechanical material removal process, using a hardened steel tool with cutting teeth to shape, smooth, or finish parts, mainly for small-scale material removal, deburring, and precision fitting. It acts like a surface finish operation, removing excess material to achieve precise dimensions.
Filing button – It is a hardened, cylindrical, or shaped steel guide used to ensure precision, repeatability, and accuracy when filing a work-piece by hand, particularly for creating specific radii or profiles.
Fill – It is the yarn oriented at right angles to the warp in a woven fabric.
Fill density – It is the weight of a unit volume of powder, normally expressed as grams per cubic centimeter, determined by a specified method.
Fill depth – It is synonymous with fill height.
Filled cable – It is a cable design, common in telecommunications and power transmission, where the internal voids are filled with a substance to prevent moisture ingress or manage heat. Common types include jelly-filled cables (telecom) using petroleum jelly for moisture blocking and oil-filled cables (power) using pressurized oil for insulation.
Filled elastomer – It is a polymer matrix (rubber) reinforced with micro-scale or nano-scale filler particles (e.g., carbon black, silica) to improve mechanical properties like tensile strength, hardness, tear resistance, and wear resistance. These materials are designed to improve performance and lower costs, normally used in automotive tyres and industrial components.
Filled particle – It is frequently used in ‘discrete element modeling’ (DEM). It is a complex particle generated by filling an outer shell with smaller, typically spherical, particles to simulate specific shapes, aggregate morphologies, and mechanical behaviours. These assemblies are used to accurately model structural, wear, and flow properties.
Filled rubber – It is a composite material consisting of a vulcanized polymer matrix (elastomer) reinforced with inorganic filler particles, very frequently carbon black or silica. It is engineered to improve tensile strength, stiffness, and abrasion resistance beyond that of pure rubber, showing non-linear visco-elasticity under load.
Filled-system thermometer – It consists of a hollow metal bulb connected by a capillary tube to a device which responds to volume or pressure changes. The system is partially or completely filled with a liquid which expands with heat and contracts when cooled.
Filled thermal system – It is a thermal system filled with a gas and operating on the principle of pressure change with temperature change. The system is normally compensated.
Filled transformer – It is also called oil-immersed / liquid-filled transformer, It is a transformer whose core and windings are submerged in a dielectric fluid (typically mineral oil) within a tank, serving to insulate and cool the unit. These transformers are highly durable, efficient at heat dissipation, and common for high-voltage outdoor applications.
Filler – It is an inert, solid particulate or fibrous material added to polymer, rubber, or construction matrices to improve mechanical properties (strength, stiffness), modify processing characteristics (flow, viscosity), and reduce production costs. Sometimes the term is used specifically to mean particulate additives. It is also an inert foreign substance added to a polymer to improve or modify its properties. In lubrication, it is a substance such as lime, talc, mica, and other powders, added to a grease to increase its consistency or to an oil to increase its viscosity. In composites, filler is a relatively inert substance which is added to a material to alter its physical, mechanical, thermal, electrical, and other properties, or to lower cost or density. Fillers are categorized as functional (property improvement) or extenders (cost reduction), normally including minerals like calcium carbonate, silica, or fibre reinforcement.
Filler applications – These applications refer to the use of different fillers in materials, which are classified based on properties such as particle size, chemical composition, and mechanical properties, to improve performance and achieve specific characteristics in materials.
Filler block – It is a structural or semi-structural component used in construction (such as filler slabs) or material science to fill voids, reduce dead weight, and lower costs. These blocks, frequently made of clay, concrete, or foam, are placed between structural elements to improve efficiency, provide insulation, and reduce concrete usage.
Filler content – It is the proportion of inorganic or organic non-polymeric materials (solid particles, fibres, or powder) intentionally added to a matrix material, such as polymers, resins, coatings, or cement, to modify its physical, mechanical, or thermal properties and reduce fabrication costs.
Filler interaction – It refers to the complex physico-chemical, surface, and mechanical relationships between solid / particulate fillers and a binder or polymer matrix. It dictates the dispersion, reinforcement efficacy, and final performance (e.g., strength, stiffness, conductivity) of composite materials. Key interactions include surface adsorption, cluster formation, and filler-filler against. filler-polymer interaction.
Filler load – It refers to the quantity or proportion of solid, inert particulate or fibrous material incorporated into a polymer, composite, or mixture to modify its properties, improve processing, or reduce costs. It is frequently measured by weight or volume fraction, directly influencing viscosity and material performance.
Filler materials – These are substances added to plastics, composites, or matrices to improve mechanical / thermal properties, reduce production costs, or improve processing. These materials are also used in welding and brazing as filler metals (rods, wires, pastes) to fill gaps between parts, creating strong, cohesive joints.
Filler metal – It is a metal or alloy added during welding, brazing, or soldering to fill the gap between two work-pieces, forming a solid joint upon cooling. It is important for providing structural integrity, filling joint gaps, and offering specific properties like corrosion resistance, frequently selected based on base metal compatibility.
Filler network – It is a microscopic or macroscopic 3D, interconnected structure of filler particles dispersed within a matrix (frequently polymers or rubber). It forms a continuous percolating pathway which considerably improves mechanical properties (modulus, reinforcement), electrical conductivity, and thermal stability when a critical concentration is exceeded.
Filler particles – These are solid, inorganic or organic additives incorporated into polymers, cements, or resins to improve engineering properties, such as stiffness, strength, and thermal stability, or to reduce material costs. They are classified by shape (spherical, platelet, fibrous) and improve performance through interfacial bonding with the matrix. These particles are mainly used to improve mechanical properties (modulus, hardness, toughness), provide UV (ultra-violet) protection, or act as an extender to lower costs. Common fillers include calcium carbonate, talc, silica, mica, carbon black, and fly ash.
Filler particulates – These are solid, non-fibrous particles (spheres, flakes, or irregular shapes) added to polymers, rubbers, or composites to improve stiffness, hardness, wear resistance, or thermal conductivity, and to reduce material costs. They strengthen composites by sharing loads, with particle size and surface chemistry critical for reinforcing properties. These are normally particles with low aspect ratios (1:1), distinct from fibrous fillers, frequently smaller than 100 nano-meters for high-reinforcement rubbers (e.g., carbon black, silica).
Filler ply – It is an additional layer of material (such as fibre-glass, carbon fibre, or kevlar) inserted into a laminate stack to bridge gaps, fill voids, or increase local thickness. It is used to maintain smooth surface contours when joining parts of different thicknesses or to fill empty spaces created by complex geometries. The main purpose is to fill areas where structural plies cannot fully cover the tool or to transition smoothly between different thicknesses. Filler plies are typically placed in the middle of a stack, not on the surface.
Filler rod – It is a metallic wire, frequently in stick or rod form, used in welding (particularly tungsten inert gas, TIG / Gas tungsten arc welding, GTAW and oxy-fuel) to add filler metal into a joint, bridging gaps between base metals to create a strong, durable, and cohesive weld. Filler rods are normally composed of ferrous or non-ferrous alloys, frequently containing higher levels of deoxidizers to reduce oxidation and improve joint strength. These rods provide reinforcement, prevent cracking (especially in alloys), and fill gaps, ensuring the weld is not weaker than the base material.
Filler surface – It refers to the interfacial boundary of solid particles (e.g., minerals, silica, fibres) which contacts a polymer matrix. It acts as the critical interface for adhesion and stress transfer, where larger surface areas typically enable better reinforcement, mechanical property improvement, and modified rheological behaviour. The surface facilitates interaction between the filler and the polymer, directly affecting the composite’s stress-strain transmission, stiffness, and overall mechanical performance. Filler surfaces are frequently coated (e.g., with stearate or coupling agents) to improve dispersion, alter wettability, and improve the interphase region properties. Higher specific surface areas improve interfacial contact, leading to more efficient stress transmission, but can also increase viscosity and affect processing.
Filler system – It refers to the comprehensive integration of solid additives, particulate, fibrous, or functional, into a base matrix (such as plastics, rubber, cement, or composites) to modify physical, mechanical, or thermal properties, reduce raw material costs, or improve processing characteristics. These systems are engineered to achieve specific performance targets, such as increased stiffness, wear resistance, or thermal conductivity, rather than merely acting as cheap extenders.
Filler volume fraction (Vf) – It is the ratio of the volume of filler particles (Vfiller) to the total volume of a composite material (Vtotal), defined as Vf = Vfiller / Vtotal. It is a dimensionless quantity ranging from 0 to 1, important for determining the mechanical, thermal, and rheological properties of polymer composites, asphalt, and concrete. Frequently expressed as a percentage or fraction, it helps tailor properties like stiffness, strength, and toughness by controlling how much reinforcing agent is added. High filler volume fractions normally increase the modulus (stiffness) but can decrease tensile strength if poor bonding exists between particles and the matrix.
Filler wire – It is a is a consumable material, typically in the form of a wire, rod, or cored electrode, added to the joint area during welding, brazing, or soldering. It is used to bridge the gap between two pieces of base metal, melting along with them to form a cohesive, solid joint.
Fillet – It is a concave corner piece which is normally used at the intersection of casting sections. It is also the radius of metal at such junctions as opposed to an abrupt angular junction. Fillet is also a radius (curvature) imparted to inside meeting surfaces. In composites, fillet is a rounded filling or adhesive which fills the corner or angle where two adherends are joined.
Fillet geometry – It refers to the shape and dimensions of fillets in bonded joints, which influence the stress distribution and fatigue behaviour, with larger fillet radii normally resulting in improved fatigue strength and crack initiation life.
Fillet radius – It is a rounded, concave transition between two intersecting surfaces, typically used to strengthen metal parts and reduce stress concentrations. It eliminates sharp interior corners which act as fatigue crack initiators, improving structural integrity and longevity. Fillets are necessary in casting, welding, and machining to facilitate smoother material flow and tool access.
Fillet radius ratio – It is a dimensionless parameter defined as the ratio of the radius of a fillet (r), the curved transition at a corner, to a characteristic dimension of the component, such as the thickness (t) of the material or the diameter (d) of a shaft.
Fillet weld – It is a weld of approximately triangular cross section joining two surfaces approximately at right angles to each other in a lap joint, T-joint, or corner joint.
Fillet weld break test – It is a test in which the sample is loaded so that the weld root is in tension.
Fillet weld leg – It is the distance from the joint root to the toe of the fillet weld.
Fillet weld size – For equal leg fillet welds, it is the leg lengths of the largest isosceles right triangle which can be inscribed within the fillet weld cross section. For unequal leg fillets, it is the leg lengths of the largest right triangle which can be inscribed within the fillet weld cross section.
Fillet weld throat – It is the minimum distance minus any convexity between the weld root and the face of a fillet weld.
Fill factor – It is the quotient of the fill volume of a powder over the volume of a green compact after ejection from the die. It is the same as the quotient of the powder fill height of the compact over the height of the compact. It is the inverse parameter of compression ratio.
Fill height – It is the distance between the lower punch face and the top plane of the die body in the fill position of the press tool.
Filling algorithm – It is a computational method used to identify and populate the interior of a region within a multi-dimensional space, such as a 2D image, a 3D mesh, or a network topology.
Filling depth – It refers to the vertical distance from the final, designed surface level down to the original ground surface (or base level), indicating the quantity of material (soil, rock, waste) needed to raise low-lying land, fill excavations, or construct embankments, typically measured in units of distance.
Filling materials – These are solid, semi-solid, or particulate substances, such as soil, sand, gravel, or specialized aggregates, used to raise land levels, fill voids, backfill excavations, or improve material properties (e.g., strength, density, cost-reduction) in construction and manufacturing. These materials are to be compacted to ensure structural stability.
Filling station – It is a facility designed for the safe storage and retail dispensing of motor fuels (gasoline, diesel) and lubricants. Technically, it includes underground storage tanks (USTs), piping systems, vapour recovery systems, and calibrated dispensing pumps, frequently needing environmental and fire safety engineering controls to manage volatile liquids.
Filling yarn – It is the transverse threads or fibers in a woven fabric. Those fibers running perpendicular to the warp. It is also called weft.
Fill position – It is the position of the press tool which enables the filling of the desired quantity of powder into the die cavity.
Fill ratio – It is the ratio of the volume of loose powder in a die to the volume of the compact made from it.
Fill shoe – It is the part of the powder feed system which delivers the powder into the die cavity.
Fill volume – It the volume which a powder fills after flowing loosely into a space which is open at the top, such as a die cavity or a measuring receptacle.
Film – It is a thin, not necessarily visible, layer of material.
Film adhesive – It is a high-performance, solid, B-staged (partially cured) structural adhesive sheet, frequently reinforced with a carrier, which activates under heat and pressure to join materials. It eliminates mixing, provides consistent bond line thickness, and offers superior strength for demanding applications in composites. It is a synthetic resin adhesive, normally of the thermosetting type, in the form of a thin, dry film of resin with or without a paper or glass carrier.
Film badge – This photographic film is a type of dosimeter used for the measurement of ionizing radiation exposure for personnel monitoring purposes. The film badge can contain two or three films of differing sensitivities, and it can also contain a filter which shields part of the film from certain types of radiation.
Film blowing – It is also called blown film extrusion. It is a plastics engineering process which converts thermoplastic resin into thin, tubular films by melting the material, extruding it through an annular die, and inflating it into a continuous ‘bubble’ with air. The tube is stretched biaxially, cooled by air rings, collapsed, and wound, normally used for bags and packaging.
Film-boiling process – It is a quench-cooling process where a hot metal surface, typically over 1,000 deg C in industrial operations, is immersed in a liquid coolant (water, polymer, oil), forming a continuous, stable insulating vapour blanket. This vapour layer reduces the heat transfer rate since the vapour has considerably lower thermal conductivity than the liquid, leading to a slow, uniform cooling stage known as the ‘film boiling regime’ or ‘Leidenfrost point’.
Film boiling regime – It is a boiling process where a continuous vapour film blankets the heating surface, preventing direct contact between the liquid and the surface, which leads to high surface temperatures and the potential for equipment damage. This regime occurs when the heat flux exceeds the critical heat flux (CHF) limit, resulting in an important thermal excursion.
Film casting – It is a manufacturing process used to create thin, uniform polymer films by extruding molten material through a slot die onto a cooled rotating chill roll or by coating a solution onto a substrate, followed by solidification. It produces high-clarity, high-precision plastic sheets for packaging and coating.
Film casting method – It refers to techniques for forming polymer films, with doctor blade and slot die casting being main methods. Slot die casting is particularly noted for its ability to produce uniform films on a moving substrate at a constant velocity, allowing for flexibility in film thickness and high-speed processing.
Film coefficient – It is also known as the convective heat transfer coefficient. It is a parameter which quantifies the rate of heat transfer between a solid surface and a fluid (liquid or gas) per unit area, driven by a temperature difference. It represents the effectiveness of convection.
Film coefficient of heat transfer – It is also known as the convective heat transfer coefficient. It is a measure of the rate of heat transfer between a solid surface and a fluid (liquid or gas) per unit area per unit temperature difference. It quantifies the efficiency of convective heat transfer, representing the thermal resistance of a stagnant or laminar boundary layer of fluid adjacent to the surface.
Film condensation – It is a heat transfer process where vapour contacts a cold, wetted surface and transitions to liquid, forming a continuous film. This film acts as an insulating layer, reducing heat transfer efficiency compared to dropwise condensation. It is normally used in industrial condensers since it is stable and predictable, with analysis typically based on Nusselt’s theory.
Film cooling – It is a high-temperature metallurgical technique where coolant gas (such as air) is injected through discrete holes or slots onto the surface of components like turbine blades. This creates a thin, protective boundary layer which insulates the material from hot gases, improving durability and preventing structural fatigue.
Film density – It is defined as a key property of deposited films that influences various characteristics such as electrical resistivity, index of refraction, and mechanical deformation. It is affected by factors like the angle-of-incidence of depositing particles and energetic particle bombardment, which can enhance surface coverage and reduce porosity. Film density also defines the mass per unit volume of a deposited material, frequently indicating porosity or quality.
Film extrusion – It is a continuous polymer processing technique which converts thermoplastic resin into thin, flexible films by melting, extruding through a die, and cooling, normally used for packaging, and industrial coatings. It involves creating a homogeneous melt (frequently using high-density poly-ethylene, Low-density polyethylene, or linear low-density polyethylene), followed by either blown film extrusion (inflating a bubble) or cast film extrusion (using chill rolls) to determine final thickness and mechanical properties.
Film growth process – It refers to the methods by which thin films are formed on substrates, mainly categorized into three modes namely Volmer–Weber (island growth), Frank–Van der Merwe (layer-by-layer growth), and Stranski–Krastanov growth, each characterized by distinct bonding behaviours between the deposited material and the substrate.
Film heat transfer coefficient – It is also called the film coefficient or heat transfer coefficient. It, is a measure of the rate of heat transfer between a fluid and a solid surface. It represents how much heat flux (in watts per square meter) is generated by a unit temperature difference (in Kelvin) between the fluid and the surface, with units of watts per square meter-kelvin. Factors like fluid velocity, viscosity, and surface geometry all influence this coefficient, with higher velocities and viscosities generally leading to higher coefficients.
Film layer – It is a thin, continuous material sheet, ranging from nano-meters to micro-meters, applied to a substrate for protective, functional, or decorative purposes. Engineered films often consist of multi-layers (polymers, organics, or inorganics) designed to improve properties like barrier resistance, optical traits, or adhesion.
Film materials – These consist of thin, flat layers of material, ranging from nano-meters to micro-meters, applied to a substrate, designed for specialized mechanical, electrical, optical, or barrier functions. These materials, including polymers, metals, and ceramics, are engineered for high transparency, low electrical resistance, and high-temperature resistance.
Film module – It typically refers to a photo-voltaic (solar) panel constructed by depositing thin layers of semiconductor materials, e.g., cadmium telluride (CdTe), copper-indium-gallium-diselenide (CIGS), and amorphous silicon (a-Si), onto a substrate. These modules are characterized by their flexibility, light weight, and high temperature performance compared to traditional silicon.
Film orientation – It is the process of stretching polymer films (during or after extrusion) to align molecular chains in specific directions, machine direction (MD) or transverse direction (TD), improving mechanical properties like tensile strength, stiffness, and barrier performance. This induces anisotropy, increasing toughness while reducing elongation and permeability.
Film plane – It is also called sensor plane. It is the exact, flat surface inside a camera where light is focused by the lens onto the recording medium (film or digital sensor). It is perpendicular to the optical axis and acts as the crucial reference point for focusing and measuring, frequently marked externally on the camera body with a ‘phi’ symbol.
Film preparation – It is defined as the process of applying a thin, functional layer of material (typically ranging from a few nano-meters to several micro-meters) onto a substrate to modify its physical, chemical, mechanical, electrical, or optical properties. It is a key surface engineering technique used in electronics, optics, and packaging to create uniform layers with specific functionalities.
Film resistance – It is the electrical resistance which results from films at contacting surfaces, such as oxides and contaminants, which prevent pure metallic contact.
Film resistor – It is a fixed-value, passive electrical component created by depositing a thin, conductive, or resistive film (metal, metal-oxide, or carbon) onto an insulating ceramic or glass substrate. These resistors are engineered for precision, low noise, and stability, with resistance values controlled by cutting a helical path into the film.
Film rupture – It refers to two main phenomena namely the breakdown of a protective surface oxide film (often in corrosion) or the thinning and breaking of a thin liquid film. It typically occurs when stress, creep, or destabilizing forces (like van der Waals forces) exceed the stability of the film, leading to exposure of underlying materials or dewetting. Film rupture is the breakdown of protective layers along grain boundaries or low-index crystallographic planes due to slip bands crossing the crack tip, leading to dissolution until repassivation occurs. This process allows for increased flow of solvent and solvated ions at the crack tips, preventing dissolution from being inhibited by corrosion products.
Film, silicon – It is a material which can be deposited using plasma chemical vapour deposition (CVD), allowing for the formation of large area junctions on different surfaces, including curved ones, through the incorporation of impurity gases during the deposition process.
Film silicon modules – These refer to photo-voltaic systems which utilize thin-film silicon technology, characterized by their versatility in producing both rigid and flexible modules, high energy yield, and superior performance at high temperatures. These modules are applicable in different settings, including consumer products, building-integrated photo-voltaics, and remote area power systems.
Film silicon solar cells – These are thin film silicon solar cell. These are second-generation, low-cost photo-voltaic devices created by depositing thin layers (1 micro-meter to 2 micro-meters) of silicon, typically amorphous silicon (a-Si) or micro-crystalline silicon (mc-Si), onto substrates like glass, metal, or plastic through chemical vapour deposition (CVD). Unlike rigid wafer cells, they offer flexibility, lower material consumption, and suitability for large-area manufacturing, though they generally have lower efficiencies (6 % to 8 %) than traditional, thicker mono-crystalline silicon cells.
Film solar cells – These are photovoltaic cells produced at low cost by utilizing an additive deposition process on top of a low-cost substrate, but they normally show lower efficiency compared to bulk cells because of limited solar spectrum absorption and higher non-radiative recombination rates.
Film strength – It is the relative resistance of a bisque to mechanical damage. It is an imprecise term denoting ability of a surface film to resist rupture by the penetration of asperities during sliding or rolling. A high film strength is mainly inferred from a high load-carrying capacity and is seldom directly measured.
Film technology – It refers to the design, synthesis, and application of thin (nano-meters to micro-meters) or thick material layers onto substrates to alter surface properties, create micro-structures, or fabricate electronic / optical components. It involves additive manufacturing techniques like vacuum deposition (physical vapour deposition / chemical vapour deposition) or printing, normally used in semiconductor manufacturing, coating, and micro-electro-mechanical systems (MEMS).
Film theory – It is also called Whitman’s two-film theory. It models mass transfer between phases by assuming a stagnant, thin film at the interface where resistance is concentrated. It simplifies complex turbulent transfer by treating it as molecular diffusion across this boundary, critical for designing absorbers and strippers. The theory emphasizes that most resistance to mass transfer arises from the liquid films rather than from the well-mixed bulk phases. It posits that while the bulk phases are well-mixed, the area at the interface consists of a thin, stagnant layer (film). All resistance to mass transfer is assumed to exist within this thin film, rather than the bulk phases.
Film thickness – In a dynamic seal, it is the distance separating the two surfaces which form the main seal.
Film uniformity – It is the consistency of a thin film’s physical or chemical characteristics, mainly thickness, but also composition or electrical properties, across a substrate surface and between different manufacturing runs. It is important for semiconductor, optical, and coating applications, where variations in thickness can lead to device failure.
FILO principle – It means ’First In, Last Out’ i.e., the first object or item in a stack is the last object or item to leave the stack. It is a storage method in which the most recently received stock is used first. This means that the newest products are sold or consumed first, while the older stock remains in the warehouse for longer.
Filter – It a substance with pores through which a gas or liquid is passed to separate out floating matter. It is also a device containing a filter. In photography, it is a transparent material (as coloured glass) which absorbs light of some wave-lengths and is used to change light. In electrical engineering, it is a circuit which selectively alters a signal based on its frequency components. In powder metallurgy, metal filters are porous products made either from wires and fibres or from sintered powders. In microscopy, filter is a semi-transparent optical element which is capable of absorbing unwanted electro-magnetic radiation and transmitting the remainder. A neutral density filter attenuates relatively uniformly from the ultra-violet to the infra-red, but in several applications highly wave-length-selective filters are used.
Filterability – It defines a fluid’s ability to pass through a filter medium without causing rapid blockage or excessive pressure drop. It is an interactive property between a suspension and a filter, important for determining operational efficiency and maintaining high flow rates (permeability) while ensuring a clear filtrate.
Filter aid – It is a solid, porous particle agent used to improve filtration by forming a permeable, incompressible lattice structure (filter cake) which traps solids and prevents blinding of the filter septum. These inert materials, such as diatomite or perlite, increase porosity and permeability, allowing high-speed filtration of slimy or fine solids while maintaining high flow rates.
Filter ash – It is fine, inorganic, particulate residue captured within filtration systems (such as bag filters or electro-static precipitators) during industrial combustion or gasification. Formed from fuel impurities, it is smaller in particle size than bottom ash, frequently containing heavy metals, calcium, zinc, and magnesium compounds.
Filter bandwidth – It is the range of frequencies a filter passes with minimal attenuation, typically defined as the difference between the upper (Fh) and lower (Fl) cut-off frequencies where the signal power drops by 3 dB (50 % power) relative to the centre frequency, expressed as ‘BW = Fh – Fl’. This specifies the passband width and determines the data rate or frequency range a system processes.
Filter bank – It is an array of band-pass filters in digital signal processing (DSP) which separates an input signal into multiple frequency sub-bands, or recombines them, using analysis and synthesis stages. It enables efficient sub-band processing, such as in compression, feature extraction, or multi-rate systems, frequently achieving perfect reconstruction of the original signal.
Filter bed – It is a structure within a granular bed filter where filtration media, such as silica sand or granules, captures dust and particles from a flowing gas, leading to the formation of a dust cake which improves filtration efficiency.
Filter cake – It is the accumulated, compacted solid residue which remains on a filter medium (such as a cloth or screen) after a slurry, a mixture of solid particles and liquid, has been subjected to filtration or dewatering. It is the main end product of industrial dewatering processes, designed to separate valuable minerals or metal concentrates from water, or to remove waste materials from process solutions.
Filter candle – It is a rigid, cylindrical, and porous filtration element, typically made of ceramic, sintered metal, or specialized alloys, designed to remove fine solid particles from liquid slurries or hot gas streams, frequently operating in high-temperature or highly corrosive environments. In metallurgical processing, these candles are used for clarifying solutions, recovering valuable materials (like precious metal catalysts), and gas cleaning at temperatures up to 1,000 deg C.
Filter capacitor – It is a filter capacitor is a passive electronic component designed to remove unwanted alternating current (AC) ripples or noise from a direct current (DC) signal, typically in power supply rectifier circuits. By functioning as a reservoir of electrical energy, it charges during voltage peaks and discharges during dips, smoothing the pulsating DC into a stable, continuous voltage. It smooths the direct current voltage produced by a rectifier stage.
Filter capacity – It is the total volume of fluid (liquid or gas) a filter can process before needing replacement, cleaning, or when the pressure drop exceeds a specified limit. It is frequently measured as dirt-holding capacity (for depth filters) or by the rate of solids collected (cake formation).
Filter chamber – It is frequently referred to as a chamber filter press or recessed plate filter. It is a specialized, batch-operated filtration unit used to separate solid particles from metallurgical slurries, such as iron, alumina, or mineral processing tailings. It consists of an enclosed space created between adjacent, recessed filter plates covered by filter cloth.
Filter circuit – It is an electronic circuit designed to pass specific signal frequencies while blocking or attenuating others. In power supply applications, filter circuits are used to remove AC (alternating current) ripple from rectified, pulsating DC (direct current) output to create a smooth, stable direct current voltage using components like inductors, capacitors, and resistors.
Filter cloth – It is a specialized, porous medium, typically woven or non-woven fabric, designed to separate solid particles from liquids (slurries) or gases, mainly for mineral processing, ore washing, tailings treatment, and smelting. It acts as the main barrier in filtration equipment such as filter presses, disc filters, and vacuum belt filters, enabling the recovery of valuable metals while treating waste-water.
Filter coefficient – It is a measure of the efficiency of a filter medium in capturing inclusion particles or impurities from a molten metal stream (such as molten aluminum or steel). It quantifies the likelihood of a particle being trapped as it passes through the filter material. The filtration coefficient indicates how easily fluid passes through a material or, conversely, how efficiently the filter removes particles from the fluid. It is important for characterizing the performance of metal filters, particularly in removing inclusions from liquid metals.
Filter cutoff frequency – it is also called corner frequency. It is the boundary point in a system’s frequency response where the filter begins to considerably attenuate (reduce) an input signal. It is typically defined as the frequency where the power output drops to half (around 3 decibels down) of its maximum passband power. The point distinguishing the pass-band (allowed frequencies) from the stop-band (rejected frequencies). It marks the frequency where the output voltage drops to around 70.7% of the pass-band amplitude.
Filter design – It refers to the process of creating devices or mediums to remove inclusions, impurities, and slag from molten metal during casting. The main goal is to improve the purity, mechanical properties, and structural integrity of the final cast metal by refining the flow and filtering out infusible impurities. It is also the process of creating digital filters by specifying their characteristics, utilizing various methods such as Kaiser window and Butterworth, as well as employing graphical user interfaces to analyze and modify filter parameters like poles and zeros in the complex plane.
Filter design problem – It involves developing a system to separate solid particles from a liquid or gas (slurry / aerosol) by creating a, high-efficiency, durable barrier which minimizes fluid flow resistance. It is an optimization challenge that balances filtration efficiency (retention of particles) with permeability (throughput), while ensuring the filter medium survives the physical and chemical environment.
Filter drum – It is also called ‘rotary vacuum drum filter’ (RVDF). It is a continuous solid-liquid separation device. It consists of a large, perforated cylindrical drum, partially submerged in a slurry trough, covered with filter media (cloth, metal mesh) and connected to a vacuum system. As the drum rotates, a vacuum pulls the liquid through the filter media, while solids form a ‘filter cake’ on the outer surface, which is subsequently scraped off.
Filtered arc – It is also called filtered cathodic vacuum arc (FCVA). It is a physical vapour deposition (PVD) coating technique which uses magnetic fields to guide ionized plasma from an electric arc source while filtering out neutral macro-particles. This process produces high-quality, dense, and defect-free thin films (e.g., diamond-like carbon) suitable for high-value engineering applications like semi-conductors and micro-electro-mechanical systems (MEMS).
Filtered cathodic arc – It is a physical vapour deposition (PVD) technique which uses a magnetic field to guide ionized plasma from a cathodic arc source to a substrate while filtering out large, neutral particles (macro-particles). It produces highly dense, smooth, and high-purity coatings, notably diamond-like carbon (DLC) / tetrahedral amorphous carbon (ta-C).
Filtered image – It is an output created by modifying an original image’s pixel values to reduce noise, improve features, or remove unwanted artifacts using mathematical operations. It involves applying a kernel (mask) to convolve the image, modifying local pixel intensity based on its neighbourhood.
Filtered signal – It is a signal which has been processed to remove, attenuate, or reduce unwanted frequency components, noise, or artifacts. By applying filters (analog or digital), the signal’s quality is improved to isolate desirable information for improved accuracy and reliability in applications such as signal processing, control systems, and electronics. Its purpose is to extract desired signal components or to suppress unwanted noise.
Filtered surface – It refers to a, normally, planar medium designed to separate solids from fluids by trapping particles on its surface, frequently forming a filter cake, while allowing filtrate to pass. These surface filters (e.g., screens, meshes) are ideal for removing large particles and protecting downstream processes, often requiring back-washing.
Filter effect – It refers to the mechanism by which molten metal filters (typically ceramic foam or mesh) remove impurities, mainly non-metallic inclusions like oxides, slags, and carbides, from the melt before it solidifies into a casting. The effect is fundamentally a combination of physical and mechanical separation techniques designed to improve the cleanliness and mechanical properties of the final casting.
Filter efficiency – It measures the ability of a filter medium to capture contaminants (like inclusions, slag, or dross) from molten metal, expressed as the percentage of particles retained compared to those which enter. It is important for improving metal purity, reducing porosity, and ensuring the mechanical properties of castings. The filter efficiency (E) is frequently expressed as the percentage of particles of a given size removed from the fluid ‘E = [(C0 – C1)/C1] x 100 %’, where ‘C0’ is the contaminant concentration upstream (before) and ‘C1’ is the concentration downstream (after).
Filter elements – These are the core, removable, and replaceable parts of a filtration system which contain the actual media responsible for trapping and removing solid impurities or inclusions from molten metal, gases, or liquids. While the filter housing provides structure, the element does the active filtering. Filter elements remove inclusions (slag, oxide films) from molten metal or particles from industrial fluids, improving casting quality and preventing machinery damage. Ceramic foam filter elements are inter-connected cellular structures (frequently alumina, zirconia, or silicon carbide) are used mainly for filtering aluminum, iron, and steel castings. Porous metal / sintered filter elements are robust, porous structures made from sintered stainless steel, nickel, or bronze, used for high-temperature and high-pressure applications. Woven wire mesh filter elements are stainless steel mesh, frequently pleated to increase surface area, and are used for re-usable, fine filtration. Bag / candle filters are cylindrical or bag-shaped elements which are used for cleaning hot gases in metallurgical processing (up to 1,000 deg C). Performance metrics for filtering elements efficiency is measured by particle separation efficiency (frequently 99 % or higher), differential pressure, and dirt-holding capacity.
Filter fabric – It is also called filter cloth. It is a porous, flexible medium, typically made of woven or non-woven synthetic fibres, glass fibres, or metal mesh, used to separate solid particles from liquids (slurries) or gases. It acts as a permeable barrier which retains solid materials (filter cake) while allowing the fluid to pass through. It is used in filter presses, pressure filters, and vacuum filters to dewater mineral slurries and separate valuable metals from waste. It is used in high-temperature gas cleaning to capture particulate emissions during smelting and roasting processes. It is frequently made from high-strength synthetic materials like poly-propylene, polyester, nylon, or special materials like PTFE (poly tetra-fluoro-ethylene, Teflon) to resist strong acids, alkalis, and high temperatures.
Filter form – It is a porous component designed to remove non-metallic inclusions, slag, dross, and gases from molten metal streams, improving the quality of the final casting. These filter forms operate under high temperatures and are important in ensuring the structural integrity of alloys, particularly aluminum and steel. Key types of filter forms are ceramic foam filters, sintered metal filters, and filter medium.
Filter function – It is a mechanical or physical unit operation used to separate solid particles (inclusions) from a fluid phase (liquid metal or gaseous effluent) by passing the mixture through a porous material or medium. The filter medium retains the unwanted solids, allowing the purified fluid to pass through, resulting in a refined liquid metal or cleaned gas. Filter function is also a mathematical function used in signal processing to manipulate or modify signals, normally used as low-pass, high-pass, or band-pass filters, with different characteristics such as pass-band ripple and roll-off rate. Different types include Butterworth, Chebyshev, Bessel, and elliptic filters, each with unique properties regarding attenuation, phase response, and roll-off behaviour.
Filter gain matrix – It is a weighting matrix used within a Kalman filter algorithm to update the estimated state of a process by balancing between theoretical model predictions and noisy, real-time sensor measurements. It defines how much weight is given to new measurement data against the predicted state estimate, allowing for precise tracking of variables which cannot be directly measured in harsh industrial environments, such as alumina concentration in aluminium smelting.
Filter housing – It is the outer, pressure-rated casing or vessel which encloses filter elements, such as cartridges, bags, or baskets, to separate impurities and contaminants from liquid or gas streams. It serves as the structural framework that ensures the filter media stays in place, prevents bypass (unfiltered fluid escaping), and maintains system integrity under high operating pressures and temperatures, normally made from stainless-steel, poly-propylene, or poly-vinyl chloride (PVC).
Filtering algorithm – It is a computational procedure designed to extract useful information from a dataset while removing unwanted components such as noise, errors, or irrelevant data. Types of filtering algorithms are (i) recursive estimation (state-space filters), (ii) signal and digital processing filters, (iii) data and feature selection filters, and (iv) information and content filtering.
Filtering distribution – It is the posterior probability distribution of the current state variables in a dynamic system, conditioned on all noisy observations received up to a specific time. It is a fundamental concept in Bayesian state estimation, where the goal is to recursively estimate the true state of a system as new data arrives.
Filtering effect – It is the process of removing unwanted components, such as particles from fluids or noise from signals, from a system, allowing only desired elements to pass. It acts as a selective mechanism based on physical properties (size) or operational frequencies (signal bandwidth) to improve quality, performance, or purity. Filtering effect refers to the efficiency of a filtration system in capturing particles, which is influenced by mechanisms such as inertia, diffusion, and interception, as well as factors like particle size, airflow, and filter structure.
Filtering efficiency – It is the ability of a filter medium (such as ceramic foam filters used in molten metal filtration) to retain, capture, and remove suspended particles, such as solid inclusions (e.g., silicon carbide, SiC), oxides, or slag, from a liquid metal stream. It is calculated as the percentage of particles retained by the filter compared to the initial concentration, with typical high-performance filters designed to remove over 90 % of targeted particulates. Filtration efficiency (E) is expressed as the percentage of contaminants removed ‘E = [(Mu -Md) / Mu] x 100 %’, where ‘Mu’ is the upstream quantity / concentration of contaminants, and ‘Md’ is the downstream quantity / concentration of contaminants.
Filtering face-piece respirator – It is a negative-pressure, disposable, air-purifying particulate respirator where the entire facepiece functions as the filtering medium. Engineered to form a tight seal against the face, it filters airborne particles (dust, mist, fumes, microbes) while the wearer breathes.
Filtering method – It is defined as a physical, mechanical, or computational process used to separate unwanted components (particulate matter, noise, contaminants, or data) from a fluid stream (liquid / gas) or data set. The process typically involves forcing the material through a filtering medium or applying a mathematical algorithm to restrict specific components based on size, chemical properties, or frequency.
Filtering theory – It comprises mathematical methods to manipulate signals or estimate system states by removing unwanted noise, interference, or specific frequency components. It enables frequency selection (low-pass, high-pass) in electrical networks or state prediction in dynamic systems using algorithms like Kalman filters.
Filter layer – It is a porous medium (such as sintered metal, wire mesh, or gravel) designed to remove impurities, inclusions, or solid particles from molten metal or fluids. It functions as a surface or depth barrier, trapping contaminants, frequently forming a ‘filter cake’ on top, to ensure high-purity metal. It can be thin (screens, membranes) or thick (depth beds of ceramic, sand, or porous metal).
Filter length – It normally refers to the physical dimensions of the filtering medium (such as a ceramic foam filter or mesh) which the molten metal or fluid is required to pass through, frequently directly relating to the efficiency of impurity removal and the pressure drop across the filter. Filter length is also defined as the number of coefficients in the finite impulse response (FIR) filter, which determines the filter’s characteristics and performance. In the context of mean filtering, it represents the number of data points used to compute the average for filtering.
Filter mat – it is also called filter blanket It is a type of fibrous, non-woven, or porous filter medium used to capture solid particulate matter from fluid or gas streams. These mats are typically high-loft or thick, porous pads composed of randomly arranged, bonded fibres (such as fibre-glass, polyester, or metal) which create a tortuous path for fluid flow. High-quality filter mats frequently have a progressive structure, where the fiber density increases toward the clean-air side, ensuring high dust-holding capacity and preventing surface clogging. These mats are used to separate inclusions from molten metals, filter industrial gases, or act as pre-filters in HVAC (heating, ventilation, and air conditioning) and air handling systems to protect machinery.
Filter order – It refers to the number of stages, chambers, or consecutive filtration steps applied to a slurry to achieve desired separation, solid washing, or cake dryness. While ‘filter order’ is mainly a term in signal processing, in the context of industrial filtration systems like pressure filters, the concept relates to the configuration and sequence of the filtration process.
Filter output – It refers to the refined molten metal, or filtrate, which has successfully passed through a filtration medium (such as a ceramic foam filter, bed filter, or mesh) while impurities, known as inclusions, dross, or slag, are retained. This output is characterized by considerably reduced inclusions and higher cleanliness, which directly improves the quality of the final metal product.
Filter parameters – These are the quantitative specifications which define the performance, structure, and efficiency of filtering media (such as ceramic foams, fibre meshes, or sand) used to remove inclusions, oxides, and impurities from molten metal or to filter gases and liquids. These parameters dictate how well a filter retains contaminants while allowing the molten metal to flow through without clogging.
Filter radius – It is a specified user-defined parameter which modifies the elemental criterion of a specific element based on a weighted average of the criteria within a fixed neighborhood, helping to suppress checkerboard effects and control the minimum size of features in the design domain.
Filters (bag houses) – Fabric filters are also known as bag houses. They use filtration to separate dust particulates from dusty gases. They are one of the most efficient and cost -types of dust collectors available. Dust-laden gases enter the fabric filter and pass-through fabric bags which act as filters. The bags can be of woven or felted cotton, synthetic, or glass-fibre material in either a tube or envelope shape. The high efficiency of these filters is due to the dust cake formed on the surfaces of the bags. The fabric filters mainly provide a surface on which dust particulates collect.
Filter smoke number – It is a standardized measurement, frequently defined as per ISO (International Organization for Standardization) standards ISO 10054 and ISO 8178-3, which quantifies the soot concentration or darkness of exhaust gases from combustion engines, particularly diesel engines, by measuring the blackening of a filter paper. It is a critical metric for combustion optimization and environmental monitoring, allowing for the estimation of solid particulate mass emissions.
Filter surface – It refers to a, normally thin, porous medium (such as woven wire mesh, ceramic foam, or treated paper) designed to separate solid inclusions or impurities from molten metal or fluids by trapping particles larger than the pore size mainly on the upstream surface. Unlike depth filters which trap particles throughout their volume, surface filters operate by direct interception, creating a high-efficiency screen where particles form a ‘filter cake’ on top of the medium.
Filter transfer function – It is frequently applied in metallurgical process control, sensor data analysis, and material analysis. It is a mathematical representation, typically in the frequency domain, which defines how a system (the filter) transforms an input signal into an output signal. It is normally defined as the ratio of the Laplace transform of the output signal to the Laplace transform of the input signal, assuming zero initial conditions.
Filter tube – It is a rigid or semi-rigid, cylindrical, porous, or perforated element used to remove impurities, inclusions, and oxide fragments from molten metals, gases, or liquids. They are typically utilized in high-temperature or corrosive industrial environments, including foundry processes, to improve the purity and mechanical properties of metal alloys.
Filter vessel – It is an enclosed pressure system designed for thin-cake pressure filtration, equipped with candle filters which consist of a dip pipe, perforated core, and filter sock, facilitating the efficient separation of solids from liquids and enabling different processes such as cake washing and drying.
Filter weight – It refers to the mass of a filter medium, frequently used for separating solid particles (like slag, metal oxides, or dust) from liquid or gaseous phases. This includes weighing the filter before and after sampling to calculate particulate concentration (e.g., milli-grams per cubic meter) or determining the efficiency of filter media based on particle loading.
Filter weights – These are the numerical values assigned to electrodes during calibration in spatial filtering approaches, where higher absolute weights amplify the influence of an electrode’s recorded data on classification outcomes. These weights can reflect the correlation of recorded signals, allowing for the enhancement of signal-to-noise ratios, but do not necessarily indicate the quality of the recordings from those electrodes.
Filter wheel – It is a motorized or manual mechanical device which holds a set of optical filters (such as colour, neutral density, or polarizers) arranged on a disc. It rotates these filters into an optical path (e.g., in a microscope or camera) to quickly change the wavelength, intensity, or polarization of light being used to analyze a material, such as a metal sample in metallography.
Filter width – It is the smallest particle size a filter medium can effectively retain. It directly influences the filtration flow rate, pressure drop, and the efficiency of separating solids from molten metal or slurry, with smaller widths leading to finer particle retention but higher resistance.
Filtrate – It is the clear liquid or gas which has passed through a filter medium during the filtration process, separated from suspended solid particles. It is the clarified product (frequently called the liquor or permeate) which is collected after the solid matter, referred to as the ‘filter cake’ or ‘residue’, has been retained.
Filtrate control – It refers to the techniques and additives used to manage the quantity of liquid (filtrate) which separates from the drilling mud and penetrates into a porous rock formation. The main goal of filtrate control is to minimize this liquid invasion to maintain wellbore stability, prevent damage to the producing formation, and prevent the sticking of drilling tools.
Filtrate volume – It refers to the total quantity of liquid (filtrate) which passes through a filter medium (such as a mesh or cloth) per unit of time during the separation of solids from liquids. It represents the cleared, liquid product separated from solid particles or metal pulps, frequently important in mineral processing and metal refining.
Filtration – It is a physical separation process that separates solid matter and fluid from a mixture using a filter medium which has a complex structure through which only the fluid can pass. It removes coarse suspended matter and sludge from coagulation or from water softening systems. Gravel beds and anthracite coal are common materials used for filter beds. Softening is the treatment of water to remove dissolved mineral salts such as calcium and magnesium, known as hardness, in boiler feedwater. Softening methods include the addition of calcium carbonate (lime soda), phosphate, and / or zeolites (crystalline mineral compounds).
Filtration control – It refers to the techniques, materials, and operational parameters used to manage the separation of solid particles from a liquid (slurry) or gas, specifically to control the rate of fluid loss, the moisture content of the final product, and the permeability of the filter cake.
Filtration efficiency – It measures the percentage of contaminants (such as non-metallic inclusions) removed from molten metal or liquid suspensions by a filter, calculated as the difference between upstream and downstream contaminants. It defines the filter’s performance, often represented by the formula ‘E = 100 x [(Mu – Md)/Mu], where ‘Mu’ is upstream and ‘Md’ is downstream contamination.
Filtration element – It is the core, replaceable component within a filter housing responsible for physically separating solid contaminants (such as metallic debris, slag, or carbon particles) from liquid fluids (such as hydraulic oil, lubricants, or cooling water) or gases. It serves as a barrier which allows the fluid to pass through while trapping contaminants, ensuring optimal machinery operation and preventing premature wear.
Filtration of particles from gas streams – A major class of particulate air pollution control devices relies on the filtration of particles from gas streams. A variety of filter media is employed, including fibrous beds, packed beds, and fabrics. Fibrous beds used to collect airborne particles are typically quite sparsely packed, usually only around 10 % of the bed volume being fibers. Packed bed filters consist of solid packing normally in a tube and tend to have higher packing densities than do fibrous filters. Both fibrous and packed beds are widely used in the ventilation systems. Fabric filters are frequently used to remove solid particles from industrial gases, whereby the dusty gas flows through fabric bags and the particles accumulate on the cloth. The physical mechanisms by which the filtration is accomplished vary depending on the mode of filtration.
Filtration process – It is a mechanical or physical unit operation used to separate solid particles (residue) from a liquid or gaseous suspension (slurry or gas stream) by passing the mixture through a porous medium, frequently called a filter medium or septum. The filter medium retains the solid particles while allowing the liquid, referred to as the ‘filtrate’ to pass through. In mining and mineral processing, this is an important solid-liquid separation technique used to reduce moisture content from concentrates and tailings, maximizing the recovery of valuable metal and reducing transport costs.
Filtration rate – It is the volume or mass of filtrate (liquid) which passes through a unit area of filter medium per unit of time. It is a critical performance parameter used to measure the efficiency of solid-liquid separation, normally expressed in units such as cubic meter per square meter per hour. The filtration rate is typically calculated as ‘filtration rate = volume of filtrate / (filter area x time)’.
Filtration unit – It is a mechanical or physical system designed to separate solid particles (such as inclusions, impurities, or precipitates) from a fluid (such as molten metal, slurry, or process water) by passing it through a porous medium which retains the solids. These units are critical in metallurgical processes to ensure material purity, protect downstream machinery, and manage environmental waste. The purpose of the filtration unit is to remove undesired particulates, inclusions, or slag from a liquid phase, such as molten metal or chemical solutions, to achieve higher product purity. The unit uses a filter medium, such as ceramic foam, sand, porous metal, or cloth, which traps particles while allowing the liquid (filtrate) to pass.
Fin – It is the thin projection formed on a forging by trimming or when metal is forced under pressure into hair-line cracks or die interfaces. In refractories, fin is a thin layer of material on a face of a brick or block which projects beyond the edge.
Final annealing – It is an imprecise term used to denote the last anneal given to a non-ferrous alloy prior to shipment.
Final checklist – It is a structured, comprehensive document used in the closing stages of a project, design, or manufacturing process to verify that all work, inspections, and documentation meet predetermined specifications and quality standards. It serves as a quality control tool (or ‘punch list’) to ensure no steps are missed, defects are addressed, and safety standards are met before final handover, sign-off, or product shipment.
Final chlorination – It is also called chlorination refining. It is the culminating stage of a pyro-metallurgical process where chlorine gas (Cl) or a chloride agent is introduced into a molten metal bath to remove impurities, improve purity, and achieve specific alloy compositions. It is widely used as a refining step for crude metals, such as titanium, magnesium, or aluminum, where the chlorine reacts selectively with impurity metals to form volatile chlorides which escape the melt, or stable, insoluble chlorides which can be separated.
Final configuration – It refers to the desired, end-state shape, dimension, and geometry of a metal part after it has undergone all forming, casting, or machining processes. It is the final form specified in engineering drawings before the product is considered completed.
Final consumer – It is also known as end-user. It is an individual, organization, or entity which purchases and utilizes a finished metal product or component for its intended purpose, without further processing, transformation, or resale. The final consumer marks the end of the production chain.
Final control element – It is the last device in a process loop, typically a control valve, damper, or variable-speed drive, which physically adjusts the process variable (flow, temperature, pressure) based on controller signals. It directly manipulates operations like fuel gas flow, cooling water, or gas composition in furnaces and smelters. It serves as the physical actuator modifying the process medium, completing the closed-loop control system, such as regulating oxygen flow into a furnace.
Final densification – It is the third and final stage of liquid-phase sintering (LPS), where the micro-structure consists of connected solid grains with liquid residing in the remaining spaces. It is the process by which a powder compact achieves maximum density by eliminating the final remaining pores, frequently resulting in full densification (99 % to 100 % theoretical density).
Final density – In powder metallurgy, it is the density of a sintered product.
Final destination – In materials flow analysis (MFA), final destination refers to the ultimate end-use or application of a material, rather than its initial, intermediate, or intermediary industrial applications.
Final draft international standard – It is the penultimate stage in the development of an International Organization for Standardization (ISO) or International Electrotechnical Commission (IEC) standard, representing the final, technically-resolved draft before formal publication. It serves as the official ‘yes / no’ ballot stage for national member bodies, where the content is considered functionally complete and only minor editorial changes are permitted before approval.
Final inspection – It is the last, critical quality control check performed on a finished product or project before delivery, shipment, or occupancy. It ensures all specifications, functional requirements, and safety standards are met, preventing defects and ensuring customer compliance. It is frequently used for final sign-off. In manufacturing, It is a last-chance check to identify defects before shipping, covering appearance, functionality, and packaging to ensure the customer receives what was ordered. In construction, it is conducted by local authorities or engineers to confirm a structure is safe, complete, and fully complies with building codes before issuing an occupancy permit. The core objective of final inspection is to verify quality, prevent defective products from reaching the customer, reduce warranty claims, and ensure reliability.
Final instability effect – It is frequently referred to as deformation instability, plastic instability, or failure. It is defined as the phenomenon occurring when the work-hardening capacity of a metal is exhausted, causing the strain to localize and leading to the immediate onset of failure.
Final investment decision – It is the critical project milestone where owners or investors approve funding and formally sanction the construction of a project, normally following the completion of ‘front-end engineering design’ (FEED). It marks the transition from planning to full-scale execution, triggering engineering, procurement, and construction (EPC) contracts.
Final microstructure – It is the specific, stable arrangement of phases, grains, and defects (such as dislocations or precipitates) within a metal, resulting from its final processing, cooling rates, and heat treatments. It dictates the material’s final physical properties, including strength, hardness, ductility, and corrosion resistance.
Final part shaping – It refers to the concluding manufacturing processes used to bring a metal component to its precise, final dimensions, shape, and surface finish. While primary shaping processes (like casting or rough forging) create the overall geometry, final shaping, frequently considered a secondary process, ensures the component meets exact tolerance requirements and functional specifications.
Final polishing – It is a polishing process in which the primary objective is to produce a final surface suitable for microscopic examination.
Final pressure – It is the pressure of a fluid after accounting for pressure losses because of the friction and resistances within a system, calculated from the initial pressure and the total pressure drop. It also refers to the compaction or solidification pressure applied at the end of a processing step (such as powder compaction, moulding, or specialized casting) to achieve the desired density, structural integrity, and shape of the metal part.
Final radius – It is frequently termed final bend radius or inside radius after spring-back. It is the actual radius of a formed part after the pressure from a bending tool is released. It is the final internal curvature of the bent material, which typically differs from the tool radius because of the elastic recovery (spring-back). Final radius also represents the radius of a metal atom joined by a metallic bond. It is the one-half of the total internuclear distance between two adjacent metal ions (atoms) in a metallic lattice.
Final setting time – Concerning binders, refractories, or cementitious materials used in metal casting (like mould-making), the final setting time is the time elapsed between the moment water (or a liquid binder) is added to the powder and the moment the mixture completely loses its plasticity, becoming a solid, rigid mass. At this stage, the material has attained sufficient firmness to withstand a specific, defined pressure and can no longer be molded or shaped.
Final shaping – It is frequently identical with secondary forming or net-shape manufacturing. It refers to the concluding production processes which bring a metal component to its precise, specified dimensions, surface finish, and geometrical tolerances. While primary shaping (such as casting or rough forging) creates the initial, approximate form, final shaping refines this structure, frequently when the metal is cold, to meet exact engineering requirements. Key aspects of final shaping are near-net against net shape, precision and tolerances, surface finish, and surface hardening.
Final sink – In metallurgical material flow analysis (MFA) and environmental engineering, a final sink refers to the final destination in the environment or waste management system where a substance (such as a metal or impurity) accumulates at the end of its life cycle, typically where it is no longer recovered, recycled, or technically accessible for further use. It is the end point of material dissipation, where valuable materials are lost to the environment or disposed of permanently (e.g., landfills, mining tailings).
Final slag – It is the byproduct formed at the end of high-temperature metallurgical refining, consisting of flux and impurities (gangue) removed from ore or hot metal. It is a liquid mix of oxides / silicates, normally separated from metal by density, which controls final metal quality and is frequently recycled or repurposed.
Final steady-state temperature (Ta or Tss) – It is defined as the stable, time-independent temperature achieved at any given point within a material when the rate of heat gain equals the rate of heat loss. It is the condition where thermal equilibrium is reached, meaning that after a specific heating or cooling process starts, the internal energy of the material becomes constant, and its temperature no longer changes over time.
Final stress – It is frequently termed as final residual stress or final working stress. It refers to the combined, total stress state remaining within a material after all manufacturing, treatment, and loading processes have been completed. It represents the net result of different stress-inducing factors, such as mechanical forming, thermal gradients during quenching, and metallurgical phase transformations.
Financial analysis – It is the process of evaluating an organization’s financial performance and position by examining financial statements and other financial data. It involves analyzing the relationships between different items on the balance sheet and income statement to understand the organization’s financial health, profitability, and overall financial strength.
Financial asset – It is an intangible asset which holds monetary value and can be easily converted into cash or used to generate income. It represents a claim to future financial benefits, such as cash flows or ownership stakes. Examples include cash, bank deposits, stocks, bonds, and mutual funds.
Financial audit – It is the independent, systematic examination of project-based financial data, budgetary spending, and resource utilization (labour, materials) to ensure accuracy, compliance with contracts, and adherence to accounting standards. It verifies that project costs align with actual progress, mitigating risks of fraud or mismanagement.
Financial capital – It consists of the financial assets or economic resources which a business or individual uses to fund their operations, investments, and growth. It encompasses money, credit, and other financial instruments that can be used to acquire real assets or other forms of capital, ultimately contributing to the generation of future revenue and wealth.
Financial mechanism – It refers to the systems, structures, and instruments used to channel and manage financial resources. It can involve several entities and processes, such as governments, financial institutions, and international organizations, to facilitate investments, support specific projects, or address financial barriers.
Financial management – It is the process of planning, organizing, directing, and controlling the financial resources of the organization to achieve specific goals. It encompasses activities like raising capital, managing investments, controlling expenses, and ensuring profitability.
Financial net present value – It is a key performance indicator (KPI) used to determine the profitability and viability of a project (e.g., building a new smelter, upgrading a refinery, or developing a mine) by comparing the present value of future cash inflows to the present value of cash outflows over the project’s life. It basically answers the question, what is the total value in today’s money of all future profits from a project, after paying for all capital and operational costs.
Financial ratios – These are calculations which use data from an organization’s financial statements to assess its financial health and performance. They provide insights into several aspects like profitability, liquidity, solvency, and efficiency, enabling investors, analysts, and managers to compare an organization’s performance over time or against its peers.
Financial reporting – It is the structured process of documenting, analyzing, and communicating the financial performance and position of the organization. It goes beyond standard accounting to address industry-specific complexities such as mineral reserves valuation, high capital expenditure (CAPEX), and environmental rehabilitation costs.
Financial statement analysis – It is the systematic, in-depth evaluation of the organization’s financial documents, specifically the balance sheet, income statement, and cash flow statement, to assess its operational efficiency, profitability, and financial health. In the capital-intensive and cyclical metallurgical industry, this analysis is used to measure the ability of the organization to manage high fixed costs, debt, commodity price volatility, and inventory levels.
Financial support policies – These policies refer to targeted economic measures, financial instruments, and regulatory frameworks designed to facilitate funding for different activities such as mining, smelting, refining, and metal production activities. These policies, implemented by governments and financial institutions, aim to lower financing costs, stimulate investment in new technology or green initiatives, and support the operational stability of companies in the primary and secondary sectors.
Finding coefficients – It refers to determining numerical parameters which describe the physical, chemical, or thermodynamic behaviour of metals, alloys, and impurities during processing. These coefficients are critical for designing casting, purification, and alloying processes. Common types of coefficients found in metallurgical engineering include partition / segregation coefficient, coefficient of thermal expansion (CTE), heat transfer coefficient, activity coefficient, and stoichiometric coefficients.
Fine aggregate component – It refers to small-sized, inert, granular materials that pass through a 4.75 milli-meter sieve and are typically retained on a 0.075 milli-meter (75-micro-meters) sieve. They are important fillers which fill the voids between coarse aggregates, providing stability, density, and improved workability to cement, mortar, and asphalt mixtures.
Fine aggregate replacement – It is the substitution of conventional sand in concrete or mortar with alternative, frequently sustainable or waste materials, such as copper slag, coal bottom ash (CBA), or recycled rubble, to improve performance, reduce costs, and mitigate environmental impacts. It involves partially or fully replacing aggregates passing through a 4.75 milli-meter sieve.
Fine-blanking – It is a high-precision, cold-forming process which produces components with fully sheared, smooth edges and high dimensional accuracy in a single stroke. Unlike conventional stamping, which uses fracture to separate metal, fine-blanking uses a triple-action press with specialized V-ring tools, high-pressure pads, and a counterpunch to achieve net-shape parts with almost no burr or edge roll, effectively combining cutting and cold extrusion. It allows for tighter tolerances (frequently within 0.0075 milli-meters and higher accuracy.
Fine-blanking press – Fine-blanking process needs a controlled sequence of movements with a precise top dead centre. The strict blanking clearance of the dies does not change, even under high levels of stress. Fine-blanking presses, hence, are to meet the stringent precision needs, including slide gibs, high frame rigidity, and parallelism of die clamping surfaces. Both mechanical and hydraulic systems are used for the main slide drive.
Fine bubble – It is normally a gas bubble with a diameter smaller than 100 micro-meters. These bubbles are characterized by their high specific surface area, negative surface charge, and long stability in liquid media compared to conventional bubbles. Under ISO (International Organization for Standardization) standard ISO 20480-1, fine bubbles are classified into two categories namely (i) micro-bubbles with diameter ranging from 1 micro-meter or more to less than 100 micro-meters, and (ii) ultra-fine bubbles (or nano-bubbles) with diameter of less than 1 micro-meter.
Fine chemicals – These are high-cost industrial products which have well-defined purity. These are high-purity, complex inorganic substances or compounds produced in limited quantities using batch processing. Unlike bulk metals, they are tailored to exacting specifications, offering high value and purity for specialized applications.
Fine coal – It normally refers to coal particles with a diameter smaller than 1 milli-meter (or 1,000 micro-meters, normally defined within the range of 150 micro-meters to 0.5 milli-meter or 1 milli-meter. Particles smaller than 0.15 milli-meters (150 micro-meters) are frequently referred to as ultra-fine coal. These fines are generated through intensive mining mechanization, coal handling, and the crushing / grinding of run-of-mine coal, typically constituting 10 % to 20 % of the coal processing plant feed.
Fine crumb rubber – It is a finely ground, recycled rubber material derived from end-of-life automotive and truck scrap tires, with a particle size normally ranging from 0.425 milli-meter down to 0.075 milli-meter (typically classified as 40 mesh to 80 mesh or higher). It is produced by removing steel and fabric reinforcement, leaving high-purity rubber granules, frequently produced through ambient milling, cryogenics, or micro-milling. In construction applications, it serves as a lightweight material which improves the durability, flexibility, and elasticity of composite materials, such as rubberized concrete or asphalt.
Fine droplet – It refers to a small, atomized particle of molten metal, typically ranging in size from a few micro-meters to under 500 micro-meters in diameter, produced during atomization or spray processes, which quickly solidifies into powder or coatings. These droplets are characterized by their high surface-area-to-volume ratio, facilitating rapid solidification and high-cooling rates, which are important for producing fine, homogeneous microstructure powders.
Fine-edge blanking – It is a high-precision, hybrid metal forming process combining shearing and cold extrusion to produce parts with exceptionally smooth, perpendicular edges and superior flatness. Unlike conventional stamping, it uses a triple-action press, a V-ring, blanking punch, and counter-pressure, to eliminate the fracture zone and tearing, achieving near-net-shape parts with near-zero edge roughness.
Fine-edge blanking and fine piercing – These are high-precision cold-shearing processes used in metallurgy to produce components with clean, fully sheared, and dimensionally accurate edges. Unlike conventional stamping, which produces a rough, fractured edge, fine blanking uses a triple-action press and specialized tooling to compress the material before and during the shearing process, eliminating the typical fracture zone.
Fin efficiency – It is the ratio of actual heat transfer from a fin to the ideal heat transfer if the entire fin surface is at the constant base temperature. It measures how effectively a fin utilizes its material for heat dissipation, typically resulting in a value between 0 and 1, where higher efficiency indicates a smaller temperature drop along the fin.
Fin extension – It refers to the mechanism which allows the fins of a stabilizer, such as the Denny-Brown stabilizer, to be extended or retracted as needed for stability control. This process is part of the overall fin housing mechanism which operates using hydraulic pressure supplied by the servo pump.
Fine gold – It is the fineness which is the proportion of pure gold in jewelry or bullion expressed in parts per thousand. Hence, 925 fine gold indicates 925 parts out of 1,000, or 92.5 % is pure gold.
Fine grain – It refers to a material structure with small, densely packed crystal grains, normally smaller than 20 micro-meters to 65 micro-meters (below 0.025 milli-meter diameter). These structures increase toughness, hardness, and yield strength by restricting dislocation movement. It is frequently produced by adding grain refiners (aluminum, titanium, vanadium).
Fine-grained heat-affected zone – It is a specific region within the heat-affected zone (HAZ) of a weld, characterized by its fine-grained micro-structure. This region forms when the peak temperature during welding reaches a level which allows for the complete transformation of the steel into austenite, but not to the extent that considerable grain growth occurs. The fine-grained heat-affected zone is typically found at temperatures between the Ac3 transformation temperature (the temperature at which austenite begins to form) and 1,100 deg C.
Fine-grain microstructures – These represent solid metal structures characterized by a high density of small, uniformly distributed grains and increased grain boundary area. Typically defined by an average grain size of less than 65 micro-meters, these structures are created through controlled nucleation and specialized processing.
Fine-grain processing – It is a set of techniques designed to reduce the average grain size of a metal (typically to 5 micro-meters to 65 micro-meters or less), improving both yield strength and toughness simultaneously. It acts as a strengthening mechanism by increasing grain boundaries which impede dislocation movement, frequently achieved through alloying, rapid cooling, or thermo-mechanical treatment.
Fine grain size – It refers to a microstructure with a high density of small, individual crystalline grains (typically 65 micro-meters or below). This structure is characterized by a higher number of grain boundaries, which restrict dislocation motion, resulting in superior strength, toughness, and improved ductility compared to coarse-grained materials.
Fine-grain steels – These structural steels with a refined, small crystalline micro-structure created through specialized processing. These steels offer higher yield strength, superior toughness, and better brittle fracture resistance than coarse-grained steels, frequently achieved through microalloying and controlled rolling or heat treatment.
Fine grinding – It is precision grinding process which uses extremely fine abrasive (50 micrometers and finer). It is a high-precision, low-feed abrasive machining process which uses diamond or cubic boron nitride (CBN) wheels to produce exceptionally flat, parallel surfaces and high-quality finishes. It bridges the gap between traditional grinding and lapping, offering superior accuracy and material removal.
Finely ground – It refers to the reduction of ore, concentrate, or metal powders to a very small particle size, typically designed to increase surface area for chemical reactions, improve mineral liberation, or facilitate powder metallurgy.
Fine mesh – It refers to a woven metal screen (typically stainless steel, copper, or brass) with a high number of openings per linear inch (normally 50 or above). It is used for precise separation, sifting, and filtration of materials, characterized by small aperture sizes, frequently between 0.034 millimeters and 0.16 millimeters, ensuring high-strength and accurate separation of small particles.
Fine micro-structure – It is a uniform, small-grained structure (typically below 10 micro-meters) observed through microscopy, featuring high-density grain boundaries and controlled phase distribution. It is engineered through rapid cooling or processing (e.g., metal injection moulding, MIM) to improve mechanical properties like strength, hardness, and toughness, frequently exceeding conventional material performance.
Fineness – It is a measure of the purity of gold or silver expressed in parts per thousand.
Fineness modulus – It is an empirical index number representing the average size of particles in an aggregate sample, calculated by summing the cumulative percentages retained on standard sieves and dividing by 100. A higher fineness modulus (FM) indicates coarser, while a lower fineness modulus indicates finer aggregate (typically 2.3–3.1 for sand).
Fineness of enamel – It is a measurement of the degree to which a frit has been milled in wet or dry form. It is normally expressed in grams residue retained on a certain type of mesh screen from a 50 cubic meters sample or a 100 grams sample.
Fine particulate matter – It frequently referred to as PM2.5 in metallurgical contexts, consists of airborne solid or liquid particles with an aerodynamic diameter of 2.5 micro-meters or smaller. These particles are generated during high-temperature metallurgical processes like smelting and refining, and they pose significant health risks because of their ability to penetrate deep into the lungs.
Fine particulate materials – These normally refer to solid particles, powders, or dust with a size typically less than 2.5 micro-meters in diameter, normally referred to as PM2.5. These materials are frequently generated during high-temperature processes or mechanical treatments. Fine particles (PM2.5) are smaller than 2.5 milli-meters, while ‘ultra-fine’ particles are generally less than 0.1 micro-meters. These are considerably smaller than coarse particles (PM10), which range between 2.5 micro-meters and 10 micro-meters.
Fine particulates – These normally refer to solid airborne particles with an aerodynamic diameter of 2.5 micro-meters or less (PM2.5), generated during crushing, grinding, smelting, or dry stamping. These particles include metal dust (copper, iron, zinc), fumes, and carbon, frequently remaining suspended in the air for long periods. Ultrafine particles, a subset of this category, are less than 0.1 micro-meters (PM0.1). Fine particulates are generated by industrial processes such as smelting, casting, and finishing, frequently created by condensation of vapourized metal or abrasion.
Fine pearlite – It is a high-strength, two-phase micro-structure in steel consisting of very closely spaced alternating lamellae (layers) of ferrite and cementite (Fe3C). It forms during rapid cooling (around 540 deg C to 600 deg C) or isothermal transformation, where low transformation temperatures restrict carbon diffusion, creating a finer lamellar spacing compared to coarse pearlite.
Fine-pitch threads – These are screw threads with a smaller distance between ridges (pitch) and a higher number of threads per inch (TPI) compared to coarse threads of the same diameter (1 milli-meter pitch is equivalent to 18 TPI). They provide tighter tolerances, higher tensile strength, and better vibration resistance, normally used in precision engineering, aerospace, and automotive industries.
Fine powder – It normally refers to metal particles with a median size around 10 micro-meters or smaller, which are used to achieve high sintering density and superior material properties. While conventional powders are frequently below 40 micro-meters, the term ‘fine’ is particularly used to distinguish powders used in advanced applications like metal injection moulding (MIM) and high-resolution additive manufacturing.
Fine resolution – It refers to the ability of imaging techniques (such as scanning electron microscopy) or measurement instruments to detect, distinguish, and analyze very small features, phases, or metallurgical changes. A ‘fine resolution’ system is capable of high-level detail, distinguishing small differences in micro-structure or composition.
Fines – It is the product which passes through the finest screen in sorting crushed or ground material. It is also the sand grains which are substantially smaller than the predominating size in a batch or lot of foundry sand. It is also the portion of a powder composed of particles smaller than a specified size, normally 44 micrometers. In refractories, fines are small-sized fraction of a mixture of particles used in the manufacture of a refractory.
Fine-tuning – It is the process of taking a pre-trained foundation model and further training it on a smaller, curated, domain-specific dataset to adapt it for specialized tasks, styles, or knowledge domains. While pre-training gives a model general intelligence, fine-tuning imparts organization-specific expertise and behavioural nuances, allowing it to behave as a digital expert rather than a general assistant.
FINEX process – It is a smelting-reduction process for the production of hot metal (HM). This process is based on the direct use of non-coking coal. The FINEX process can directly use iron ore fines without any kind of agglomeration. In the FINEX process, fine iron ore is preheated and reduced to fine direct reduced iron (DRI) in three stage fluidized bed reactor system with reduction gas produced from melter gasifier. The fluidized bed reactors enable the FINEX process to use fine ores instead of lump ore or pellets. The FINEX process uses high purity oxygen, resulting in an export gas with only low quantities of nitrogen. As its net calorific value is more than two times of the blast furnace top gas, it can be partially recycled for reduction work or can be used for heat or energy generation.
Fine silver – It is the silver with a fineness of three nines (999), which is equivalent to a minimum content of 99.9 % silver (Ag) with the remaining content unrestricted.
Finger guard – It is the protective barriers or devices designed to prevent personnel from accessing moving parts of a conveyor, necessitating routine checks for compliance and effectiveness.
Fin heat exchanger – It is a device which improves heat transfer between fluids, typically a gas and a liquid, by extending the surface area using metal fins attached to a primary surface, such as tubes or plates. It improves efficiency, especially where one fluid has a low convective coefficient (like air), allowing for a compact design.
Finish – It is the surface condition, quality, or appearance of a metal. It is the quantity of metal allowed for machining. It is the stock on a forging or casting to be removed in finish machining. In foundry, it is the hand work on a mould after the pattern has been withdrawn. It is the forging operation in which the part is forged into its final shape in the finish die. If only one finish operation is scheduled to be performed in the finish die, this operation is to be identified simply as finish, normally first, second, or third finish designations are so termed when one or more finish operations are to be performed in the same finish die. In composites, It is the chemical finish applied to glass and other fibres, after sizing has been removed, to facilitate resin wetting, resin bonding, and good environmental performance of the cured laminate.
Finish allowance – It is the quantity of excess metal surrounding the intended final configuration of a formed part. It is sometimes called forging envelope, machining allowance, or cleanup allowance.
Finish annealing – It is a sub-critical annealing treatment applied to cold-worked low-carbon or medium-carbon steel. Finish annealing, which is a compromise treatment, lowers residual stresses, hence minimizes the risk of distortion in machining while retaining majority of the benefits to machinability contributed by cold working.
Finished rolled products – These are the products which have been manufactured by rolling and which are normally not further hot worked in the steel plant. The cross-section is uniform over the whole length. These are normally defined by a standard, which fixes the normal size ranges and the tolerances on shape and dimension. The surface is normally smooth, but reinforcing bars or floor plates, for example, can have a regularly raised or indented pattern.
Finished size – It refers to the final, specified dimensions (such as diameter, thickness, or width) of a metal product after all processing, such as hot rolling, cold working, machining, or heat treatment, has been completed. This size represents the usable product which meets tolerance requirements, including any needed surface finishes or dimensional corrections, such as those applied in powder metallurgy to correct for thermal expansion or contraction.
Finished steel – It is the steel which is ready for the market and has been processed beyond the stages of billets, blooms, and slabs. These steel products can be broadly divided into four categories namely (i) bar, rod, and sectional products, (ii) plate and sheet products, (iii) coated steel products, and (iv) pipe and tube products.
Finished stock – It means stock which has been manufactured and which is ready for packing, shipment or sale.
Finisher – It is the die impression which imparts the final shape to a forged part.
Finisher impression – Within closed-die forging, it is the final cavity in a set of forging dies which imparts the exact desired shape, dimensions, and surface finish to the work-piece. It produces the finished forging to its final tolerances, ensuring the metal fills all corners and details of the die.
Finishes – These refer to the final processes applied to the surface of a metal component to modify its texture, appearance, and functional properties. These treatments are performed after fabrication (such as casting, machining, or rolling) to improve durability, corrosion resistance, and aesthetic appeal.
Finish flash – It refers to excess, unwanted material attached to a work-piece, typically forming a thin web, fin, or burr at the parting line of a casting, forging, or moulding.
Finish forging – It is the final, high-pressure shaping stage in a multi-step forging process, where preformed metal is compressed into closed dies to achieve precise dimensional accuracy, final geometry, and refined grain structure. It eliminates voids and optimizes grain flow, improving material toughness and fatigue resistance.
Finish grinding – It is the final grinding action on a work-piece, of which the objectives are surface finish and dimensional accuracy.
Finishing – It refers to the final step in the manufacturing process, where the surface of a metal part is modified to improve its performance, durability, and appearance. It involves cleaning, coating, polishing, or altering the surface, either by removing material or adding a new layer, to achieve specific dimensions, a smoother surface, and enhanced resistance to wear and corrosion.
Finishing annealing and pickling (FAP) lines – These are very frequently called annealing and pickling (APL) lines. These are continuous industrial production line used to treat metal strips, mainly stainless-steel or high-grade silicon steel, after hot or cold rolling. It combines heat treatment (annealing) to alter the material’s internal structure with chemical treatment (pickling) to clean the surface, restoring ductility and achieving a bright, oxide-free finish.
Finishing block – It is also known as no-twist block or no-twist mill. In wire rod mills, it represents one of the key elements. Only through this development, it has become possible to safely roll thin wire rods at speed of over 120 metres per second. The finishing block can be of 4, 6, 8, and 10 roll stands for twist free rolling. A primary gearbox drives the roll units through two common shafts. Finishing blocks having two different sizes of roll units are available, with 170 milli-meters / 150 milli-meters diameter rolls and 225 milli-meters / 200 milli-meters diameter rolls. All roll units are identical and inter-changeable.
Finishing die – It is the die set which is used in the last forging step.
Finishing drawing – The finishing drawing has a close relationship with the elevation drawings as it also talks about the smaller details of a facility. This drawing is important for maintaining the aesthetic value of the structure.
Finishing facilities – It is that portion of the plant complex which processes semi-finished products (slabs or billets) into saleable products. Finishing operations can include rolling mills, pickle lines, tandem mills, annealing facilities, temper mills, and coating lines.
Finishing mill – It is that rolling mill which produces saleable products.
Finishing operations – These are final manufacturing steps which improve a metal part’s surface quality, appearance, and durability after rough machining. These processes, including polishing, plating, grinding, and coating, improve corrosion resistance, reduce surface friction, achieve precise tolerances, and remove surface flaws.
Finishing stand – It is the last stand in a rolling mill, which determines the surface finish and final gauge.
Finishing temperature – It is the temperature at which hot working is completed. It refers to the temperature at which the final hot deformation process, such as hot rolling or forging, is completed before the material begins to cool. It is a critical parameter in thermo-mechanical processing since it directly controls the micro-structure, grain size, and final mechanical properties of the metal (specifically steel).
Finishing train – It is the final series of rolling stands in a hot mill, where a hot transfer bar (typically from a roughing mill / intermediate mill) is rolled down to its final, desired thickness and width. It is the last stage of hot deformation before the rolled product is coiled or bundled / stacked, and it is important for achieving specific dimensions and controlling the microstructure of the metal. It typically consists of 4 to 7 consecutive stands. During this stage, the material undergoes intense hot deformation, dynamic recrystallization, and strain accumulation. The finishing train controls the final grain structure, such as refining the austenite grains, which dictates the final mechanical properties (like strength and toughness).
Finish machining – It is a machining process which is analogous to finish grinding.
Finish mark – It is a symbol placed on an engineering drawing to indicate that a specific surface of a part is to be machined or finished to a certain texture, roughness, and quality. It indicates that the surface needs post-processing, such as milling, grinding, or turning, rather than being left as a raw casting, forging, or hot-rolled surface. Its purpose is to designate which surfaces need machining (material removal) to achieve required tolerances, fitment, or aesthetic standards. Historically, a ‘V’ shape has been used, but International Organization for Standardization standard ISO 1302:2002 use a ‘check mark’ symbol. The symbol typically includes a number (e.g., in micro-meters) specifying the maximum allowable surface roughness (Ra). Symbols can also indicate the direction of the surface pattern (e.g., parallel, perpendicular, or circular) created by the machining tool.
Finish stock allowance – It is frequently referred to as machining allowance. It represents the extra layer of material left on a work-piece, such as a casting or forging, intentionally added beyond the final desired dimensions. This extra stock provides material which can be removed during finishing operations (milling, turning, grinding) to achieve final dimensional accuracy, a specific surface finish, and to remove surface defects.
Finish-to-finish – In a finish-to-finish relationship, a successor activity cannot finish until a predecessor activity has finished.
Finish-to-start – In a finish-to-start relationship, a successor activity cannot start until a predecessor activity has finished.
Finish trim – It is the flash removal from a forging. It is normally performed by trimming, but sometimes by band sawing or similar techniques.
Finish welding – It is the final stage of the metal fabrication process involving the refinement, smoothing, and cleaning of a weld seam after the initial welding (fusing) process is completed. This process improves both the structural integrity and aesthetic quality of the welded joint, ensuring the component meets specific design, safety, and performance standards. Finish welding is also production welding carried out in order to ensure the agreed quality of the casting.
Finite band-width – It refers to the smallest range of frequencies outside of which the Fourier transform of a signal is zero. In practical terms, it indicates the limited range of frequencies which a signal can occupy for processing or measurement purposes.
Finite conductivity fracture – It is a hydraulic fracture with a specific, limited capacity to transmit fluids, where a meaningful pressure drop occurs inside the fracture during production. Defined by a dimensionless conductivity normally less than 300, it causes a characteristic bilinear flow behaviour, differing from infinite-conductivity fractures. Finite conductivity fracture is a planar crack produced by hydraulic fracturing (or acidizing) where the flow capacity is not high enough to treat it as a perfectly conductive path.
Finite control-set model predictive control – It is an advanced control strategy for power electronics and drives which uses a system model to predict future behaviour over a finite horizon. It selects the optimal switching state from a finite set of feasible actions to minimize a predefined cost function, eliminating the need for traditional modulator stages.
Finite cylinder – It refers to a cylindrical component or specimen with a defined, limited length (h) and radius (r), where boundary conditions at both the ends (top and bottom) and the side surfaces considerably affect its behaviour. Unlike an infinite cylinder, which assumes length is irrelevant, the finite cylinder is used to model realistic, finite-sized components such as castings, industrial billets, forging parts, or test samples subjected to heat treatment or mechanical load.
Finite deformation – It refers to large, permanent changes in a metal’s shape or configuration during processing (e.g., forging, rolling, extrusion), where strain is substantial and non-linear, making initial and current geometries distinct. Unlike small-strain theory, it involves large rotations and stretches, frequently analyzed using tensors to track material behaviour. It involves substantial shape changes, characteristic of metalworking, where total strain is calculated, frequently using the logarithmic strain.
Finite difference analysis – It is a numerical method used to approximate solutions to complex differential equations governing physical processes, such as heat transfer during casting, solidification, or diffusion, by discretizing the material domain into a grid of discrete points (nodes). It works by substituting continuous derivatives in governing equations with finite differences (algebraic approximations) between neighbouring grid points, turning complex problems into a system of linear algebraic equations.
Finite difference approach – It consists of a numerical method which approximates differential equations governing a system by replacing differential operators with discrete differences, utilizing a chosen sampling rate to improve accuracy. This method is implemented in digital simulators to facilitate efficient computations.
Finite difference form – It is a numerical technique used to solve complex partial differential equations (PDEs) governing thermal, physical, and chemical processes, such as heat transfer during solidification, iron ore sintering, or diffusion. It works by discretizing the continuous domain (like a metal ingot or sintering bed) into a grid of discrete nodes or ‘finite’ cells, replacing continuous derivatives with algebraic difference equations which approximate the change in properties between neighboring points.
Finite difference formula – It consists of a mathematical expression which approximates derivatives of a function using values of the function at discrete points, typically using operators such as forward difference, backward difference, and central difference to compute these approximations.
Finite difference method – It is a numerical technique used to approximate solutions to differential equations, particularly governing heat transfer and diffusion equations, by replacing continuous derivatives with discrete difference approximations at specific grid points (nodes). It is widely used for modeling thermal histories, solidification, phase transformations, and heat treatment processes.
Finite difference solution – It is a numerical technique used to model metallurgical processes (such as solidification, heat treatment, or diffusion) by approximating continuous differential equations with algebraic equations. It defines the solution by dividing the material’s geometry into a discrete, uniform grid of nodes (mesh) and calculating field variables, such as temperature, concentration, or phase fraction, at these specific points through iterative algebraic steps.
Finite difference thermal model – It is a numerical simulation method used to predict the spatial and temporal temperature distribution within a metal during processing (such as welding, casting, heat treatment, or additive manufacturing). It works by dividing the component’s geometry into a structured, discrete grid of nodes and replacing the governing partial differential equations of heat transfer with algebraic difference equations.
Finite-difference time-domain – It is a popular numerical analysis technique used in computational electrodynamics to model complex electromagnetic systems by directly solving Maxwell’s equations in both time and space. By discretizing space into a ‘Yee lattice’ (staggered grid) and stepping through time. Finite-difference time-domain (FDTD) simulates wave propagation, scattering, and broadband interactions for structures with complex geometries.
Finite domain – It refers to a bounded, discrete, and manageable 3D region of a material which is analyzed to predict its physical properties, such as stress, strain, temperature distributions, or micro-structure evolution. It is the spatial region defined for numerical simulation techniques (very frequently the finite element method (FEM) or fictitious domain methods), where the continuum is sub-divided into smaller elements to solve complex, non-linear governing equations, such as those used in heat treatment, solidification, or welding simulations.
Finite duration – It refers to a process, event, or phenomenon which occurs within a defined, limited time interval rather than extending indefinitely. It is characterized by having a distinct beginning (e.g., ignition of welding, application of a load) and a distinct end (e.g., cooling to room temperature, completion of phase transformation).
Finite elasto-plasticity – It refers to the study of material behaviour which encompasses both elastic and plastic deformations within a finite strain range, needing modifications to numerical methods for accurate modeling of such non-smooth problems.
Finite element analysis – It is also called finite element modeling (FEM). These are numerical techniques in which the analysis of a complex part is represented by a mesh of elements inter-connected at node points. The coordinates of the nodes are combined with the elastic properties of the material to produce a stiffness matrix, and this matrix is combined with the applied loads to determine the deflections at the nodes, and hence, the stresses. All of the above is done with special analysis / modeling software. These approaches also can be used to solve other field problems in heat transfer, fluid flow, and acoustics etc.
Finite element approximation – It is a numerical technique which models the behaviour of metallic materials by sub-dividing a complex, continuous work-piece (such as in casting, forging, or rolling) into a large number of smaller, simpler parts called finite elements. These elements are connected at nodes to form a mesh, which is then used to solve complex partial differential equations (PDEs) for mechanical, thermal, or metallurgical behaviour.
Finite element calculations -These refer to the computational process which analyzes face deformations by establishing a local relationship between forces and displacements through a mesh of geometrically defined elements. This method involves transmitting forces applied at nodes through adjacent elements to result in node displacements and element deformations.
Finite element computations – These refer to the numerical analysis method used to solve complex problems by discretizing a structure into smaller elements. This process involves forming and solving the governing equations for elemental and global systems, which are represented in matrix form, to estimate outcomes such as displacements and stresses.
Finite element context – It refers to the application of variational methods, particularly the finite element method, to solve boundary value problems through local polynomial interpolation and piecewise polynomial solutions. This approach utilizes techniques such as barycentric coordinates and the Rayleigh–Ritz–Galerkin method to achieve approximations with certain regularity based on interpolation data.
Finite element equations – These refer to the mathematical equations derived from the assumed displacement profiles in small discretized elements of a problem domain, which are assembled to form a global equation which can be solved for the entire displacement field in mechanics problems.
Finite element formulation – It is defined as a method in which the distribution of a dependent variable within an element is expressed as a linear combination of polynomials, utilizing interpolation or shape functions which depend on the order of the element and nodal values.
Finite element heat flow solver – In the context of the casting process, it is a numerical tool used to simulate the transient thermal behaviour, specifically conduction, convection, and latent heat release, as molten metal pours into a mould, solidifies, and cools. It operates by discretizing the casting and mould geometry into smaller elements (mesh) and solving the heat transfer equations at the nodal points to predict temperature gradients, solidification rates, and thermal defects.
Finite element matrix equations – These refer to the mathematical formulations derived from the variational principle and finite element discretization, which express the relationships between nodal displacements, electrical potentials, forces, and other parameters in a coupled system, represented through matrices such as the structural mass, damping, and stiffness matrices.
Finite element mesh – It refers to the set of all smaller elements of finite dimensions into which a whole domain is divided in the finite-element method. This discretization is important for solving differential equations in several engineering applications.
Finite element method – It is a computational, numerical technique used to analyze the physical behavior of metals and alloys by breaking down a complex, continuous structure into smaller, simpler, and interconnected pieces called finite elements. This method is widely used to simulate manufacturing processes (like casting, rolling, or forging) and to predict the mechanical properties, stresses, strains, and microstructural evolution of materials under various conditions.
Finite element method mesh – It refers to the discretization of a problem space into discrete elements, typically triangles in 2D and tetrahedra in 3D, used in the finite element method (FEM) to solve field equations simultaneously for the complete system. This mesh is important for accurately modeling complex geometries and phenomena, particularly in applications like imaging and sensor design.
Finite-element method models – These models discretize complex metal components into small, inter-connected elements (meshing) to simulate physical behaviours like stress, strain, heat flow, and phase transformations. These models, defined by nodes and material properties, allow analysis of deformation, metallurgical phase changes during processing, and failure mechanisms without physical testing.
Finite-element method modeling – It is a numerical simulation technique which divides complex metal components into small, interconnected elements (meshing) to analyze material behaviour under conditions like heat treatment, forming, or casting. It predicts stresses, strains, deformation, and solidification to optimize manufacturing and alloy performance.
Finite-element models – These are numerical, computer-based simulations which discretize complex metallic components into smaller ‘elements’ to analyze material behaviours like stress, deformation, heat transfer, and phase transformations. These models predict structural integrity, casting solidification, and thermo-mechanical properties (e.g., in welding or quenching), improving manufacturing efficiency.
Finite element results – These refer to the solutions obtained from a finite element analysis, which can be evaluated by assessing the residuals which indicate the extent to which these solutions satisfy the governing differential equations. These results are used to identify discretization errors and guide model refinement.
Finite element simulation – It is a numerical method used to solve ordinary and partial differential equations over complex geometric domains, allowing for the analysis of different physical behaviours such as eigenfrequencies and deformation modes in components or systems.
Finite-element simulation software – It is a computer-aided engineering (CAE) tool which uses the ‘finite element method’ (FEM) to predict the behaviour, micro-structure evolution, and structural integrity of metallic materials and components during manufacturing processes or under operating conditions. It breaks down complex, continuous metallic objects into smaller, discrete elements (a mesh) to solve partial differential equations related to thermal, mechanical, and phase-transformation phenomena.
Finite element solution – It refers to the approximate solution of complex engineering analysis problems achieved by dividing the actual system into smaller interconnected pieces, called finite elements, and solving for the system’s behaviour by satisfying equilibrium equations at nodes and ensuring compatibility of displacements between the elements.
Finite-endurance range – In fatigue, it refers to the number of load cycles a material can withstand before failure, typically within a specific stress range which is above the endurance limit (if one exists) but below the stress level which causes immediate failure. It is a critical concept for designing components expected to experience cyclic loading, as it helps engineers predict how long a material lasts under those conditions.
Finite energy – It refers to a property of signals where the total energy, calculated as the integral of the square of the signal’s amplitude over time, is a finite value. In the context of aperiodic signals, this energy can be related to its distribution over frequencies using Parseval’s energy relation.
Finite game – It is a mathematical model ’G – (N, S, C)’ featuring a fixed set of players ‘N’, defined strategy sets ‘S’ for each player, and clear payoff functions ‘C’, ensuring the game ends in a finite number of moves. Each player’s payoff function is a mapping from the product of their strategy sets to real numbers.
Finite impulse response – It is a class of digital filters whose response to an impulse return to zero in finite time. It is a type of digital filter whose impulse response is of finite duration, where the current output is calculated solely from the current and previous input values.
Finite impulse response filter – It is a type of digital filter whose impulse response settles to zero in a finite number of samples. It is a non-recursive system which calculates output by performing a weighted sum of current and previous input samples, without using previous output values (feed-back).
Finite line source model – It is a 3D analytical method used in engineering to calculate the transient temperature response around geothermal heat exchangers (boreholes) of specific length. It improves on the ‘infinite line source’ (ILS) by accounting for axial heat conduction, realistic heat exchanger length, and ground surface temperature changes.
Finite loss – It refers to the measurable attenuation, dissipation, or distortion of energy (such as electricity, heat, or fluid pressure) within a system which has defined, limited boundaries. Unlike an ideal ‘loss-free’ model, a system with finite loss experiences a specific, non-zero reduction of energy.
Finite plate – It refers to a metallic plate with defined, measurable boundary edges, where the stress distribution is considerably affected by these boundaries (e.g., edges, holes, or cracks). This differs from an infinite plate model, which assumes boundaries are too far away to influence local stresses. Finite plate is a 2D or 3D structural component where the planform dimensions (length and width) are finite, as opposed to an infinite sheet.
Finite span – It refers to a structural or aerodynamic component with a specific, limited length, introducing three-dimensional end effects. Unlike an infinite or two-dimensional model, a finite span wing creates tip vortices because of the pressure differences between upper / lower surfaces, inducing drag and reducing efficiency.
Finite-state machine – It is a mathematical model of computation normally represented as a graph, with a finite number of nodes describing the possible states of the system, and a finite number of arcs representing the transitions that do or do not change the state, respectively. Such a machine is mostly used to model computer programmes and sequential logic. There are two types of finite-state machines namely Mealy machines, where the output values are determined based on the current state together with the current input, and Moore machines, where the output is determined solely based on the current state. It is a mathematical model used to design, control, and model systems with a finite number of distinct operating modes. It defines system behaviour based on states, transitions, inputs, and outputs, facilitating structured development of hardware, software protocols, and robots.
Finite strain – It refers to a measure of deformation in materials, specifically representing changes in length or area during large and possibly inhomogeneous deformations. It can be quantified using different finite strain tensors, such as the Lagrangian (or green–Lagrangian) finite strain tensor and the logarithmic (Hencky) strain tensor.
Finite strain theory – It analyzes materials undergoing large deformations and rotations where infinitesimal assumption fails, needing a strict distinction between undeformed and deformed configurations. It is important for materials like elastomers, and plastically deforming metals.
Finite strip element – It is a specialized numerical discretization tool used in structural engineering to analyze structures with regular, constant geometry (prismatic) along one axis, such as folded plates or bridges. It acts as a hybrid of the finite element method (FEM), utilizing simpler, larger ‘strips’ with polynomial / series functions, making it more computationally efficient than standard finite element method for specific geometries.
Finite strip method – It is an efficient numerical technique in structural engineering used for analyzing prismatic structures (like thin-walled members, bridges, and plates) by discretizing them into strips. It is a variant of the finite element method’ (FEM) which reduces computational effort by using polynomial functions for the cross-section and trigonometric series (sine / cosine functions) along the length.
Finite temperature difference – It refers to a non-zero, measurable temperature gradient (delta T is above zero) between a heat source, sink, or working fluid, driving heat transfer at a finite rate. Unlike theoretical reversible processes (zero gradient), real-world engineering systems rely on these gaps, which cause exergy destruction (irreversibility) and dictate device efficiency.
Finite time interval – It refers to a specific, bounded duration, within which a system operates or a process occurs, rather than over infinite time. It is important for analyzing tracking performance, stability, and convergence within a limited timeframe.
Finite time stability – It is the property of a nonlinear system which allows it to converge to an equilibrium point within a finite time, specifically when the system is stable at that point and there exists a time function such that the state approaches zero as time approaches a finite value. If this holds for the entire state space, the system is considered globally finite time stable.
Finite union – It is the combination of a limited number of sets where each element is included only once, resulting in a set which contains elements from each of the original sets without duplication. It implies that the resulting set has a definitive, countable size, especially if all individual sets are finite.
Finite volume code – It consists of a numerical method used in computational fluid dynamics to discretize fluid flow equations by storing flow variables at the centers of mesh elements, facilitating the analysis of complex geometries and turbulent flows.
Finite volume method – It is a numerical technique for solving partial differential equations (PDEs) by discretizing the domain into control volumes, ensuring strict conservation of quantities like mass and momentum, making it essential for ’computational fluid dynamics’ (CFD). It is widely used for fluid flow, heat transfer, and engineering applications.
Finite zero – It is a specific value of ‘s’ (complex frequency) which causes the numerator polynomial ‘Ns’ of a transfer function Fs = Ns/Ds’ to equal zero. These are roots of the numerator which make the system output zero, acting as opposites to poles.
Finmet process – It is a direct reduction technology which uses a series of four fluidized bed reactors to convert iron ore fines (under 12 millimeters) into hot briquetted iron (HBI). It uses hydrogen-rich gas from steam-reformed natural gas to reduce ore at high pressure, producing 93 % metallized hot briquetted iron.
Finned-disk test -. In the finned-disk thermal shock test, the sample is cycled between a moderate-temperature environment and a high-temperature environment, which causes thermal expansion and contraction. Since thermal conductivity plays a substantial role in this type of test, gray iron shows much higher resistance to cracking than compacted graphite iron. Major cracking occurs in less than 200 cycles in compacted graphite iron samples, while the unalloyed gray iron develops minor cracking after 500 cycles and major cracking after 775 cycles. Because of its higher high-temperature strength, alloyed gray iron is even more resistant to thermal fatigue.
Finned-disk thermal shock test – It is an accelerated environmental test designed to evaluate the durability, crack resistance, and material integrity of cast components (frequently casting dies, engine parts, or heat exchangers) by subjecting them to rapid, extreme temperature cycling. This test mimics the severe working conditions which cause ‘thermal fatigue’ or ‘heat checking’ in materials.
Finned tubes – They are tubes where fins have been added on the outside to increase the contact area with the outside fluid, to exchange heat and between the fluid inside the tube and the fluid outside the tube. These tubes are the main components of heat exchangers.
Finned tube heat exchanger or economizer – Finned tube heat exchanger is used to recover heat from low to medium temperature exhaust gases for heating liquids. Applications include boiler feed water preheating and air preheating etc. The finned tube consists of a round tube with attached fins which maximize surface area and heat transfer rates. Liquid or air flows through the tubes and receives heat from hot exhaust gases flowing across the tubes. A finned tube exchanger where boiler exhaust gases are used for feed water preheating is generally referred to as a boiler economizer.
Finning – It is a defect in casting, It is a defect occurring in investment casting where a thin, sharp ridge of metal extends perpendicularly from the surface of a casting. This is caused by molten metal filling cracks in the ceramic shell or mould during solidification. Finning is also a cold-forming or manufacturing process used to attach thin, extended metal sheets (fins) to tubes to increase surface area, normally for heat exchanger applications.
Finstock – It is narrow strip in the thickness range 0.2 millimeters to 0.4 millimeters used for finning of heat exchanger tubes in applications such as air conditioning.
Fin surface – It refers to the surface of a fin, which is an internal component designed to improve heat transfer in a multi-purpose finned heat exchanger (MPFHE) by increasing the heat transfer area and improving heat exchange efficiency.
Fin tube heat exchanger – It is a device used to transfer heat between two fluids (typically a fluid inside the tube and gas / air outside) by extending the surface area of tubes with attached fins, hence considerably increasing heat transfer efficiency. These are important for heating, cooling, and heat recovery applications where one fluid has a considerably lower heat transfer coefficient than the other, such as in HVAC (heating, ventilation, and air conditioning) and power generation industries.
Fire alarm system – It consists of a network of automated and manual devices designed to detect smoke, heat, or combustion, and alert building occupants through notification appliances. It acts as a safety system to initiate evacuation and, in different designs, alerts emergency services through a central control panel.
Fire assay – It is an assaying method normally used for the determination of precious metal content.
Firebrick – It is a refractory brick, frequently made from fireclay, which is able to withstand high temperature (1,500 deg C to 1,600 deg C) and is used to line furnaces, ladles, or other molten metal containment components.
Firebrick, insulating – It is a refractory brick which is characterized by low thermal conductivity and low heat capacity.
Fire classification – It is a systematic categorization of fires based on the type of combustible material involved (fuel source), aimed at determining appropriate extinguishing agents and safety measures. It aids engineers in designing fire suppression systems, selecting building materials, and ensuring compliance with safety standards.
Fireclay – It is a mineral aggregate which has as its essential constituent the hydrous silicates of aluminum with or without free silica. It is used in commercial refractory products.
Fireclay, nodular – It is a rock containing aluminous or ferruginous nodules, or both, bonded by fireclay.
Fireclay, plastic or bond – It is a fireclay of sufficient natural plasticity to bond non-plastic materials.
Fireclay plastic refractory -It is a fireclay material tempered with water and suitable for ramming into place to form a monolithic furnace lining which attains satisfactory physical properties when subjected to the heat of furnace operation.
Fireclay refractory bricks – These bricks are manufactured from unfired refractory bond clay and fireclays (chamotte), fired refractory clay or similar grog materials. Fireclay refractory bricks have two main components namely 18 % to 44 % of alumina (Al2O3) and 50 % to 80 % of silica (SiO2). The variety of clays and manufacturing techniques allows the production of several brick types appropriate to particular applications. The usefulness of fireclay refractory bricks is largely because of the presence of mineral mullite, which forms during firing and is characterized by high refractoriness and low thermal expansion. There are five standard classes of fireclay bricks namely (i) super duty, (ii) high duty, (iii) medium duty, (iv) low duty, and (v) semi silica.
Fire cracks – Fire cracks are thermo-shock cracks which form under a very sharp cooling rate on the roll surface. When the heated roll surface with a thermal gradient perpendicular to the roll surface during the revolution of the roll is quenched by the cooling water, surface tensile stress is built up. When the tensile stress reaches the tensile strength of the roll material, then cracks (fire cracks) are initiated. These cracks are only formed under tensile stress.
Fire-cracker core – It is a small, specialized core used to create a narrow vent or opening which connects a blind riser (a riser which does not extend to the top of the mould) to the outside atmosphere. It allows trapped air and gases to escape from a blind riser, preventing back-pressure which otherwise stop the riser from filling completely. It is frequently a cylindrical or specially shaped sand core inserted into the upper part of the mould (the cope).
Fire-cracker welding – It is a variation of the shielded metal arc welding process in which a length of covered electrode is placed along the joint in contact with the work-pieces. During the welding operation, the stationary electrode is consumed as the arc travels the length of the electrode.
Fire crack transfer marks – Fire crack transfer marks are patterns of elevations which recur periodically and run at right angle to the direction of rolling. They can be easily detected with naked eye or with low magnification because of their characteristics. During hot rolling, the surface of the rolls is subjected to continuous heating and quenching. With inadequate cooling and the use of unsuitable roll material, stress cracks can occur in the roll grooves. These crack depressions in the roll surface leads to elevations on the rolled product. Although fire crack transfer marks are smoothed in subsequent passes, they can lead to other surface defects such as cracks and laps.
Fired boilers – These are devices used to generate hot water or steam through the combustion of fossil fuels, facilitating heating in different applications. They can be classified into fire-tube and water-tube types, depending on the arrangement of combustion gases and the fluid being heated.
Fired electrical generating station – It is a thermal power station which generates electricity by burning fossil fuels, such as coal, oil, or natural gas, or biomass to produce heat. This heat is used to create high-pressure steam in a boiler, which drives a steam turbine connected to an electrical generator. It is designed for the conversion of chemical energy stored in fuel into electrical energy through several stages normally thermal, mechanical, and finally electrical.
Fired electricity generation – It refers to the production of electrical power through the combustion of fossil fuels, such as coal or natural gas, in generating facilities.
Fire design – It is the application of scientific, mathematical, and structural principles to plan, predict, and mitigate the effects of fire on buildings and systems. It involves developing heat release rate (HRR) curves, selecting materials, and creating structural strategies to protect occupants, property, and the environment.
Fire detection – It is the systematic process of identifying, designing, and implementing electronic systems to detect incipient fires by sensing smoke, heat, flames, or gas. It involves engineering reliable, automated detection methods to trigger alerts for timely occupant evacuation and fire suppression activation. Fire detection systems act as the initial defense, consisting of several engineered components.
Fired furnace – It is also called fired heater. It is an engineered industrial device which uses combustion of fuel (gas, liquid, or solid) to generate heat, typically applied directly to process materials or fluids within tubes. It is used extensively to reach high temperatures. It consists of a refractory-lined radiant fire-box and a convection section.
Fired generation – It refers to power plants which produce electricity by burning fuel, typically coal, natural gas, or oil, to create heat, which then drives turbines (steam or gas) connected to electrical generators. It is a main thermal energy conversion process where chemical energy is converted into electricity. It involves a boiler or combustor to produce steam or hot gas, and a turbine-generator set.
Fired heater – It is an industrial device used industrial plants to heat liquids or gases to high temperatures (frequently over 540 deg C) by direct combustion of fuel. They consist of a burner, combustion chamber (radiant section), and convection section, utilizing heat transfer through radiation and convection to raise process fluid temperatures flowing through tubes.
Fired mould – It is a shell mould or solid mould which has been heated to a high temperature and is ready for casting.
Fired power plant – It is a thermal engineering facility which generates electricity by burning fossil fuels (coal, natural gas, or oil) to produce high-pressure steam. This steam drives turbines connected to generators. These plants consist of fuel handling, combustion (boiler), steam, and water systems designed for continuous, high-efficiency energy conversion.
Fired tubular reformer – It is a high-temperature industrial furnace used to produce hydrogen or syngas hydrogen or syngas by reacting hydrocarbon feedstocks (like methane) with steam over a catalyst. It consists of several vertical catalyst-filled alloy tubes heated externally by burners in a radiant furnace box to temperatures up to 1,000 deg C, enabling endothermic reforming reactions.
Fire exposure – It is the subjection of materials, structures, or systems to heat, flames, and combustion products. It defines the thermal boundary conditions (temperature, heat flux) used to evaluate structural integrity and fire safety, frequently classified as standard (standardized furnace tests) or design / real fires (actual anticipated fire load).
Firefly algorithm – It is a nature-inspired optimization algorithm based on the flashing patterns and behaviour of fireflies, which involves fireflies being attracted to brighter ones while moving randomly when no brighter firefly is present. It uses attractiveness variations calculated based on the distance among fireflies and is utilized in different applications such as load frequency control and optimizing switching angles in inverters.
Fire-fighting – Fire is one of the major hazards present in a steel plant. A well-planned fire-fighting system is necessary for combating the fires.
Fire-fighting drawing – This drawing is drawn before the construction of a facility. The drawing shows the pattern of the placement of the fire hoses, points, water outlets, and everything connected with fire-fighting. The drawing also lays out the fire protection plan and safety systems which are to be set in place.
Fire hazard – It is a material, substance, equipment, or process which increases the likelihood of a fire starting, intensifies its spread, or hinders safe evacuation. It involves the interaction of fuel (solid / liquid / gas), ignition sources (spark / heat / flame), and oxygen.
Fire hazard analysis – It is an assessment of the risks from fire within an individual fire area in a facility analyzing the relationship to existing or proposed fire protection. This includes an assessment of the consequences of fire on safety systems and the capability to safely operate a facility during and after a fire.
Fire house – It is also called fire station. It is a specialized structure designed to store emergency apparatus (engines, trucks) and provide living / working spaces for personnel. It is a critical infrastructure component, optimized for rapid deployment and frequently featuring specialized systems for vehicle exhaust removal, power drops, and high-load flooring.
Fire investigation – It is the systematic process of determining the cause and origin of a fire, which involves collecting and analyzing evidence despite the challenges posed by the fire’s destructive nature. This process frequently needs collaboration among different agencies, especially when crimes or important incidents are suspected.
Fire loss – It is the monetary cost of restoring damaged property to its pre-fire condition. When determining the loss, the estimated damage to the facility and contents is to include replacement cost, less salvage value.
Fireman – Fireman is a person whose job is to stop unwanted fires from burning. Fireman is also a person who tends a furnace or the fire of a steam engine or steamship.
Fire point – Fire point is the temperature at which a fluid gives off vapour in sufficient quantity to ignite and continue to burn when exposed to a spark or flame. Like flash point, a high fire point is required of desirable hydraulic fluids.
Fire precautions – These are planned, active, and passive measures implemented to minimize fire risks, protect life, and secure property. These technical, structural, and procedural strategies include detecting hazards, providing escape routes, and installing suppression systems to prevent outbreaks or control fire consequences.
Fire prevention – It is the concept of preventing outbreaks of fire, of reducing the risk of fire spreading and of avoiding danger to persons and property from fire.
Fire protection – It is a broad term which encompasses all aspects of fire safety, including building construction and fixed building fire features, fire suppression and detection systems, fire water systems, emergency process safety control systems, emergency fire-fighting organizations (fire departments, fire brigades, etc.), fire protection engineering, and fire prevention. Fire protection is concerned with preventing or minimizing the direct and indirect consequences of the fire.
Fire protection engineering – It is the application of science and engineering principles to protect people, property, and their environments from the harmful and destructive effects of fire and smoke. It encompasses engineering which focuses on fire detection, suppression and mitigation and fire safety engineering which focuses on human behaviour and maintaining a tenable environment for evacuation from a fire. Fire protection engineering frequently includes fire safety engineering.
Fire protection system – It is the system designed to detect and contain or extinguish a fire, as well as limit the extent of fire damage and enhance life safety.
Fire-refined copper – It is the copper which has been refined by the use of a furnace process only, including refinery shapes, and by extension, as well as the fabricators’ products made therefrom. Normally, when this term is used alone it refers to fire-refined tough pitch copper without elements other than oxygen being present in considerable quantities.
Fire resistance – It refers to a material’s ability to withstand fire exposure for a specific duration without failing structurally or losing its ability to contain fire. It is a measure of how long a material can maintain its load-bearing capacity, integrity, and insulation when exposed to fire. Essentially, itis the degree to which a material can resist the effects of fire.
Fire resistance performance – It is the ability of a structural element or assembly to withstand fire exposure for a specified duration by maintaining its structural stability, integrity, and insulation under defined conditions. It is a measure of passive fire protection designed to prevent premature collapse, hinder fire spread, and ensure safe evacuation.
Fire resistance test – It is a standardized evaluation which measures the ability of building materials, components, or assemblies (like walls, doors, floors) to withstand fire exposure for a specified duration. It assesses performance criteria, structural stability, integrity, and insulation, to prevent the spread of heat and fire, ensuring safety and building code compliance.
Fire resistant hydraulic fluids – These fluids generate less heat when burnt than those of mineral oil-based fluids. These fluids are mainly used in situations where there are chances of fire hazards. These fluids are made of lower heat value compared to those of mineral oil-based fluids, such as water-glycol, phosphate ester, and polyol esters. International Organization for Standardization (ISO) have classified these fluids as HFAE (soluble oils), HFAS (high water-based fluids), HFB (invert emulsions), HFC (water glycols), HFDR (phosphate ester), and HRDU (polyol esters).
Fire resistant steels – These steels have been developed for construction applications where increased high temperature strength provides improved protection to a building structure during a fire. Improved fire protection, in turn, helps to prevent building collapse caused by reduced load carrying capability of steel structures at high temperature, or provides the building occupants higher time to escape the building in the event of such a collapse.
Fire retardant treatment – It is a process which applies chemicals (coatings, impregnations, or additives) to materials, such as wood, textiles, or plastics, to inhibit, suppress, or delay combustion, ignition, and flame spread. It improves fire safety by slowing heat development and improving surface burn characteristics without necessarily making materials ‘fireproof’.
Fire risk assessment – It is a systematic, technical evaluation used to identify fire hazards, analyze potential fire scenarios (like explosions or structural failures), and implement engineering controls to reduce risks to personnel, assets, and operations. It combines fire science, consequence modeling, and safety regulations to ensure structural integrity and functional safety.
Fire-safe – This is a term used to describe the fire resistance ability of a valve when exposed to fire. In order to qualify for this certification, a valve is required to be exposed to fire for a 30-minute period. Once acceptable leakage (through the test valve and also external leakage) has been confirmed, the valve is considered to be fire-safe.
Fire safety – It is a risk-based approach to fire safety.
Fire safety design – It refers to the planning and implementation of measures to ensure safety during a fire, including guidelines for evacuation routes, compartmentation, and structural considerations to protect occupants and minimize casualties. It is particularly important for both new constructions and the upgrading of old buildings to meet modern safety standards.
Fire safety management – It is the systematic, proactive approach to controlling fire risks through risk assessment, compliance, and technical, engineered solutions. It involves applying engineering principles to design systems (sprinklers, alarms, smoke control) and manage infrastructure to prevent ignition and protect life and property.
Fire suppression – It involves designing active systems which detect and extinguish or control fires before they spread, typically using gaseous, chemical, or foam agents instead of water to protect sensitive equipment. These systems,, including lean agents and CO2 (carbon di-oxide) systems, act by interrupting the fire triangle (heat, fuel, oxygen) automatically.
Fire triangle – It is a safety model representing the three basic components needed for combustion namely fuel (combustible material), heat (ignition source), and oxygen (oxidizing agent). If any side of this triangle is removed, fire cannot start or gets extinguished.
Fire tube – It refers to a type of boiler in which water is contained in a cylindrical shell and hot gases pass through tubes within that shell, normally used for generating low pressure steam for heating purposes.
Fire-tube boiler – Fire tube boiler consists of numbers of tubes through which hot gasses are passed. These hot gas tubes are immersed into water, in a closed vessel. In this boiler one closed vessel or shell contains water, through which hot gas tubes are passed. These hot gas tubes heat up the water and convert the water into steam and the steam remains in same vessel.
Firewall – It is a network security system, implemented through hardware, software, or both, which monitors and controls incoming and outgoing network traffic based on predefined security rules. It serves as a protective barrier, separating trusted internal networks from untrusted external networks (e.g., the internet). Firewall acts as gatekeepers, analyzing data packets to permit or block access, ensuring only authorized traffic passes.
Firewater system – It is an active fire protection network designed to supply, transport, and distribute water to control or extinguish fires in industrial, commercial, or residential facilities. It consists of a dedicated water source (tanks / raw water), pumping systems (diesel / electric), a pipe network (ring main), and discharge devices like sprinklers or hydrants, adhering to national codes.
Firing – It is the controlled heat treatment of ceramic ware in a kiln or furnace to develop the desired final properties.
Firing angle – It is also known as the triggering or delay angle. It is the precise electrical angle (in degrees or radians) within an AC (alternating current) cycle at which a thyristor (silicon-controlled rectifier, SCR) is triggered into conduction. It is measured from the zero-crossing point of the input voltage wave-form. Controlling firing angle regulates the average power delivered to a load.
Firing method – It refers to the specific technique, process, or mechanism used to introduce heat, initiate combustion, or control the energy input in systems such as boilers, furnaces, kilns, or combustion engines. It defines how fuel is brought into contact with air / ignition to cause burning, directly impacting efficiency and temperature control.
Firing process – It is a high-temperature heat treatment of moulded, dry, or green ceramic materials within a kiln to induce physical and chemical changes (sintering) which create durable, hardened components. It involves controlled stages, heating, soaking (holding peak temperature), and cooling, to achieve specific densities, strengths, and microstructural properties, typically up to 1,400 deg C or higher.
Firing range – It is frequently termed turn-down ratio (TDR). It is the range of burner capacity (firing rate) where stable combustion occurs. It defines a burner’s stability and operational capability. It is the ratio of maximum firing rate to minimum firing rate, dictating how much a burner can modulate its heat output while maintaining safe, efficient performance, typically 3:1 to 6:1.
Firing stage – It is the controlled, high-temperature heat treatment of formed ceramic materials, typically in a kiln between 850 deg C and 1,350 deg C, to induce chemical and physical transformations like sintering, vitrification, and hardening. It converts raw materials into a durable, solid, and non-recyclable product by eliminating moisture and organic components.
Firing temperature – It is the peak temperature attained during a heat-treating or sintering process, designed to initiate critical physical and chemical transformations in a material (e.g., ceramics, metal powders, or pellets) to achieve desired structural, mechanical, or physical properties.
Firing time – It is the period during which the ceramic ware remains in the firing zone of the furnace to mature a ceramic or porcelain enamel coating.
Firmware – It is the software of a computer which is never or rarely altered during its working life, e.g., the control computer programme for an automotive ignition system.
First aid – It is the skilled application of accepted principles of treatment on the occurrence of an accident or in the case of sudden illness, using facilities or materials available at the time. It is the immediate care given to a person who is injured.
First angle projection – In the first angle projection, the front view is the basis (reference) and the other views are drawn as ‘shadows’ of that view. That is, the left- hand side view for example is drawn on the right side of the front view. Similarly, the top view (plan) is drawn at the bottom of the front view etc.
First block, second block, and finish – It is the forging operation in which the part to be forged is passed in progressive order through three tools mounted in one forging machine. Only one heat is involved for all three operations.
Finite impulse response (FIR) filters – These are digital signal processing (DSP) algorithms with an impulse response which settles to zero in finite time, as they use no feedback loops. These stable, non-recursive systems are important for processing sensor data, such as eddy current inspection signals or ultrasonic thickness measurements, providing linear phase response and high, accurate filtering without oscillation.
First-order equation – Within metallurgical kinetics and extractive processes, first-order equation is a mathematical relationship which defines the rate of a process, such as leaching, reaction, or decomposition, as directly proportional to the concentration of a single reactant.
First-order filter – It is a type of analog or digital signal processor which uses only one energy-storage element (reactive component, such as a single capacitor or inductor) or, in digital terms, one previous output value. It is characterized by a gradual transition between the passed and rejected frequencies, specifically offering a roll-off rate of 20 decibels (dB) per decade (6 decibels per octave).
First-order linear differential equation – It is a mathematical equation which relates a material property (such as temperature, concentration, or grain size) and its first derivative (rate of change) to time or space. The equation is ‘linear’ in the dependent variable and ‘first-order’ since it only includes the first derivative.
First-order reaction – It is a process where the reaction rate is directly proportional to the concentration of a single reactant, raised to the first power. Common in kinetics (e.g., radioactive decay, diffusion), the rate depends linearly on one concentration, and the reaction half-life is constant, independent of initial concentration.
First order reliability method – It is a probabilistic technique used to estimate the probability of material or structural failure by linearizing the limit state function (using a first-order Taylor series) at the most probable point of failure. It determines reliability by analyzing uncertainties in material properties (e.g., yield strength) and loads, converting them into a safety index. First order reliability method (FORM) is a probabilistic design tool which calculates the probability of failure (Pf) when material properties, loads, or geometry are uncertain.
First order shear deformation theory – It is frequently termed Mindlin-Reissner plate theory. It is a structural mechanics model which analyzes thick plates and composites by accounting for transverse shear deformation. It assumes straight lines normal to the midplane remain straight but not perpendicular after deformation, normally needing a shear correction factor for accuracy. It is mainly used for modeling moderately thick plates, laminated composites, and functionally graded materials (FGMs), where shear effects are substantial.
First-order transition – It is a change of state associated with crystallization or melting in a polymer.
First ply failure – It is the point where the weakest lamina (ply) in a laminate reaches its ultimate stress or strain, leading to initial cracking, normally in the matrix. It represents a conservative safety limit where individual, frequently non-critical, layer damage begins before total laminate failure.
First-rank tensor – It is a mathematical representation of a vector quantity which needs one direction to be described, such as electric current density, thermal flux, or Burgers vectors. It is characterized by three components in 3D space (v1, v2, v3) which follow specific transformation rules under coordinate rotations.
Fir-tree crystal – It is a type of dendrite crystal.
Fir-tree root – It is a multilobed, serrated fastening mechanism, specifically in power generation, to secure turbine or compressor blades to a rotating rotor disc. The profile resembles a fir tree in cross-section, designed to distribute high centrifugal loads across multiple lobes or teeth, allowing for higher stress capacity compared to simple dovetail roots. The root consists of several curved or angled serrations (lobes) that mesh with a corresponding groove in the disk. This design provides a larger contact area, reducing stress on each individual lobe and minimizing the risk of failure. These roots are mainly used in the ‘hot end’ (turbine section) of gas turbines and the last stage of low-pressure (LP) steam turbines, where extreme centrifugal forces and temperatures exist.
Fiscal year – It is a 12-month or 52-53-week period an organization uses for budgeting, accounting, and financial reporting. It does not have to align with the January 1–December 31 calendar year and is typically chosen to match operational cycles, such as peak seasons, for more accurate performance tracking. It is a consistent 12-month period for financial tracking, frequently chosen to align with operational cycle.
Fischer-Tropsch (FT) catalyst – It is a metal-based material, typically iron (Fe), cobalt (Co), or ruthenium (Ru), used to convert syngas (carbon mono-oxide + hydrogen) into liquid hydro-carbons. Operating at 150 deg C to 300 deg C, these catalysts facilitate polymerization, with iron favoured for coal / biomass to liquids (higher sulphur tolerance) and cobalt for natural gas to liquids (high activity).
Fischer-Tropsch chemistry – It refers to the process of converting synthesis gas, mainly consisting of carbon mono-oxide and hydrogen, into liquid hydro-carbons through a series of reactions, producing a range of products such as olefins, paraffins, and oxygenated compounds. This process is characterized by its exothermic nature and is influenced by factors such as temperature, feed gas composition, pressure, and catalyst type.
Fischer-Tropsch diesel – It is a synthetic fuel derived from syngas via the Fischer-Tropsch synthesis process, typically resulting in a pure, highly paraffinic mixture. It is a high-quality fuel produced by converting syngas (carbon mono-oxide and hydrogen) from coal, natural gas, or biomass into liquid hydrocarbons using metal-based catalysts. It is characterized by zero sulphur / aromatics, high cetane numbers (above 70), and excellent engine performance. The process uses iron or cobalt catalysts at specific temperatures and pressures.
Fischer-Tropsch hydro-carbon synthesis – It is a process which converts synthesis gas, derived from coal or natural gas, into liquid hydrocarbons using catalysts such as iron or cobalt in different types of reactors, including fixed bed and slurry bubble column reactors.
Fischer-Tropsch liquids – These are synthetic hydro-carbon mixtures produced from synthesis gas (syngas), a mixture of carbon mono-oxide (CO) and hydrogen (H2), through a catalytic chemical process. These liquids represent a high-quality synthetic crude (syn-crude) or designer fuel which is remarkably clean compared to conventional, petroleum-derived products. Fischer-Tropsch liquids are mainly composed of paraffinic (alkane) hydro-carbons. They are produced in a wide variety of hydro-carbon chain lengths (typically C5 to C100+).
Fischer-Tropsch liquid fuel – It is a synthetic hydro-carbon fuel produced from syngas, a mixture of carbon mono-oxide and hydrogen, derived from coal, natural gas, or biomass. It uses catalytic conversion to create ultra-clean, sulphur-free, high-cetane diesel, kerosene, and jet fuel. It is frequently used to produce high-quality synthetic lubricants and paraffins.
Fischer-Tropsch method – It refers to a process which converts carbon mono-oxide and hydrogen, derived from the gasification of coal, into higher hydro-carbons through Fischer-Tropsch synthesis, resulting in products like waxes, gasoline, and alcohol.
Fischer-Tropsch process – It is a catalyzed chemical reaction which converts synthesis gas, a mixture of carbon mono-oxide (CO) and hydrogen (H2), into liquid hydro-carbons (fuels and waxes). This synthesis relies on transition metal catalysts, mainly iron (Fe) or cobalt (Co), to catalyze the polymerization of hydro-carbons at 200 deg C to 350 deg C.
Fischer-Tropsch products – These are synthetic, high-purity liquid hydro-carbons, waxes, and oxygenates produced by converting syngas (carbon mono-oxide + hydrogen) over metal catalysts (iron or cobalt). These products are mainly linear alkanes (paraffins) used to create sulphur-free diesel, kerosene, and lubricants, serving as alternatives to petroleum-derived materials.
Fischer-Tropsch reactor – It is a heterogeneous gas-solid catalytic reactor which converts synthetic gas (carbon di-oxide and hydrogen) into liquid hydro-carbons, mainly for synthetic fuels and waxes. It utilizes metallic catalysts (iron or cobalt) to facilitate exothermic polymerization of syngas, normally operating between 150 deg C to 350 deg C.
Fischer-Tropsch synthesis – It is a catalytic chemical process which converts synthesis gas (syngas), a mixture of carbon mono-oxide (CO) and hydrogen (H2) derived from coal, natural gas, or biomass, into synthetic liquid hydro-carbons. It acts as a metal-catalyzed polymerization, typically using iron or cobalt catalysts to produce synthetic fuels and wax.
Fischer-Tropsch synthesis reactor – It is a specialized heterogeneous catalytic reactor designed to convert synthesis gas (syngas), a mixture of carbon mono-oxide (CO) and hydrogen (H2), into liquid hydrocarbon fuels (diesel, gasoline, waxes) and chemicals. This reactor serves as a, ‘carbon chain building’ unit, utilizing iron or cobalt-based catalysts supported on different substrates to facilitate exothermic polymerization.
Fish bone diagrams – These are casual diagrams which show the causes of a specific event. Common uses of these diagrams are (i) product design and quality defect prevention, and (ii) to identify potential factors causing an overall effect. Each cause or reason for imperfection is a source of variation. These diagrams are also known as cause-and-effect analysis diagrams.
Fisher information – It quantifies the quantity of information obtainable about a specific material parameter (e.g., lattice parameter, defect density) from experimental measurements. It sets the theoretical limit on the precision of estimating that parameter, playing an important role in optimizing scattering techniques, microstructure imaging, and data interpretation.
Fisher information matrix (FIM) in metallurgy and materials science acts as a quantitative measure of the sensitivity of experimental observations (such as diffraction patterns, microstructure images, or sensor data) to changes in unknown, underlying physical parameters (such as phase fractions, alloy composition, grain size, or thermodynamic variables). It defines the ‘sharpness’ of the likelihood function, a high Fisher information indicates that the experimental data provides precise information about the parameters, while low information indicates a ‘blunt’ or ambiguous result.
Fisher’s linear discriminant – It is a supervised machine learning technique used for dimensionality reduction and classification, defining a method to find the optimal linear projection which maximizes class separation. It is normally applied to distinguish between different materials, phases, or quality grades (e.g., contaminated against uncontaminated) based on high-dimensional data, such as spectral intensities or microscopic features. Linear discriminant identifies a linear combination of features (e.g., specific wave-lengths in hyperspectral imaging of materials) which maximizes the distance between the mean values of different material classes.
Fisher’s exact test – It is a non-parametric statistical significance test used in the analysis of contingency tables where sample sizes are small. The test is useful for categorical data which result from classifying objects in two different ways. It is used to examine the significance of the association (contingency) between two kinds of classifications.
Fisher sub-sieve sizer – It is an instrument which is used to determine the average particle size of powders by measuring the air permeability of a compacted powder bed. It is a commercially available permeability instrument which calculates the average particle size based on the resistance of the powder to airflow. The Fisher sub-sieve sizer is normally used for powders where a sieve analysis is not suitable, such as very fine powders. Fisher sub-sieve sizer operates on the principle of air permeability. It measures how easily air can pass through a compacted sample of the powder.
Fish-eye – It is an area on a steel fracture surface which is having a characteristic white crystalline appearance. Fish-eye is also a weld defect, which is a discontinuity found on the fracture surface of a weld in steel which consists of a small pore or inclusion surrounded by an approximately round, bright area.
Fish-eye fracture – It is a characteristic feature found on the fracture surface of high-strength steels and welded metals subjected to cyclic loading (fatigue) or tensile stress. It appears as a bright, circular, or elliptical zone surrounding a small, darker-appearing central flaw. This failure mode is frequently associated with the high-cycle fatigue (HCF) or very high-cycle fatigue (VHCF) of metals.
Fishing angles – In railway engineering, fishing angle is required to ensure proper transmission of loads from the rails to the fish plates. The fishing angles is to be such that the tightening of the plate does not produce any excessive stress on the web of the rail.
Fishing operation – It refers to the set of procedures, techniques, and specialized tools used to locate, engage, and retrieve lost or stuck equipment from a well-bore. These operations are important to clear obstructions which hinder normal drilling or completion, hence minimizing downtime and preventing the need to abandon the well.
Fish-mouth fracture – It is the macroscale appearance of a longitudinal fracture in an internally pressurized pipe, tube, or pressure vessel.
Fish-mouthing – It is the pronounced wide cracking over the entire surface of a coating having the appearance of alligator hide. It is also the longitudinal splitting of flat slabs in a plane parallel to the rolled surface.
Fish plate – It is also known as a splice bar or joint bar. It is a metal bar, typically made of steel, which connects the ends of two rails to create a continuous track. Fish plates are a crucial part of rail-to-rail fastenings, ensuring the proper alignment and continuity of the track for safe train operation.
Fish-scale – It is a scaly appearance in a porcelain enamel coating in which the evolution of hydrogen from the base metal (iron or steel) causes loss of adhesion between the enamel and the base metal. The scales are somewhat like blisters that have cracked partway around the perimeter but still remain attached to the coating around the rest of the perimeter.
Fish-tail – In roll forging, it is the excess trailing end of a forging. It is frequently used, before being trimmed off, as a tong hold for a subsequent forging operation. In hot rolling or extrusion, it is the imperfectly shaped trailing end of a bar or special section which is to be cut off and discarded as mill scrap.
Fish-tail defect – It is a rolling or extrusion defect where the ends of a metal work-piece develop a concave, split shape resembling a fish’s tail. Caused by non-uniform deformation where surface layers flow faster than the centre, it results in wasted material, frequently seen in bar / section rolling and extrusion. It is a specific type of end defect, also known as ‘tailpipe’, which creates a concave, split appearance on the rear end of a rolled bar or extruded product.
Fish-tailing – It is also known as a fish tail defect or tailpipe. It is a common failure or defect found in metal forming, casting, and welding, characterized by an irregular, flared material shape which resembles a fish’s tail. It typically occurs because of non-uniform metal flow and can lead to weak joints or damaged, uneven surfaces.
Fissile isotopes – These are isotopes which can sustain a nuclear fission chain reaction, specifically uranium-235, plutonium-239, and uranium-233. Among these, only uranium-235 occurs naturally, while plutonium-239 and uranium-233 are produced through the transmutation of fertile materials.
Fissile material – It is the material which is fissionable by thermal (slow) neutrons. The three main fissile materials are uranium-233 (U-235), and plutonium-239 (Pu-239). Although this term has sometimes been used as a synonym for fissionable material, it has now acquired this more restrictive meaning.
Fissile uranium – It refers to isotopes, mainly uranium-235, capable of sustaining a nuclear chain reaction when struck by low-energy (thermal) neutrons. This refers to fissile material (like enriched U-235) which can fission readily, unlike fertile material (U-238) which needs high-energy neutrons and is not inherently fissile.
Fission – Fission creates the release of energy where heavy element atoms are split up into smaller atoms, producing free neutrons and large quantities of energy. The energy is derived from small changes in mass which is converted to energy (E = mc2).
Fissionable elements – These are isotopes which can undergo fission, such as uranium-235, plutonium-239, and uranium-233, which are subject to substantial health scrutiny because of their properties.
Fission event – it is the process in which a heavy, unstable nucleus (such as uranium-235, uranium-233, or plutonium-239) absorbs a neutron, becomes highly unstable, and splits into two or more smaller, lighter nuclei known as fission fragments. This event is not just a nuclear reaction. It is an important damage-producing event within the solid fuel lattice. A single fission event releases a massive amount of energy, roughly 200 MeV (million electron volts), which is immediately converted into kinetic energy of the fragments and heat.
Fission fragments – These are the two (occasionally three, in ternary fission) highly energetic, positively charged, and unstable nuclei produced when a heavy, fissionable nucleus (such as uranium-235 or plutonium-239) splits after capturing a neutron. These fragments are the direct, primary nuclei born from the fission event, typically in the mass range of gallium (Ga) to dysprosium (Dy), before they undergo radio-active decay to become stable fission products.
Fission product behaviour – It refers to the study of the characteristics, chemical states, migration, and physical changes of elements (fission products) generated during the nuclear fission process within a fuel material. This field focuses on how these products affect the fuel’s chemistry, micro-structure, and physical properties (such as swelling) during steady-state operation, power transients, and accident conditions.
Fission products – These are the smaller atoms produced when a large atom undergoes fission, frequently extremely radioactive.
Fission rate – It is the number of nuclear fission events occurring per unit volume per unit time, typically expressed in units of fissions per cubic centimeter per second. It is a critical parameter for quantifying the amount of fuel consumed (burn up) and for modeling the production of fission gas bubbles, which impact the structural integrity and swelling of fuel rods.
Fissure – It is a small crack-like weld discontinuity with only slight separation (opening displacement) of the fracture surfaces. The prefixes macro or micro indicate relative size. In mining, it is an extensive crack, break, or fracture in rocks.
Fit – It defines the relationship between two mating parts (typically a hole and a shaft) based on their dimensional tolerances and allowances before assembly. It determines whether the parts are going to assemble with a gap, with no gap but free positioning, or with complete tightness.
Fit capability – It is frequently quantified through fit capability indices. It refers to the ability of a production process to consistently manufacture mating components (such as a shaft and a hole) which satisfy defined assembly requirements, including clearances, tolerances, and functional performance. It extends the concept of process capability from single parts to the interaction between two parts, ensuring they fit together reliably without exceeding specified variability.
Fitness for purpose – It is one of the objectives of standards. Standards help in identifying the optimum parameters for the performance of a process, product, or services and the method for evaluating product conformity. Standards also lay down conditions for using the process, product, or service, as otherwise any failure of the process, product, or service because of improper use can be attributed by the user to a deficiency or lack of quality of the process, product, or service.
Fits and tolerances – These define the allowable dimensional variation and the tightness / looseness between mating metal parts (e.g., shaft and hole) in assembly. Tolerances are the permitted deviation from a nominal dimension. Fits determine if the assembly is a clearance (loose), interference (tight), or transition (either) type.
Fitted coordinate system – It is a boundary-fitted approach which transforms the physical plane onto a square numerical plane for computational analysis, facilitating the discretization of governing equations using numerical methods.
Fitted mesh – It refers to a mesh surface which conforms to the interface of fluid domains, allowing for accurate tracking of the free surface and ensuring sharp interfaces during numerical calculations. This approach reduces the need for interface markers and facilitates the efficient prescription of boundary conditions, while also needing careful management of mesh quality to maintain numerical stability and convergence.
Fitting – It is a device which is used for connecting elements in fluid lines e.g., elbows, tees, nipples, unions, and flanges etc.’
Fixation point – It refers to a specific, localized point, line, or area where a structural component is constrained, or fastened.
Five-axis CNC (computer numerical control) spring-makers – These are advanced computer-controlled machines designed to produce complex wire forms and springs by moving cutting tools and wire guides along five distinct axes simultaneously. These machines typically utilize three linear axes (x, y, z) and two rotational axes (frequently ‘a’ and ‘b’ or ‘b’ and ‘c’) to shape wire, enabling the creation of intricate spring geometries in a single setup, which increases efficiency, precision, and reduces production time by roughly 30 % to 40 %.
5G mobile communication technology – It refers to the application of fifth-generation mobile communication technology (high-speed, low-latency, massive connectivity) to digitize, automate, and secure manufacturing processes. It succeeds 4G wireless broadband technology (long-term evolution, LTE) and previous generations. It aims to provide significantly faster data speeds, lower latency, and increased capacity compared to previous generations, enabling new applications and services. 5G mobile communication technology is a global standard developed by the 3rd generation partnership project (3GPP). It enables real-time monitoring, AI (artificial intelligence) quality inspection, remote-controlled cranes, and predictive maintenance in challenging, high-interference environments. 5G mobile communication technology enables smart manufacturing through IoT (internet of things) devices.
Five-high leveller – It has only one row of the intermediate rolls between work rolls and backup roll, normally in the lower frame, while its upper frame contains only work rolls and back-up rolls as in four-high levellers. Hence, it gives better capability for shape correction than the six-high leveller, while preventing marking on one side of the strip surfaces.
Five-number summary – It is the summary for a numeric variable, the least value (minimum), the lower quartile, the median, the upper quartile, and the greatest value (maximum), in that order. These are shown graphically in a boxplot.
Five-S (5S) – It is a structured work=place organization and lean management methodology designed to improve efficiency, safety, and productivity by reducing waste. Derived from Japanese principles, it focuses on organizing, cleaning, and maintaining a work area through five steps namely Sort (Seiri), Set in Order (Seiton), Shine (Seiso), Standardize (Seiketsu), and Sustain (Shitsuke).
5-whys analysis – It is a simple, iterative problem-solving technique used to identify the root cause of an issue by asking ‘why?’ five times. By peeling away layers of symptoms, this method moves beyond immediate, superficial fixes to uncover fundamental process or system failures, preventing recurrence.
Fixed assets – These are possessions such as buildings, machinery, and land which are unlikely to be converted into cash during the normal operational cycle.
Fixed automation – It is normally custom-engineered, special-purpose equipment to automate a fixed sequence of operations. It is used in high volume production with dedicated equipment, which has a fixed set of operation and designed to be efficient for this set. Continuous flow and discrete mass production systems use this automation. Fixed automation is normally associated with high production rates and inflexible design of the product.
Fixed axis – It refers to a stationary line around which a rigid body, such as a machine component, rotates. During rotation, this axis remains unmoving in the inertial frame of reference, meaning the object’s rotation does not change its orientation in space.
Fixed bed – It refers to a reactor or vessel filled with a stationary (fixed) bed of solid particles, such as ore, coke, or catalyst pellets, through which a fluid (gas or liquid) flows, typically in a vertical direction. The key distinction is that the solid material (the bed) does not move significantly, while the reactant gas or liquid passes through the void spaces between the particles.
Fixed bed gasifier – It is a type of reactor used for coal or biomass gasification, where solid feed material (coal, coke, or ore) is supported on a grate and moves slowly downward under gravity, forming a fixed bed which is penetrated by gasifying agents (air, oxygen, or steam). These gasifiers are frequently referred to as ‘moving bed’ gasifiers since the bed descends as solid fuel is consumed.
Fixed bed operation – It is a process where solid material, frequently catalysts, reductants, or ores, is held stationary inside a reactor (a bed) while liquid or gas reactants pass through it. These semi-continuous systems are mainly used for heat transfer, mass transfer, or catalytic reactions like roasting, reduction, and refining.
Fixed bed reactor – It is a vessel containing a stationary bed of solid materials, typically catalysts, reducing agents (like coke), or ore, through which reactant gases or liquids flow. It is characterized by high, consistent packing of particles, low operating costs, and effective thermal control in industrial-scale gas reactions, such as reduction.
Fixed blade – It is also called stator guide vane / nozzle guide vane in a turbine. It is a stationary component attached to the casing, designed to direct high-temperature working fluid onto rotor blades at an optimal angle while accelerating it through converging shapes. Fixed blades are designed to withstand high thermal fatigue, creep, and oxidation. These blades are frequently constructed from nickel-based superalloys to withstand temperatures often exceeding 1,000 deg C. They are designed to withstand high temperatures which lead to oxidation and erosion. These blades frequently involve complex internal channels for air cooling, which helps maintain the material below its softening point.
Fixed camera – It is a stationary imaging device installed in a rigid position with a set field of view (FOV) to monitor specific production lines, machinery, or material surfaces. Unlike PTZ (pan-tilt-zoom) cameras, fixed cameras do not move during operation, providing consistent, high-speed, and high-resolution data necessary for automated defect detection, surface quality inspection, and process control.
Fixed capital investment – It refers to the total cost needed to design, construct, and install a manufacturing plant, making it fully operational. It represents a long-term, non-disposable investment in physical assets, such as furnaces, crushers, and buildings, which are not consumed during the production process but are used to generate revenue over several years.
Fixed carbon – It is the solid, combustible, non-volatile carbon residue remaining after coal, coke, or biomass is heated to drive off moisture and volatile matter, typically at 900 deg C to 950 deg C. It is the carbon remaining after volatile matter escapes, but it is not 100% pure carbon, as it can contain small amounts of sulphur, nitrogen, oxygen, and hydrogen. It represents the main solid fuel component and reducing agent, calculated as 100 – (ash + moisture + volatile matter) %.
Fixed cavity – It typically refers to the stable, stationary, or non-moving part of a mould or die set. It represents the ‘female’ or concave half of the mould which shapes the external surface of the casting, which is attached to the stationary platen of a casting machine.
Fixed component – It refers to an element, cost, or item which remains constant and does not change with the volume of production, activity levels, or time. It is a foundational element in organizational management which provides stability, predictability, and is typically established through contracts, depreciation schedules, or lease agreements.
Fixed costs – These are those costs which do not increase with the volume of production, e.g., the depreciation, interest on capital, and overhead labour costs etc.
Fixed cross-section – It refers to a structural member whose cross-sectional shape, area, and properties remain constant along its entire longitudinal axis. It represents a uniform profile used to ensure consistent structural strength, stiffness, and distribution of stress, such as in extruded beams, shafts, or columns.
Fixed dummy block – It is a hardened steel component permanently attached to the stem of an extrusion press, acting as a direct extension of the ram to push a heated metal billet through a die. Unlike traditional ‘floating’ (loose) dummy blocks, fixed blocks remain connected to the ram during the return stroke, eliminating the need for manual handling, improving safety, reducing dead cycle time, and providing better centering.
Fixed duration – It is a task in which the time required for completion is fixed.
Fixed effect – It is an unobserved characteristic of subjects which is both a predictor of the study endpoint and correlated with one or more explanatory variables in a regression model. Left unaddressed, it leads to biased regression estimates.
Fixed end – It is the point on a conveyor system where components are permanently secured, requiring occasional checks for stability and proper attachment.
Fixed end moments – These are the internal bending moments developed at the supports of a restrained (fixed) beam or member when subjected to external loading. Since the supports prevent rotation and deflection, they produce resistive moments, ensuring the slope at the ends remains zero.
Fixed-feed grinding – It is the grinding in which the wheel is fed into the work, or vice versa, by given increments or at a given rate.
Fixed field – It is a data structure in which every data element is defined by a specific, constant position and length within a record. Unlike delimited fields, fixed fields do not use separators (like commas) to differentiate data, instead, the software relies on character position to identify the data.
Fixed grain – It refers to a specific, immovable particle within a larger granular system (such as in a silo or hopper), frequently used in experiments to study clogging, flow dynamics, and the formation of arch structures.
Fixed grid – It is a, normally rectangular, structured layout or mesh with constant spacing between points or cells. It is characterized by unchanging, pre-defined boundaries, dimensions, or spectral channels which do not adjust dynamically to content or demand. Fixed grids offer high computational efficiency and structural simplicity in engineering and networking.
Fixed guard – It is the stationary protective barriers installed on equipments to prevent access to hazardous areas, needing regular inspections for integrity and compliance.
Fixed-land bearing – It is an axial-load or radial-load bearing equipped with fixed pads, the surfaces of which are contoured to promote hydrodynamic lubrication.
Fixed lens – It is a camera lens with a single, non-adjustable focal length, meaning it cannot zoom in or out. Since they lack complex zooming mechanisms, these lenses typically offer superior image sharpness, wider maximum apertures (better low-light performance), and a more compact, lightweight design compared to zoom lenses.
Fixed link – It is a kinematic link (rigid body) within a mechanism that remains stationary, acting as the reference frame or base, while other links move relative to it. It is important for defining the motion of mechanisms, such as the ground link in a four-bar linkage.
Fixed-load or fixed-displacement crack-extension-force curves – These are the curves got from a fracture mechanics analysis for the test configuration, assuming a fixed applied load or displacement and generating a curve of crack-extension force against the effective crack size as the independent variable.
Fixed mandrel – It is a device for producing hollow extrusions of regular cross section. The tapered mandrel is attached to the main extrusion ram and passes through the hollow billet. As the ram moves forward the mandrel passes, with the billet, through the die giving a product, slightly tapering in wall thickness along its length. The mandrel is tapered to facilitate its removal when extrusion is complete.
Fixed membrane – It is a specialized, permselective barrier which acts as a stationary inter-phase, controlling the transport of materials (liquids or gases) between two phases. These membranes are ‘fixed’ in the sense that they are supported by a structure and do not move within the process, frequently acting as separating agents in fixed-plate heat exchangers, membrane contactors, or as supported liquid membranes.
Fixed offshore platforms – These are structures designed for the extraction of resources from the sea floor, needing specialized contractors for fabrication and installation, with careful consideration of design for transportation, lifting, and installation.
Fixed oil – It is an imprecise term denoting an oil which is difficult to distill without decomposition.
Fixed-pad bearing – It is an axial-load or radial-load bearing equipped with fixed pads, the surfaces of which are contoured to promote hydrodynamic lubrication.
Fixed platforms – These are permanent offshore structures, typically used for oil / gas drilling or production in shallow to moderate waters (normally below 150 meters to 500 meters), anchored to the seabed with piled steel jackets or concrete caissons. They are designed with high stiffness and natural periods well below wave frequencies, allowing them to remain stable and resist environmental loads.
Fixed plug – It refers to a hardened, stationary mandrel or tool used during tube drawing, tube sinking, or wire drawing to define the final internal diameter (ID) and wall thickness of a metallic tube. The plug is placed inside the tube at the die’s conical convergent zone, controlling the inner diameter (ID) while the die controls the outer diameter (OD). Unlike ‘floating plugs’, a fixed plug is held in place by a long, rigid rod (plug rod) which passes through the tube and connects to a stationary bench, maintaining its position within the die.
Fixed point – It normally refers to a stationary component in a mechanical system (a pivot or anchor) or a steady-state condition in a dynamical system. It also refers to a number format with a fixed decimal / radix position for consistent, precise calculations.
Fixed-point algorithm – It mainly refers to an iterative computational method used to find a state or value which remains unchanged under a specific transformation. Depending on the engineering branch, this can refer to either numerical methods for solving equations or hardware-specific arithmetic.
Fixed-point arithmetic – It is a method of representing fractional numbers using a pre-determined number of integer bits, where the binary point remains in a fixed position. Used mainly in embedded systems and ‘digital signal processing’ (DSP) for efficiency, it allows arithmetic operations to be performed using fast integer hardware without a dedicated floating-point unit.
Fixed-point number – It is a real number representation method in computing where the radix point (binary or decimal) is locked in a specific, predetermined position. It represents fractional values using integer arithmetic, making it faster and more resource-efficient than floating-point for embedded systems and ‘digital signal processing’ (DSP).
Fixed poly-crystal constitutive law – It is also called static poly-crystal constitutive law. It is a mathematical framework which relates the mechanical response (stress, strain, strain rate) of a poly-crystalline material to its micro-structure, typically assuming a fixed set of grain orientations and shapes (non-evolving textures) during deformation. It is fundamentally a micro-macro homogenization approach designed to bridge single-crystal behaviour with the bulk behaviour of a poly-crystalline aggregate.
Fixed-position stop system – It is a method of addressing problems on assembly lines by stopping the line at the end of the work cycle, i.e., at a fixed position, if a problem is detected which cannot be solved during the work cycle.
Fixed position welding – It is the welding in which the work is held in a stationary position.
Fixed price contract – A fixed price contract pays an agreed-upon fee and does not incorporate other variables, such as time and cost.
Fixed rate – It refers to a constant, unchanging interest rate applied to financial contracts or a set fee structure which remains stable regardless of fluctuating market conditions, providing predictability for long-term projects, equipment financing, and manufacturing investments. It ensures consistency in loan repayments and budget planning.
Fixed reference frame – It is a coordinate system, defined by an origin and three orthogonal axes (x, y, z), which remains stationary relative to a specific observer or a fixed base, frequently considered inertial (not accelerating). It serves as the base for measuring position, velocity, and acceleration. It is important for consistent motion analysis and Newtonian mechanics.
Fixed resistor – It is a passive two-terminal electrical component designed to introduce a specific, constant ohmic resistance into a circuit. Unlike variable resistors, its resistance value is set during manufacturing and cannot be adjusted, serving important engineering functions such as limiting current flow, dividing voltages, and setting biasing.
Fixed roof tank – It is an above-ground, cylindrical steel storage vessel with a permanently attached cone, dome, or flat roof, designed mainly to store low-volatility liquids at or near atmospheric pressure. It features vapour-tight welded construction, pressure-vacuum (breather) valves, and a permanent vapour space above the liquid.
Fixed speed wind energy conversion system – It is a design where the wind turbine rotor operates at a nearly constant speed, determined by grid frequency, regardless of wind speed. It typically uses a squirrel cage induction generator (SCIG) directly connected to the grid, featuring high reliability, low cost, simple construction, but limited speed flexibility.
Fixed speed system – It is a configuration where a motor or generator operates at a constant rotational speed (revolutions per minute, rpm) determined by the grid frequency or mechanical gear ratio, regardless of load or input fluctuations. Common in industrial motors and early wind turbines, they prioritize simplicity, robustness, and lower initial costs over energy efficiency.
Fixed stop – It is a permanent or adjustable physical reference point within a tool, die, or machine used to precisely locate a work-piece or limit the motion of a machine component.
Fixed structure – It refers to a built, load-bearing assembly rigidly connected to its foundation to resist movement, such as a bridge, skyscraper, or offshore platform. It denotes a permanent, stationary arrangement of elements, frequently featuring rigidly fixed joints, or fixed beams, which transfer all forces and prevent rotation. These structures are designed for permanency and stability, featuring components (like beams and columns) connected to work together against external forces, such as wind or seismic loads. It is also an estimation algorithm which uses the same set of models at all times.
Fixed transmitter – It is a device operated at a permanent, known, and unchanging location, typically used for point-to-point, point-to-multipoint, broadcasting, or fixed radio-communication services. These high-power or fixed-location stations (e.g., fixed micro-wave links) are distinguished by their immobility.
Fixed tube sheet heat exchanger – It is a type of shell-and-tube exchanger where the tube bundle is securely welded or bolted at both ends directly to the outer shell, preventing removal of the tube bundle. It is the most economical and common design, featuring straight tubes, high-pressure capability, and suitability for applications needing minimal fluid cross-contamination.
Fixture – It is a specialized work-holding or support device used to securely locate, support, and hold a work-piece in a specific position and orientation during machining, welding, inspection, or assembly operations. Unlike jigs, fixtures do not directly guide the cutting tool, but they provide the stability needed to achieve high accuracy, repeatability, and inter-changeability of parts.
Fixture hardening – It is also known as press quenching or die quenching. It is a specialized metallurgical heat treatment process used to minimize distortion and control dimensional changes in metal parts, typically gears, rings, or bearing races, during the quenching phase of hardening. It involves placing the heated (austenitized) work-piece into a specialized fixture or die immediately before or during the rapid cooling (quenching) process to constrain its shape while it shrinks.
Fixturing – It is the placing of parts to be heat treated in a constraining or semi constraining apparatus to avoid heat-related distortions.
Flag – It is a marker inserted adjacent to the edge at a splice or lap in a roll or foil.
Flag operation – It normally refers to the use of a variable, bit, or signal (the flag) to indicate a specific condition, state, or to control the flow of a process. It acts as a signaling mechanism, setting a flag to ‘on’ (1/true) or ‘off’ (0/false) to prompt a particular action or note that a milestone has been reached.
Flake – It is a short, discontinuous internal crack in ferrous metals which is attributed to stresses produced by the localized transformation and hydrogen-solubility effects during cooling after hot working. In fracture surfaces, flakes appear as bright, silvery areas with a coarse texture. In deep acid-etched transverse sections, they appear as discontinuities which are normally in the midway to centre location of the section. It is also termed hairline cracks and shatter cracks.
Flake graphite – It is the graphitic carbon, in the form of platelets, which is occurring in the micro-structure of gray iron.
Flaking – It is the removal of material from a surface in the form of flakes or scale-like particles. It is also a form of pitting resulting from fatigue.
Flake morphology – It defines the physical geometry, shape, thickness, size, and surface texture, of particles, powders, or microstructural components, typically resulting from material processing like crushing, milling, or solidification. It determines bulk density, material handling characteristics, and mechanical properties, such as in metallic flake powder metallurgy or graphite flake structures.
Flake powder – It is flat or scale-like particles whose thickness is small compared to other dimensions. Flake powder refers to metal or other material powders which have a flattened, thin, and frequently irregular shape, resembling a flake or scale. These powders are typically produced by milling spherical or other shaped powders using low-energy ball milling techniques. The resulting flake shape provides a high specific surface area and can impact the properties of materials made using these powders.
Flame – It is the product of a highly exothermic reaction and can be regarded as a body of gaseous material consisting of reacting gases and finely dispersed carbonaceous particles (soot). Flames are of two types based on their shape. They are (i) round flame, and (ii) flat or rectangular flame. These are the two most common flame shapes produced by the burners. Also, flames can be luminous or non-luminous.
Flame and plasma guniting mixes – These are guniting mixes which make use of oxy-gas, oxy-acetylene, and oxy-hydrogen torches or plasma torch for flame spraying and flame-plating of refractory compounds. The plasma torch can double to triple the gas temperature of fuel torches, but at such increased cost that it might be economically impractical for refurbishing furnace refractories.
Flame annealing – It is the annealing in which the heat is applied directly by a flame.
Flame arrestor – It is a passive safety device which allows the flow of gases or vapours while physically blocking the propagation of a flame front. It functions by extinguishing the flame through high-surface-area metal components, preventing flash-back or explosion transmission into tanks, piping systems, or atmospheric vents. Its purpose is to prevent the spread of a fire or explosion by cooling the flame front below the ignition temperature of the gas. The device contains an element, frequently crimped metal ribbon, wire mesh, or a perforated plate, which provides a large surface area, acting as a heat sink to absorb thermal energy from the flame.
Flame-assisted spray pyrolysis – It is a technique for producing thin films or nano-particles by atomizing a metal precursor solution and passing it through a high-temperature flame (e.g., oxy-liquefied petroleum gas / methane). The flame evaporates the solvent, decomposes precursors, and drives oxidation or pyrolysis, resulting in highly crystalline, pure, and uniform deposits.
Flame cleaning – It is the cleaning metal surfaces of scale, rust, dirt, and moisture by use of a gas flame.
It is a surface preparation process which uses an intense oxy-acetylene or hydro-carbon gas flame to remove contaminants, rust, and old paint from steel surfaces. The heat causes rapid thermal expansion, inducing scaling of oxides (spalling) and surface oxidation, followed by wire brushing to remove residue.
Flame combustion – It is a high-temperature, rapid gas-phase oxidation reaction which emits heat and light, characterized by a localized reaction zone with sharp temperature and concentration gradients. Flame systems involve fuel vapourization and turbulent mixing with an oxidizer (normally air) to achieve efficient, controlled energy release for applications like combustion engines, furnaces, and heaters.
Flame cone – It refers to the inner, high-temperature, distinct luminous region of a premixed flame (such as a Bunsen burner flame or welding torch). It is frequently described as the ‘inner cone’ or ‘main flame’ zone where fuel and oxidant are initially mixed and combustion begins, normally featuring a blue or white colour.
Flame cutting – The preferred term is oxygen cutting which is a group of cutting processes used to sever or remove metals by means of the chemical reaction between oxygen and the base metal at high temperatures. In the case of oxidation-resistant metals, the reaction is facilitated by the use of a chemical flux or metal powder.
Flame detection – It is the process of using specialized sensors, known as flame detectors, to identify and respond to the presence of a flame or fire. These detectors work by sensing the unique characteristics of flames, such as specific wavelengths of light (ultraviolet and / or infrared) or the heat they generate. This allows for early fire detection, triggering alarms or initiating fire suppression systems to mitigate potential hazards
Flame detector – It is a device which indicates if a fuel (liquid, gaseous, or pulverized) is burning, or if ignition has been lost. The indication can be transmitted to a signal or to a control system.
Flame envelope – It is the boundary of a combustion zone where fuel and oxidizer react, typically defined as the visible flame edge or a specific isotherm (e.g., 540 deg C or 1,200 K). It defines the shape, height, and thermal impact area of a fire, such as a plume or droplet flame.
Flame exposure – It is the interaction of flames with materials, characterized by heat flux, temperature, and duration. It involves convective and radiative heat transfer which triggers material degradation, charring, or ignition. Key metrics include flame impingement, emissivity, and adiabatic surface temperature.
Flame failure devices -These are also known as photo-cells or magic eyes. These devices are used to prevent dangerous occurrences whereby fuel continues to enter the furnace in the event when the flame unexpectedly goes out during normal operation. Modern devices detect a specific frequency within the electro-magnetic spectrum which is emitted by a flame. When activated, they force a shut down and lock out of the burner requiring manual reset. As with level limiters, they are to be fail safe, of high integrity, and self-monitoring.
Flame front – It is the leading, narrow edge of a combustion zone separating unburned reactants from burned products, where rapid chemical reactions, heat release, and, typically, laminar / turbulent transport processes take place. It is frequently modeled as a thin layer moving relative to the reactants (deflagration) or a shock wave (detonation). It constitutes a zone of intense heat and mass diffusion, acting as a discontinuity where chemical energy is released.
Flame fusion – It is also known as the Verneuil process. It is a crystal-growth technique for producing synthetic single-crystal gemstones (such as ruby, sapphire, and spinel) by melting powdered raw materials using an oxy-hydrogen flame. It is considered the founding method of modern industrial crystal growth, utilizing extremely high temperatures (around 2,200 deg C) to melt powder, which then crystallizes into a cylindrical crystal called a ‘boule’.
Flame hardening – It is a process for hardening the surfaces of hardenable ferrous alloys in which an intense flame is used to heat the surface layers above the upper transformation temperature, where upon the work-piece is immediately quenched.
Flame heating-surface quenching – It is a heat treatment process which uses oxy-fuel gas flames to rapidly heat the surface of a hardenable steel component (typically 0.4 % to 0.6 % carbon) above its austenitizing temperature (Ac3). Immediately following, the surface is rapidly cooled (quenched), normally with water jets, to produce a hard, wear-resistant martensite layer while retaining a tough, ductile, and unhardened core.
Flame impingement – It is the direct contact of a flame, generated by fuel combustion, with a surface, such as burner tubes, furnace walls, or process pipes. While used deliberately for high-rate industrial heating (e.g., smelting), it frequently represents a failure condition, causing localized hotspots, severe corrosion, reduced efficiency, and premature material failure.
Flame ionization detection – It is a technique used to detect hydro-carbons in the atmosphere, characterized by its insensitivity to nitrogen, moisture, and carbon di-oxide, while producing a non-specific response to different hydro-carbon compounds. It can identify the presence of hydro-carbons but cannot distinguish between different compounds.
Flame ionization detector – It is a scientific instrument that measures analytes in a gas stream. It is frequently used as a detector in gas chromatography. The measurement of ions per unit time makes this a mass sensitive instrument.
Flamelet – It is a localized flame structure within a turbulent combustion process, which is analogous to a laminar flame and is influenced by flame stretch and curvature. Flamelet models simplify the coupling of chemistry and transport by using look-up tables for chemical species while addressing the transport of progress variables.
Flame measurement – It is the quantitative assessment of combustion parameters, such as temperature, velocity, emissivity, and geometry (length / shape), to optimize industrial combustion processes, efficiency, and safety. It involves diagnosing flame behaviour, ensuring stability, and reducing emissions in burners, furnaces, and engines, frequently using optical (infra-red / ultra-violet) or spectroscopic methods.
Flame plating – It is also known as flame spraying. It is a thermal spray coating process where heat from a flame is used to melt or soften coating materials (like metals or ceramics) in powder or wire form. These molten or softened particles are then propelled onto a substrate to form a protective or functional coating. This technique is used to improve surface properties like wear resistance, corrosion resistance, and hardness.
Flame propagation – It is the process by which a combustion reaction front moves through a combustible mixture (gases, vapour, or solids), driven by thermal energy transfer from hot products to unburned fuel. It is key to understanding combustion efficiency in engines and fire safety, frequently governed by laminar burning velocity or turbulence. It occurs due to heat transfer and mass transfer from the burning zone to the adjacent, cold mixture.
Flame propagation rate – It is the speed of travel of ignition through a combustible mixture.
Flame propagation speed – It is the rate at which a flame front travels through a combustible mixture relative to the unburnt gas, driven by heat and mass transfer. It is a key parameter (typically 15 centimeters per second to 1 meter per second for laminar, higher for turbulent) used in combustion design to optimize efficiency, stability, and determine fuel characteristics like detonation resistance.
Flame research – It is the systematic, experimental, and computational investigation of combustion processes to understand flame dynamics, chemical kinetics, and heat release. It focuses on optimizing efficiency and reducing emissions in engines, industrial burners, and propulsion systems, while also analyzing fire safety and material flammability.
Flame resistance – It is the ability of a material to extinguish flame once the source of heat is removed. Flame resistance applies to critical end uses. Flame resistant materials can be derived from inherently flame resistance fibres (such as aramids), from additives or modified monomers in the case of manufactured fibres, or by the application of a finish, essential in the case of natural fibres.
Flame-resistant fibres – These are materials designed to resist ignition, inhibit flame propagation, and self-extinguish when removed from a heat source. These fibres are defined by high thermal stability, high char-forming potential, and a limiting oxygen index (LOI) typically above 25 %, meaning they need high oxygen levels to burn.
Flame retardancy – It refers to the ability to resist ignition, reduce heat release, and slow or extinguish flame spread. While typically associated with polymers, in metallurgy-adjacent applications (e.g., metal coating, composites), it involves adding materials like phosphorus, nitrogen, or inorganic hydroxides to create protective barriers or release non-combustible gases.
Flame retardancy mechanisms – These are chemical or physical processes which interfere with the combustion cycle, fuel, heat, and oxygen, to prevent ignition, reduce burning speed, and promote self-extinguishing. Techniques include endothermic heat absorption, dilution of fuel gases, free radical scavenging, and forming protective surface barriers (char) to isolate materials from heat and oxygen.
Flame retardancy properties – These refer to the characteristics of a material which prevent the spread of flame or slow down the rate of burning, enabling it to resist combustion and self-extinguish upon contact with a heat source. These properties are evaluated through different tests, including limiting oxygen index, flame spread tests, and heat release tests.
Flame retardant low smoke – It refers to specialized electrical cables, wires, or sheathing materials engineered to resist the spread of fire while producing minimal smoke and toxic fumes when burned.
Flame retardants – These are certain chemicals which are used to reduce or eliminate the tendency of a resin to burn.
Flame safeguard – It is a control which sequences the burner through several stages of operation to provide proper air purge, ignition, normal operation, and shutdown for safe operation.
Flame scanner – Flame scanner is a device used to observe the flame in a boiler. If the flame is extinguished for any reason, the flame scanner sends a signal to close the fuel supply valve to prevent a possible explosion.
Flame sensor – It is an electronic device designed to detect and respond to the presence of a flame. These sensors work by sensing the unique characteristics of light, infrared radiation, or ultraviolet radiation emitted by a flame. They are crucial in safety systems, ensuring that equipment operates correctly and detecting potential fire hazards early.
Flame spray – It is a thermal coating process where metallic or ceramic material (wire, rod, or powder) is melted using an oxy-fuel combustion flame and propelled by compressed air onto a substrate. It creates protective coatings for corrosion protection, wear resistance, and surface restoration, characterized by lower costs and suitability for large components.
Flame spray gun – It is a thermal spray device used to melt coating materials, such as metal wire or powder, using an oxy-fuel flame (typically oxygen combined with acetylene, propane, or hydrogen) and propel them onto a substrate. It creates protective coatings for corrosion resistance, surface reclamation, and wear improvement.
Flame spraying – It is a thermal spraying process in which an oxy-fuel gas flame is the source of heat for melting the surfacing material. Compressed gas may or may not be used for atomizing and propelling the surfacing material to the substrate.
Flame spray pyrolysis – It is an industrial, high-temperature gas-phase engineering process used for the rapid, one-step synthesis of functional nano-sized metal oxides. Liquid metal precursors are atomized into a spray, ignited, and combusted, converting them into nano-particles through nucleation and growth. It is highly prized for producing customizable, crystalline, and high-purity nano-powders.
Flame stability – It is the ability of a combustion flame to remain ignited and anchored at a burner, avoiding extinction (blow-out) or traveling back into the supply line (flash-back) despite variations in fuel flow, air velocity, or mixture composition. It is an important aspect of combustor design which balances fuel speed with flame propagation speed, ensuring reliable operation, high combustion efficiency, and safety.
Flame straightening – It is the correcting distortion in metal structures by localized heating with a gas flame.
Flame synthesis – It refers to a technique for synthesizing metal and metal oxide particles using a flame, which enables the creation of catalysts with minimal post-treatment steps and the ability to produce multi-component materials. This process can be classified into flame spray pyrolysis (FSP) for combustible solutions and flame-assisted spray pyrolysis (FASP) for non-combustible solutions.
Flame temperature – It is the maximum theoretical temperature achieved when a fuel and oxidizer react completely without losing heat to the surroundings or performing work. It is the maximum temperature a premixed flame can reach for a given equivalence ratio, assuming the flame is the sole heat source and any heat transfer results in a lower temperature. It represents an energy balance where all heat of combustion raises product gas temperatures. It considerably influences heat transfer in the lower zones of a blast furnace, with typical target values set between 2,000 deg C and 2,200 deg C.
Flame treatment – It is a surface modification process which uses an oxygen-rich gas flame to clean, oxidize, and activate the surface of materials (mainly polymers) to improve printability, bonding, and wetting. It works by breaking molecular bonds and introducing polar functional groups, raising surface tension for better coating adhesion.
Flame tube – It is a heat-resistant tube within a combustion chamber where the actual burning of fuel occurs. It can also refer to a component in a Rubens tube, which is an apparatus for demonstrating acoustic standing waves.
Flame velocity – It is also called burning velocity. It is the speed at which a laminar or turbulent flame front propagates relative to the unburned gas mixture, normally measured in centimeter per second or meter per second. It represents the rate at which fuel and oxidizer are consumed, acting as an important parameter for burner design and engine combustion.
Flame zone – It refers to the specific region within a flame where rapid combustion, substantial heat release, and intensive chemical reactions occur, frequently divided into preheat, reaction, and recombination sub-zones. It is characterized by high temperatures and the presence of intermediate species like carbon mono-oxide (CO) and hydrogen (H2).
Flaming combustion – It is a rapid, high-temperature, gas-phase oxidation reaction (exothermic) which produces visible light (flames) and substantial heat release. It occurs when vapourized fuels or pyrolysis gases mix with an oxidizer (normally oxygen), sustained by a self-perpetuating chain reaction. It involves the gas-phase burning of volatile gases released from solid or liquid fuel through pyrolysis or vapourization.
Flammable gas – It is a substance which exists entirely as a gas at normal atmospheric temperature and pressure, capable of igniting and burning when mixed with air / oxygen and provided with an ignition source. Key parameters include a lower flammable limit (LFL), upper flammable limit (UFL), and auto-ignition temperature.
Flammability – It is susceptibility to combustion.
Flange – It is a formed pipe fitting consisting of a projecting radial collar with bolt holes to provide a means of attachment to piping components having a similar fitting. It is the end piece of flanged-end valves.
Flange assembly – It is a method of connecting pipes, valves, pumps, and other equipment in a piping system, forming a mechanical, non-permanent joint which can be disassembled for cleaning, maintenance, or repair. It functions as a secure connector, providing strength and a leak-proof seal by pressing two machined surfaces together.
Flange connection – It is a method of connecting piping and valves which allows for disassembly for purposes such as cleaning, maintenance, repair, or inspection, typically using bolts and nuts with a gasket for sealing. Flanges are designed as per standards, which specify size and pressure class requirements.
Flange contact – It refers to the interaction and physical touching between two mating flange surfaces, typically occurring under bolt load to create a seal, or in specific mechanical scenarios such as railway wheel flange interaction with tracks. It ensures structural integrity, seals joints against pressure, and maintains proper alignment in pipelines, machine housings, and structural steel.
Flange coupling – It is a very widely used rigid coupling and consists of two flanges keyed to the shafts and bolted. The main features of the design are essentially (i) design of bolts, (ii) design of hub, and (iii) overall design and dimensions.
Flanged joint – It is a detachable, bolted connection between two pipes, valves, pumps, or other equipment components, designed for pressure sealing in piping systems. It consists of two flanges (flange assembly), a gasket inserted between them, and a set of bolts and nuts which provide the clamping force needed to create a leak-proof seal.
Flange end valve – In flange end valve, there is a raised area of a flange face which affords a seal with a mating flange face by means of a flat gasket of the same diameter as the raised face. Raised face flanges seal with a flat gasket made of materials designed for installation between the raised faces of two mating flanges (both with raised faces). The raised faces have a prescribed texture to increase their gripping and retaining force on this flat gasket. Some users of raised face flanges specify the use of spiral wound gaskets.
Flange face – It is the machined surface of a pipe flange which contacts a gasket to create a pressure-retaining seal. It is a critical component in piping systems, designed to ensure integrity and prevent leaks, with types and finishes determined by standards based on pressure and temperature requirements.
Flanging -It is bending a sheet along a curved line. In sheet metal work, flanging refers to a process where the edge of a metal sheet is bent at a specific angle, typically 90-degree, to create a flange. This can be done to reinforce the edge, create a connection point for other parts, or improve the part’s appearance. Flanging is a versatile process used in several industries.
Flange joint – It is a detachable, mechanical connection used to join two piping components (pipes, valves, or fittings) by bolting together two identical flanges, typically with a gasket between them to ensure a leak-proof seal. It enables easy assembly, disassembly, and maintenance in piping systems.
Flangeless valve – It is valve style common to rotary control valves. Flangeless valves are held between the flanges by long through-bolts (sometimes also called wafer-style valve bodies).
Flange load – It refers to the forces acting on a flange connection, mainly comprising internal pressure (hydrostatic end force), bolt tensioning force, and gasket sealing load. These loads, divided into assembly, operating, and gasket seating loads, determine the needed bolt size, quantity, and flange thickness, ensuring structural integrity and preventing leakage. It is the total force compressing the gasket to create a seal. It is the effective pressure resulting from the bolt loading.
Flange shape – It is a protruding rim, ridge, collar, or edge designed to strengthen a structure, guide movement, or create a sealed connection between pipes, tubes, or machine components. Typically, it is flat and circular with bolt holes, they enable assembly and disassembly for maintenance, normal in piping systems and structural steel, frequently designed to standards.
Flange tap – It is a pressure measurement tapping point located in an orifice flange, positioned exactly 25.4 milli-meters upstream and 25.4 milli-meters downstream from the orifice plate face. Mainly used in flow measurement, these taps allow differential pressure (dP) transmitters to measure pressure changes, facilitating accurate fluid flow calculation.
Flange weld – It is a weld which is made on the edges of two or more members to be joined, normally light gauge metal, at least one of the members being flanged.
Flange weld size – It is the weld metal thickness which is measured at the weld root.
Flange width – It refers to the horizontal dimension of the top or bottom flange in I-beams, H-beams, or T-beams, determining bending strength and lateral stability. In composite construction, it is defined as the ‘effective flange width’ the portion of a slab which acts with the beam, calculated based on beam span, spacing, and shear lag effects rather than total slab width.
Flanging – It is a cold sheet metal forming process that bends or creates a projecting rim, edge, or collar (a ‘flange’) on a flat or curved metal work-piece, such as a sheet, cylinder, or pre-punched hole. It typically involves bending the metal edge to a 90-degree angle to reinforce the part, remove sharp edges, or provide a surface for joining, such as welding or bolting.
Flank – It is the end surface of a tool which is adjacent to the cutting edge and below it when the tool is in a horizontal position, as for turning.
Flank face – It is also called relief face. It is the surface of a cutting tool which is located below and adjacent to the cutting edge. It is the surface which faces the newly machined, finished surface of the work-piece. Unlike the rake face, which engages with the chip, the flank face’s main role is to provide clearance to prevent the tool from rubbing against the work-piece.
Flank of tooth – It is the functional side surface of a gear tooth located below the pitch circle (or pitch cylinder), extending down to the root fillet. It is the part of the tooth profile which contacts the corresponding tooth on a mating gear, important for power transmission, wear management, and load distribution.
Flank wear – It is the loss of relief on the flank of the tool behind the cutting edge because of the rubbing contact between the work and the tool during cutting. It is measured in terms of linear dimension behind the original cutting edge.
Flank wear land – It is the abrasion-induced, roughly flat surface formed on the relief (flank) face of a cutting tool, caused by friction against the newly machined work-piece surface. It is measured as width from the original cutting edge, acting as a main indicator of tool life and dimensional accuracy.
Flap mode – It refers to a mode shape of a wind turbine blade characterized by mainly out-of-plane deformation, with some coupling to in-plane and torsional motions because of the blade’s stiffness and twist. The first flap mode has the lowest natural frequency and is associated with the least stiff direction of the blade.
Flapper gate – It is an articulated or pivoting plate strategically used to guide material selectively on a conveyor system, demanding periodic evaluations for precise functioning.
Flapping – It is the rapid, unstable oscillation of a link or route between active and inactive states.
Flare-bevel-groove weld – It is a weld in a groove which is formed by a member with a curved surface in contact with a planar member.
Flare-V-groove weld – It is a weld in a groove which is formed by two members with curved surfaces.
Flare stack – an elevated vertical pipe which is used so that ignition and combustion of the discharge take place at a considerable height. A flare stack is a part of a flare system in an industrial plant where all over-pressurized gases and liquids are released by a pressure safety valve and burnt to prevent over-pressurizing some of the equipment and facilities in a plant.
Flare system – It is a safety engineering, pressure relief, and disposal system in industrial plants which safely combusts flammable waste gases, liquids, or vapours from relief valves, vents, and blow-down systems. It acts as a final line of defense against over-pressure, converting hazardous hydro-carbons into carbon di-oxide and water.
Flare test, steel – It is a standardized non-destructive testing method used to evaluate the surface quality and integrity of steel products, particularly focusing on the presence of surface defects such as cracks, laps, or inclusions which can compromise the material’s performance. It involves heating a steel sample to a specified temperature and then observing the surface for the formation of characteristic surface flares or deformation patterns which indicate underlying flaws or structural irregularities. Fundamentally, the flare test assesses the steel’s ability to withstand thermal and mechanical stresses without showing surface anomalies which can lead to failure during service. It is an important component of quality assurance in steel manufacturing, especially for products subjected to high-temperature or dynamic loading conditions. The test provides insights into the microstructural stability, surface cleanliness, and defect susceptibility of steel, fitting within the broader framework of materials characterization and quality control protocols.
Flare test, tubes and pipes – It is a test applied to tubing, involving tapered expansion over a cone. It is similar to the pin expansion test. It is a destructive quality control method used to determine the ductility, malleability, and forming behaviour of tubes or pipes. It involves expanding one end of a tube sample using a conical mandrel until it reaches a specified diameter or percentage increase without creating cracks.
Flare tip – It is the specialized burner assembly at the top of a flare stack designed to safely and efficiently ignite and combust vent gases from industrial processes. Engineered with high-temperature, corrosion-resistant materials, it includes flame retention devices to ensure stable combustion over a wide range of velocities, preventing flame lift-off and reducing environmental impact.
Flaring – It consists of forming an outward acute-angle flange on a tubular part. It is also forming a flange by using the head of a hydraulic press. Flaring of the waste gas is the process of burning off unwanted or excess flammable gases, frequently produced during industrial operations, rather than releasing them directly into the atmosphere. This controlled burning converts the gases into less harmful substances like carbon di-oxide and water vapour, reducing the environmental impact, particularly from potent greenhouse gases like methane.
Flaring test – It is a destructive quality control procedure used to determine the ductility, malleability, and forming behaviour of metal tubes. The test involves forcing a tapered tool into the end of a tube, expanding it until it forms a flared cone, and examining it for surface cracks
Flash – In forging, it is the metal in excess of which is needed to fill the blocking or finishing forging impression of a set of dies completely. Flash extends out from the body of the forging as a thin plate at the line where the dies meet and is subsequently removed by trimming. Since it cools faster than the body of the component during forging, flash can serve to restrict metal flow at the line where dies meet, hence ensuring complete filling of the impression. In casting, it is a fin of metal which results from leakage between mating mould surfaces. In welding, it is the material which is expelled or squeezed out of a weld joint and that forms around the weld. In powder metallurgy, flash is the excess metal forced out between the punched and the die cavity wall during compacting or coining. In composites, a flash is that portion of the charge which flows from or is extruded from the mould cavity during the moulding. It is extra plastic attached to a moulding along the parting line, which is to be removed before the part is considered finished.
Flash allowance – In flash butt welding (FBW), flash allowance is the total length of material (or the quantity of shortening of the work-pieces) consumed during the flashing stage, where the surfaces are heated by arcing to a plastic state before being forged together.
Flash analog-to-digital converter – It is an ultra-high-speed, parallel-architecture circuit which converts analog voltages into digital signals in a single clock cycle. It uses a ladder of ‘2 to the power– 1’ comparators to simultaneously compare input voltage against reference levels, making it the fastest ADC (analog-to-digital converter) type, typically used in giga-hertz-range applications. They are ideal for high-speed applications, such as radar and digital oscilloscopes, but limited by high power consumption and high component count (e.g., 255 comparators for 8-bit resolution).
Flash annealing – It consists of annealing of a work-piece by rapid heating and a short dwell time at the appropriate temperature.
Flash-back – It is a recession of the welding or cutting torch flame into or back of the mixing chamber of the torch.
Flash-back arrestor – It is an important safety device used in oxy-fuel welding, cutting, and allied processes to prevent a flame from traveling backward (flashback) into the equipment, hoses, and gas cylinders. It acts as a safety barrier to protect personnel and equipment from damage or explosions caused by the reversal of gas flow.
Flash butt welding – It is a non-standard term for flash welding.
Flash chamber – It is a vessel which separates a high-pressure liquid-vapour mixture into liquid and vapour components, normally used in refrigeration and chemical processing. Placed after an expansion valve, it allows flashing (partial vapourization) to occur, sending liquid to the evaporator and bypassing vapour to the compressor to improve system efficiency and cooling capacity.
Flash converter – It is a high-speed analog-to-digital converter that uses a parallel network of comparators and a resistor ladder to convert analog signals into digital data in a single clock cycle. It is designed for maximum speed, frequently used in video, radar, and ultra-high-speed data acquisition.
Flash coat – It is a thin metallic coating normally less than 0.05 millimeters in thickness.
Flash design – It refers to the engineering of the space within a die where this excess material flows, important for ensuring the main part is fully formed.
Flash dimensions – The main dimensions of a flash section are the flash land width and flash thickness.
Flash distillation – It is a single-stage separation process where a pressurized, heated liquid mixture is partially vapourized by suddenly dropping its pressure through a valve into a flash drum. This instantaneous vaporization separates the mixture into a vapor phase (enriched with lighter components) and a liquid phase (enriched with heavier components) at equilibrium.
Flash drum – It is a pressure vessel used to separate a liquid-vapour mixture into its respective phases, frequently after a pressure reduction allows ‘flash evaporation’. It is a single-stage separation unit where preheated or pressurized liquid, when released through a valve into the drum, partially vapourizes.
Flash extension – It is that portion of flash which is remaining on a forged part after trimming. It is normally included in the normal forging tolerances.
Flash-extension tolerances – These tolerances define the maximum allowable length of excess metal (flash) which extends beyond the designed parting line of a forging or casting after it has been forced between the dies. It measures how far the flash extends outwardly from the body of the forging.
Flash evaporation – It is a rapid, partial vapourization process occurring when a pressurized, saturated liquid passes through a throttling device (e.g., valve) into a lower-pressure vessel (flash drum), causing instant ‘flashing’ to vapour and cooling the liquid. It is an isenthalpic, equilibrium process used to separate components or create potable water.
Flash fire – It is a rapid, subsonic fire which spreads through a diffused, pre-mixed flammable vapour, gas, or dust cloud without producing substantial damaging over-pressure. It is characterized by high heat flux, frequently around 84 kilo-watt per square meter, short duration (normally below 3 seconds), and flames traveling from the ignition point back to the source.
Flash gutter – Within the field of closed-die forging, a flash gutter is a specially designed, shallow groove or recess in the forging die, located just outside the main die cavity and beyond the flash land. Its main purpose is to accommodate excess metal (known as ‘flash’) which is squeezed out of the main impression during the forging process.
Flashing – It is the phenomenon by which a fluid vapourizes because of sudden pressure drop across a valve. Particularly, it occurs when the downstream pressure is below the upstream vapour pressure value. Beside physical damages, the occurrence of flashing within a control valve, results in a decreased ability of the valve to convert pressure drop across it into mass flow rate. In flash welding, it is the heating portion of the cycle, consisting of a series of rapidly recurring localized short circuits followed by molten metal expulsions, during which time the surfaces to be welded are moved one toward the other at a pre-determined speed.
Flashing rate – It represents the kinetics of this process, how fast the liquid converts to vapour per unit time.
Flash ironmaking technology (FIT) using hydrogen – This technology is based on the direct gaseous reduction of iron oxide concentrate in a flash reduction process. It has the potential to reduce energy consumption by 32 % to 57 % and lower carbon di-oxide emissions by 61 % to 96 % compared with the average present blast furnace-based operation. This technology reduces iron ore concentrate in a flash reactor with a suitable reductant gas such as hydrogen or natural gas, and possibly bio / coal gas or a combination thereof. This technology is suitable for an industrial operation which converts iron ore concentrate (less than 100 micrometers) to metal without further treatment. This transformative technology produces iron while bypassing palletization or sintering as well as coke making steps. Further, the process is intensive because of the fact that the fine particles of the concentrate are reduced at a fast rate at 1,150 deg C to 1,350 deg C. Hence, the needed residence times in this process is of the order of seconds rather than the minutes and hours needed for pellets and even iron ore fines. 90 % to 99 % reductions take place in 2 seconds to 7 seconds at 1,200 deg C to 1,500 deg C. The residence time is a combination of speed of reaction because of the temperature, size of the feed material and quantity of excess gas / distance from equilibrium line. The energy need of the process with hydrogen as reduction gas is 5.7 giga joules per ton of liquid iron. The heating portion of the reactor is where the induction heating coil heats up the graphite susceptor. The susceptor heats up refractory wall by radiation. Both susceptor and refractory heat up the gas and particle by convection and radiation. After being heat up to the temperature, gas and particles enter the reaction zone, where good insulation is assumed so wall condition is set to be adiabatic. After the reaction zone, there is a cooling zone with cooling panel to cool gas and particles.
Flash land -It is the configuration in the blocking or finishing impression of forging dies which is designed to restrict or to encourage the growth of flash at the parting line, whichever can be needed in a particular case to ensure complete filling of the impression.
Flash land thickness – It is often simply called flash thickness. It is the minimum vertical gap between the top and bottom forging dies at the parting line. It represents the thickness of the narrow passage, the ‘land’, through which excess metal is forced to escape during the final stage of die closure.
Flash land width – It is the flat, short, horizontal area of the die impression immediately surrounding the cavity where the flash is restricted.
Flash-less forging – It is also known as true closed-die forging or precision forging. It is a manufacturing process where metal is plastically deformed within a completely closed die cavity to produce a near-net or net-shaped component without forming excess flash (material which escapes the die).
Flash line – It is the line left on a forging after the flash has been trimmed off. It is a surface imperfection which appears as a thin, raised ridge or fin of excess material on a cast, forged, or injection-moulded part. It is formed where the two halves of a die or mould meet, frequently resulting from a slight gap or misalignment during the production process.
Flash memory – It is a non-volatile, solid-state semi-conductor storage technology which retains data without power. Engineered using floating-gate MOSFET (metal-oxide-semiconductor field-effect transistor) transistors, it allows for electrical erasure and reprogramming in blocks rather than single bytes, enabling fast, high-density, and durable data storage.
Flash mixer – It is a high-speed, mechanical device used in metallurgical processing and water treatment to quickly and uniformly disperse reagents, coagulants, or slurry chemicals into a liquid within seconds. It ensures immediate, homogeneous mixing before further treatment stages, such as flotation or flocculation.
Flash mixing – It is typically associated with flash smelting, a high-intensity, continuous process used to produce non-ferrous metals (such as copper and nickel) from sulphide minerals. It is defined as the rapid and turbulent mixing of fine, dried sulfide concentrate particles with oxygen or oxygen-enriched air in a reaction shaft. This intense mixing initiates immediate ignition and oxidation of the particles, utilizing the heat generated by the exothermic reaction to melt the concentrate, forming matte and slag almost instantly.
Flashover – It is the near-simultaneous ignition of all combustible materials in an enclosed area, marking the transition from a growing fire to a fully developed fire. It occurs when intense thermal radiation (around 20 kilo-watt per square meter) from a hot ceiling layer (500 deg C to 600 deg C) causes everything in the room to ignite.
Flash pan – It is the machined-out portion of a forging die that permits the flow through of excess metal.
Flash pickling – It normally refers to a specialized, rapid form of surface cleaning designed to remove light oxide layers, flash rust, or surface contaminants from metals, frequently conducted as a quick, intense treatment before further processing like plating, painting, or galvanizing. It is a chemical surface treatment that uses acids, such as hydrochloric (HCl) acid or sulphuric (H2SO4) acid, to remove scale, rust, and surface impurities. The ‘flash’ aspect suggests a quick immersion or application to achieve immediate cleaning without excessive base metal attack. The main objective is to produce a clean, slightly etched, uniform surface which improves coating adhesion and removes surface contaminants (like flash rust) which can hinder subsequent manufacturing steps.
Flash plate – It is a very thin final electro-deposited film of metal (less than 2.5 micro-meters thick).
Flash plant – It is a geothermal power station which generates electricity by rapidly dropping the pressure of high-temperature (above 180 deg C) geothermal fluid, causing it to ‘flash’ (vapourize) into steam to drive turbines. It is the most common geothermal technology, frequently using single, double, or triple-flash techniques to maximize efficiency.
Flash point – Flash point is the minimum temperature at which the lubricant’s vapours ignite when tiny flame is brought near. Fire point is the minimum temperature at which the lubricant’s vapours burn constantly for 5 seconds when tiny flame is brought near. Both flash point and the fire point are to be higher than the maximum achievable ambient temperatures.
Flash point temperature – It is the temperature at which a fuel forms a mixture which ignites upon exposure to a spark or flame. It is an important factor for classifying fuels as per their hazard levels and ensuring their safe storage and transportation.
Flash power plant – It is a type of geothermal electricity generation facility which converts high-pressure, high-temperature (typically above 180 deg C) liquid-dominated geothermal fluid into electricity. It works by reducing the pressure of the hot water in a flash tank, causing it to ‘flash’ (rapidly vapourize) into steam, which then drives a turbine.
Flash process – It is a rapid, single-stage equilibrium separation technique where a heated or pressurized liquid mixture is suddenly subjected to a lower pressure, causing instantaneous vapourization of lighter components. This technique, normally used for separation and purification, produces a vapour stream rich in volatile substances and a liquid stream of heavier components.
Flash removal – It is also called deflashing. It is the process of eliminating excess material, known as ‘flash’ or ‘burrs’, from a metal part which has been moulded, cast, or forged. This flash is normally a thin sheet of material which forms at the parting line where two halves of a mould meet or leaks from the die, leaving behind unwanted material which is to be removed for the part to meet dimensional specifications.
Flash saddle – It is also called flash gutter. It is the space or ‘reservoir’ surrounding the land, designed to collect the excess metal after it passes through the land, preventing the dies from cracking or failing to close.
Flash smelting – It is a process used in the production of non-ferrous metals from sulphide minerals, where fine mineral particles and fluxes are ignited in a furnace with oxygen or oxygen-enriched air, resulting in complex interactions involving fluid flow, heat transfer, and chemical reactions. It is a highly efficient, continuous pyro-metallurgical process used to produce non-ferrous metals, mainly copper and nickel, from sulphide ores. It works by injecting fine, dried concentrate and flux with oxygen-enriched air into a furnace, where rapid flash oxidation of sulphide particles occurs within seconds, providing the heat needed to melt the charge. The concentrate burner mixes fine ore, oxygen-enriched air, and flux. The mixture falls through a reaction shaft, where particles ignite and oxidize rapidly (autogenous reaction) within 2 seconds to 3 seconds. The process produces a high-grade molten metal matte (e.g., copper-iron-sulphur), iron-silicate slag, and sulphur di-oxide (SO2) rich gas, which is utilized to produce sulphuric acid. This method offers high productivity, low fuel consumption (because of utilizing heat from sulphides), high sulphur capture rates, and high-intensity smelting. The two main types are (i) the Outokumpu flash furnace (vertical reaction shaft), and (ii) Inco flash furnace (end-wall burners).
Flash steam – When hot condensate under pressure is released to lower pressure, part of it is re-evaporated, becoming what is known as flash steam. The term is traditionally used to describe steam issuing from condensate receiver vents and open-ended condensate discharge lines from steam traps.
Flash tank – It is a pressure vessel used to separate liquid-vapour mixtures into individual components by reducing pressure, causing high-pressure liquid (frequently condensate) to ‘flash’ into low-pressure steam. This allows for the recovery of heat energy for low-pressure systems, reducing waste and improving energy efficiency.
Flash temperature – It is the maximum local temperature generated at some point in a sliding contact. The flash temperature occurs at areas of real contact because of the frictional heat dissipated at these areas. The duration of the flash temperature is frequently of the order of a micro-second. The term flash temperature can also mean the average temperature over a restricted contact area, e.g., between gear teeth.
Flash thermography – It is an active, non-contact non-destructive testing (NDT) technique which detects internal defects, voids, or delaminations in materials. It works by applying a brief pulse of thermal energy (flash) to the surface and using an infrared camera to record the subsequent cooling behaviour.
Flash thickness – It is the minimum gap between the top and bottom die impressions, determining how much pressure is built up within the die.
Flash time – It is the time between paint application and baking. Normally a considerable quantity of solvent is lost during this interval, and this solvent loss prevents popping problems in the oven.
Flash trap – It is a specifically designed area at the mating edge of parts which captures excess material (flash) as it is pushed out. Its purpose is to conceal or contain the flash, preventing it from marring the finished surface, strengthening the joint, and minimizing the need for secondary trimming operations. A ‘double flash trap’ can completely conceal flash in plastic welding, while in forging, the trap acts as a ‘brake’ to ensure the main cavity fills completely while retaining the excess in a controlled, manageable area.
Flash-trimming – It is a secondary manufacturing operation in metallurgy, specifically within forging and casting processes, used to remove excess material known as ‘flash’ or ‘burrs’ from a finished part.
Flash vapourization – It is a process which utilizes equilibrium principles between vapour and condensate phases to achieve separation, involving a series of flash tanks where pressure is decreased to promote the vaporization of lower molecular weight components.
Flash vessel – It is a pressure vessel used to separate a liquid-vapour mixture into individual liquid and vapour components. It works by allowing a high-pressure liquid to flash (rapidly evaporate) through a pressure drop, exploiting density differences to separate phases, frequently for steam recovery or flash distillation.
Flash, weld – It refers to the excess material which protrudes from a weld joint, typically forming beads or flash on the surface. In applications where high purity is critical, such as in semi-conductor industries, the presence of weld flash can create ‘dead flow’ areas which can lead to contamination.
Flash welding – It is a resistance welding process which produces coalescence at the faying surfaces of abutting members by a flashing action and by the application of pressure after heating is substantially completed. The flashing action, caused by the very high current densities at small contacts between the parts, forcibly expels the material from the joint as the parts are slowly moved together. The weld is completed by a rapid upsetting of the work-pieces.
Flash zone – It is the specific section of a distillation column (typically atmospheric or vacuum towers) where the heated, partially vapourized feedstock enters. It is designed to rapidly separate the incoming feed into a vapour phase (which rises) and a liquid phase (which drops to the stripping section), frequently utilizing vapour horns to facilitate this separation. Flash zone achieves immediate, equilibrium-based separation of vapour and liquid phases from a high-velocity, two-phase feed entering the distillation tower. It is normally positioned in the lower third of a distillation column, above the bottom stripping section and below the main fractionation trays or packing.
Flask – It is a metal or wood frame which is used for making and holding a sand mould. The upper part is called the cope, while the lower part is called the drag. Flask is also a vessel or container, very frequently a type of glassware, widely used in laboratories for a variety of purposes, such as preparing, holding, containing, collecting, or volumetrically measuring chemicals, samples, or solutions, or as a chamber in which a chemical reaction occurs. Flasks come in a number of shapes and sizes but are typically characterized by a wider vessel ‘body’ and one or more narrower tubular sections with an opening at the top.
Flask bar – It is also called flask rib. It is a reinforcing member attached within the cope (top half) or drag (bottom half) of a moulding flask. These bars, frequently made of wood or metal, span across the flask to provide structural support to the rammed sand, preventing it from sagging, shifting, or falling out of the flask during handling, turning over, and the pouring of molten metal. Flask bars hold the sand mold together, specifically in the cope, which is susceptible to sagging due to gravity. These bars prevent ‘drop-outs’ or sagging, which can cause casting defects. Bars are normally designed to fit within the flask and provide rigidity to the entire sand assembly. Small flasks for hand moulding can use wooden bars, while larger flasks use cast or fabricated steel bars.
Flask clamp – It is a specialized mechanical device used to securely hold together the different parts of a molding flask, specifically the cope (top), drag (bottom), and sometimes the cheek (middle), during the sand-casting process. Fire clamps ensure the mold remains tightly sealed during the pouring of molten metal, preventing the two halves from separating because of the upward pressure (buoyancy) of the liquid metal. These clamps prevent material leakage and ensure accurate alignment between the cope and drag, which avoids defects like misalignment and mismatch in the final casting.
Flask pin guides – These are reamed holes or specialized lugs / bushings mounted on the flask which receive the pins.
Flask pins – These are hardened steel pins, frequently tapered or straight, which are attached to one part of the flask (normally the drag) and fit into corresponding holes on the other part (the cope).
Flask pins and guides – These are precision alignment hardware used to ensure that the two halves of a moulding flask, the cope (top) and the drag (bottom), align perfectly. They maintain the accuracy of the mould cavity when the cope is lifted to remove the pattern and then replaced for pouring molten metal.
Flask, slip – It is a removable flask which can be stripped vertically from the mould. It is a flask designed to be removed from the sand mould after it has been packed, allowing the same flask to be used for multiple molds.
Flask, snap – It is a type of moulding flask, a rigid frame used to hold sand when creating a mould, which has separable, hinged sides. Unlike ‘tight’ flasks which stay with the mould during pouring, snap flasks are designed to be removed from the sand mould before the metal is poured, allowing a single flask to produce multiple moulds in a single shift. These are normally made of wood or aluminum with a hinge at one corner and a locking mechanism (like a cam or lever) at the opposite corner.
Flask, tight – It is a type of flask designed to remain in place around the sand mould during the entire pouring and solidification process.
Flat back – It refers to a type of casting pattern which has a completely flat surface on its rear side. This flat surface typically sits directly on the joint of the mould (parting line), meaning the entire pattern lies within one half of the moulding flask, either the cope or the drag. Since the rear side is flat, it is easier to manufacture and align during the moulding process.
Flat back dies – These are specialized tools typically used in high-volume thread rolling or forming processes to create threads on fasteners, such as screws and bolts. These consist of two flat metal templates, one stationary and one moving, which hold thread patterns, using cold extrusion forming to mould the material into the desired shape.
Flat back machining – It refers to the process of creating a flat, planar surface on a metal work-piece, frequently as a preparatory step to create a datum surface for subsequent operations or to achieve a specific thickness. This involves removing material, frequently in the form of chips, using methods such as face milling, shaping, or grinding to ensure the surface is level and meets tolerances.
Flat-bed machine – It is a tool or machine tool characterized by a horizontal, flat work surface or needle bed designed for stability, accessibility, and precision. It is used for holding work-pieces or facilitating linear, flat operations across different applications, including CNC (computer numerical control) machining.
Flat belt conveyor – The active side of belt in this conveyor, remains flat supported by cylindrical rollers or flat slider bed. The conveyor is normally short in length and suitable for conveying unit loads like crates, boxes, packages, and bundles etc. in manufacturing, shipping, warehousing, and assembly operations. Flat belts are used conveniently for conveying parts between work-stations or in an assembly line in mass production of goods.
Flat blade – It refers to a turbine, impeller, or fan blade characterized by a straight, non-curved profile, frequently used for high-shear, radial flow applications. These blades are favoured for their simple construction, robust nature, and efficiency in breaking apart particles or handling contaminated, high-temperature gases (e.g., Rushton turbines). These blades have straight paddle shapes, lacking curvature. They are frequently used in radial blade impellers, providing high-shear mixing or in industrial exhaust fans. They provide high torque and strong radial flow. They are excellent for dispersing gas, mixing liquid-liquid emulsions, and handling solids because they offer easy repair and maintenance.
Flat die – It is a type of hardened tool steel component, normally featuring rectangular, grooved plates, used in pairs for the cold-forming or thread-rolling of metal fasteners, such as screws, bolts, and studs. These dies are designed to create external threads by placing a blank work-piece between a stationary die and a moving (reciprocating) die, which causes the metal to flow into the desired thread shape through pressure rather than cutting.
Flat-die forging – It consists of forging of the metal between flat or simple-contour dies by repeated strokes and manipulation of the work-piece. It is also known as open-die forging, hand forging, or smith forging.
Flat die rollers – These are important components in pellet mills which compress raw material against a stationary or rotating horizontal, perforated metal plate (the flat die) to extrude it into pellets. Mainly used for small-to-medium scale biomass or feed production, they create high friction and pressure to form dense, cylindrical pellets.
Flat die rolling – It refers mainly to a thread-rolling process used to produce external threads on cylindrical work-pieces (blanks) by deforming the metal between two flat, hardened steel dies. One die remains stationary while the other moves in a linear, reciprocating motion, rolling the blank to form threads without cutting the metal.
Flat drill – It is a rotary end-cutting tool constructed from a flat piece of material. It is provided with suitable cutting lips at the cutting end.
Flat edge trimmer – It is a machine for trimming notched edges on shells. The slide is cam driven so as to get a brief dwell at the bottom of the stroke, at which time the die, sometimes called a shimmy die, oscillates to trim the part.
Flat face, flange – Typically flat face is used on pump facings or on fibre-glass flanges where the torque of compressing the gasket can damage the flange body. Their principal use is to make connections with cast iron flanges. They are mainly used for rubber lined equipments of chemical plants. They are also used for equipments operating under low pressure. Since the width of the gasket is more, the gasket seating force is more.
Flat fading channel – It is a wireless communication channel where the channel gain is approximately constant and linear across the entire signal bandwidth, meaning all frequency components fade together. It occurs when the signal bandwidth is much smaller than the coherence bandwidth of the channel.
Flat flame burner – It is a type of burner designed to produce a wide, flat flame which spreads across a surface, of a type of burner designed to produce a wide, flat flame that spreads across a surface, frequently the walls of a furnace or kiln, rather than a concentrated jet flame. These burners are characterized by their ability to generate a large area of radiant heat transfer, making them suitable for applications where even heating is crucial, such as in aluminum and glass melting or steel heat treating. It transfers heat to the surrounding refractory wall or roof by highly turbulent convection. The refractory then radiates heat uniformly to the load. Minimum forward velocity results in uniform radiant heating with no flame impingement. It converts the refractory expanse of a furnace wall or roof into a uniform-heat, radiating surface which is capable of high rates of radiant heat transfer over wide areas.
Flat gate – It is also called knife gate. It is wide gate with narrow opening into the mould. It is used to pour thin, flat castings.
Flat geometry – It is a geometric form control defining the condition where all elements of a surface exist in a single, perfectly straight plane. It ensures a surface has no irregularities such as twists, bows, or curvatures, making it an important specification for mating parts, sealing surfaces, and precision machining.
Flat glass – It is a flat glass product, also known as plate glass or plain glass, which is colourless and transparent, mainly used to transmit light, insulate sound, and preserve heat in applications such as doors and windows.
Flat head fasteners – It is frequently called countersunk fasteners. These fasteners are designed to sit flush with or below the surface of the material they are securing, creating a smooth, even finish. This flush fit is achieved because the head of the fastener is tapered, allowing it to sit within a countersunk hole. They are commonly used in applications where aesthetics is important.
Flat histogram – It refers to a histogram where the frequency of data points across all bins (or intervals) is approximately uniform or equal. Unlike a natural dataset which frequently shows peaks and valleys (e.g., a normal distribution), a flat histogram displays a mostly horizontal, uniform distribution. This concept is important in fields needing high-efficiency sampling, such as statistical mechanics (Monte Carlo simulations), digital image processing (contrast improvement), and data mining.
Flat honing – It is a low-velocity abrading process, similar to honing, which uses a large, flat honing surface to simultaneously finish a large number of flat parts.
Flat membrane – It is also called flat sheet membrane. It is a thin, planar, semi-permeable barrier used mainly in separation processes, such as membrane bioreactors (MBRs), filtration, and water treatment. Unlike hollow fibre types, these sheets are typically rectangular, easy to fabricate, and stackable in modules for high-surface-area filtration.
Flatness – It is simply the amount of space between the plate and a perfectly flat surface. It is a measure the form of a surface, which indicates whether all of the points along the surface lie in the same plane. It is symbolized in Geometric Dimensioning and Tolerancing (GD&T) by a parallelogram, flatness and is particularly useful when two surfaces are to be assembled together to form a tight seal. Flatness of rolled steel sheets depends on the roll deflection.
Flatness and concentricity – These are ‘geometric dimensioning and tolerancing’ (GD&T) characteristics used to ensure that metal components are manufactured within specific dimensional limits to function correctly in assemblies.
Flatness tolerance – It consists of a three-dimensional geometric tolerance which controls how much a product surface can deviate from a flat plane. The permitted deviation depends upon the thickness of the sheet or plate varying between 0.2 % and 0.5 % of its width and length, normally measured over a 1 metre length.
Flat panel displays – These are lightweight, thin video display technologies which utilize emergent methods, resulting in screens less than 100 millimeters thick, with high resolution and contrast. They are normally used in devices such as cellular phones, laptops, and digital cameras, and include types like LCDs (liquid crystal displays), OLEDs (organic light-emitting diodes), and plasma display panels.
Flat panel technology – It refers to lightweight, slim electronic displays (typically below 100 millimeters thick) used for visual output in devices like smartphones, televisions, and laptops. Engineered for high resolution, low power consumption, and portability, they have largely replaced cathode ray tube (CRT) technology using mechanisms such as LCDs (liquid crystal displays), OLEDs (organic light-emitting diodes), and LEDs (light-emitting diodes).
Flat plate – It is a planar, uniform-thickness component (structural or mechanical) typically supported directly by columns without beams (in construction) or used as a heat exchange surface. It is used to simplify structural analysis, improve architectural flexibility, manage boundary layers in fluid flow, or maximize surface area in thermal systems.
Flat plate airfoil – It is an infinitely thin (or very thin), flat, two-dimensional surface used in aerodynamics to produce lift and drag when placed at an angle of attack to a flow. It serves as the baseline model for aerodynamic theory, including thin-airfoil theory, and operates by creating a pressure difference between its upper and lower surfaces.
Flat plate boundary layer – It is the layer of fluid which develops along a flat plate held edgeways to a free stream, where a laminar boundary layer begins at the leading edge and transitions to a thicker turbulent boundary layer towards the trailing edge, influenced by shear stresses and flow characteristics.
Flat plate collector – It is a specialized heat exchanger, serving as the core component of active or passive solar thermal systems. It absorbs incoming solar radiation (both direct and diffuse) using a blackened surface, converting it into thermal energy, which is then transferred to a working fluid (liquid or air) for low-to-medium temperature applications, typically ranging from 30 deg C to 70 deg C.
Flat plate heat exchanger – It is a compact engineering device designed for efficient thermal transfer between two fluids, without mixing them, by passing them through alternating, narrow channels between stacked, corrugated metal plates. These plates, typically made of stainless steel or titanium, are clamped, brazed, or welded together to form a highly compact, high-surface-area heat exchanger.
Flat plate module – It is a structural or functional unit, normally in solar engineering, consisting of flat, parallel surfaces, such as interconnected photo-voltaic cells or absorption plates. Designed for efficiency and simplicity, these components are typically used to collect sunlight for electricity (photo-voltaic) or thermal energy (solar thermal) while offering high compactness.
Flat-plate photo-voltaic / thermal (PVT) system – It is a hybrid technology which simultaneously converts solar radiation into electricity and useful heat, utilizing a single, non-concentrating collector. It optimizes space and increases overall efficiency by cooling the PV (photo-voltaic) cells with a fluid (water or air) to reduce electrical losses.
Flat plates – These are normally defined as solid, planar metallic components with a uniform thickness, frequently produced to be used as base plates, surface plates for metrology, or as intermediate products in manufacturing. These plates are normally produced through sand casting or continuous slab casting methods.
Flat position – It is the welding position which is used to weld from the upper side of the joint. The face of the weld is approximately horizontal.
Flat-position welding – It consists of welding from the upper side, the face of the weld being horizontal. It is also called down hand welding.
Flat products – These products refer to the products which consist of strips, sheets and plates. These are finished steel products which are produced from slabs / thin slabs in rolling mills using flat rolls.
Flat return idlers – The flat return idler consists of a long single roll, fitted at each end with a mounting bracket. Idler roll length, bracket design, and mounting-hole spacing allow for adequate transverse belt movement without permitting the belt edges to contact any stationary part of the conveyor or its frame.
Flat-rolled products – These are metal materials (typically steel or aluminum) processed by passing through cylindrical rolls to reduce thickness, increase length, and achieve uniform dimensions. They are defined by a high width-to-thickness ratio, mainly taking the form of sheets, strips, or plates, which are either coiled or cut to length for industries like automotive and construction.
Flat rolled steels – These are the steel produced in flat rolling mills utilizing relatively smooth and cylindrical rolls. The width to thickness ratio of flat rolled products is normally fairly large. Examples of flat rolled steel are hot rolled plates, sheets and coils, cold rolled sheets and coils, and coated sheets and coils, and tin mill products etc.
Flat rolling – Rolling of strips and plates is normally referred to as flat rolling. The objectives of the process are reducing of the thickness of the work-piece, and increasing its length and thereby changing its mechanical and metallurgical attributes.
Flat rolling mills – These are those rolling mills which roll flat products.
Flat rolling process – It is a method of metalworking where strips and plates are produced by reducing the thickness of the work-piece and increasing its length, hence altering its mechanical and metallurgical properties. This process can be performed at different temperatures classified as hot, warm, or cold rolling.
Flat sheet membranes – These are planar, thin-film, semi-permeable filters to separate solids, micro-organisms, and impurities from liquids, mainly used in submerged membrane bio-reactors (MBR). Known for strong anti-fouling properties and simple, robust construction, they consist of a thin selective layer supported on a substrate and are ideal for waste-water treatment.
Flat springs – These springs are made from flat strips of material (normally metal) which store and release energy when deflected by an external load. Unlike helical springs, which are typically made from coiled wire, flat springs are cut or pressed from sheet metal. These springs are used in several applications and are ideally suited for applications where space is limited or where the spring can be used as part of mounting assembly. The flat spring design allows forming of specific features and profiles for a unique application and mounting location.
Flat substrate – It is a rigid or flexible base material with a planar surface used to support, deposit, or build thin films, electronic circuits, or coatings. It serves as the foundation for manufacturing processes, such as semi-conductor fabrication, thin-film deposition, or adhesive bonding, needing specific flatness to ensure functional performance.
Flat surface – It is a two-dimensional, planar feature with zero theoretical curvature, containing length and width but no depth. It is a surface where all points lie within a single plane, characterized by being smooth, even, and free from bumps, dips, or waviness. Flatness is frequently defined within a strict tolerance zone (e.g., 0.05 millimeters) to ensure functional contact and prevent stress failures in assemblies.
Flat surface pulley – It is a pulley featuring a straight cylindrical drum face, devoid of crown contours, needing regular inspections for wear, equilibrium, and proper alignment.
Flatteners – They are also known as levellers or straighteners. They carryout shape corrections of the strip to ensure flatness before further processing during the unwinding of a coil. It is the first operation during the unwinding a coil. The process consists of bending the unwound strip back and forth over a series of work rolls to alternately stretch and compress the upper and lower surfaces. The process removes the coil set. Removing coil set needs permanent yielding in the outer 20 % of the top and bottom surfaces of the steel. The central 80 % of the thickness remains unchanged. Flatteners are appropriate for this type of shape correction. Only end bearings support the simplest flatteners, with no backup rolls used. Closing the entry roll gap risks deflection of the unsupported centre, potentially leading to creating edge waves in the coil.
Flattening – It is a preliminary operation performed on forging stock to position the metal for a subsequent forging operation. It also consists of the removal of irregularities or distortion in sheets or plates by a method such as roller levelling or stretcher levelling.
Flattening and levelling – These are mechanical processes used to correct shape defects (such as bows, waves, or twist) in metal sheets, plates, or coils, frequently simultaneously reducing internal residual stresses. While sometimes used interchangeably, they represent different levels of precision and intensity in the metal-working process.
Flattening dies – These are the dies used to flatten sheet metal hems, i.e., dies which can flatten a bend by closing it. These dies consist of a top and bottom die with a flat surface which can close one section (flange) to another (hem, seam).
Flattening test – It is a quality test for tubing in which a sample is flattened to a specified height between parallel plates.
Flat-top chain conveyor – It consists of a particular group of carrier chain conveyors, which can be rolling or sliding type, with specially designed chain links or with flat plate attached to the chain links so as to provide a continuous, smooth, level top surface to carry small articles like bottles, and cans, etc. at a high speed. These conveyors are widely used in canning and bottling plants. Different types of chains and / or attachments are used such as hinged-joint continuous flat top sliding type, plate-top sliding or rolling type, crescent-shaped plate top type. The crescent plate design is particularly suitable for carousel-type operation to turn in a horizontal curve, a typical example being the baggage handling conveyors in the arrival section of an airport.
Flat-top chains – These are intended only for conveying. They can replace conveyor belts and belt drives as the material can be carried directly on its links. An individual link is normally made out of a steel plate with barrel-shaped hollow protrusions on its bottom side. The links are connected to preceding and succeeding links by passing a pin through these protrusions underneath the links. The nature of these joints allows movement only in one direction. These chains are used almost exclusively on conveyors. In practice, the flat-top chains are basically special types of slat conveyors. Wear is the most important parameter in the design of the flat-top chains. Joint wear and top plate and track wears are of the greatest concerns. Top plate and sprocket wears are also of some concern.
Flat top rib – In metallurgy and metal fabrication, it is a structural reinforcing feature formed onto a sheet metal surface, characterized by a trapezoidal cross-section with angled sides and a flat, plateau-like top. These ribs are used to increase the rigidity, bending stiffness, and load-bearing capacity of flat metal parts without adding substantial weight or thickness.
Flat-to-trough transition zones – It is the transition length between pulley and deepest trough station. This length is to be sufficiently high to prevent major additional tensions in the conveyor belt edges. It Influences the needed conveyor belt breaking strength.
Flat type wire rope – In flat type wire rope, the strands are combined in such a way that the outer circumference of the rope is flat in shape. This rope has a smooth surface and hence the surface pressure due to coming into contact with the groove of the drum and the sheave is smaller than that of ordinary ropes. It is also superior in its wear resistance nature. In general, the triangular strand and the shell strand are used the most. The flat strand is also being used at certain places.
Flat web – It refers to a thin, platelike element of a forged or structural part which connects thicker, projecting elements such as ribs, bosses, or flanges. It is characterized by its relatively flat, sheet-like geometry, frequently aligning with the parting line (the plane where two die halves meet) in closed-die forging processes.
Flat wedge – It is a type of simple machine, typically shaped as a triangular prism with one thick, flat end and two sloped sides tapering to a thin edge. It is used to transform a force applied to its flat end into a considerably larger force perpendicular to its sloped sides, facilitating tasks such as cutting, splitting, lifting, or securing objects in place.
Flat wire – It is a roughly rectangular or square mill product, narrower than strip, in which all surfaces are rolled or drawn without any previous slitting, shearing, or sawing.
Flaw – It is a near synonym for discontinuity but with an undesirable connotation. It is a non-specific term frequently used to imply a crack-like discontinuity. The preferred terms are discontinuity and defect.
Flaw detection – It is the process of identifying, locating, and characterizing imperfections, such as cracks, voids, or inclusions, within materials or components using non-destructive testing (NDT) methods. It ensures structural integrity by detecting critical defects which can lead to failure, frequently using ultrasonic, magnetic particle, or eddy current techniques.
Flaw growth – It is also called crack propagation. It is the stable expansion of pre-existing, microscopic, or macroscopic defects in materials under cyclic (fatigue) or sustained (stress corrosion) loading. It is an important aspect of fracture mechanics, wherein cracks grow from an initial, allowable size until they reach a dangerous size, leading to final, catastrophic failure.
Flaw size – It defines the dimensions of discontinuities (cracks, voids, inclusions) in materials, critical for fracture mechanics and damage tolerance. It ranges from initial manufacturing imperfections to maximum allowable sizes before failure.
Fleissner process – This is a very old process for drying low-rank coals. This process is based on the principle that uneven shrinking of the coal and consequent disintegration can be prevented by controlled removal of the water. The saturated steam atmosphere prevents evaporation until the lump is heated, and then loss of water can be controlled by gradual reduction of the steam pressure. It is a thermal drying process, in which the action of high-pressure steam on a lump of lignite produces these effects. As the temperature rises and the pressure increases part of the colloidal water is expelled from the lump as a liquid. The lump shrinks as water leaves and the cells collapse, and when the pressure is lowered, more water leaves by evaporation caused by the sensible heat stored in the lump. When the pressure is lowered further by vacuum, additional moisture is evaporated, which cools the lump. Many methods of drying are based on Fleissner process.
Fleming’s left-hand rule for motors – It is a mnemonic for visualizing the relationship between the magnetic field, the current, and the force on a current-carrying conductor. It states that if a person holds his / her left hand with his / her thumb, forefinger, and middle finger mutually perpendicular, and if the forefinger points in the direction of the magnetic field and the middle finger points in the direction of the current, then the thumb points in the direction of the force (or motion) on the conductor.
Fleming’s right-hand rule – It also known as the generator rule. It is a mnemonic used to determine the direction of induced current in a generator when a conductor moves within a magnetic field. It states that if a person extends his / her right hand with his /her thumb, forefinger, and middle finger mutually perpendicular, the middle finger points in the direction of the induced current. The forefinger points in the direction of the magnetic field, and the thumb points in the direction of motion of the conductor.
Fleming valve – It is the first important vacuum tube device, used as a radio detector.
Flex circuits – These are also called flexible printed circuits (FPCs). These are conductive patterned circuits and components engineered on thin, flexible insulating substrates (normally polyimide or polyester). They allow for bending, folding, and twisting, making them ideal for space-constrained, lightweight, and dynamic applications where rigid PCBs (printed circuit boards) fail.
Flex fuel vehicle – It is an internal combustion vehicle designed to run on gasoline, ethanol, or any blend of both using a single fuel system. Engineered with specialized sensors and an intelligent ECM (electronic control module), it detects the fuel mixture and automatically adjusts spark timing and fuel injection for optimal combustion.
Flexible alternating current transmission system – It is a power electronics-based system used in alternating current (AC) power grids to improve controllability, increase power transfer capacity, and improve voltage stability. They are static devices, e.g., ‘static VAR compensator’ (SVC), ‘static synchronous compensator’ (STATCOM) which regulate parameters like impedance and voltage to optimize flow paths.
Flexible adhesives – These are specialized polymer-based bonding agents, such as poly-urethanes or silicones, designed with low modulus and high elongation (frequently above 10 %) to withstand movement, vibration, and thermal expansion. Unlike rigid adhesives, they maintain structural integrity and bond strength between dissimilar materials, reducing stress concentrations in engineering applications.
Flexible automation – This type of automation has the flexibility and is used to manufacture a variety of products. In this automation system operators give high-level commands in the form of codes entered into computer identifying product and its location in the sequence and the lower-level changes are done automatically. Each production machine receives settings / instructions from computer. The machines automatically load / unload required tools and carries out their processing instructions. After processing, products are automatically transferred to next machine. It is typically used in job shops and batch processes where product varieties are high and job volumes are medium to low. However, this type of automation is associated with lower production rates and products which needs frequent changing due to their dependence on the demand.
Flexible cam – It is an adjustable pressure-control cam of spring steel strips which is used to get varying pressure during a forming cycle.
Flexible circuit board – It is a type of printed circuit board (PCB) made with a flexible substrate, allowing it to bend or flex without breaking. Unlike rigid printed circuit boards, flexible circuit boards can be shaped to fit into compact or uniquely designed electronic devices. They are typically made of thin, flexible materials like polyimide or polyester, with conductive traces built on them. Flexible circuit boards can be bent, folded, or twisted, making them ideal for applications where space is limited or where the circuit needs to move.
Flexible conveyor – It is a conveyor system with movable sections for adaptable material handling, needing regular inspections for flexibility, alignment, and overall functionality.
Flexible couplings – These couplings are normally used to transmit driving torque between a prime mover and a rotating element of the equipment. Although designed to accommodate misalignment, normally it is desired not to use a flexible coupling to compensate for misalignment of the rotating element of the equipment and driver shafts. The purpose of the flexible coupling is to compensate for temperature changes in the couplings and shafts, and to permit axial movement of the shafts without interference with each other while power is transmitted from the driver to the rotating element of the equipment.
Flexible electrodes – These are thin, conductive, and mechanically deformable conductors designed to bend, twist, or stretch without losing functionality, frequently used in wearable electronics, and flexible batteries. They are engineered by depositing conductive materials onto flexible substrates.
Flexible electronics – These are also called flex circuits. These are electronic devices fabricated by mounting components on flexible plastic, metal, or paper substrates, allowing them to bend, twist, and fold without sacrificing functionality. Engineered for conformability, they enable lightweight, thin, and frequently stretchable applications, such as flexible displays, and sensors.
Flexible fuel vehicle – It is an internal combustion vehicle designed to run on more than one fuel, typically gasoline blended with ethanol (up to 83 % to 100 %) or methanol, using the same engine and fuel system. Engineered for versatility, these vehicles automatically adjust combustion parameters, such as injection timing and spark advance, through an ECU (electronic control unit) based on real-time ethanol sensors.
Flexible hinge, flexure pivot bearing – It is a type of bearing guiding the moving parts by flexure of an elastic member or members rather than by rolling or sliding. However, it is to be noted that only limited movement is possible with a flexure pivot.
Flexible joint – It is a specialized connector which links two components while allowing for controlled movement, such as rotation, misalignment correction, or axial expansion. These joints absorb vibration, thermal expansion, and mechanical stress, protecting systems from damage. They are typically made of elastomeric materials (rubber), metal bellows, or fabrics, frequently used in piping, automotive, and structural applications.
Flexible joint expansion – It is a resilient link connecting conveyor sections, engineered to accommodate thermal expansion, necessitating periodic examinations to uphold proper functioning and prevent issues.
Flexible jumper – It is a short, pliable connector used to bridge two points in mechanical or electrical systems to accommodate vibration, movement, or thermal expansion. It is important for absorbing fatigue in dynamic environments where rigid connections fail, typically made of flexible pipe (subsea) or conductive braided copper / aluminum (electrical).
Flexible manufacturing system – It is a manufacturing system in which there is some quantity of flexibility which allows the system to react in case of changes, whether predicted or unpredicted. This flexibility is normally considered to fall into two categories, which both contain numerous sub-categories. The first category is called routing flexibility, which covers the system’s ability to be changed to produce new product types, and the ability to change the order of operations executed on a part. The second category is called machine flexibility, which consists of the ability to use multiple machines to perform the same operation on a part, as well as the system’s ability to absorb large-scale changes, such as in volume, capacity, or capability.
Flexible moulds – These are moulds made of rubber or elastomeric plastics, used for casting plastics. They can be stretched to remove cured pieces with undercuts.
Flexible packages – These are packaging forms made from materials such as paper, plastic, and aluminum foil which can be thin, lightweight, and compact. These packages include wraps, bags, sacks, and pouches, and can be combined with rigid structures for improved product protection.
Flexible packaging – It is a type of packaging where the container’s shape can be easily changed, frequently made from materials like plastic, film, paper, or aluminum foil. These packages are known for being lightweight, easily opened, and frequently recyclable, making them suitable for several products.
Flexible pipe – It is a composite, multi-layered conduit designed to transport fluids while showing high bending flexibility and relatively low bending stiffness. Composed of unbonded polymer and helical steel layers that move independently, these pipes accommodate large deflections, vibrations, and thermal expansion, normally used in high-pressure / high-temperature offshore sub-sea applications.
Flexible plate – It is a thin, flat structural component designed to undergo substantial elastic deformation, bending, or vibration while maintaining mechanical integrity. These plates resist loads through bending stiffness, frequently in two directions, rather than just tension, and are used to absorb movement or distribute loads.
Flexible power plant – It is a term used for a generation facility designed to rapidly adjust power output, start-up / shut down quickly, and operate efficiently at low minimum loads to balance the variability of renewable energy sources. These plants provide essential grid services, including ramping, load following, and frequency response, to maintain stability.
Flexible printed circuit board – It is a patterned arrangement of printed circuitry and components which utilizes a flexible base material, typically polyimide or polyester, rather than rigid substrate. These circuits allow for 3D packaging, bending, and folding, providing substantial weight, space, and reliability advantages over traditional wire harnesses and rigid boards.
Flexible printed circuits – These are also called flex circuits. These are electronic assemblies featuring conductive traces printed onto thin, flexible insulating substrates (normally polyimide or polyester). Engineered to be bent, folded, or permanently shaped, flexible printed circuits (FPCs), frequently sourced from specialized manufacturers, enable high-density component mounting, reduced assembly errors, substantial weight savings, and improved reliability over rigid boards.
Flexible reduction sizing (FRS) block – This block has been developed for rolling higher grades and simultaneously improving the metallurgical properties of the rolled product. This is a four-strand block with speed shift gear boxes. It is installed down line of a no-twist wire rod block. On the flexible reduction sizing block all dimensions can be finish rolled with the advantage of one family rolling, which means that only one pass size is used in each stand over the whole size range. Due to the cooling section in between the no-twist block and flexible reduction sizing block, thermo-mechanical rolling becomes feasible. There are several good design features in this block.
Flexible riser – It is a multi-layered, composite pipe used in offshore engineering to transport fluids (oil, gas, water) between sub-sea facilities and floating production units. Engineered for high pressure, temperature, and fatigue resistance, they connect floating structures to the sea-bed while accommodating significant vessel motion, typically in deep-water applications.
Flexible rolling – It is an advanced, continuous sheet metal forming technology which creates components with varying thickness (Tailor rolled blanks) or variable 3D cross-sections by actively controlling the roll gap during the rolling process. It produces load-optimized, lightweight parts.
Flexible rotor – It is a rotating shaft which undergoes substantial elastic deflection (bending) during operation, typically when operating at, near, or above its first critical speed (natural frequency). Unlike rigid rotors, their mass distribution changes with speed, needing multi-plane balancing to manage bending modes rather than just bearing forces.
Flexible skin – It refers to a specialized, thin, and durable material layer, frequently a polymer or composite, engineered to be light-weight, durable, and adaptable to complex, changing geometries. It is designed to stretch and contract while maintaining structural integrity, serving as a protective or functional outer layer.
Flexible structure – It refers to a material or assembly designed to bend, twist, or stretch under load without breaking, frequently achieved through specialized atomic arrangements, specific alloy compositions, or composite engineering. Unlike brittle materials, flexible metals can absorb, distribute energy, and return to their original shape (elasticity) or permanently reshape (ductility).
Flexible substrate – It is a thin, bendable base material, typically polymer, metal foil, or ultra-thin glass, which supports the deposition of functional films (such as conductive metals) while maintaining structural integrity, electrical performance, and conformability to non-planar surfaces. Unlike rigid substrates, these materials are necessary for flexible electronics, roll-to-roll manufacturing, and wearable devices.
Flexible target – It refers to setting goals, objectives, or constraints which allow for adjustments, deviations, or adaptations based on changing circumstances, rather than adhering to rigid, fixed parameters. This approach prioritizes adaptability and long-term success over strict, immediate compliance, often utilizing tolerance bands. It also refers to a target used in deposition processes (like sputtering or laser ablation) which is designed for adaptability, allowing for the creation of customized, variable, or composite coatings, rather than relying on a single, uniform material. In a broader sense, flexibility in metallurgical processes (like steelmaking or metal forming) refers to the capability to adapt to changing demands, varying raw materials, or to create components with tailored properties which change along their length.
Flexible thin slab casting (fTSC) unit – It is the first-generation process for thin slab casting and rolling process from Danieli which consisted of flexible thin flexible thin slab casting (fTSC) connected to thin slab rolling unit (fTSR) through a tunnel furnace. Flexible thin slab casting unit has been able to cast slab of thickness 60 millimeters. The caster has been of vertical curved design, having funnel mould with soft reduction and air mist cooling.
Flexible thin slab rolling (fTSR) unit – It is the first-generation process or thin slab casting and rolling process from Danieli consisted of flexible thin slab casting (fTSC) unit connected to thin slab rolling unit (fTSR) through a tunnel furnace. Flexible thin slab rolling (fTSR) unit rolling mill is for rolling of 60 millimeters coming from flexible thin slab casting (fTSC) unit connected through a tunnel furnace. The rolling unit has been consisted of a finishing mill with 6 to 7 rolling stands in cluster configuration.
Flexible tooling – It is an advanced, adaptable manufacturing methodology using reconfigurable components (e.g., modular dies, pins, or soft moulds) to produce different part geometries without needing new, permanent tools. This approach cuts costs and lead times by automating setup changes, making it ideal for low-volume production or rapid prototyping.
Flexible tooling process – It refers to a variant of resin transfer moulding (RTM) where one tool face is replaced by a flexible film, allowing resin flow driven by vacuum and gravity effects to impregnate a dry fiber pack in a defined mould cavity.
Flexible tube valve – It is a special valve using a flexible sleeve or tube which acts as the closure element. Pressure applied to the jacket space surrounding the outside of the tube controls the opening and closing of the valve.
Flexibility – It is the quality or state of a material which allows it to be flexed or bent repeatedly without undergoing rupture.
Flexibility coefficient (Fij) – It is the displacement (translational or rotational) at a specific coordinate (node) ‘i’ caused by a unit load (force or moment) applied at another coordinate ‘j’ assuming a linear elastic system. It represents how easily a structure deforms, serving as the inverse of the stiffness matrix. The displacement at point ‘I’ because of a unit load at point ‘j’ is given by Fij = displacement ‘I’ / force ‘j’.
Flexibility matrix – It is a square matrix of flexibility influence coefficients, where each coefficient represents the deflection at a specific point because of a unit load applied at another point within a system. It is the inverse of the stiffness matrix and facilitates the analysis of displacements in structural systems under different loading conditions.
Flexibility method – It is also called force method. It is a structural analysis technique used to solve statically indeterminate structures by releasing redundant supports or members, turning them into a determinate system. It calculates unknown ‘redundant’ forces by ensuring that deformations in the released structure remain compatible with the original structure’s geometry.
Flexibility principle – This principle states that all other things being equal, a good layout is one which provides flexibility. Flexibility factor includes consideration because of changes in material, equipment, process, man, supporting activities, and installation limitations etc. It means easy changing to new arrangements or it includes flexibility and expendability of layouts.
Flexibility, wire rope – The flexibility of a wire rope is a measure of how easily the rope allows itself to bend around a given diameter. The flexibility of the wire rope is among other things dependent on the line pull. The flexibility of an unloaded rope can be measured by the sag of a rope under its own weight. The flexibility of a steel wire rope typically increases with an increasing number of strands and wires in the rope. The flexibility is also influenced by the lay lengths of the strands, of the rope core and the rope, as well as by the gaps between wires and strands.
Fleximat belts – Fleximat is a trade name. Fleximat belts are specialized, high-performance conveyor belts featuring a woven steel cord fabric core designed to reinforce rubber belts. Unlike traditional steel cord belts which only provide longitudinal strength, Fleximat belts integrates both longitudinal and transverse steel cords in a single, flexible ply to protect against cuts, tears, and heavy impact, making them ideal for handling sharp, heavy materials in steel works and mining.
Flex joint – It is also called flexible joint. It is a specialized, frequently elastomeric or metallic component which connects two rigid structures while allowing limited, controlled articulation, movement, or rotation. These joints are designed to absorb vibration, accommodate thermal expansion / contraction, and correct misalignments without inducing structural damage or high stress in piping, machinery, or offshore drilling risers.
Flexo-electricity – It is the coupling between an electric polarization and a strain gradient (non-uniform deformation) in dielectric materials, generating electricity when bent or twisted. Unlike piezo-electricity, which needs specific crystal symmetries, flexo-electricity is a universal property of all insulators which becomes considerably improved at the micro / nano-scale.
Flexo-electric coefficient – It a measure of the ability of a dielectric material to generate electric polarization in response to a strain gradient. It quantifies the electro-mechanical response of materials, particularly ferro-electric ceramics, under mechanical stress.
Flexo-electric effect – It is an electro-mechanical coupling phenomenon where a strain gradient (non-uniform deformation) induces electrical polarization (direct effect), or an electric field gradient induces strain (converse effect). Unlike piezoelectricity, this effect occurs in all dielectrics, particularly at the micro / nano-scale where high strain gradients are generated.
Flexo-graphic printing – It is a high-speed, modern rotary relief technique using flexible photo-polymer plates to transfer low-viscosity, fast-drying inks directly onto absorbent and non-absorbent substrates. It utilizes an anilox roller for precise ink metering and ‘kiss pressure’ to print on materials like plastic films, foil, and paper.
Flex roll – It is a movable jump roll designed to push up against a metal sheet as it passes through a roller leveler. The flex roll can be adjusted to deflect the sheet any quantity up to the roll diameter.
Flex rolling – It consists of passing metal sheets through a flex roll unit to minimize yield-point elongation in order to reduce the tendency for stretcher strains to appear during forming.
Flexural analysis – It is the process of evaluating how structural elements, such as beams, slabs, or composites, resist bending moments and deformation under loads. It involves determining the stress, strain, deflection, and load-carrying capacity of a member, ensuring it can withstand, for example, tensile cracks and compressive failure during bending.
Flexural axis – It is the longitudinal line in a structural member (such as a beam) along which a transverse load can be applied without inducing any torsional deformation or twist. It represents the locus of the shear centres for all cross-sections along the beam, ensuring pure bending. It is the specific axis of a beam where the shear force and the torsional moment are balanced, ensuring that bending occurs without twisting.
Flexural behaviour – It defines how a material or structural member (like beams or slabs) bends, deforms, and resists loads when subjected to forces perpendicular to its longitudinal axis. It encompasses the analysis of stresses (tension and compression), strains, and structural failure mechanisms under bending, crucial for ensuring stability in structural design.
Flexural bearing – A flexural bearing is a bearing which allows motion by bending a load element. A typical flexure bearing is just one part, joining two other parts. For example, a hinge can be made by attaching a long strip of a flexible element to a door and to the door frame. Another example is a rope swing, where the rope is tied to a tree branch.
Flexural capacity – It is also called flexural strength. It is the maximum bending moment a structural member (like a beam or slab) can resist before yielding or failing. It measures a component’s capacity to withstand lateral loading, representing the peak stress reached within the material before it fails, often tested using three or four-point loading tests. It is the ability of a structure to withstand bending stresses, crucial for ensuring safety against deformation or failure.
Flexural capacity of a beam – It is the maximum bending moment a structural member can resist before failure or yielding, defining its structural strength under transverse loads. It depends on the cross-sectional geometry, material strength, and reinforcement, representing the internal moment capacity which ensures safety. It is the ability to withstand bending, which creates tensile stress at the bottom (convex face) and compressive stress at the top (concave face).
Flexural member – It is a structural element, such as a beam, girder, or joist, designed mainly to resist transverse loads, which induce bending moments and shear forces. These members experience both compression (normally top) and tension (normally bottom) within their depth because of the loading. Common examples include I-sections, channels, angles, and hollow sections.
Flexural modulus – Within the elastic limit, it is the ratio of the applied stress on a test sample in flexure to the corresponding strain in the outermost fibre of the sample. Flexural modulus is the measure of relative stiffness.
Flexural reinforcement – It refers to steel bars (reinforcement bar), fibres, or strengthening materials, e.g., fibre reinforced polymers (FRP) placed within structural members (beams, slabs) to resist tensile and compressive stresses caused by bending moments. It increases load-bearing capacity and controls cracking in concrete by taking the tension which concrete cannot sustain, preventing brittle failure.
Flexural rigidity – It is a measure of a beam’s ability to resist bending, which is based on its material deformation properties and geometry. It is quantified using the Euler–Bernoulli beam theory, which assumes that the structure behaves as a homogeneous, linearly elastic, and isotropic beam.
Flexural stiffness – it is a criterion for measuring the deformability of a structure, which depends on the elastic modulus of the material and the moment of inertia related to its cross-sectional geometry.
Flexural strength – It is a property of solid material which indicates its ability to withstand a flexural or transverse load. It is the maximum stress which can be borne by the surface fibres in a beam in bending. The flexural strength is the unit resistance to the maximum load before failure by bending, normally expressed in force per unit area.
Flexural strengthening – It is the process of improving the load-carrying capacity of reinforced concrete beams by applying fibre-reinforced polymer (FRP) strips or laminates to the tension face, with fibres oriented along the beam’s longitudinal axis.
Flexural stress amplitude – It refers to the magnitude of the alternating bending stress component within a fatigue cycle, specifically representing half the difference between the maximum and minimum bending stresses on the outer fibres of a structural member. It measures the intensity of oscillating bending forces acting on beams, plates, or other components subjected to cyclic loading.
Flexural testing – It is a method used to evaluate the mechanical behaviour of materials under bending loads, measuring parameters such as flexural strength, flexural modulus, and deflection. This testing is important for applications involving active materials in bending structures, such as adaptive systems.
Flexural-torsional buckling – It is a structural instability phenomenon occurring in slender, thin-walled members where, under loading, they buckle by simultaneously twisting (torsion) and bending laterally (flexure). This failure mode happens when the member’s flexural and torsional rigidities are low, leading to instability before yielding.
Flexural vibration – It is also called bending vibration. It is a type of mechanical vibration where a structural member (like a beam or plate) bends, causing transverse displacement perpendicular to its neutral axis. It involves coupled shear forces and bending moments, typically analyzed using Euler-Bernoulli beam theory (for thin structures) or Timoshenko beam theory (for thick structures).
Flexural waves – These are also called (or bending waves) are mechanical waves that propagate through structural elements like beams, plates, or rods, characterized by out-of-plane, transverse motion perpendicular to the structural axis. They involve bending deformation, are highly dispersive (higher frequencies travel faster), and are governed by fourth-order differential equations rather than simple linear wave equations.
Flexure – It is a term used in the study of strength of materials to indicate the property of a body, normally a rod or beam, to bend without fracture.
Flexure hinges – These are compliant joints which connect two rigid elements, allowing them to rotate relative to each other through their bending ability. They are important in the design of compliant mechanisms and come in several forms, each suited for specific applications based on structure and working range.
Flexure test – It measures a material’s behaviour under simple beam loading to determine its ability to resist deformation and rupture, specifically calculating flexural strength and modulus. It involves applying a load to a sample supported at two points, creating maximum stress on the outer fibres until failure or specified deflection.
Flicker noise – It I also called 1/f noise or pink noise. It is a low-frequency electronic noise whose power spectral density is inversely proportional to frequency, becoming dominant at lower frequencies (typically below a few kilo-hertz). It is caused by charge carrier traps, impurities, and dangling bonds in semi-conductors, resulting in resistance fluctuations.
Flight conveyor – it is a conveyor comprising of one or more endless strands of chain with spaced transverse flights or scrapers attached which push granular bulk material along a shaped trough. The material can be loaded at any point into the trough and discharge can also be affected at various points through openings in the trough floor, closed by sliding gates. Both upper and lower strand can be used for transporting materials in opposite directions. These conveyors normally work at speed range of 30 metres per minute to 50 metres per minute to handle free flowing materials of small to moderate size to move them in both the directions. These are used for handling coal, ashes, sand, gravel, ore, wood chips, saw dust, chemicals, grains, and cereals etc., normally for loading bunkers and bins and also used under floor for removal of metal chips / cut pieces. One flight conveyor can handle two or more materials simultaneously by making two or more material flow troughs / channels side by side and designing the flights to match individual troughs. These conveyors are built rugged for long life and low maintenance.
Flights – Flights or lifters are most commonly seen in rotary dryers. They are, however, sometimes utilized in low temperature kilns in order to shower the material and increase heat transfer efficiency.
Flint fireclay – It is a hard or flint-like fireclay occurring as an unstratified massive rock, practically devoid of natural plasticity and showing a conchoidal fracture.
Flip channel – It is also called phase-flip channel. In quantum engineering, it is a noise model representing a qubit transmission channel which alters the quantum phase of a qubit, mapping a state (a ‘Z’ operation) with probability ‘p’. It is used for modeling phase-flip errors and developing error-correction protocols in quantum communication networks. It is a quantum channel which applies a phase-flip operation (Z-gate) to a qubit with probability ‘p’, and leaves it alone with probability ‘1 – p’.
Flip-chip devices – These are semiconductor components (dies) assembled face-down onto substrates, utilizing conductive bumps (solder, gold, or copper) for direct input / output (I/O) connection, rather than wire bonding. This method reduces signal path lengths, increasing speed and reducing inductance. Key benefits include high-density, compact packaging suitable for advanced electronics.
Flip-flop circuit – It is a bistable multi-vibrator circuit used in digital electronics to store 1 bit of data (0 or 1), acting as a fundamental memory element. It has two stable states, set (1) and reset (0), and changes state only upon receiving an external trigger signal, typically synced with a clock pulse.
Float – It is the pieces of rock which have been broken off and moved from their original location by natural forces such as frost or glacial action. In networking, float of an activity represents the excess of available time over its duration. Total float is the amount of time by which the completion of an activity can be delayed beyond the earliest expected completion time without affecting the overall project duration. Free float is the time by which the completion of an activity can be delayed beyond the earliest finish time without affecting the earliest start of subsequent (succeeding) activities.
Floatability – It is the condition which ensures a floating structure does not sink, relying on Archimedes’ principle, which states that the buoyancy force is to counterbalance the weight of the structure.
Float collar – It is a specialized, short-length casing coupling installed near the bottom of a casing string (normally 1 to 3 joints above the shoe) during oil and gas well construction. It contains an integral check valve which prevents cement slurry backflow, enables casing to float (reducing rig load), and serves as a landing seat for cementing plugs.
Floating bearing – It is a bearing which is designed or mounted to permit axial displacement between shaft and housing.
Float glass – It is a type of high-quality, flat, and transparent glass produced by floating molten glass on a bed of liquid tin, creating uniform thickness and distortion-free surfaces. As the standard for over 90 % of flat glass production, it is typically produced in soda-lime-silica composition and serves as the base material for further processing into tempered, laminated, or mirrored glass.
Float glass process – It is a method for producing flat glass by floating molten glass (around 1,100 deg C) on a molten tin bath, creating a high-quality, distortion-free surface with uniform thickness without grinding. This continuous process includes melting, tin bath forming, annealing, and inspection, producing the base material for architectural and automotive applications.
Floating ball valve – It is a ball valve having a non-trunnion-mounted ball. The ball is free to float between the seat rings and hence causes higher torques.
Floating crane – These cranes are used mainly in the constructions of bridges and ports. They are also used for occasional loading and unloading of especially heavy or awkward loads on and off the ships. Some floating cranes are mounted on a pontoon; others are specialized crane barges with a lifting capacity sometimes exceeding 9,000 tons. These cranes are used to transport entire bridge sections. Floating cranes are also used to salvage sunken ships.
Floating die – In metal forming, it is a die which is mounted in a die holder or a punch which is mounted in its holder such that a slight quantity of motion compensates for tolerance in the die parts, the work, or the press. It is also a die mounted on heavy springs to allow vertical motion in some trimming, shearing, and forming operations. In powder metallurgy, it is a die body which is suspended on springs or an air cushion which causes the die to move together with the upper punch over a stationary punch. The rate of die movement is lower than that of the upper punch and is a function of friction coefficient of the powder in relation to the wall of the die cavity.
Floating die pressing – It is the compaction of a powder in a floating die, resulting in densification at opposite ends of the compact. It is analogous to double action pressing.
Floating dummy block – It is a type of sacrificial steel tooling used in the metal extrusion process, very frequently for aluminum, which is not permanently attached to the extrusion ram (stem). Instead, it is placed separately on the billet loader or directly behind the hot billet in the container, allowing it to move or ‘float’ freely at the start of each extrusion cycle. Unlike fixed dummy blocks, floating blocks are separate from the press stem, normally located by a small stud or ‘button’ on the stem as it advances.
Floating inductor – It is an active circuit which simulates the behaviour of a physical inductor without being connected to a common ground. It uses gyrator-capacitor networks (active components like op-amps or current conveyors) to create high-value inductance in integrated circuit (IC) design where physical inductors are bulky and impractical. Unlike a grounded inductor (one terminal connected to ground), a floating inductor acts as a two-terminal element where neither terminal is connected to the common reference.
Floating liquefied natural gas facility – It is an offshore structure designed to process, liquefy, store, and transfer natural gas directly from subsea fields, acting as a floating liquefied natural gas (LNG) plant. Floating liquefied natural gas (FLNG (technology removes the need for long-distance pipelines and large onshore infrastructure, reducing environmental impact while unlocking smaller or remote gas fields.
Floating mandrel – It is a tapered mandrel which is inserted into the hollow extrusion billet. It is not attached to the extrusion ram so is left free to centre itself in a hollow billet as it moves forward through the die as the ram advances and extrusion proceeds. The resulting product tapers slightly in wall thickness along the length.
Floating net – It normally refers to a flexible, porous aquaculture cage structure supported by buoyancy components (floaters) that allow it to rise and fall with water levels. These cages consist of a netting structure attached to a frame, designed to withstand environmental loads like waves and currents. They consist of a flexible net mesh (normally poly-ethylene) attached to collars or floating frames (frequently expanded polystyrene, EPS / Styrofoam or polyethylene foam).
Floating offshore platform – It is a buoyant structure used for oil / gas extraction or wind energy, designed to operate in deep water without being fixed to the seabed. These structures achieve stability through buoyancy, anchoring systems, and weight distribution, allowing for energy harvesting and industrial operations in deeper waters.
Floating offshore wind turbine – It is an electricity-generating wind turbine mounted on a buoyant structure, moored to the seabed, and used in deep waters (typically above 60 meters) where fixed foundations are infeasible. Engineered for stability, floating offshore wind turbines (FOWTs) use specialized sub-structures to harness stronger winds farther offshore.
Floating plant – It is a buoyant, frequently modular, man-made structure designed to operate on water surfaces, including floating solar (floating photo-voltaic, FPV) arrays, floating power plants (FPPs), and marine construction vessels. These systems allow for energy production or industrial activity on water, improving cooling efficiency, reducing land use, and increasing mobility.
Floating platform – It is a buoyant, seaworthy structure moored to the seabed, designed to support payloads, such as wind turbines, oil / gas equipment, or infrastructure, in deep waters where fixed foundations are unfeasible. These systems use buoyancy and ballast for stability.
Floating plug – In tube drawing, it is an unsupported mandrel which locates itself at the die inside the tube, causing a reduction in wall thickness while the die is reducing the outside diameter of the tube.
Floating point – It is a method of numerical representation in computing which allows computers to handle real numbers (fractions and decimals) with a very high degree of precision across an extremely wide range of magnitudes. It refers to a method of numerical representation and computation used by computers to handle numerical quantities, characterized by scientific notation with a limited number of digits for the integer significand. It is defined by the Institute of Electrical and Electronics Engineers standard IEEE-754, which outlines formats, attributes, and operations associated with floating-point arithmetic.
Floating-point addition – It is the process of adding floating-point numbers, which involves extracting exponent and fraction bits, aligning mantissas by comparing exponents, adding the mantissas, normalizing the result, and assembling the final floating-point number. This operation is typically performed in hardware using a floating-point unit (FPU) for efficiency.
Floating-point number – It is a computer representation of real numbers which allows the decimal (or binary) point to ‘float’ to any position, supporting a wide range of magnitudes and fractions within limited memory. Engineered based on the Institute of Electrical and Electronics Engineers standard IEEE-754, these numbers consist of a sign bit, significand (mantissa), and exponent, approximating values to a fixed precision.
Floating-point processor – It is frequently called a floating-point unit (FPU) or math coprocessor. It is a specialized computer component designed to handle arithmetic operations on real numbers (fractions / decimals) faster than a standard CPU (central processing unit). It uses the Institute of Electrical and Electronics Engineers standard IEEE-754 to manage scientific notation (significand and exponent) for high-precision calculations.
Floating point unit – It is also called ‘math coprocessor,’. It is a specialized circuit within a computer’s processor designed to accelerate complex arithmetic operations on non-integer, fractional, or very large/small numbers. It handles operations like multiplication and addition using the Institute of Electrical and Electronics Engineers standard IEEE-754, offering higher precision and speed than standard integer arithmetic logic units (ALUs), which is critical for graphics, simulations, and signal processing.
Floating-ring bearing – It is a type of journal bearing which includes a thin ring between the journal and the bearing. The ring floats and rotates at a fraction of the journal rotational speed.
Floating roof tanks – These are specialized vertical, cylindrical steel storage vessels where the roof floats directly on top of the stored product (typically hydro-carbons), rising and falling with the liquid level. Engineered to eliminate the vapour space (ullage) above volatile liquids, these tanks minimize evaporation, improve safety by reducing fire hazards, and comply with environmental emissions regulations.
Floating slab track – It is a high-performance railway track system designed to minimize ground-borne noise and vibration. It consists of a concrete slab, with rails mounted on top, resting on resilient bearings (rubber bearings or steel springs) instead of being rigidly fixed to the tunnel or ground. By creating a ‘mass-spring’ system, floating slab track (FST) isolates the vibration at its source.
Floating solar – It is a method of installing photo-voltaic solar panels on floating structures anchored to the bed or shore of water bodies, such as reservoirs, lakes, or canals. It offers higher efficiency because of the water’s cooling effect, reduces water evaporation, and saves land.
Floating structure – It is a man-made entity designed to remain buoyant on water, using supporting pontoons or hull bodies to support payloads like buildings, infrastructure, or industrial equipment. These structures are typically moored to the seabed, offering stable alternatives to land-based construction for marine, energy, and residential use.
Floating zone – It is a crucible-free, zone-melting technique used to grow high-purity single crystals, notably silicon for electronics. A molten zone is maintained between solid rods using surface tension, preventing crucible contamination, making it ideal for refractory or reactive materials. The molten zone travels through the rod, purifying the material.
Floating zone method – It is a crucible-free, vertical zone-melting technique used to produce ultra-high-purity single crystals (typically silicon) by passing a localized molten zone through a rod. A radio-frequency (RF) coil melts a segment of a rod, which travels vertically, allowing impurities to segregate into the melt and solidify at the end, resulting in high resistivity and low oxygen / carbon contamination.
Float measurement – It is a method of measuring flow in an open channel. The water level is sampled by a float whose elevation is mechanically transmitted to a non-linear scale or is electrically linearized and converted to a standardized output signal. Contamination, fouling, mechanical abrasion, and frost can affect the float and transmitting element, and since these affect the flow profile, they are responsible for errors. Possibly the float has to be installed in a separate float chamber. Additionally, increased maintenance expenditures are to be expected. These are the reasons that a float measurement is seldom used in these applications.
Float valve – It is a mechanical, automatic flow-control device which maintains a specific liquid level in tanks, reservoirs, or cisterns. It operates through a buoyant float, attached to a lever arm or pilot, which rises with the liquid level to close the valve, preventing overflow, and falls to open it, allowing refilling.
Floc – It is short for flocculent. It is a loose, porous, and irregularly shaped aggregate formed by clumping together fine, suspended particulates in a liquid, frequently aided by chemicals. These flocs (clumps) are heavier than individual particles, enabling them to settle out (sedimentation) or float for easier separation. Flocs differ from coagulated particles by being larger, more voluminous, and held together by weaker, bridging forces.
Flocculant -it is also called flocculating agent. It is a substance added to a liquid suspension to promote the agglomeration of fine, dispersed particles into larger, loose clusters known as flocs or floccules. It is mainly used to accelerate the settling rate of fine solid particles (such as ores, clays, or mineral tailings) from a liquid phase, facilitating solid-liquid separation. Flocculants are typically high-molecular-weight polymers (natural or synthetic) which act as bridging agents. They connect fine particles together, forming a three-dimensional network that traps water and other particles.
Flocculate – It means to aggregate into larger particles, i.e., to increase in size to the point where precipitation occurs.
Flocculated biomass – It refers to the concentrated aggregation of small particulate matter, such as suspended solids, into larger, heavier clusters called flocs. This aggregation, known as flocculation, is an important unit operation used to improve solid-liquid separation through gravity sedimentation or flotation.
Flocculating – In porcelain enameling, it is the thickening the consistency of a slip by adding a suitable electrolyte.
Flocculating agent – It is a chemical additive (polymers or inorganic salts) used to aggregate suspended fine particles, micro-organisms, or colloids into larger clusters, or flocs. By improving sedimentation, filtration, or flotation, these agents speed up solid-liquid separation in water treatment, and mineral processing applications.
Flocculation – It is a physico-chemical process which helps to encourage the aggregation of viscous colloidal and delicately separated suspended matters by mixing physically and by aiding chemical coagulant. This process consists of a rapid mixing tank and a flocculation tank. The wastewater stream mixes with the coagulants in a rapid mix tank and is then passed through the flocculation basin and in the flocculation basin a slow mixing of waste occurs which allows the particles to be collected in the form of more settleable and heavier solids. A better mixing is facilitated with the help of a diffused air or the mechanical paddles. The natural organic polymers, inorganic electrolytes, and synthetic poly-electrolytes are the various different types of chemicals used for the coagulation. Depending upon the characteristics and the chemical properties of the contaminants, the specific chemicals are selected.
Flocculation point – It is the critical moment or concentration where suspended colloidal particles, destabilized by coagulants, form large, loose aggregates called flocs. It represents an optimal process point for maximum sedimentation efficiency, frequently determined by particle size analysis or specific, low-intensity mixing times which avoid floc shear.
Floccules – These are frequently referred to simply as flocs. These are small, loosely aggregated, wool-like clusters of fine particulates which form within a liquid suspension (slurry). These are formed through the process of flocculation, where fine particles, frequently colloidal, are bridged together by chemical agents to form larger masses which can be easily settled, separated, or filtered from the liquid.
Flocking – It is a method of coating by spraying finely dispersed textile powders or fibres.
Flock point – It is a measure of the tendency of a lubricant to precipitate wax or other solids from solution. It is to be noted that depending on the test used, the flock point is the temperature needed for precipitation, or the time needed at a given temperature for precipitation.
Flood – It is an overflow of an expanse of water which submerges land.
Flood coolant – It is a machining technique that delivers a high-volume, low-pressure stream of fluid (water-soluble oils, emulsions, or synthetic fluids) onto the tool-workpiece interface to dissipate heat, reduce friction, and evacuate chips. It acts as a continuous, gravity-fed shower (using M08 codes), preventing thermal distortion and promoting longer tool life.
Flooded lubrication – It is a method where a large, continuous volume of lubricant (oil or coolant) is applied to machine components or cutting zones. It ensures full coverage to reduce friction, remove heat efficiently, and wash away debris. It is normally used in heavy-duty machinery, gear-boxes, and machining operations.
Flooded screw compressor – It is a positive-displacement, helical-rotor compressor which injects large quantities of oil (or synthetic lubricant) directly into the compression chamber. This fluid acts as a coolant, sealant, and lubricant, enabling higher pressure ratios in a single stage, reduced noise, and increased efficiency compared to oil-free alternatives.
Flooding – It is the accumulation of water, or the overflowing of water from its natural or artificial confined channel (like rivers or drains), onto normally dry land. It represents a hydraulic failure where inflow exceeds the capacity of natural or engineered drainage systems, leading to inundation.
Flooding phenomenon – It is a critical limit state where the upward gas velocity in a column, pipe, or bed becomes too high, causing liquid or solid particles to be carried upward, disrupting counter-current flow. It represents a state of maximum fluid capacity, leading to dramatic increases in pressure drop, liquid buildup, and reduced efficiency. In blast furnace, flooding is a very important phenomena in the wet zone of the blast furnace. Just like channeling take place in the dry zone, the flooding is an unfavourable phenomenon in the wet zone, where the liquid is pushed off in the low temperature solid granular region above the cohesive zone. This liquid can solidify, form an arch and it can restrict the gas flow totally. In such a situation, it is called the hanging and the blast air flow in the blast furnace is reduced and even stops in severe hanging.
Flood lubrication – It is a system of lubrication in which the lubricant is supplied in a continuous stream at low pressure and subsequently drains away. It is also known as bath lubrication.
Floor chargers – These chargers are frequently referred to as vibratory furnace chargers. These are mobile, mechanized units used to transport and charge raw materials, such as scrap metal, pig iron, and alloys, directly into melting furnaces. These consist of a storage hopper, a vibrating feeder, and a discharge chute, all mounted on a mobile, motorized trolley.
Floor joist – It is a horizontal structural member used in framing to span open spaces, typically running parallel to one another between beams, girders, or bearing walls to provide main support for floors and ceilings. In engineering terms, floor joists are considered beams designed to carry live loads (occupants, furniture) and dead loads (floor materials, structure weight) to the foundation.
Floor moulding – It consists of making sand moulds from loose or production patterns of such size that they cannot be satisfactorily handled on a bench or moulding machine, the equipment being located on the floor during the entire operation of making the mould.
Floor plan drawing – This drawing is in-depth version of the floor layout. Civil floor plans are made irrespective of the fact that they are to be utilized during the construction of a building, or production shop. Applications include an understanding of the dimensions and different kinds of installment. This helps in getting an idea about the usage of the limited room space. Floor plans are normally very useful, and they are the most used location drawings. They are really the sectional plans since they show the view obtained by cutting horizontally through a building at some point above the floor level. It is assumed that one move away the top part of the building and look down at the plan of the remaining bottom part. This plan view not only shows the arrangement of the rooms and spaces and their shapes, but also shows the thickness of all the external and internal walls. Floor plans are a form of orthographic projection which can be used to show the layout of floors within buildings. They can be prepared as part of the design process, or to provide instructions for construction, frequently associated with other drawings, schedules, and specifications.
Floor sensor – It is an engineering device embedded within or installed under flooring to detect, measure, and record physical parameters, very frequently pressure or temperature, and convert them into electrical signals
Floor slab – It is a horizontal structural element, typically composed of reinforced concrete, designed to provide flat, solid surfaces for building floors or roofs. It acts as a structural diaphragm, transferring dead, live, and environmental loads to supporting beams, walls, or columns. Slabs can be ground-bearing or suspended (spanning between supports).
Floor vibration – It is the dynamic, oscillatory movement of a floor system, typically vertical, caused by human activity or machinery. It is a serviceability issue, rather than a safety issue, focusing on human comfort and limiting the annoyance caused by excessive flexibility, frequently in modern, lightweight, or long-span structures.
Flop forging – It is a forging in which the top and bottom die impressions are identical, permitting the forging to be turned upside down during the forging operation.
Floppers – On metals, these are lines or ridges which are transverse to the direction of rolling and normally confined to the section midway between the edges of a coil as rolled.
Floppy disk – It is a flexible, magnetic storage medium enclosed in a protective, rigid or semi-rigid plastic jacket, utilized for data storage and transfer. Engineered for portable secondary storage, it operates by using a magnetic read / write head on a rotating, flexible disk coated with iron oxide to record data in concentric tracks and wedge-shaped sectors.
Flora and fauna – Flora refers to the plant life of a particular region or period, while fauna refers to the animal life of a region or period. In essence, flora encompasses all plants, and fauna encompasses all animals.
Flory Huggins equation – It is defined as a thermodynamic model for polymer solutions, incorporating both configurational (entropic) contributions from molecular size differences and group-interaction contributions mainly because of the intermolecular force variations.
Flory Huggins theory – It is defined as a mean-field, lattice model theory which explains the change in Gibbs free energy upon mixing two dissimilar polymers, incorporating configurational entropy and the Flory interaction parameter to assess miscibility.
Flo-spinning – It is forming cylindrical, conical and curvilinear shaped parts by power spinning over a rotating mandrel.
Flotation – It is the concentration of valuable minerals from ores by agitation of the ground material with water, oil, and flotation chemicals. The valuable minerals are normally wetted by the oil, lifted to the surface by clinging air bubbles, and then floated off. It is also a milling process in which valuable mineral particles are induced to become attached to bubbles and float as others sink.
Flotation bank – It is a series of interconnected, industrial-scale flotation cells arranged in a row (or line) to continuously separate valuable minerals from gangue (waste). Slurry flows from one cell to the next, with air bubbles collecting hydrophobic particles and lifting them as froth, creating stages such as roughing, scavenging, or cleaning within the bank.
Flotation cell – It is a specialized metallurgical vessel used to separate valuable minerals from waste rock (gangue) by attaching hydrophobic particles to air bubbles. It creates a froth layer on top of a slurry mixture where desired, concentrated minerals are collected, while gangue sinks as tailings.
Flotation circuit – It is a mineral processing system designed to selectively separate valuable minerals from waste rock (gangue) by manipulating the hydrophobic (water-repelling) properties of particle surfaces in a slurry. It involves adding chemical reagents to the slurry, which is then aerated in tanks, allowing hydrophobic minerals to attach to air bubbles and rise to the surface as froth for removal, while gangue remains in the tank.
Flotation feed – It is the conditioned slurry or pulp, a mixture of finely ground ore, water, and reagents, introduced into flotation cells to separate valuable minerals from waste (gangue). It is prepared by grinding ore to specific sizes and treating it with chemicals to make valuable particles hydrophobic.
Flotation froth – It is the stable, air-filled foam layer formed at the top of a flotation cell, laden with valuable hydrophobic mineral particles which have attached to air bubbles and risen from the suspended slurry (pulp). It acts as a concentration mechanism, skimming off desired materials while waste rock (gangue) sinks, normally used in sulphide ore extraction.
Flotation kinetics – It refers to the rate at which minerals are separated and recovered during the flotation process, which can be described by different orders of kinetics (first, second, or higher), where deviations from first-order behaviour can indicate more complex interactions among floatable species.
Flotation machine – It is a specialized industrial device used in mineral processing to separate valuable minerals from waste rock (gangue) based on their surface hydrophobicity. These machines are normally used to treat finely ground ore mixed with water, forming a slurry (or pulp), to which reagents are added to render specific minerals hydrophobic.
Flotation plant – It is an industrial facility which separates valuable minerals from waste rock (gangue) by exploiting differences in their surface chemistry. Using chemical reagents, desired minerals are rendered hydrophobic (water-repelling) and attach to air bubbles, floating to the surface as a mineralized froth that is skimmed off.
Flotation process – The principle of the flotation process is based on the differences in the chemical properties of the mineral surface (hydrophilic, flowability). The flotation agent is used to selectively attach useful minerals or useless impurities to the bubbles for the purpose of separation. This method is also called chemical beneficiation. A standard flotation circuit starts by separating the scrubbed ore into a coarse portion (e.g., +20 mesh), and a fine portion (e.g., -20 mesh). For designing optimum flotation circuits, it is necessary to understand the processing needs, and the technical and mineralogical characteristics of the ore. Successful flotation involves proper liberation, adding the proper reagents to induce selected minerals to become hydrophobic (water repelling) or hydrophilic (water attracting). Aeration (bubbles) is added through spargers at the bottom of the flotation cell. The bubbles attract and then float the hydrophilic minerals, leaving the hydrophobic component in the underflow as tailings. The flotation circuit then concentrates and separates the desired minerals.
Flotation rate – It is a measure of the speed at which valuable mineral particles are separated from waste gangue and recovered in a flotation cell. It defines how quickly a component is transferred from the pulp to the concentrate foam, normally following first-order kinetics.
Flotation rate constant – It is a kinetic parameter representing the speed at which valuable particles attach to bubbles and are removed, typically modeled as a first-order process. It acts as a measure of floatability, lumping particle-bubble collision, attachment efficiency, and stability into a single value. It is defined as the slope of the recovery-time curve, representing the rate of mineral transfer from the pulp to the froth layer.
Flotation reagents – These are specialized chemicals added to mineral pulp during froth flotation to alter the surface properties of particles, improving the selectivity and recovery of valuable minerals from gangue. They manage hydrophobicity, allowing valuable minerals to attach to air bubbles and float to the surface while waste sinks. These reagents make targeted mineral surfaces hydrophobic (water-repelling), encouraging attachment to air bubbles.
Flow – It is the movement (slipping or sliding) of essentially parallel planes within an element of a material in parallel directions. It occurs under the action of shear stress. Continuous action in this manner, at constant volume and without disintegration of the material, is termed yield, creep, or plastic deformation.
Flowability – Flowability is the ability of a material to flow, high flowability indicates that the material can flow easily and quickly, while a high viscosity indicates that the material is more resistant to flow. In casting, it is a characteristic of a foundry sand mixture which enables it to move under pressure or vibration so that it makes intimate contact with all surfaces of the pattern or core box. In welding, brazing, or soldering, it is the ability of molten filler metal to flow or spread over a metal surface.
Flow accelerated corrosion – It is a localized corrosion mechanism which occurs in feed-water systems, mainly affecting areas of flow turbulence, where the protective oxide coating on carbon steel dissolves into a moving fluid. It is particularly prevalent in systems using high-purity feed-water and can lead to substantial corrosion damage and failures.
Flow accuracy – It is the measure of how closely a flow meter’s measured value conforms to the actual flow rate (true value) of a fluid, liquid, or gas, typically expressed as a percentage of the reading, full scale, or calibrated span. It reflects the total measurement error compared to a reference standard.
Flow analysis – It frequently referred to as ‘material flow analysis’ (MFA) or ‘substance flow analysis’ (SFA). It is a systematic, quantitative assessment of the movement, transformation, and accumulation of metallic materials, substances, and energy within a defined system (such as a factory, region, or the entire economy) over a specific time frame. It applies the principles of mass balance, based on the law of conservation of mass, to track materials from extraction and raw material processing, through manufacturing and use, to end-of-life (EoL) waste management or recycling.
Flow activation energy – It is the minimum energy needed for molecules, polymer chains, or atoms to overcome inter-molecular forces and initiate viscous flow. It represents the material’s thermal sensitivity during viscous movement, acting as an energy barrier to flow. It is normally measured in joules per mol (J/mol).
Flow arrangement – It refers to the geometric configuration and direction of fluid movement within a system, such as a heat exchanger, to optimize heat transfer, pressure, and process efficiency. It defines how fluids interact (series, parallel, or cross) and determines system performance. It refers to the configuration of modules in a separation process, which can be organized in series, parallel, or combined series-parallel sequences to optimize flow rates and purities, accommodating variations in permeability and recovery rates.
Flow assurance – It is the engineering discipline ensuring safe, economical, and uninterrupted hydrocarbon transport from the reservoir to the final processing facility, spanning the entire production system. It involves predicting and managing solid deposition (wax, hydrates, asphaltenes, scale) and flow issues (slugging) using fluid analysis and multiphase simulation. It is an engineering analysis process which ensures the economic transmission of hydro-carbon fluids from the reservoir to the end user, addressing challenges related to solid deposits such as hydrates, wax, and asphaltenes which can block flow.
Flow availability – It is also called exergy flow. It is a thermodynamics term defining the maximum theoretical useful work obtainable from a fluid stream as it reaches equilibrium with its surroundings. It represents the chemical and physical energy transport rate per unit mass, calculated for steady-state systems by accounting for both enthalpy and entropy changes compared to the environment.
Flow battery – It is also called redox flow battery. It is an electro-chemical energy storage device which stores electricity in liquid electrolyte solutions contained in external tanks. These electrolytes are pumped through a reactor stack, separated by an ion-selective membrane, where redox reactions generate electricity. These batteries are designed for large-scale, long-duration stationary storage.
Flow behaviour – It is also called flow stress behaviour. It is the instantaneous stress needed to continue deforming a metal plastically at a given strain, strain rate, and temperature. It describes how a metal deforms, moves, or changes shape under applied force beyond its elastic limit.
Flow behaviour Index (n) – It is a dimensionless power-law parameter defining a non-Newtonian fluid’s deviation from Newtonian behaviour, representing the slope of the logarithmic relationship between shear stress and shear rate. It quantifies viscosity changes under stress, namely ‘n below 1’ indicates shear-thinning (pseudo-plastic), ‘n = 1’ is Newtonian, and ‘n above 1’ is shear-thickening (dilatant).
Flow boiling instability – It is a phenomenon characterized by undesirable, coupled fluctuations in mass flow, pressure, and temperature within a two-phase boiling system. It occurs when vapour generation (boiling) causes flow resistance or oscillations, degrading thermal performance and causing mechanical vibration. It represents a, normally transient, departure from a steady-state thermal-fluid condition caused by bubble expansion or flow blockage. These instabilities are critical in micro-channel heat sinks and power systems (nuclear / boiler) as they can cause premature dry-out and failure.
Flow boiling system – It is a method where liquid is forced by an external source (e.g., pump) through a heated channel, undergoing phase change to vapour while moving. It combines convective and nucleate boiling to achieve high heat transfer rates, ideal for removing high heat fluxes in electronics cooling and power systems.
Flow brightening – It is the melting of an electro-deposit, followed by solidification, especially of tin plate. It is the fusion of a metallic coating on a base metal. It is also fusion (melting) of a chemically or mechanically deposited metallic coating on a substrate, particularly as it pertains to soldering.
Flow brush – It typically refers to a specialized tool used for the continuous application of liquids (such as adhesives, fluxes, or coatings) under pressure. It is frequently structured as a hollow brush, allowing the liquid to be fed through the handle and out through the bristles, providing a more uniform coating and higher production rate compared to traditional brushing. Flow brushes allow for a single smooth sweep application of adhesive or coating, reducing the need for multiple passes. They are particularly useful for applying substances to flat surfaces with irregular shapes.
Flow cavitation – It is the cavitation caused by a decrease in static pressure induced by changes in the velocity of a flowing liquid. Typically, this can be caused by flow around an obstacle or through a constriction, or relative to a blade or foil.
Flow cell – It is a compact chamber designed to transport liquid or gas samples continuously through a, typically, transparent region for real-time analysis, such as spectroscopy, microscopy, or particle counting. It optimizes analyte delivery, enabling non-destructive testing, precise environmental control, and high-throughput screening of cells or molecules.
Flow channel – It is a defined, confined, or open pathway which directs the movement of fluids (liquids or gases). These channels are important for controlling heat transfer, pressure drops, and velocity, normally used in hydraulic engineering, micro-fluidics, and heat exchangers. They are characterized by boundary types (rigid, free-surface) and cross-sectional geometry.
Flow characteristics – The term refers to the properties and behaviour of the flow, such as velocity, pressure, and temperature, which are obtained through mathematical equations and operational data. These characteristics demonstrate the correlation between different variables and validate the methodology used in the analysis.
Flow characteristic, valve – It is the relationship between flow through the valve and percent rated travel as the latter is varied from 0 to 100 %. This term is always to be designated as either inherent flow characteristic or installed flow characteristic.
Flow chart – A flowchart is a type of diagram that represents a workflow or process. A flowchart can also be defined as a diagrammatic representation of an algorithm, a step-by-step approach to solving a task. The flowchart shows the steps as boxes of various kinds, and their order by connecting the boxes with arrows. A flowchart shows separate steps of a process in sequential order. It is a generic tool which can be adapted for a wide variety of purposes, and can be used to describe different processes, such as a manufacturing process, an administrative or service process, or a project plan.
Flow coating – It is the process of coating a metal shape by causing the slip to flow over its surface and then allowing the excess slip to drain.
Flow coefficient – It is a constant related to the geometry of a valve, for a given travel, which can be used to establish flow capacity. It is defined as the flow of water in cubic meters per hour at a pressure drop of 0.1 mega-pascals with temperature ranging from 5 deg C to 30 deg C.
Flow compressor – It is also called dynamic compressor. It is a device which increases the pressure of a gas by continuously converting kinetic energy (velocity) into pressure energy using rotating blades (rotors) and stationary blades (stators). Mainly used in jet engines and industrial applications, they achieve high mass flow capacity with high efficiency.
Flow conditioner – It is a device installed in piping systems to eliminate flow distortions, such as swirl and asymmetric velocity profiles, caused by bends, valves, or pipe diameter changes. By rectifying the flow, it creates a fully developed profile, allowing accurate flow measurement with minimal straight pipe runs.
Flow configuration – It defines the geometric relationship, direction, and arrangement of fluid streams (parallel, counter, or cross-flow) within a system, such as a heat exchanger or reactor. It optimizes heat transfer efficiency, pressure drop, and material distribution. Common types include parallel-flow, counter-flow, and cross-flow.
Flow constraint – It defines limitations on the movement, rate, or balance of materials, energy, or data within a system. Common types include flow conservation (inflow equals outflow), capacity limits (maximum / minimum allowable throughput), and operational constraints (e.g., pressure, velocity, or temperature) to ensure system safety, optimization, and stability.
Flow control devices – They include inlet dampers on the box, inlet vanes at the inlet to the fan, and outlet dampers at the outlet of the fan.
Flow control valve – A flow control valve regulates the flow or pressure of a fluid. It normally responds to signals generated by independent devices such as flow meter or temperature gauge.
Flow counting – It is a technique used for continuous monitoring of gas streams or flowing liquids, where radioactively labeled substances pass through a counting cell filled with scintillator crystals, resulting in scintillation detection related to the activity concentration and flow rate.
Flow curve – It is a plot of true stress against true strain for a material undergoing plastic deformation. It characterizes the mechanical resistance of a material to plastic flow, acting as a direct relationship between stress and strain beyond the yield point, making it a fundamental tool in metal-forming technology, numerical modeling, and simulation, such as ‘finite element method’ (FEM).
Flow deflection – It refers to the alteration of a fluid’s (liquid or gas) path from its original direction, often caused by obstructions, guide vanes, or changing channel geometry. It is used to redirect flow, reduce noise, or control velocity. It also refers to the lateral displacement or movement of a structural member (like a beam) from its original position under applied loads.
Flow detection – It is the measurement, monitoring, and verification of the rate, volume, or velocity of liquids or gases moving through systems like pipes and channels. It uses sensors (flow meters) to convert fluid movement into signals, crucial for process control, safety, leak detection, and efficiency.
Flow diagrams – These diagrams show the structure and function of the process plants and are part of the entire set of technical documents which are needed for planning, assembly, construction, management, commissioning, operation, maintenance, shutdown, and decommissioning of a plant. Flow diagrams are a means by which information is exchanged between parties involved in the construction, assembly, operation, and maintenance of such process plants. General rules and recommendations for preparation of flow diagrams are given in ISO 15519.
Flow distribution – It refers to the spatial allocation of fluid velocity, pressure, or mass flow rate across a cross-section, such as in pipes, heat exchangers, or manifolds. It describes how evenly or unevenly fluid moves through a system, important for optimal thermal performance, reduced pressure drops, and component integrity.
Flow domain – It is the defined 3D volume or 2D area where fluid motion is analyzed, encompassing the fluid regions and boundaries (inlets, outlets, walls) of a CFD (computational fluid dynamics) model. It represents the physical space the fluid occupies, and its proper definition is crucial for setting boundary conditions, solving governing equations, and capturing flow phenomena.
Flow duration curve – It is a cumulative frequency curve which shows the percentage of time a specific stream-flow discharge is equaled or exceeded over a set period. It plots flow magnitude on the y-axis (log scale typically) and percentage exceedance on the x-axis, used heavily in for hydro-power, water supply, and pollution management.
Flow dynamics – It is the study of fluid movement and behaviour, particularly focusing on the interaction of fluids with surfaces and the resulting flow patterns, which can be analyzed and simulated using computational fluid dynamics (CFD) techniques.
Flow energy – It is also known as flow work. It is the energy needed to push a mass of fluid into or out of a control volume. It is not stored energy within the fluid itself, but rather the work done by pressure to move the fluid across a boundary. Flow energy is the product of the fluid’s pressure (P) and its volume (V). In technical applications, it is normally expressed per unit mass.
Flow energy equation – It is also called ‘steady flow energy equation’ (SFEE). It is a formulation based on the first law of thermodynamics, stating that total energy entering an open system equals total energy leaving, balancing heat, work, enthalpy, kinetic, and potential energies for steady fluid flow. It is necessary for analyzing turbines, pumps, and nozzles.
Flow equation – It is a mathematical formulation describing the behaviour of fluids (liquids or gases) based on the principles of mass, momentum, and energy conservation. Key types include the continuity equation, Bernoulli’s equation for energy conservation, and equations for calculating volumetric flow rate, necessary for designing pipe networks, nozzles, and analyzing system energy changes. Flow equations are the governing equations which describe the behaviour of fluid flow and energy transfer, typically expressed in terms of continuity, momentum, and energy, and frequently incorporate models such as the Reynolds stress turbulence model for analyzing turbulent flow fields.
Flow exergy – It is the maximum theoretical useful work obtainable as a substance flows into a system and reaches equilibrium with the environment (dead state), including both internal thermal / mechanical energy and flow work. It represents the work potential of a flowing stream, frequently called availability, and is the sum of physical, chemical, kinetic, and potential exergies.
Flow factor – It is the time needed for a standard powder sample of standard weight to flow through an orifice in a standard instrument as per a specified procedure.
Flow field – It is a mathematical, vector-based representation of fluid motion, assigning velocity vectors to every point within a region at specific times. It enables calculation of pressure, temperature, and density, necessary for modeling aerodynamics and fluid behaviour using methods like CFD (computational fluid dynamics).
Flow filtration – It is a filtration process where the majority of the feed flow moves tangentially across the surface of the filter, allowing for continuous operation and reducing the accumulation of filter cake which can obstruct the filter.
Flow fluctuations – These are sustained, frequently undesirable variations in fluid flow rates (velocity, pressure, or mass flow) within a system over time. These variations, frequently characterized as non-uniform and unsteady, occur around a mean value and can cause mechanical vibration, thermal fatigue, cavitation instabilities, and control problems in systems like reactors, pipelines, and pumps.
Flow-formed work-pieces – These are rotationally symmetric, hollow components, such as tubes, cones, or cylinders, produced through an advanced chipless metal-forming process which combines extrusion, rolling, and shear forming. This process is characterized by the plastic deformation of a thick-walled ‘preform’ (or blank) over a rotating mandrel using high-pressure rollers, which simultaneously reduces the material’s thickness and increases its length, frequently achieving near-net shapes with high precision.
Flow-forming – It is an advanced, chipless metal cold-forming process which uses rotating rollers to compress and stretch a metal preform (tube or disk) over a mandrel, considerably reducing wall thickness while increasing length. It produces high-precision, high-strength, seamless, net-shape cylindrical or conical components.
Flow graph – It is a directed graph representation, normally used in software (control flow) or systems engineering (process flow), visualizing the sequence of operations, decisions, and data paths using nodes and interconnecting lines. It abstracts complex systems to analyze, document, or test sequences, where nodes represent blocks of code or actions, and edges represent branches of control.
Flow growth – It is a deposition process in which atoms attach to steps on a substrate surface, enabling the advancement of these steps and resulting in a smooth surface morphology. This mode needs high atomic mobility to ensure that deposited atoms reach the existing steps before encountering other adatoms.
Flow gun – It is frequently referred to as a blow gun in industrial contexts. It is a hand-operated pneumatic tool designed to control the flow of compressed air or fluids for cleaning, drying, or applying materials. It uses a nozzle to distribute the pressurized liquid. Engineered for ergonomics and precision, these devices typically feature a light-weight body, a trigger-activated valve, and a nozzle which directs a high-velocity stream, frequently used in cleaning and spraying.
Flow impeller – It is a rotating, bladed component within a pump, compressor, or mixer which transfers kinetic energy from a motor to a fluid, increasing its pressure and velocity. It works by accelerating fluid outward from its centre (axial suction) to its perimeter (radial discharge), forming the core of centrifugal pump performance.
Flow in channels – It refers to liquid movement within boundaries, categorized into closed conduit flow (pipes) or open-channel flow (free surface exposed to atmosphere). Driven mainly by gravity and channel slope, it is important for hydraulic engineering), characterized by turbulent, laminar, steady, or unsteady regimes based on velocity and boundary conditions.
Flow in conduits – It is also called closed-conduit flow. It is the transportation of liquids or gases through enclosed, fully filled pipes or ducts, driven mainly by pressure differences. It is characterized by internal flow (entirely bounded by walls), where fluid-boundary interaction causes shear stress, leading to viscous friction losses, and is classified as laminar or turbulent using the Reynolds number.
Flow in ducts – It is a subset of internal fluid mechanics. It defines the motion of liquids or gases confined within closed, solid boundaries (ducts, pipes, or conduits). It is driven by pressure differences, characterized by viscous effects, and governed by principles such as continuity, friction loss, and Reynolds number, spanning laminar, transient, or turbulent regimes.
Flowing area – It refers to the effective cross-sectional area available for the movement of fluids, such as molten metal, slag, or gas, within a conduit, vessel, or reactor (e.g., pipes, blast furnaces, ladles, or continuous casting moulds). It defines the space through which molten materials move, which is important for determining the efficiency of metallurgical operations like tapping or pouring.
Flowing bottom hole pressure – It is the pressure measured at the bottom of an oil or gas well while it is actively producing fluids. It represents the sum of hydrostatic pressure, friction, and surface pressure, important for determining production rates and the reservoir’s energy. Flowing bottom hole pressure (FBHP) is lower than the static reservoir pressure to allow flow. It is the pressure exerted on the formation face when fluids (oil, gas, water) are flowing up the wellbore.
Flowing enthalpy – It refers to the total energy content of a fluid material (gas, molten metal, or slag) in motion, comprising its internal energy plus flow work. It represents the energy needed to move a unit mass of material into a furnace or reactor (e.g., in a blast furnace or converter), accounting for heat capacity, latent heat of phase changes, and pressure. It is defined as a fluid-averaged enthalpy value obtained by dividing the total specific energy flux by the total convected specific mass flux, representing the energy content of a fluid in motion. It can take the value of the liquid or gas enthalpy depending on the phase conditions.
Flowing fluid – It refers to the continuous movement and deformation of liquids or gases (such as molten metal, slag, or shielding gases) under the action of unbalanced forces or shear stress. It involves substances which cannot resist shear forces and continuously change shape, making it critical for heat and mass transfer in processes like casting, welding, and crystal growth.
Flowing material – It is the substance which moves through a specific location, such as a cross-section of a pipe, at a given flowrate, which can be measured in terms of mass or volume per unit time. It refers to the movement of liquids, gases, or slurries through processing equipment, frequently involving molten metal, slag, or gas injection in furnaces and ladles. These materials are defined by their movement rate (mass / volume over time) and are important in casting, stirring, and extraction processes.
Flowing stream – It is a natural or man-made channel conveying water or another fluid along a defined course via gravity or pressure. It involves a continuous, frequently steady, movement of liquid, where layers slide past each other, typically classified as laminar or turbulent depending on the velocity.
Flowing temperature – It is average flowing temperature which is the mean value of the flowing temperature of a gas (through a transducer, transmitter, or fixed variable) over the specified period of actual flow.
Flowing well – It is a production well (oil or water) where natural reservoir pressure, rather than a pump or artificial lift, is sufficient to force liquid to the surface, normally referred to as a ‘naturally flowing well’. These wells occur when the pressure in the aquifer or reservoir is higher than the surface pressure.
Flow injection analysis – It is an automated analytical technique defined by injecting a precise, small volume of liquid sample into a continuously moving carrier stream, which transports it through a reactor to a detector. It enables rapid analysis, high reproducibility, and reduced reagent consumption, normally used for environmental, and industrial chemical monitoring.
Flow in nozzles – It is the process where a duct of varying cross-sectional area converts a fluid’s (liquid or gas) high-pressure / potential energy into high-velocity kinetic energy. It typically involves adiabatic expansion, where pressure and temperature drop while velocity increases, frequently described using steady-flow energy and continuity equations.
Flow in porous media – It is the movement of fluids (liquids or gases) through a solid matrix containing interconnected pores. It describes how fluids move through materials like soil, rock, filters, or foams, frequently governed by Darcy’s law, which links pressure loss to flow rate based on permeability. It is the study of fluid flow behaviour through interconnected voids within a solid skeleton.
Flow instability – It is the tendency of a fluid flow to deviate from its steady state (laminar flow) and develop oscillations, turbulence, or chaotic behaviour when disturbed. It occurs when fluid inertial, viscous, or boundary forces cause small disturbances to grow rather than decay, typically leading to new flow patterns or instability.
Flow instability processes – These refer to the onset of non-homogeneous plastic deformation, where flow localization occurs rather than uniform deformation. It is a critical, frequently destructive phenomenon in metalworking where deformation concentrates into narrow zones, such as adiabatic shear bands, cracks, or voids, leading to premature failure or defects in the final alloy product.
Flow investigation – It is the systematic analysis, measurement, and simulation of fluid (liquid or gas) behaviour or power distribution within a system to determine critical parameters like velocity, pressure, direction, and magnitude. It involves studying fluid motion, including laminar, turbulent, steady, and unsteady flows, using numerical methods like computational fluid dynamics (CFD) or physical experiments such as wind tunnel testing and flow visualization.
Flow line – It typically refers to the directional alignment of grains, inclusions, and impurities within a metal which has been subjected to plastic deformation, such as forging, rolling, or extrusion. Flow lines – are the lines on the surface of painted sheet, brought about by incomplete leveling of the paint. Flow lines can frequently be revealed by etching the surface or a section of a metal part. In mechanical metallurgy, it is the paths followed by minute volumes of metal during deformation. In composites, flowline is a mark on a moulded piece made by the meeting of two flow fronts during moulding. It is also called striae, weld mark, or weld line.
Flow line principle – It normally refers to a manufacturing or process approach designed to optimize production efficiency by ensuring materials move through a sequence of stations smoothly and continuously. It is a hybrid model sitting between batch manufacturing and assembly lines, focusing on minimizing waste, reducing inventory, and minimizing delays by treating production as a continuous ‘flow’ of material.
Flow localization – It is a phenomenon where plastic deformation becomes concentrated in narrow, localized zones (shear bands) rather than occurring uniformly throughout the bulk of the material. This instability leads to a dramatic drop in the uniformity of deformation, frequently causing premature failure in manufacturing processes, such as forging or hot working, by forming microstructural defects, crack propagation, and severe softening within those zones.
Flow localization analysis – It is a predictive and diagnostic study of the phenomenon where plastic deformation becomes highly concentrated in narrow zones (shear bands) rather than being distributed uniformly throughout the material. This localization acts as a precursor to ductile fracture, premature failure, or surface defects during metal forming processes like forging, rolling, or high-speed machining. It is the concentration of strain in specific, narrow regions frequently termed shear bands, occurring because of the flow softening (negative strain hardening) where the material becomes easier to deform as it strains.
Flow mal-distribution – It is the non-uniform distribution of fluid mass flow rate among parallel flow channels, tubes, or packing in systems (like heat exchangers or columns). It represents a deviation from ideal uniform flow, leading to deteriorated heat transfer efficiency, increased pressure drops, and decreased overall system performance. Poor header / manifold design, manufacturing defects (e.g., blockages, improper distribution plates), two-phase separation, or operational fouling and vibration.
Flow marks – It is the wavy surface appearance of an object moulded from thermo-plastic resins, caused by improper flow of the resin into the mould.
Flow measurement – It is the process of quantifying the rate, volume, or mass of liquids, gases, or steam passing through a pipe, conduit, or open channel per unit of time. It is important for process control, safety, and inventory management in industrial applications.
Flow measuring device – It is an instrument used to quantify the volumetric or mass flow rate of liquids, gases, or steam moving through a pipe, conduit, or open channel. These devices measure fluid velocity or displacement to ensure process control, safety, and efficiency. Core engineering principles and types of measuring devices are differential pressure (DP), velocity-based, positive displacement (PD), ultra-sonic, variable area (rotameters), and mass flow (Coriolis).
Flow mechanism – It refers to the specific physical, thermal, or mechanical process by which a fluid (liquid or gas) moves, transports energy, or transfers mass through a system, conduit, or over a surface. It is fundamentally defined by how fluid particles behave and interact within a given boundary, governed by principles of fluid dynamics, conservation of mass, and energy. Flow mechanisms are categorized based on their behaviour, physical properties, and driving forces:
Flow meters – They measure the flow of a fluid in a pipe. Flow meters measure indirectly by measuring a related property such as a differential pressure across a flow restriction or a fluid velocity in a pipe. Flow meters also use the direct method for measured value acquisition. They measure either the flow velocity or the kinetic energy of the flow. In powder metallurgy, a flow meter is a metal cylinder whose interior is funnel shaped and whose bottom is a calibrated orifice of standard dimensions to permit passage of a powder and determination of the flow rate.
Flow model – It is a graphical or mathematical representation of how materials, data, information, or artifacts move through a system, highlighting interactions, processes, and dependencies. These models identify critical paths, bottlenecks, and handover points between roles or components, defining the directionality and hierarchy of flows.
Flow modifying devices – These are the devices which modify the flow of liquid metal in a continuous casting tundish. They assist in the flotation of inclusions, by harnessing the turbulent energy from the ladle shroud. Principal among these flow modifying devices are pour-pads, weirs, dams, baffles with holes and turbulence inhibitors. The turbulence inhibitor controls the degree of splashing of liquid metal during ladle changes or at the beginning of the casting sequences. It is also useful in increasing the plug flow, the residence time, and decreasing the dead volume. Flow modifying devices are typically manufactured by casting shapes with 70 % alumina refractories, through occasionally areas subject to strong erosive flow can necessitate a switch to magnesite-based refractories. Less costly refractory grades, such as 60 % alumina, can be used to manufacture flow modifying device shapes but have shown a propensity for premature failures in field trials when tundishes are used for multiple heat sequences.
Flow monitoring – It is the continuous measurement and analysis of the rate, volume, or mass of fluids (liquids / gases) moving through a system, using devices like flow meters. It enables process control, efficiency optimization, and proactive maintenance by identifying anomalies in velocity, pressure, or volume.
Flow nozzle – It is a differential pressure flow meter used to measure the rate of fluid flow (liquids, gases, steam) by accelerating it through a converging section to a constant-area throat, which creates a pressure drop. Based on Bernoulli’s equation, it measures high-velocity or abrasive fluids, frequently used in power generation for its structural stability. It consists of a convergent inlet section with a rounded profile and a cylindrical throat section.
Flow-off – It is large vent, normally located at the high point of a mould cavity. In addition to letting air and mould gases escape during a pour, the flow-off fills with metal and is allowed to run or flow during the final stage of pouring.
Flow operation – It is the continuous, managed movement of materials, energy, or data through a process, aimed at minimizing material consumption, reducing energy dissipation, and maintaining stable, efficient production. It is frequently distinguished by steady-state, continuous feeding of reactants and removal of products, contrasting with batch operations.
Flow parameters – These are quantitative characteristics defining fluid motion, velocity, pressure, flow rate, density, and temperature, used to analyze, control, and optimize systems. These parameters determine flow behaviour, such as turbulence or phase distribution, and are important in designing efficient hydraulic, pneumatic, and chemical processing equipment.
Flow passage – It is a designed channel, conduit, or duct which guides the movement of fluids (liquids or gases), defined by its geometry, dimensions, and wall surface characteristics. It influences fluid velocity, pressure drop, and heat transfer efficiency, frequently incorporating features like U-shapes, Z-shapes, or micro-channels to manage thermal performance, such as in fuel cells.
Flow passage geometry – It defines the physical shape, configuration, and dimensions of channels (e.g., U-shaped, rectangular, corrugated) which guide fluid flow. It dictates flow velocity, pressure drop, and thermal performance, playing an important role in heat exchangers, engines, and fuel cells to optimize efficiency and uniformity.
Flow path – It defines the specific route, channel, or direction taken by fluids (liquids / gases) between two points, such as from inlet to outlet, within a system or across a landscape. It is governed by pressure differentials and geometry, determining mass flow rates and flow patterns (e.g., streamlines). Flow path connects two flow nodes (e.g., control volumes), focusing on calculating mass flow rates where the upstream state is known and downstream pressure is often determined.
Flow patterns – Flow patterns can be considered to be laminar, turbulent, or a combination of both. Osborne Reynolds observed in 1880 that the flow pattern could be predicted from physical properties of the liquid. If the Reynolds number for the flow in a pipe is equal to or less than 2,000 the flow is laminar, from 2,000 to around 5,000 is the intermediate region where the flow can be laminar, turbulent, or a mixture of both, depending upon other factors, and beyond 5,000 the flow is always turbulent.
Flow perturbations – These refer to disturbances in a fluid flow which can amplify natural instabilities, ultimately leading to turbulent flow. These perturbations can be induced by different means, such as acoustic or mechanical forces, and play an important role in modifying flow characteristics around objects like airfoils and cylinders.
Flow phenomenon – It is the predictable behaviour of a liquid or gas as it moves, characterized by interactions with boundaries and shear forces. Key types include laminar flow (smooth, ordered), turbulent flow (chaotic, eddy-driven), and boundary layer effects. These phenomena are defined by parameters like Reynolds number, pressure, viscosity, and velocity.
Flow porosity – It is the fraction of a material’s total volume which consists of inter-connected pores, cracks, or voids which allow fluids to flow through it. Unlike total porosity, which includes all void spaces, flow porosity only counts pores which inter-connected and accessible. It is important for calculating fluid flow rates in engineering applications.
Flow principle – This principle states that all other things being equal, a good layout is one which provides for smooth and uninterrupted flow of men and materials.
Flow pressure – It is frequently associated with hydrodynamic or dynamic pressure. It is the pressure exerted by a fluid in motion, acting parallel to its direction of flow. It is the driving force, typically a differential pressure (delta P), which pushes fluid through pipes or conduits, calculated as 1/2d x V-square, where ‘d’ is fluid density and ‘V’ is velocity.
Flow quantity (Q) – It is the measurement of the volume or mass of fluid (liquid or gas) passing through a specific cross-sectional area per unit of time. It defines how much substance moves through a conduit, typically quantified as volumetric flow (Q = area x average velocity) or mass flow (m = density x volume flow rate = density x area x average velocity).
Flow radial turbine – It is also called radial-inflow turbine, or inward-flow radial turbine. It is a type of turbine which functions similarly to a centrifugal compressor with reversed flow, mainly used for smaller loads and a limited operational range. This turbine can be categorized into cantilever and mixed-flow types and is normally found in applications such as turbochargers.
Flow rail – It consists of channels or rails facilitating the smooth movement of materials in a gravity conveyor system, necessitating checks for proper flow and alignment.
Flow rate – It is the time needed for a standard powder sample of standard weight to flow through an orifice in a standard instrument as per a specified procedure.
Flow rate coefficient – It is an empirical measure of a device’s (normally a valve or fitting) capacity to allow fluid to pass, defined as the volume of fluid passing through per unit time with a specific pressure drop.
Flow reactor – It is a vessel used for continuous production, where reactants are continuously fed in and products are continuously removed, typically operating at a steady state. Unlike batch reactors, flow reactors allow for consistent, high-volume production, improved heat transfer, and precise control over reaction parameters like temperature and residence time.
Flow regime – It is the characteristic pattern, behaviour, or structure of fluid motion within a system, classified by factors such as velocity, viscosity, and phase. It defines whether flow is laminar (ordered) or turbulent (chaotic), or how phases (gas / liquid) are distributed, directly impacting heat transfer, pressure drop, and system design.
Flow regime identification – It is the process of classifying fluid behaviour, such as laminar, transitional, or turbulent, based on motion characteristics, pressure, and velocity. It is critical for analyzing pressure data, determining reservoir properties, and optimizing system efficiency by recognizing patterns like wavy, slug, or annular flow.
Flow regime map – It is a graphical tool, frequently using superficial velocity axes (e.g., gas against liquid), which delineates the boundaries between different, observed flow patterns (such as bubbly, slug, or annular flow) within a conduit. It enables engineers to predict fluid behavior and select proper pressure drop and heat transfer correlations for design.
Flow regime transition – It is the physical process where fluid behaviour changes from one flow structure to another, such as laminar to turbulent or slug to annular flow, because of the altered conditions like velocity or heat flux. It is characterized by instability, high pressure-drop changes, and a mix of characteristics from both regimes. In single-phase flow, it is the transition from orderly (laminar) to chaotic (turbulent) behaviour as the Reynolds number increases.
Flow-related defects – These are imperfections resulting from the improper, non-uniform, or unstable movement of molten metal during casting, or the improper flow of solid metal during forming processes (like forging or rolling). These defects frequently stem from issues with temperature, viscosity, or the design of the casting / forming system, leading to surface, internal, or structural discontinuities.
Flow residue – It refers to material remaining, or a residual flow, which is not the main target product or desired output of a process. This normally includes unwanted substances, waste, or byproduct streams which need further treatment, handling, or separation after passing through equipment.
Flow resistance coefficient – It is a dimensionless number which quantifies the energy loss or pressure drop of a fluid flowing through a component, such as valves, fittings, pipes, or bends. It acts as a proportionality constant, allowing engineers to calculate head loss based on velocity.
Flow resistivity – It is the airflow resistance within unit of thickness and it reflects the air permeability through porous materials. The higher the airflow resistivity, the less air permeability there is. It is the air pressure difference per unit thickness divided by the airflow velocity through a porous material. It measures a material’s resistance to airflow (permeability), mainly identifying how easily sound waves pass through fibrous or foam materials.
Flow restrictor – It is a constriction in a pipe which is placed between the pipeline supply and a device, designed to cause a pressure drop during high flow rates, allowing lower pressures to enter the system.
Flow Reynolds number (Re) – It is a dimensionless parameter defining the ratio of inertial forces to viscous forces within a fluid. It determines flow regimes, laminar (Re = below 2,000), transition (Re = 2,000 t0 4,000), or turbulent (Re = above 4,000), used for calculating pipe friction, heat transfer, and aerodynamic drag.
Flow rule for plastic strain rate – It defines the direction and magnitude of permanent deformation. It states which the plastic strain rate is proportional to the normal of the plastic potential (Q) surface, usually coinciding with the yield surface (F) in associated flow. The plastic flow rule is the principle governing the evolution of plastic strains, expressed through the relationship between the plastic multiplier and the normal to the plastic potential, which can differ from the yield function in non-associated flow scenarios.
Flow rules – These are also known as plastic flow rules. These are constitutive equations which define the direction and magnitude of plastic strain increments when a material is deformed beyond its elastic limit. These rules establish the relationship between the stress state and the corresponding plastic deformation, acting as an important component in modeling permanent shape changes.
Flow sensor – It is a device used to measure the rate or volume of liquids or gases (fluids) moving through pipes, conduits, or systems. It converts physical properties of fluid motion such as velocity, acceleration, or pressure, into readable electrical signals. These sensors are important for monitoring, controlling, and regulating flow in industrial applications.
Flow separation – It is the detachment of a fluid’s boundary layer from a solid surface, resulting in a wake, high drag, and reduced lift. It occurs when viscous forces and an adverse pressure gradient (increasing pressure) cause the fluid velocity near the wall to drop to zero and reverse direction. It is mainly triggered by adverse pressure gradients (dP/dx above zero) where flow decelerates, such as along diverging surfaces or behind thick objects. The separation point is the specific location on a surface where the velocity gradient becomes zero, causing the flow to detach.
Flow sheet – It is an illustration which is showing the sequence of operations, step by step, by which ore is treated in a milling, concentration, or smelting process.
Flow-shop scheduling – It is a method where a set of jobs flows through multiple stages in a fixed machine order, with each stage containing only one machine. This scheduling approach can be adapted to include configurations such as hybrid flow shops, where multiple machines are present at certain stages to improve capacity or accommodate specialized production requirements. It is a production strategy where a set of jobs passes through a series of machines in the same, standardized order. It minimizes the total production time (make-span) by determining the optimal sequence for jobs to pass through the machines, normally found in high-volume assembly lines.
Flow simulation – It is a subset of computational fluid dynamics (CFD). It is a digital engineering tool which uses numerical methods to simulate and analyze the behaviour of liquids and gases passing through or around components. It enables to predict fluid flow, pressure drop, velocity profiles, and heat transfer, visualizing complex dynamics to optimize designs without excessive physical prototypes.
Flow softening – It is a phenomenon where the flow stress of a metal decreases during plastic deformation after reaching a peak, typically occurring at elevated temperatures. It indicates a reduction in the force required to deform the material, caused by microstructural changes such as dynamic recrystallization (DRX), dynamic recovery, void formation, or adiabatic heating.
Flow solver – It is a specialized computational fluid dynamics (CFD) software component which solves the governing equations of fluid motion, typically the Navier-Stokes or Euler equations, to analyze and simulate fluid behaviour. Using numerical methods like finite volume or finite difference, it predicts parameters such as velocity, pressure, density, and temperature over time or at steady state.
Flow specification – It is also frequently called flowspec or flowspec rule. It is a structured definition, typically an n-tuple of network packet header fields, used in computer networking to identify specific traffic flows and define actions to be taken on them. In engineering terms, it acts as a mechanism for traffic classification and policy enforcement, allowing network devices to move beyond traditional routing based solely on destination IPs to handling traffic based on characteristics like protocol, port numbers, packet length, or source IP (internet protocol). A flow specification rule normally consists of two major parts namely matching criteria (filters) and actions.
Flow speed – It is also known as flow velocity. It is the speed at which molten metal travels through casting systems, such as runners, gates, or into the mould cavity, normally measured in meters per second. It dictates filling consistency, turbulence, and heat transfer during solidification, with high velocities frequently causing surface defects.
Flow stability – It refers to the ability of a material, frequently in a molten or plastic state, to maintain uniform deformation or consistent flow characteristics when subjected to external forces. It ensures uniform microstructure, preventing defects like crack formation or uneven material distribution during processing.
Flow strength – It is the instantaneous true stress needed to initiate and continue plastic deformation in a metal. It represents the material’s resistance to deformation during forming, increasing as the metal strain-hardens. Flow strength depends on temperature, strain, and strain rate.
Flow stress – It is the instantaneous stress needed to initiate and sustain plastic (permanent) deformation in a material, typically a metal, after it has passed its yield point. It represents the material’s resistance to deformation and is highly dependent on strain, strain rate, and temperature, increasing with strain-hardening. It is the stress needed to keep a metal ‘flowing’ or forming plastically. It is used in manufacturing to calculate forces required for processes like forging, rolling, and extrusion.
Flow stress behaviour – It is the instantaneous, stress-dependent resistance a material shows to continued plastic deformation, normally defined as the stress needed to sustain plastic flow after yielding. It is heavily influenced by strain hardening, strain rate, and temperature, defining the necessary force for metalworking processes like rolling, forging, and extrusion.
Flow stress management – It refers to the understanding, modeling, and control of the instantaneous stress needed to continue the plastic deformation of a metal (flow stress) during manufacturing processes like forging, rolling, and extrusion. It involves managing the material’s resistance to shape change by analyzing variables such as temperature, strain rate, and microstructure to ensure successful forming without damaging the work-piece or the machinery.
Flow structure – It is the spatial and temporal organization, geometry, and distribution of a fluid phase (or multiple phases) within a conduit, channel, or system. It defines the internal architecture of flow, such as bubbles, droplets, or vortices, influenced by velocity, viscosity, and boundaries, frequently described as the ‘pattern’ of movement (e.g., laminar, turbulent, stratified).
Flow table test – It is a laboratory method used to measure the consistency, workability, and flowability of highly workable or self-compacting fresh concrete (slump above 175 millimeters). It determines how a concrete sample spreads on a metal table after jolting, measuring its susceptibility to segregation and flow characteristics.
Flow temperature – in the context of heating systems, it refers to the temperature of the water as it flows out of the heat source (like a boiler) and into the radiators or heating elements. It is the temperature of the supply water which delivers heat to the space being heated.
Flow test – it is a standardized test to measure how readily a powder flows.
Flow theory – It refers to mathematical and physical models used to analyze the movement of fluids (liquids / gases), traffic, or data as continuous, steady streams from a source to a sink. Key sub-fields include fluid dynamics (laminar / turbulent / potential flow) and transportation / data flow engineering, focusing on velocity, density, pressure, and, frequently, equilibrium.
Flow through – It is a forging defect which is caused by metal flow past the base of a rib with resulting rupture of the grain structure.
Flow-through reactor – It is an experimental model designed for water treatment which allows continuous flow of water through the system, facilitating analysis of microbial inactivation and exposure to UV (ultra-violet) light. This type of reactor demonstrates a linear correlation between inactivation and fluence, although it can show lower inactivation efficiency compared to batch reactors because of phenomena such as microbial aggregation.
Flow-through tail – It is the design of a conveyor tail allows materials to pass through, demanding inspections for smooth operation and potential blockages.
Flow transmission – It refers to the transport, movement, or transfer of energy, fluids, or power through a system, such as fluids through pipes, electrical energy along cables, or mechanical torque through gears. It encompasses both the physical transfer of material and the dynamic modeling of energy propagation.
Flow transmitter – It is a device which is designed to measure the rate of flow of a fluid (liquid or gas) through a pipeline or conduit. It is an upgraded version of the flow meter. It is a flow meter with an integrated electronic circuit as an operational system. The primary purpose of flow transmitter is to provide accurate and real-time data on the flow rate of a fluid. This information is essential for process control, monitoring, and optimization.
Flow turbine – It is a mechanical device that converts the kinetic and potential energy of a moving fluid (liquid or gas) into rotational mechanical energy, typically used for power generation. It acts through blades attached to a rotor, allowing fluid to exert tangential force, creating torque that spins the turbine.
Flow turbulence – It is a fluid regime defined by chaotic, random, and three-dimensional motion, characterized by rapid fluctuations in velocity and pressure. It occurs at high Reynolds numbers, where inertial forces overwhelm viscous damping, causing high eddying, improved mixing, and increased energy dissipation compared to laminar flow.
Flow valve – It is a device which regulates fluid flow by creating a variable restriction in the flow path, with common types including globe, butterfly, and ball valves, each having distinct characteristics for controlling flow.
Flow vector – t is also called velocity vector. It defines the motion of a fluid element at a specific point and time, characterized by both magnitude (speed) and direction. Represented mathematically as v (x, y, z, t), it provides a continuous vector field which determines the velocity of particles at any location.
Flow velocity – It is the rate at which a fluid (liquid or gas) travels through a specific space, measured as distance per unit of time, normally expressed in meters per second. It represents the speed of a fluid particle’s motion or the average speed over a cross-section, defined by the formula ‘v = Q/A’, where ‘Q’ is volumetric flow rate and ‘A’ is cross-sectional area.
Flow visualization – It is the experimental or computational art of making invisible fluid motion visible to identify, analyze, and document flow patterns, vortices, and boundary layer behaviours. It provides qualitative or quantitative insights into aerodynamic / hydrodynamic phenomena, such as streamlines, wakes, and separation, by introducing tracers like smoke, dye, or light into the fluid.
Flow work – It is also known as flow energy. It is defined as the work needed to push a mass of fluid into or out of a control volume (an open system). It represents the energy necessary to maintain a continuous, steady flow of material through equipment like furnaces, reactors, or pumps.
Fluctuating load – It is a type of cyclic load which changes in magnitude, direction, or both over time, frequently causing fatigue failure below a material’s yield strength. These loads, resulting from operational, environmental, or usage patterns, create variable stresses defined by a maximum / minimum stress cycle, leading to potential cracking. Fluctuating load in electricity refers to an electrical demand which changes rapidly and irregularly over time, causing variations in voltage levels, rather than remaining constant. These loads, frequently industrial (e.g., arc furnaces, welding) or motorized (e.g., elevators, compressors), cause rapid variations in current, resulting in significant, recurring voltage fluctuations.
Fluctuating turbulent velocity – It refers to the random variations in the instantaneous velocity of a turbulent flow, which can be expressed as the difference between the instantaneous velocity and the mean velocity. These fluctuations are characterized by their unpredictable nature while still showing reproducible statistical properties.
Fluctuating velocity – It is the instantaneous difference between a fluid particle’s actual velocity and its mean velocity at a given point. It represents the random, unsteady secondary motion in turbulent flow, with its time average being zero. It represents rapid deviations from the average flow, which can be positive or negative.
Fluctuating velocity components – These refer to the variations in velocity within a fluid flow, characterized by stream-wise and cross-stream components which can be quantified as dimensionless root mean square (RMS) values. These components show different behaviours in different sections of a flow system, such as higher fluctuations in a reducer section compared to a straight pipe section.
Fluctuating vorticity – It refers to the rapid, chaotic variations in the rotational motion of fluid particles within a turbulent flow. It is defined as the non-steady component of vorticity separated from the mean vorticity representing the intense creation, stretching, and transport of eddies which cause energy dissipation.
Fluctuations in wind speed – These are rapid variations in wind velocity, magnitude and direction, around a mean value over short time intervals, frequently caused by atmospheric turbulence. These variations are formally modeled as a non-stationary random process, normally defined as the difference between the instantaneous wind speed and the mean wind speed
Flue – It is a passage for products of combustion.
Flue chimney – It is a vertical passageway designed to safely exhaust combustion by-products (smoke, gases, heat) from a heating device to the outside atmosphere. It ensures safe dilution of toxic gases, maintains proper pressure (draft) for optimal device operation, and protects building structures from high temperatures and corrosive condensation.
Flue gas – It is the gas exiting to the atmosphere through a flue, which is a pipe or channel for conveying exhaust gases, as from a fireplace, oven, furnace, boiler or steam generator. It frequently refers to the exhaust gas of combustion.
Flue gas desulphurization – It is a set of technologies which are used to remove sulphur compounds, mainly sulphur di-oxide (SO2), from the exhaust (flue) gases of power plants and other industrial facilities before they are released into the atmosphere. This process helps to reduce air pollution and prevent the formation of acid rain.
Flue gas desulphurization (FGD) systems – These are pollution control technologies designed to remove sulphur di-oxide (SO2) from the exhaust gases of fossil-fuel power plants, waste incinerators, and other industrial processes, typically achieving removal efficiencies of 90 % to 98 %. These systems are important for preventing acid rain and meeting environmental regulations by converting hazardous sulphur di-oxide into a stable, frequently marketable, by-product like synthetic gypsum (CaSO4.2H2O).
Flue gas monitoring and control – In electric arc furnace steelmaking, chemical energy recovery rate from exhaust gases can be increased by 50 % by adjusting oxygen injection levels for post combustion based on real time carbon-mono-oxide and carbon di-oxide readings in flue gases, instead of using preset values. Electricity savings of 12 to 15 kilowatt hours per ton of steel are estimated by using this technology.
Flue gas recirculation (FGR) – It is an emission control technique used in combustion systems (boilers, furnaces) to reduce nitrogen oxides (NOx) by redirecting a portion of the exhaust gas back into the combustion chamber. This inert gas lowers the peak flame temperature and acts as a diluent, reducing the formation of thermal NOx.
Flue-gas stack – It is also known as a smoke stack, chimney, or simply a stack. It is a type of chimney, a vertical pipe, channel or similar structure through which flue gases are exhausted to the outside air. Flue gas stacks are often quite tall, up to 420 metres, to increase the stack effect and dispersion of pollutants.
Fluent conveying – It is a conveying method which allows materials to move seamlessly on the conveyor, requiring regular assessments for smooth flow and minimal friction.
Flue temperature – It is the measurement of exhaust gases (carbon di-oxide, water vapour, and nitrogen) within a chimney, pipe, or duct (flue) after combustion, typically ranging from 100 deg C to over 900 deg C depending on the system. It is important for monitoring furnace efficiency, preventing condensation (frequently above 70 deg C), and ensuring safe operation.
Fluff pulp – It is a specialized, long-fibre chemical softwood pulp engineered for high bulk, rapid absorption, and excellent fluid retention in absorbent products. Produced through the Kraft process, it is engineered for easy defibration, enabling it to be ‘fluffed’ into a soft, fibrous, porous, and lightweight mass which provides structural integrity to absorbent cores.
Fluid – It is a liquid, gas, or other material which can continuously move and deform (flow) under an applied shear stress, or external force. Fluids have zero shear modulus, or, in simpler terms, are substances which cannot resist any shear force applied to them.
Fluid added mass – It is the inertia added to an accelerating submerged body since it is to move surrounding fluid. It acts as an additional mass, calculated as the product of fluid density, body volume, and a shape-dependent coefficient, frequently reducing the natural frequency of structures. The force needed to accelerate a body in a fluid is higher than in a vacuum. This extra force is proportional to the acceleration and the ‘added mass’ of the fluid being displaced.
Fluid bearings – Fluid bearings support their loads solely on a thin layer of liquid or gas. They are usually of two types namely (i) hydrostatic bearings where load is supported by high pressure fluid and (ii) hydrodynamic bearings where load is supported by a lubricant film. Hydrostatic bearings are externally pressurized fluid bearings, where the fluid is usually oil, water or air, and the pressurization is done by a pump. Hydrodynamic bearings rely on the high speed of the journal (the part of the shaft resting on the fluid) to pressurize the fluid in a wedge between the faces. Hydrodynamic bearings support a rotating shaft and transmit its axial load to a machine foundation by floating it on a self-renewing film of oil. Fluid bearings are frequently used in high load, high speed or high precision applications where ordinary ball bearings would have short life or cause high noise and vibration. They are also used increasingly to reduce cost. Fluid bearings use a thin layer of liquid or gas fluid between the bearing faces, typically sealed around or under the rotating shaft.
Fluid bed gasifiers – These are specialized reactors which convert solid fuel (coal, biomass, waste) into synthetic gas (syngas) by suspending feed particles in a fluidized bed of hot inert material (e.g., sand) using gasifying agents (air, oxygen, or steam). They are engineered for excellent mixing, uniform temperature distribution, high efficiency, and feedstock flexibility.
Fluid bulk modulus – It is a measure of a fluid’s resistance to compression, defined as the ratio of the change in pressure to the fractional change in volume (volumetric strain). It represents how incompressible a fluid is, calculated as ‘K = -V dP/dV’, where a higher value indicates a less compressible fluid. The negative sign indicates that an increase in pressure (dP) causes a decrease in volume (dV).
Fluid catalytic cracker – It is an important, high-capacity unit which converts heavy, high-boiling hydro-carbon fractions (like vacuum gas oil) into high-octane gasoline, olefinic gases, and other valuable products. It uses a powdered catalyst, which behaves like a fluid when aerated, to catalyze cracking reactions in a riser-reactor.
Fluid catalytic cracking process – It is a process which converts heavy, high-molecular-weight hydro-carbons into high-octane gasoline, diesel, and olefin-rich light gases. It operates by contacting heated feedstock with a powdered, zeolite-based catalyst in a fluidized state within a reactor-regenerator system, utilizing thermal decomposition (cracking) to maximize lighter product yields.
Fluid cavity – It is a hollow space or enclosed volume filled with a fluid (liquid or gas) which interacts with surrounding structural components, frequently used in finite element analysis (FEA) to simulate pressurized systems like airbags, tanks, or tires. It involves coupled analysis where the deformation of the structure affects the fluid pressure and vice versa, normally assuming uniform pressure and temperature throughout the cavity. Fluid cavities are normally modeled by defining a surface which fully encloses a specific volume, linked to a ‘cavity reference node’ which dictates the pressure and volume behaviours.
Fluid-cell process – It is a modification of the Guerin process for forming sheet metal. The fluid-cell process uses higher pressure and is mainly designed for forming slightly deeper parts, using a rubber pad as either the die or punch. A flexible hydraulic fluid cell forces an auxiliary rubber pad to follow the contour of the form block and exert a nearly uniform pressure at all points on the work-piece.
Fluid coke – It is the carbonization product of high-boiling hydrocarbon fractions produced by the fluid coking process, consisting of spherulitic grains with a spherical layer structure. It is characterized by a volatile matter content of around 6 % and is normally less graphitizable and isotropic compared to delayed coke, making it unsuitable for certain applications in synthetic graphite production. It is a solid, spherulitic carbon material produced by the fluid coking process, a continuous thermal cracking technique which upgrades heavy petroleum residues. It forms as thin, layered, spherical grains around heated seed coke particles (150 micro-meters to 200 micro-meters) within a fluidized bed reactor.
Fluid coking process – It is a continuous, non-catalytic thermal cracking process used to convert heavy, low-value vacuum residues into lighter, high-value hydrocarbon products (naphtha, gas oils) and solid coke. It uses two fluidized bed vessels, a reactor and a burner, where feedstock is sprayed onto hot, fluidized coke particles, allowing continuous operation at 480 deg C to 590 deg C.
Fluid column – It is a vertical, continuous body of liquid or gas contained within a pipe, vessel, or wellbore. It creates pressure at its base proportional to its height (h), density (d), and gravity (g), calculated as ‘P = d x g x h’. This concept is important for calculating hydrostatic pressure, managing drilling stability, and designing fluid transport systems.
Fluid concentration – It defines the proportion of a solute (e.g., cutting fluid, salt) within a solvent (e.g., water) or the mass per moles of a component per unit volume of the total mixture. It represents the mixing state of a solution, used to optimize lubrication, chemical reactivity, and process control in industrial applications.
Fluid cross-section – It is the two-dimensional surface area occupied by a fluid, measured on a plane perpendicular (normal) to the direction of flow. It represents the ‘slice’ of a pipe, channel, or stream tube which the fluid passes through at any given point along its path.
Fluid density (d) – It is defined as the mass (m) per unit volume (V) of a fluid, expressed as ‘d = m/V’, typically measured in kilograms per cubic meter. It indicates how much molecular mass is packed into a space, directly influencing buoyancy, hydrostatic pressure (d x g x h), and flow dynamics, and it varies based on temperature and pressure.
Fluid displacement – It is the process where a solid object or another fluid takes the place of an existing fluid, pushing it aside. It measures either the volume of an immersed object (equal to the volume of fluid moved) or the weight of water displaced by a floating vessel (equal to the vessel’s weight). It is also the process of removing an existing wellbore fluid and replacing it with a suitable fluid for subsequent well operations, focusing on efficient removal while minimizing costs and rig time. It involves using spacers to ensure fluid separation and cleanliness in the casing and tubing, thereby preventing contamination and corrosion of the packer fluid.
Fluid distribution – It refers to the spatial arrangement, velocity, or pressure variation of a fluid (liquid or gas) within a system, such as in pipelines, reactors, or reservoirs. It involves managing how fluid is transported, distributed, and allocated across a specific volume or surface, frequently aiming for uniformity, such as in spray nozzles, or specific pressure profiles, as in manifold design.
Fluid domain – It is the specific, bounded, three-dimensional volume of space filled by a fluid (liquid or gas) where flow, heat transfer, or pressure is simulated. Defined in CFD (computational fluid dynamics), it represents the control volume for analysis, separating fluid regions from solid structures to model internal flows (e.g., pipes) or external flows (e.g., around a wing).
Fluid dynamics – It is the sub-discipline of fluid mechanics studying the motion of liquids and gases and the forces acting upon them. It focuses on analyzing flow behaviour (velocity, pressure, density, and temperature) interacting with boundaries, like pipes, airfoils, or machinery, using principles of conservation of mass, momentum, and energy to optimize design.
Fluid efficiency – It normally refers to how effectively a system utilizes fluid, manages energy during fluid transport, or minimizes losses (leakage / friction). In hydraulic components, it is defined as the ratio of actual power output or volume delivered to the theoretical maximum, frequently expressed as the product of volumetric and hydromechanical efficiencies. It is also the ratio of the stored volume within a fracture to the total fluid injected, with higher fluid efficiency indicating lower fluid leak-off and greater effectiveness in creating fractures.
Fluid element – It is an infinitesimally small, isolated volume or ‘chunk’ of fluid, used to analyze flow fields, derive motion equations, and apply laws of physics (like conservation of mass / momentum). As a continuum model, it allows engineers to neglect molecular irregularities to analyze stress, pressure, and velocity at a specific, localized point.
Fluid end – It is the high-pressure, fluid-handling module of a reciprocating pump (such as a mud pump or fracturing pump) which converts mechanical energy from the power end into hydraulic power. It is the ‘front line’ of the pump, responsible for taking in low-pressure fluid and discharging it at high pressure, frequently exceeding 100 mega-pascals. In engineering terms, the fluid end (or hydraulic module) is a structural, normally forged, steel block containing internal passages, valves, and plungers which directly interact with the working fluid.
Fluid energy – It refers to the mechanical energy possessed by liquids or gases because of their velocity (kinetic energy), elevation (potential energy), or pressure, enabling them to do work. It is harnessed from natural flows (wind / hydro) or generated through pressurized systems (hydraulics / pneumatics) to drive turbines, actuators, and machinery, frequently analyzed using Bernoulli’s principle.
Fluid energy diagram – It normally refers to a graphical representation of the total energy possessed by a flowing fluid, including its pressure, velocity, and elevation components, frequently plotted alongside the physical layout of a piping or channel system. It is mainly used to analyze energy losses, pump heads, and turbine power within hydraulic and fluid power systems.
Fluid energy mills – The general principle of operation in a fluid energy mill is that the material to be ground is fed into a grinding chamber in a high speed, high pressure and, often, high temperature jet of air (or other gas). The particles collide violently and this causes comminution to take place. Various designs of fluid energy mill exist, the most common being the micronizer. This mill has a shallow circular grinding chamber and a series of peripheral jets set tangentially to a common circle. The turbulence causes bombardment which effects a rapid reduction in particle size. A centrifugal classification system keeps larger particles within the chamber while allowing fine particles to leave. In a well-designed fluid energy mill, there is normally almost no contact between the charge and the mill lining. These mills are suitable for hard or soft materials to be reduced to 0.02 mm or less. This method of milling tends to be energy intensive and slow but is suitable where the product is highly sensitive to heat or contamination from grinding media.
Fluid enthalpy (H) – It is a thermodynamic property representing the total energy content of a fluid, defined as the sum of its internal energy (U) and pressure-volume work (PV). Mathematically it is ‘H = U + PV’. It indicates the energy needed to move the fluid into a system and maintain it, frequently used to analyze heat transfer at constant pressure.
Fluid erosion – It is the progressive loss of original material from a solid surface because of the mechanical interaction between that surface and a fluid, a multi-component fluid, and impinging liquid, or solid particles.
Fluid film – It is a thin layer of lubricant (liquid or gas) which completely separates two moving machine surfaces, preventing direct contact and reducing friction and wear. It supports loads through viscous forces, typically acting within a gap on the order of a micro-meter or less.
Fluid film lubrication – It is a lubrication regime where moving surfaces are completely separated by a thin, pressurized layer of lubricant (typically 0.1 micro-meter to 10 micro-meters), preventing direct surface contact. The lubricant supports the load through viscous forces, minimizing friction and wear to very low levels.
Fluid flow -It is normally the motion of a fluid which is subjected to different unbalanced forces. It is mainly a part of fluid mechanics and fluid flow normally deals with the dynamics of the fluid. The motion of the fluid continues till different unbalanced forces are applied to the fluid.
Fluid-flow analysis – It is the application of fluid mechanics principles to study, simulate, and optimize the movement of molten metals, slags, gases, and slurries during metallurgical processing. It involves analyzing behaviours such as velocity, pressure, temperature, and turbulence, frequently using ‘computational fluid dynamics’ (CFD) to predict how these flows affect heat transfer, mass transfer, and final product quality.
Fluid flow characteristics – These characteristics describe the behaviour, properties, and movement of liquids or gases (velocity, pressure, density, temperature) as they travel, mainly governed by viscosity, density, and applied forces. These characteristics define how a fluid deforms under stress and are classified into patterns such as laminar (smooth) or turbulent (chaotic), and steady (constant) or unsteady (time-dependent) flow.
Fluid flow measurement – It is the quantification of the rate of movement (velocity, mass, or volume) of liquids or gases through closed conduits or open channels, frequently using devices like orifice plates, turbine meters, or ultrasonic sensors. It is important for monitoring process efficiency, ensuring quality control, and determining material usage in applications such as industrial pipelines.
Fluid flow, pipe – It is the flow of a fluid in a pipe. There are three fluid flow regimes in a pipe namely laminar, turbulent, and a transition region. The conditions which lead to each type of flow behaviour are system-specific. Fluid flow simulations for various Reynolds numbers can be used to clearly identify and quantify when flow gets transition from laminar to turbulent.
Fluid flow problems – These problems involve analyzing the motion of liquids and gases (fluids) caused by pressure differences or shear stress. Defining these problems involves determining flow characteristics, such as velocity, pressure, density, and temperature, using principles of conservation of mass, momentum, and energy to solve for system performance.
Fluid flow rate – It is the volume or mass of a fluid (liquid or gas) which passes through a specific cross-sectional area per unit of time. It is an important parameter for monitoring process control, water management, and manufacturing systems.
Fluid flow system – It is an integrated arrangement designed to transport, control, or utilize liquids, gases, or slurries in motion, encompassing components like pipes, pumps, valves, and turbines. These systems analyze fluid behaviour using principles of conservation of mass, momentum, and energy to optimize process performance, pressure, and velocity.
Fluid force (F) – It refers to the pressure and shear stresses exerted by liquids or gases on solid surfaces or within the fluid itself. Key components include pressure (normal force), viscous shear (parallel force), and body forces (gravity). It is calculated as ‘F = P x A’ or ‘F = d x g x h x A’.
Fluid forming – It is a modification of the Guerin process. Fluid forming differs from the fluid-cell process in that the die cavity, called a pressure dome, is not completely filled with rubber, but with hydraulic fluid retained by cup-shaped rubber diaphragm.
Fluid-forming presses – These are very frequently referred to as hydroforming presses. These are specialized metal-forming machines which use high-pressure fluid, normally water or a water-oil emulsion, to shape metal sheets or tubes into complex, high-strength geometries. Unlike conventional stamping which uses both a solid punch and die, fluid forming typically uses only one solid mould (die) and uses pressurized fluid to act as the other half of the tool, ensuring even pressure distribution, high accuracy, and reduced material thinning.
Fluid friction – It is the frictional resistance because of the viscous or rheological flow of fluids.
Fluid hammer – It is normally known as water hammer or hydraulic shock (liquid hammer). It is a pressure surge or wave caused by the sudden stop or change in direction of a fluid in motion. In industrial, chemical, and metallurgical processes, it is an important phenomenon which can cause severe mechanical damage, such as pipe ruptures, valve failures, and structural vibration.
Fluid head – It represents the pressure exerted by a column of fluid, measured as a vertical height (meters). It defines the mechanical energy per unit weight of the fluid, frequently used to calculate pressure (P = d x g x h) or pump performance (total head). Key types include static pressure, potential (elevation), and velocity heads.
Fluidics – It is a technology which uses the flow characteristics of liquids or gases (fluids) to perform sensing, control, logic, and amplification functions without moving parts. Frequently, small fluid jets are used to control much larger flows, simulating electronic circuits (logic / amplification) using fluid pressure and flow dynamics rather than electricity.
Fluid in motion – It describes the continuous movement and deformation of liquids or gases when subjected to unbalanced shear forces. It is the study of how fluids flow and adapt to boundaries, fundamentally characterized by velocity, pressure, and density variations, typically analyzed through fluid dynamics and fluid kinematics.
Fluid interface – It involves manipulating the boundaries between immiscible fluids (liquid-liquid or liquid-gas) to create advanced materials, sensors, and functional surfaces. By managing interfacial tension, particle assembly (Pickering emulsions), and stimuli-responsive behaviour, this field enables precise control over surface properties, coating technologies, and high-performance, responsive mechanical sensors.
Fluid inventory – It refers to the total quantity (mass or volume) of a working fluid, such as refrigerant, hydraulic oil, or process gas, contained within a system, pipeline, or vessel at any given time. It represents the total fluid present in the entire operating volume, frequently including a slight excess beyond the minimum needed for saturation to maintain performance and ensure stability.
Fluidity – It is the ability of liquid metal to run into and fill a mould cavity. In case of coking coal, fluidity is measured by Gieseler plastometer. In this test fine coal (not pulverized) is heated slowly and as it melts and passes through its plastic range; its fluidity is measured. Results are expressed as maximum fluidity in ‘dial divisions per minute’ (ddpm). Characteristics temperatures recorded are initial softening temperature, maximum fluidity temperature, and re-solidification temperature. The plastic range, which is the temperature range during which the coal is in plastic state, is also important. All coking tests are sensitive to oxidation but the Gieseler plastometer test is by far the most sensitive.
Fluidize – It means imparting fluid like properties to powders or sands.
Fluidization – It is a process similar to liquefaction whereby a granular material is converted from a static solid-like state to a dynamic fluid-like state. This process occurs when a fluid (liquid or gas) is passed up through the granular material. When a gas flow is introduced through the bottom of a bed of solid particles, it will move upwards through the bed via the empty spaces between the particles. At low gas velocities, aerodynamic drag on each particle is also low, and thus the bed remains in a fixed state. Increasing the velocity, the aerodynamic drag forces will begin to counteract the gravitational forces, causing the bed to expand in volume as the particles move away from each other. Further increasing the velocity, it will reach a critical value at which the upward drag forces will exactly equal the downward gravitational forces, causing the particles to become suspended within the fluid. At this critical value, the bed is said to be fluidized and will exhibit fluidic behavior. By further increasing gas velocity, the bulk density of the bed will continue to decrease, and its fluidization becomes more intense until the particles no longer form a bed and are ‘conveyed’ upwards by the gas flow.
Fluidization index – It is defined as the bed pressure drop divided by the hydrostatic pressure created by the weight of the bed.
Fluidized bed – It is a contained mass of a finely divided solid which behaves like a fluid when brought into suspension in a moving gas or liquid.
Fluidized-bed boiler – In modern large-capacity coal-fired boilers, coal is burnt in suspension. Fluidized-bed combustion ensures burning of solid fuel in suspension, in a hot inert solid-bed material of sand, limestone, refractory, or ash, with high heat transfer to the furnace and low combustion temperatures (800 deg C to 950 deg C). The combustor-bed material consists of only 35 % coal. Fluidized-bed combustion is comprised of a mixture of particles suspended in an upwardly flowing gas stream, the combination of which shows fluid-like properties. Fluidized-bed burners are capable of firing a wide range of solid fuels with varying heating value, ash content, and moisture content.
Fluidized-bed coating – It is a method of applying a thermoplastic or thermosetting resin coating to a heated article which is immersed in a dense-phase fluidized bed of powdered resin and thereafter heated in an oven to provide a smooth, pinhole -free coating.
Fluidized bed combustion – It is a combustion technology which is used to burn solid fuels. In its most basic form, fuel particles are suspended in a hot, bubbling fluidity bed of ash and other particulate materials (sand, limestone etc.). through which jets of air are blown to provide the oxygen needed for combustion or gasification. The resultant fast and intimate mixing of gas and solids promotes rapid heat transfer and chemical reactions within the bed. Fluidized bed combustion furnaces are capable of burning a variety of low-grade solid fuels, including most types of coal, coal waste and woody biomass, at high efficiency and without the necessity for expensive fuel preparation (e.g., pulverizing). In addition, for any given thermal duty, fluidized bed combustion furnaces are smaller than the equivalent conventional furnace, sand hence offer considerable advantages over the latter in terms of cost and flexibility.
Fluidized bed combustion system – It is an advanced industrial combustion technology where solid fuel (coal, biomass) is burned in a suspended, turbulent state within a hot bed of sand or ash, fluidized by upward-flowing air. This method provides excellent heat transfer, high efficiency, and low emissions by allowing efficient, low-temperature combustion (750 deg C to 900 deg C).
Fluidized bed furnace – It is a combustion or thermal processing device where solid fuel (like coal or biomass) or material is suspended in an upward flow of gas, acting like a turbulent ‘boiling’ fluid. This enables high-efficiency, uniform temperature, and improved heat transfer, frequently used in power generation and waste incineration.
Fluidized bed gasification -it is a process which converts solid feedstock (coal, biomass) into syngas by suspending it within a hot, fluidized bed of inert material (e.g., sand, ash) at 750 deg C to 900 deg C. A gasifying agent (air, steam, or oxygen) flows upward at high velocity, providing superior mixing, high heat transfer rates, and uniform temperature control.
Fluidized bed gasifier – It is a reactor which converts solid feedstock (like biomass or coal) into combustible syngas by suspending the fuel in a bed of inert material (sand, ash, or char) using upward-flowing oxidizing gas (air, oxygen, or steam). It operates at 750 deg C to 900 deg C with high heat / mass transfer, uniform temperatures, and handles diverse, low-grade fuels effectively.
Fluidized-bed heating – It is heating carried out in a medium of solid particles suspended in a flow of gas.
Fluidized bed process– It is a technique where solid particles are suspended in an upward-flowing gas or liquid stream, causing the bed to behave like a boiling fluid. This high-efficiency method enables superior heat and mass transfer, rapid temperature control, and continuous operation for chemical reactions, drying, coating, and combustion.
Fluidized-bed quenching – It is a heat-treatment process where hot metal parts are cooled by immersion in a bed of fine-grained particles (typically aluminum oxide or sand) which are fluidized by an upward flow of gas. This method provides rapid, uniform heat transfer, comparable to liquid quenching, while minimizing distortion, cracking, and residual stresses.
Fluidized bed reactor -It is a chemical reactor used to conduct multi-phase reactions, where solid catalytic particles are suspended in an upward-flowing gas or liquid stream. At high fluid velocities, the bed behaves like a boiling liquid, enabling high heat / mass transfer rates, uniform temperature, and continuous operations.
Fluidized bed reduction – In the fluidized bed reduction process, the finely divided solid is a powdered ore or reducible oxide, and the moving gas is reducing. The process operation is carried out at high temperature in a furnace.
Fluidized bed scrubber – It is a type of scrubber which circulates boiler ash and lime between a scrubber and fabric filter, hence also called circulating fluidized bed scrubber (CFBS). Flue gas enters the circulating fluidized bed scrubber (with or without ash) at the bottom of the up-flow vessel, flowing upward through a venturi section that accelerates the gas flow rate, causing turbulent flow. The turbulator wall surface of the vessel causes highly turbulent mixing of the flue gas, solids, and water for 4 seconds to 6 seconds to achieve a high capture efficiency of the vapour phase acid gases and metals contained within the flue gas. The gas and solids mixture then leaves the top of the scrubber.
Fluidized bed technology – It is a process which suspends solid particles in an upward-moving gas or liquid stream, creating a turbulent, fluid-like mixture which maximizes contact between solid and gas phases. This technique offers superior mixing, high efficiency, and uniform temperature control for processes like combustion, gasification, drying, and coating. The process occurs when a fluid (gas or liquid) passes through a bed of granular solid material at a velocity high enough to suspend the particles, allowing the bed to show properties of a fluid.
Fluid kinematics – It is the branch of fluid mechanics which studies fluid motion, including velocity, acceleration, and deformation, without considering the forces or moments causing that motion. It focuses on describing the ‘how’ of flow patterns (laminar against turbulent, steady against unsteady) using Lagrangian or Eulerian descriptions.
Fluid layer – It is a thin region of fluid (liquid or gas) adjacent to a solid surface where viscous forces dominate. In this layer, fluid velocity increases from zero at the surface, because of the ‘no-slip condition’, to the free-stream velocity. This layer impacts drag and heat transfer.
Fluid leak-off – It refers to the fluid flow and associated pressure drops which occur perpendicularly into the formation during hydraulic fracturing, considerably influencing the crack length and fracture dimensions.
Fluid level – It is the measured height of a liquid (or sometimes gas) within a container, tank, or process vessel. It refers specifically to the vertical distance from a reference point (normally the bottom of the container) to the top surface of the liquid. It is a critical, frequently automated, measurement used to manage volume, prevent overflow, and control process safety using sensors, gauges, and analog or digital signals.
Fluid life – It is the ability of the molten alloy to fill the mould cavity, flow through thin narrow channels to form thin walls and sections, and conform to fine surface detail. In addition to temperature of the molten metal, fluid life also depends on chemical, metallurgical, and surface tension factors. Hence, the fluid life of each alloy is different. Fluid life determines the minimum wall thickness and maximum length of a thin section. It also determines the fineness of cosmetic detail that is possible. Hence, knowing that an alloy has limited fluid life suggests that the part is to feature softer shapes (i.e., generous radii, etc.), larger lettering, finer detail in the bottom portion of the mould, coarser detail in the upper portions of the mould, more taper leading to thin sections, and so forth.
Fluid load – It is the force or pressure exerted on a structure by liquids or gases, encompassing both static weight (hydrostatic pressure) and dynamic impact (hydrodynamic force). These loads are important in structural analysis, designed for tanks, pipelines, and submerged structures to ensure they can withstand internal or external fluid forces.
Fluid loss control – It is the engineering practice of managing the volume of liquid phase (filtrate) from drilling mud or cement slurry which filters into a permeable formation, achieved by using additives to create an impermeable filter cake. It is vital for preventing formation damage, ensuring wellbore stability, reducing costs, and preventing differential pressure sticking. It is the regulation of filtrate volume passing through a filter medium (formation) under pressure.
Fluid mass – It is the measure of the quantity of matter within a defined volume of liquid or gas, calculated as density (d) multiplied by volume (V), or as the mass flow rate (m) over time (t). It is a conserved quantity in fluid dynamics (continuity equation) which along with pressure, determines the behaviour, buoyancy, and acceleration of fluids.
Fluid mass flow rate (m) – It is the mass of fluid passing per unit time, calculated by multiplying density (d), cross-sectional area (A), and velocity (v), represented as ‘m =d x A x v’. It is fundamental for system analysis (pipe flow, jets). Unlike volumetric flow rate, mass flow is conserved in incompressible and compressible flows.
Fluid mechanics – It is the engineering branch studying how fluids (liquids, gases, and plasmas) behave at rest or in motion and how they interact with solid boundaries. It focuses on forces, pressure, and velocity related to fluid flow and is essential for designing machinery, and pipelines.
Fluid mixture – It involves the design and optimization of systems to combine immiscible or miscible liquids and gases, important for improving heat transfer / mass transfer, homogeneity, and reaction rates in different industries. Key techniques include mechanical agitation, turbulent flow analysis, and computational fluid dynamics (CFD) to model behaviour, reduce energy consumption, and manage rheological properties.
Fluid model – It is a mathematical or physical representation used to simulate the behaviour, properties (density, viscosity), and motion of liquids or gases. These models simplify complex molecular reality into continuum, ideal, or numerical frameworks, e.g., Navier-Stokes, computational fluid dynamics (CFD), to analyze flow, pressure, and thermal-hydraulic performance.
Fluid momentum – It is the quantity of motion of a fluid, calculated as the product of its mass and velocity, or density times velocity per unit volume. It is a vector quantity which forms the basis of the momentum equation, derived from Newton’s second law, which states that the net force on a fluid is equal to its rate of change of momentum.
Fluid motion – It refers to the movement of liquids and gases as they continuously deform under shear stress. It describes how fluid particles transport momentum and energy, normally analyzed using fluid dynamics to predict behaviour in systems like pipes, turbines, and aerodynamics. Key types include laminar flow (ordered) and turbulent flow (chaotic).
Fluid movement – It is the continuous deformation and translation of liquids or gases under applied shear stress, resulting in the transfer of mass, momentum, and energy. It involves fluid particles changing positions or shapes relative to their container or surroundings because of the pressure differences and viscosity.
Fluid particle – It is a fundamental concept in fluid mechanics, representing an infinitesimal, yet finite, mass of fluid (gas or liquid) large enough to contain a huge number of molecules. It is considered a continuous, identifiable piece of matter which moves with the flow, retaining its identity while deforming under shear stress.
Fluid permeability – It is the capacity of a porous medium (like rock, soil, or foam) to transmit fluids, measuring how easily liquids or gases flow through interconnected pore spaces. It is a fundamental property determined by pore structure and is quantified, frequently through Darcy’s law, based on pressure, viscosity, and flow rate.
Fluid phase – It is a state of matter, liquid, gas, or supercritical fluid, which continuously deforms (flows) under applied shear stress, lacking a fixed shape. Unlike solids, fluid phases cannot resist shear forces and are characterized by high molecular mobility, where particles move freely. It is frequently analyzed as a carrier phase in multiphase flow.
Fluid pound – It is a condition in reciprocating rod pumps (beam pumps) where the plunger hits the liquid surface in the barrel during the downstroke because the pump barrel was not completely filled with liquid during the upstroke. It indicates the pump capacity exceeds the well’s production rate, causing harsh, audible impacts, rod damage, and potential equipment failure.
Fluid pressure – It is defined as the normal (perpendicular) force exerted by a static or dynamic fluid (liquid or gas) per unit area on a submerged surface or container wall. It acts equally in all directions at a specific depth, measured in Pascals, representing the compressive intensity of the fluid, which increases with depth and density.
Fluid properties – These are the physical and chemical characteristics, such as density, viscosity, pressure, and surface tension, which define how a fluid (liquid or gas) behaves at rest or in motion. These properties depend on pressure, temperature, and composition, allowing engineers to predict flow, deformation, and heat transfer behaviour.
Fluid reactant – It is a gas or liquid substance which flows, acts as a participant in a chemical reaction, and commonly reacts with a solid particle, another liquid, or another gas. These reactants drive processes involving mass transfer, needing modeling of diffusion and reaction kinetics.
Fluid resistance – It is the opposition encountered by an object moving through a fluid, such as air or water, which hinders its motion. This resistance can be attributed to interactions between the object and the fluid.
Fluid saturation – It is the fraction or percentage of a porous medium’s total pore volume occupied by a specific fluid (oil, gas, or water). It is an important environmental parameter defining how much of each phase is present, with the sum of all fluid saturations equal to 100 % (or 1).
Fluid separation process – It is a technique used to divide a mixture (gas or liquid) into distinct components based on physical or chemical property differences, such as density, volatility, or solubility. These important unit operations, including distillation, absorption, and membrane filtration, are used for product purification, component recovery, or pollution control in industrial applications.
Fluid shear stress (S) – It is the frictional force exerted by a flowing fluid parallel to a solid boundary per unit area, resulting from the fluid’s viscosity and velocity gradient. It causes fluid layers to slide over one another and acts parallel to the surface, calculated as ‘S = F/A’ for Newtonian fluids as ‘S = M x dv/dy’, where ‘S’ is shear-stress, ‘M’ is dynamic viscosity of the fluid, ‘v’ is the velocity gradient or rate of shear strain.
Fluid side – It refers to the specific domain, surface, or flow stream occupied by a liquid or gas in a system, particularly when interacting with a solid boundary (e.g., pipe wall, heat exchanger surface) or another fluid phase. It is a core concept in fluid mechanics, heat transfer, and computational fluid dynamics (CFD) used to differentiate where the fluid properties (viscosity, density, pressure) are calculated separately from the solid structure.
Fluid simulation – It is the computational modeling and analysis of liquid or gas behaviour using numerical methods to predict flow velocity, pressure, and temperature within a defined domain. Frequently performed through computational fluid dynamics (CFD), it replaces physical testing by solving conservation laws (mass, momentum, energy) to optimize systems like aerodynamics, piping, or heat exchangers.
Fluid specific gravity (SG) – It is a dimensionless ratio comparing a fluid’s density to the density of a reference substance, typically water at 4 deg C (around 1,000 kilo-grams per cubic meter) for liquids, and air for gases. It indicates how much heavier or lighter a fluid is compared to the reference, with ‘SG below 1’, indicating the fluid is lighter than water.
Fluid state – It is a state of matter, specifically liquids or gases, which continuously deforms (flows) under applied shear stress, regardless of how small that force is. Unlike solids, fluids cannot resist tangential forces when at rest, allowing them to take the shape of their container.
Fluid stream – It is a continuous, moving quantity of liquid, gas, or vapour, frequently bounded by a conduit or path, transporting mass and energy. It is characterized by velocity, density, pressure, and thermal properties which can vary along the flow path. Key types include laminar flow (smooth, ordered) or turbulent flow (irregular, mixed).
Fluid–structure interaction – It is the interplay between fluid dynamics and structural mechanics, where fluids interact with and affect the behaviour of structures. It is important to analyze ‘fluid–structure interaction (FSI) as a whole rather than studying fluid and structure separately.
Fluid surface – It is the interface between a liquid and another medium (gas or liquid) where molecular forces create an apparent thin, elastic film, frequently termed a ‘free surface’ when subject to constant pressure. It is defined by its ability to resist expansion, possess surface tension, and exhibit capillarity. Engineering applications focus on its behavior under surface tension, wetting, and pressure, as seen in tanks and flow systems.
Fluid system – It is a designed arrangement of components, such as pipes, pumps, valves, and reservoirs, used to transport, control, or utilize liquids or gases to perform work, manage energy, or process materials. These systems operate based on fluid mechanics principles (dynamics and statics), regulating pressure and flow to enable functions like lubrication, cooling, or hydraulic power.
Fluid temperature distribution – It is the nonuniform variation of thermal energy throughout a fluid medium, mapped across spatial coordinates (e.g., depth, radius) and time, influenced by flow conditions, heat source locations, and heat transfer mechanisms. It defines the thermal profile, such as warmer fluid rising or heated fluid exiting a pipe.
Fluid transport equations – These equations refer to a set of coupled, non-linear partial differential equations which describe the relationships between velocity and pressure within a fluid system. These equations are complex and typically need numerical simulation techniques for their solution, especially in turbulent flow scenarios.
Fluid velocity – It is a vector quantity representing the time rate of change of a fluid particle’s position, defining both the speed and direction of a liquid or gas at any point in space. It is a fundamental transport concept important for calculating flow rates, determining Reynolds numbers, and designing hydraulic or aerodynamic systems. Fluid velocity includes both magnitude (speed) and direction.
Fluid viscosity – It is a fundamental property measuring a fluid’s internal resistance to flow, shear stress, or deformation. Representing thickness or internal friction, it dictates how fluids behave under motion (e.g., pipe flow, lubrication). It is quantified as the ratio of shear stress to the velocity gradient.
Fluid withdrawal – It is the extraction of liquids or gases (such as oil, water, or gas) from natural or artificial reservoirs, impacting pressure and fluid dynamics. It involves managed removal, frequently through selective, localized suction, to optimize recovery, control stratification, or supply demand.
Flume – It is a specially designed, man-made open channel or chute, normally elevated above ground, used to transport water, regulate flow, or precisely measure discharge. Flumes accelerate flow through converged sidewalls or a dropped floor to allow for water level-to-flow rate measurements (frequently +/- 5 % accuracy).
Flume experiments – These refer to controlled laboratory studies conducted using flumes, which are channels designed to mimic natural stream conditions, allowing for the examination of sediment transport, bedform development, and hyporheic exchange processes under easily oservable and variable conditions. These experiments enable people to investigate the effects of different parameters on streambed interactions by utilizing tracers to monitor exchanges between the stream and sediment.
Flume tanks – These are specialized recirculating water channels used to simulate ocean currents, waves, or river flows for testing scale models. They bridge the gap between computer modeling and real-world trials, enabling testing of underwater technologies and hydraulic structures in a controlled environment.
Fluoborate nickel plating solutions – These solutions are typically based on nickel fluoborate [Ni(BF4)2], which are utilized for high-speed electroplating and electroforming because of their high solubility, allowing for high metal concentrations and rapid deposition rates. These baths operate with high conductivity and provide fine-grained, ductile deposits, making them particularly useful for engineering applications and plating on challenging substrates.
Fluorescence – It is a type of photo-luminescence in which the time interval between the absorption and re-emission of light is very short.
Fluorescence emission – It involves tailoring the light emission properties of molecules, suc. Key methods include structural modifications to increase conjugation, managing the Stokes shift, and utilizing surface-modified fluorescence (SMF) with metal nano particles, which can improve or quench emission, depending on the distance between the entities (frequently below 10 nano-meters).
Fluorescence imaging – It involves designing advanced optical systems, contrast agents, and detectors to visualize molecular processes in real-time with high sensitivity and specificity. It utilizes near-infrared (NIR) light, specialized cameras, and exogenous agents like ‘indocyanine green’ (ICG) for detection.
Fluorescence imaging technique – It enables visualization of molecular processes by detecting emitted light from fluorophores upon excitation. Key aspects include developing high-sensitivity, multi-colour, and super-resolution systems and creating targeting fluorescent probes for real-time monitoring.
Fluorescence intensity – It involves manipulating the emission output of fluorophores through structural design, environmental control, or energy transfer mechanisms to improve detection sensitivity, frequently using techniques like ‘metal-enhanced fluorescence’ (MEF), quantum dots, or fluorescence resonance energy transfer (FRET). Key strategies include optimizing excitation power, increasing absorption cross-section, and minimizing quenching to achieve higher relative fluorescence units (RFU).
Fluorescence resonance energy transfer – It is a distance-dependent, non-radiative physical process where an excited donor fluorophore transfers energy to an acceptor fluorophore through dipole-dipole coupling. Operating over short distances (1 mano-meters to 10 nano-meters), it acts as a molecular ruler to detect conformational changes and intermolecular interactions.
Fluorescence imaging – It is a method used to study the location or concentration of molecules through the detection of emitted light after a molecule absorbs light, which occurs in a non-invasive manner with high sensitivity and specificity. This technique relies on the Stokes shift, where emitted light is of a longer wavelength than the absorbed light, allowing for the discrimination between excitation and emission signals.
Fluorescence lifetime – It involves tailoring the time a molecule spends in an excited state (typically nano-seconds) before emitting a photon. It is achieved by altering the fluorophore’s local environment or through structural modifications, influencing radiative and non-radiative decay rates to improve detection in sensors, imaging, and security materials.
Fluorescence lifetime imaging microscopy – It is an advanced imaging technique which maps the spatial distribution of nano-second excited-state lifetimes of fluorophores, rather than just intensity, to create pixel-by-pixel images. Engineered to be independent of fluorophore concentration, ‘fluorescence lifetime imaging microscopy (FLIM) measures local environmental factors, such as pH, viscosity, and oxygen concentration, and fluorescence resonance energy transfer (FRET) efficiency with high sensitivity, offering superior distinction between overlapping signals and background noise.
Fluorescent colour – It is a type of colourant (pigment or dye) which absorbs light energy at a specific wave-length, frequently invisible ultra-violet (UV) or short-wave-length blue light, and immediately re-emits it as visible light at a longer wavelength. This process, known as fluorescence, allows the color to appear considerably brighter and more saturated than conventional colours. Fluorescent materials absorb light in the ultra-violet or visible range, exciting electrons in the pigment molecules. Since the electrons return to their ground state, they release energy as visible light. Day-light fluorescent pigments (DFPs) are the most common industrial form, consisting of fluorescent dyes dissolved in a transparent synthetic polymer resin. They are stimulated by daylight and produce a ’glowing’ effect. Fluorescent colours can reflect or emit 200 % to 300 % of the light of the same colour present in the incident spectrum, compared to a maximum of 90 % for conventional colours.
Fluorescent crack detection – It is a highly sensitive non-destructive testing (NDT) method used to identify surface-breaking discontinuities in non-porous materials. It involves applying a liquid dye containing fluorescent pigments which seeps into defects through capillary action, which then glow under ultraviolet (UV-A) light to reveal cracks, seams, porosity, or laps.
Fluorescent gold nano-clusters – These are ultra-small aggregates of gold atoms (typically below 2 nano-meters, containing a few to a hundred atoms) which show strong, size-dependent photo-luminescence because of the discrete, molecular-like energy levels. Fluorescent gold nano-clusters (AuNCs) behave like ‘super-atoms’ since their size is comparable to the Fermi wavelength of an electron, causing continuous energy bands to break into discrete levels.
Fluorescent lamp – It is a type of electric lamp which relies on a phosphor coating to produce visible light from the ultraviolet light generated by a mercury discharge.
Fluorescent magnetic-particle inspection – It is the inspection with either dry magnetic particles or those in a liquid suspension, the particles being coated with a fluorescent substance to increase the visibility of the indications.
Fluorescent penetrant inspection – It is the inspection using a fluorescent liquid which penetrates a surface opening. After the surface has been wiped clean, the location of any surface flaws can be detected by the fluorescence, under ultraviolet light, of back-seepage of the fluid.
Fluorescent screen – It is a material which absorbs X-rays and re-emits the absorbed energy in the form of visible light photons, allowing for the conversion of X-ray patterns into visible patterns.
Fluorescent spectrum – It is a graphical representation (plot) showing the intensity of emitted light as a function of wave-length or wave-number. It is a unique characteristic of a fluorescent material (fluorophore) which reveals its energy transitions, molecular structure, and surrounding environment.
Fluorescent tube – It is a glass tube, typically filled with Argon gas and a small amount of mercury, with tungsten electrodes coated with electron-emissive material at both ends. It is a low-pressure, gas-discharge lamp which uses electricity to excite mercury vapour, producing ultra-violet (UV) radiation. This ultra-violet light strikes an internal phosphor coating, which fluoresces to emit visible light. Engineered for high efficacy (50 lumens per watt to 100 lumens per watt), it operates with a ballast / choke for stabilization.
Fluorescent yield – An electron is ejected from an atomic orbital by the photoelectric process with two possible results either X-ray photon emission or secondary (Auger) electron ejection. One of these events occurs for each excited atom, but not both. Hence, secondary electron production competes with X-ray photon emission from excited atoms in a sample. The fraction of the excited atoms which emits X-rays is termed the fluorescent yield. This value is a property of the element and the X-ray line under consideration. Low atomic number elements also have low fluorescent yield. Coupled with the high mass absorption coefficients which low-energy X-rays show, the detection and determination of low atomic number elements by X-ray spectrometry is challenging.
Fluoride – It is an inorganic, mono-atomic anion of fluorine, with the chemical formula F- (also written [F]-, whose salts are typically white or colourless. Fluoride salts typically have distinctive bitter tastes, and are odourless. Its salts and minerals are important chemical reagents and industrial chemicals, mainly used in the production of hydrogen fluoride for fluoro-carbons. Fluoride is classified as a weak base since it only partially associates in solution, but concentrated fluoride is corrosive and can attack the skin.
Fluoride coatings – These are specialized surface treatments, mainly used on magnesium alloys and related materials, which involve the formation of a dense, insoluble, and tightly bonded layer of metal fluorides (typically magnesium fluoride, MgF2). These coatings are utilized to drastically improve corrosion resistance, improve bio-compatibility and modulate degradation rates of bio-degradable metals.
Fluoride conversion coatings – These are a type of chemical surface treatment applied mainly to magnesium (Mg) and its alloys to improve corrosion resistance, bio-compatibility, and adhesion for subsequent paint or coatings. This metallurgical process involves converting the native surface of the magnesium metal into a dense, insoluble layer, mainly magnesium fluoride (MgF2), through a chemical or electro-chemical reaction with fluorine-containing solutions, such as hydrofluoric acid (HF).
Fluoride release – It refers to the process by which fluoride ions are liberated from glass-ionomer cements, mainly originating from the glass components during the setting reaction, and occurs through both short-term and long-term phases, influenced by the fluoride gradient in the surrounding environment.
Fluorimetry – It is also called fluorometry. It is an analytical technique used to detect and quantify substances by measuring the intensity of fluorescent light emitted by a sample. It operates on the principle that certain molecules, after being excited by absorbing light at a specific, shorter wavelength (typically ultra-violet-visible spectroscopy range), immediately release energy by emitting light at a longer wave-length.
Fluorinated ethylene propylene – It is a melt-processable thermoplastic copolymer of tetra-fluoro-ethylene and hexa-fluoro-propylene, offering excellent chemical resistance, transparency, and flexibility. It is used for coatings, tubing, and wire insulation, typically applied through spray coating (cured at around 380 deg C), extrusion, or injection moulding, with a melting point around 260 deg C.
Fluorinated materials – These are carbon-based compounds (polymers, liquids, gases) engineered by incorporating fluorine atoms, creating strong carbon-fluorine (C-F) bonds. These materials are defined by high chemical inertness, low surface energy, extreme hydrophobicity, and superior thermal stability. Common examples include poly-tetra-fluoro-ethylene (PTFE,) poly-vinylidene fluoride (PVDF), and fluorinated ethylene propylene (FEP), widely used in electronics.
Fluorinated membranes – These are high-performance separation materials by incorporating fluorine atoms (e.g., in poly-tetra-fluoro-ethylene (PTFE,) poly-vinylidene fluoride (PVDF), or per-fluoro-sulphonic polymers) into the membrane structure to provide extreme chemical, thermal, and oxidative stability. These materials are defined by their low surface energy, exceptional hydrophobicity, and high selectivity, making them indispensable for applications like fuel cell proton exchange membrane (PEMs), membrane distillation, and carbon capture.
Fluorinated polyimides – These are high-performance polymers incorporating fluorine atoms or fluorine-containing groups (e.g., -CF3) into their backbone, typically replacing hydrogen atoms. They are engineered to improve solubility, lower dielectric constants, and increase hydrophobicity and optical transparency compared to traditional aromatic polyimides. These materials maintain high thermal stability (frequently above 400 deg C), high mechanical strength, and superior chemical resistance, making them ideal for micro-electronics, and gas separation membranes applications.
Fluorinated polymers – These are advanced radical polymerization of monomers like tetra fluoro ethylene (TFE) and vinylidene fluoride (VDF), offer exceptional chemical inertness, high thermal stability (above 200 deg C), low friction, and low dielectric constants. Key techniques involve controlling main-chain, side-chain, and per-fluorinated ionomer structures through radical, emulsion, or suspension polymerization, creating materials for harsh chemical, electrical, and optical environments.
Fluorinated sample – It involves modifying material surfaces or structures by introducing fluorine atoms to improve chemical stability, hydrophobicity, and interfacial performance, particularly in energy storage and polymers. This technique, frequently using direct fluorination, creates low-surface-energy, corrosion-resistant, and high-performance interfaces.
Fluorine (F) – It is a chemical element with atomic number 9. It is the lightest halogen and exists at standard conditions as pale yellow diatomic gas. Fluorine is extremely reactive since it reacts with all other elements except for the light noble gases. In its elemental form it is highly toxic. It is used mainly as a compound, frequently fluorite (fluorspar) or cryolite, to act as a flux. It lowers melting points, improves fluidity, and removes impurities during steelmaking and aluminum smelting. It is important for extracting metal from ore and facilitating smelting processes.
Fluorine atom – It is the lightest halogen, possessing seven electrons in its outer shell, and is characterized by its highest reactivity and electronegativity of 4 on the Pauling scale.
Fluorine-bearing environments – These environments refer to industrial, geological, or processed conditions where fluorine compounds (such as fluorite, cryolite, or calcium fluoride) are present, frequently causing substantial chemical, physical, and metallurgical effects. These environments are characterized by high reactivity, where fluorides act as a powerful fluxing agent (a ‘cleansing agent’) or as an additive which reduces the viscosity of slags, aids in impurity removal, and lowers melting temperatures.
Fluorite – It is also known as fluorspar. It is a mineral consisting of calcium fluoride (CaF2) used mainly as a fluxing agent. It lowers the melting point of ore, increases the fluidity of slag, and facilitates the removal of impurities, specifically in the production of steel, aluminum, and magnesium.
Fluoro-carbon finish – It is a treatment applied to surfaces, very frequently, architectural metals, and industrial components, to provide superior water, oil, stain, and dirt repellency, along with extreme corrosion resistance. It functions by utilizing fluoro-carbon compounds to drastically lower the surface energy of the material, typically to less than 10 milli-Newtons per meter to 20 milli-Newtons per meter, causing liquids to bead and roll off.
Fluoro-carbon elastomers – These are a class of high-performance synthetic rubber characterized by a saturated, carbon-carbon backbone with fluorinated pendant groups. These are engineered to provide exceptional resistance to aggressive chemicals, heat, and high-temperature environments. Fluoro-carbon elastomers are highly fluorinated, carbon-backboned polymers which offer superior chemical resistance to oils, fuels, solvents, and acids. They are defined by their fluorine content (typically 50 % to 73 %) and are classified under ISO (International Organization for Standardization) standard ISO 1629.
Fluoro-carbon rubber – It is a high-performance, synthetic fluoro-elastomer material designed for demanding applications needing exceptional chemical, heat, and aging resistance. It is defined by its saturated carbon-backbone polymer chain, which is heavily fluorinated, providing high chemical inertness, low permeability, and thermal stability in harsh environments. Its temperature resistance is high, with a typical continuous service range of -20 deg C to +200 deg C (with specialized grades extending from -40 deg C to +250 deg C or higher).
Fluoro-carbons – Fluoro-carbons are chemical compounds with carbon-fluorine (C-F) bonds. They are a group of synthetic halogen-substituted methane and ethane derivatives containing atoms of chlorine and fluorine. Compounds which contain several carbon-fluorine bonds frequently have distinctive properties, e.g., improved stability, volatility, and hydrophobicity. Fluoro-carbons which contain chlorine are called chloro-fluoro-carbons (CFCs). Chloro-fluoro-carbons normally known by commercial names such as Freon, Arcton, and Frigen. Because of their unique combination of non-flammability and general inertness, chloro-fluoro-carbons are used as refrigerants, aerosol propellants, foam-blowing agents, solvents, glass chillers, and polymer intermediates, as well as in fire extinguishers and anesthetics.
Fluoro-chemicals – These are synthetic compounds containing carbon-fluorine (C-F) bonds, known for exceptional thermal stability, chemical inertness, and low surface energy, which provides superior water, oil, and soil repellency. They are widely used in engineering as surfactants, polymers (e.g., poly-tetra-fluoro-ethylene), refrigerants, and industrial coatings.
Fluoro-elastomers – These are high-performance, synthetic fluoro-carbon-based rubbers designed for extreme environments, featuring superior resistance to high temperatures (above 200 deg C), oils, chemicals, and ozone. They are defined by their carbon-fluorine polymer backbone, offering low gas permeability and high compression resistance, mainly used for specialized O-rings, seals, and gaskets.
Fluorometric analysis – It is a method of chemical analysis which measures the fluorescence intensity of the analyte or a reaction product of the analyte and a chemical reagent.
Fluorophore – It is a fluorescent chemical compound which can re-emit light upon light excitation. Fluorophores typically contain several combined aromatic groups, or planar or cyclic molecules with several pi-bonds. Fluorophores are sometimes used alone, as a tracer in fluids, as a dye for staining of certain structures, or as a probe or indicator (when its fluorescence is affected by environmental aspects such as polarity or ions). More generally they are covalently bonded to macro-molecules, serving as markers (or dyes, or tags, or reporters). Fluorophores are notably used to materials in a variety of analytical methods, such as fluorescent imaging and spectroscopy.
Fluorophore system – It refers to the application of fluorescent chemical compounds (fluorophores), such as organic dyes, quantum dots, or specialized rare-earth chelates, to metallic surfaces or within metal-organic frameworks to enable advanced characterization, imaging, and sensing, frequently in combination with high-resolution microscopy. These systems are utilized to map microstructural features, detect fatigue cracks, or monitor micro-environmental parameters like pH or metal ion concentration, frequently taking advantage of metal-induced fluorescence properties.
Fluoro-plastic – It is a plastic based on polymers made from monomers containing one or more atoms of fluorine, or copolymers of such monomers with other monomers, the fluorine-containing monomer(s) being in highest quantity by mass.
Fluoro-polymers – These are high-performance plastics defined by a carbon backbone bonded with fluorine atoms, offering exceptional chemical inertness, low surface energy (non-stick), and high thermal stability. Engineered for extreme environments, they are classified as perfluorinated (e.g., poly-tetra-fluoro-ethylene) or partially fluorinated (e.g., poly-vinylidene fluoride, and fluorinated ethylene propylene) thermoplastics, used extensively for corrosion resistance, electrical insulation, and low friction.
Fluoroscopy – It is an inspection procedure in which the radiographic image of the subject is viewed on a fluorescent screen. It is normally limited to low-density materials or thin sections of metals because of the low light output of the fluorescent screen at safe levels of radiation.
Fluoro-silicone – It is a high-performance synthetic elastomer combining the silicone backbone (-Si-O-Si-) with fluorinated side groups (tri-fluoro-propyl), providing exceptional resistance to fuels, oils, solvents, and extreme temperatures (-60 deg C to +260 deg C). Engineered for harsh environments, it is widely used for static sealing in several applications. Such as chemical processing.
Fluoro-sulphates – These are a class of chemical compounds containing the Fluoro-sulphate anion [(FSO3)-], acting as salts of fluoro-sulphuric acid (HSO3F) or as organic esters (R-OSO2F). In advanced chemical synthesis, these are recognized as highly reactive yet stable electrophilic building blocks and versatile intermediates, frequently used in ‘click’ chemistry which is a modular approach to chemical synthesis (SUFeX which stands for sulphur(VI) fluoride exchange and which is a type of click chemistry reaction) as less toxic, more atom-economical alternatives to triflates.
Fluoro-vinyl-methyl-silicone rubber – It is a specialized elastomer combining the siloxane backbone of silicone with fluorinated side chains (tri-fluoro-propyl) and vinyl groups. Engineered for harsh environments, it offers exceptional resistance to fuels, oils, solvents, and ozone, while operating in extreme temperatures from roughly -60 deg C to +260 deg C.
Fluorspar – It is also called fluorite. It is the mineral form of calcium fluoride (CaF2). It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon. The Mohs scale of mineral hardness, based on scratch hardness comparison, defines value 4 as fluorspar. Pure fluorite is colourless and transparent, both in visible and ultraviolet light, but impurities normally make it a colourful mineral and the stone has ornamental and lapidary uses. Industrially, fluorspar is used as a flux for smelting, and in the production of certain glasses and enamels. The purest grades of fluorite are a source of fluoride for hydrofluoric acid manufacture, which is the intermediate source of the majority of the fluorine-containing fine chemicals.
Flush bottom valves – These valves are generally at the lowest point of a tank or reactor and used to drain out contents. They are unique since it leaves no dead space in the valve when it is closed. This eliminates the problem of product build-up within the valve.
Flushed zone – It is a critical concept in formation evaluation (well logging) which refers to the region immediately adjacent to a borehole wall where drilling mud filtrate has almost completely displaced the original formation fluids (water, oil, or gas). It refers to the area in permeable formations where there is substantial fluid invasion by mud filtrate, observable through the separation of micro- and deep resistivity curves, providing a qualitative indication of permeability.
Flushing – It is a procedure for hydraulic systems of cleaning the fluid to a pre-determined standard. In pipelines for flushing, a fluid (normally water) is introduced into the pipes which are to be cleaned. This fluid, with a pressure calibrated according to the result to be achieved, transports the contaminants, cleaning the pipes.
Flushing operation – It is the process of circulating a fluid (liquid or gas) through a piping system, hydraulic circuit, or piece of machinery to remove contaminants such as construction debris, rust, mill scale, or sludge, ensuring the system is clean for startup or operational efficiency. It is a critical pre-commissioning activity designed to protect sensitive equipment, like bearings, pumps, and valves, from damage caused by particulate matter.
Flushing procedure – It is an important pre-commissioning or maintenance process which uses high-velocity fluid (water, oil, or air) to remove debris, rust, scale, or contaminants from piping systems. It ensures system cleanliness, protects sensitive components, and ensures operational reliability. The purpose is to prevent equipment failure by removing construction debris, construction residue from process piping systems.
Flushing screen – It is a filtering component used during fluid system cleaning to remove contaminants, particles, and debris. It protects critical equipment, like pumps, bearings, and seals, by capturing particles during high-velocity oil or water flushing procedures. These screens prevent damage to system components from internal contamination. Flushing screens protect sensitive equipment from debris (metal filings, rust, construction dirt).
Flush plan – It is an engineered, standardized piping arrangement which circulates fluid to or from the mechanical seal chamber of a centrifugal pump. Its main purpose is to create an ideal environment, properly lubricated, cooled, and clean, to protect the seal faces from damage, reduce friction, prevent premature failure, and improve the overall reliability of the pump. These systems are normally codified by the standards, allowing engineers and manufacturers to select the optimal configuration for specific process conditions (e.g., hot, cold, dirty, or hazardous fluids).
Flute – As applied to drills, reamers, and taps, it is the channels or grooves formed in the body of the tool for providing cutting edges and for permitting passage of cutting fluid and chips. As applied to the milling cutters and hobs, it is the chip space between the back of one tooth and the face of the following tooth.
Fluted bearing – It is a sleeve bearing with oil grooves normally in an axial direction.
Fluted core – It is an integrally woven reinforcement material consisting of ribs between two skins in a unitized sandwich construction.
Fluted rollers – These are rollers with a grooved or ribbed surface to improve material grip, necessitating periodic checks for wear, alignment, and proper functionality.
Fluting – It is forming longitudinal recesses in a cylindrical part, or radial recesses in a conical part. It is also a series of sharp parallel kinks or creases occurring in the arc when sheet metal is roll formed into a cylindrical shape. It also consists of grinding the grooves of a twist drill or tap. In bearings, it is a form of pitting in which the pits occur in a regular pattern so as to form grooves. Ridges can occur with or without burnt craters. The general cause involves vibration together with excessive wear or excessive load. Fluting is also electric discharge pitting in a rolling-contact bearing subject to vibration.
Flutes – These are elongated grooves or voids which connect widely spaced cleavage planes.
Flux – It is a chemical substance which reacts with gangue minerals to form slags, which are liquid at furnace temperature and low enough in density to float on the molten bath of metal or matte. In metal refining, it is a material added to a melt for removing undesirable substances, like sand, ash, or dirt. Fluxing of the melt facilitates the agglomeration and separation of such undesirable constituents from the melt. It is also used as a protective covering for certain molten metal baths. Lime or limestone is normally used to remove sand, as in iron smelting and sand is used to remove iron oxide in copper refining. In brazing, cutting, soldering, or welding, flux is the material used to prevent the formation of, or to dissolve and facilitate removal of, oxides and other undesirable substances. This term flux is also applied to the quantity of particles or energy which crosses a unit area per unit time. The unit of flux is the number of particles or energy, per square centimeter per second. In galvanizing, flux consists of the chemicals used to protect steel from oxidation prior to entering the molten zinc containing pot.
Flux component – It normally refers to the specific portion of a vector field (magnetic or electric) passing perpendicularly through a defined surface. It is the scalar measure of field flow, important for calculating induced voltage in electromagnetics or quantifying material flow.
Flux composition – It is a formulated mixture of chemicals, typically inorganic salts, borax, silica, or organic resins, designed to remove oxides, prevent oxidation, and lower the melting point of impurities (slag) during welding, soldering, brazing, or smelting. These mixtures create a clean, wettable surface to improve bonding efficiency.
Flux concentrator – It is a device, typically made from high-permeability, low-power-loss magnetic materials (like ferrites or soft magnetic composites), used to improve, direct, and localize magnetic flux around current-carrying conductors. It increases heating efficiency in induction systems, shields neighbouring components from unwanted heat, and improves power density, acting as a magnetic core.
Flux-controlled memristor – It is a two-terminal nonlinear passive element where the charge is a function of magnetic flux, characterized by memductance. It shows a pinched hysteresis loop in the plane, with resistance changing in response to voltage / flux history, frequently used in non-volatile memory and memristive switching.
Flux cored arc welding – It is an arc welding process which joins metal by heating them with an arc between a continuous tubular filler-metal electrode and the work. Shielding is provided by a flux contained within the consumable tubular electrode. Additional shielding may or may not be obtained from an externally supplied gas or gas mixture.
Flux cored electrode – It is a composite filler metal electrode consisting of a metal tube or other hollow configuration containing ingredients to provide such functions as shielding atmosphere, deoxidation, arc stabilization, and slag formation. Minor quantities of alloying materials can be included in the core. External shielding may or may not be used.
Flux-cored wire – It is a continuous, tubular, consumable welding electrode featuring a metal sheath filled with fluxing agents, metal powders, and deoxidizers. It is used in ‘flux-cored arc welding’ (FCAW) to provide superior weld penetration, high deposition rates, and arc stability, frequently acting as a self-shielding filler metal, allowing welding in windy or outdoor conditions without external gas.
Flux cover (metal bath dip brazing and dip soldering) – It is a layer of molten flux over the molten filler metal bath.
Flux creep – It is the thermally activated, slow, and logarithmic decay of trapped magnetic flux vortices out of pinning centres in Type II super-conductors. It generates a small, time-dependent electrical resistance (resistive voltage) below the critical current density, limiting the performance of super-conducting magnets by causing slow decay of trapped magnetic fields.
Flux cutting processes – These processes are well suited to materials which at form refractory oxides, such as stainless steels. Finely pulverized flux is injected into the cutting oxygen before it enters the cutting torch. The torch has separate ducts for preheat oxygen, fuel gas, and cutting oxygen. When the flux strikes the refractory oxides which are formed when the cutting oxygen is turned on, it reacts with them to form a slag of lower-melting temperature compounds. This slag is driven out, enabling oxidation of the metal to proceed. The operator needs to have an approved respirator for protection from toxic fumes generated by the process.
Flux density – In magnetism, the number of flux lines per unit area passing through a cross section at right angles. It is given by B = mu H, where ‘mu’ and ‘H’ are permeability and magnetic-field intensity, respectively.
Flux differential scanning calorimetry – It is also called heat flux differential scanning calorimetry (hf-DSC). It is a thermal analysis technique which measures the difference in heat flow between a sample and an inert reference within a single, temperature-controlled furnace. It identifies endothermic / exothermic transitions (melting, curing, glass transition) based on the temperature difference across a heat-conducting sensor, directly determining heat flow.
Fluxed pellets – These are iron ore pellets which have been manufactured with the addition of fluxes like limestone or dolomite. These fluxes are added to adjust the basicity of the pellets, which impacts the slag formation and softening-melting behaviour during the blast furnace process. This adjustment can improve the efficiency and reduce emissions in blast furnace operations.
Fluxed sinter – It is a type of iron ore sinter where a flux (like limestone or burnt lime) is added to the sinter mix. This addition helps to create a more basic sinter, which is beneficial for the subsequent blast furnace process. Specifically, fluxed sinter has a higher basicity ratio (CaO/SiO2) compared to acid sinter, and it helps to neutralize the acidic components in the blast furnace burden, improving the slag’s ability to remove impurities.
Flux, electric – In electromagnetism, electric flux is the measure of the electric field through a given surface, although an electric field in itself cannot flow. Electric flux is the property of an electric field that may be thought of as the number of electric lines of force (or electric field lines) that intersect a given area. Electric field lines are considered to originate on positive electric charges and to terminate on negative charges.
Flux-gate magnetometer – It is an instrument which is used in geophysics to measure total magnetic field.
Flux inclusions – It is the flux carried out onto the steel from the top flux blanket incorporated in the wet process. It occurs only in the wet galvanizing process.
Fluxing – Fluxing is the use of a hot zinc ammonium chloride pre-flux solution to condition the cleaned steel prior to its immersion in the molten zinc. It is the process by which steel is dipped in aqueous zinc ammonium chloride to remove undesirable substances and to protect it from further oxide formation prior to entering the galvanizing bath.
Flux Jacobian – It is the partial derivative of the physical flux vector with respect to the conservative state vector. It represents the rate of change of flux relative to state changes, forming a matrix used to linearize non-linear governing equations, such as in implicit time-stepping methods.
Flux jump – In the context of superconducting materials, it is a sudden, avalanche-like penetration of magnetic flux into a Type-II superconductor. It is a form of thermomagnetic instability where a rapid change in magnetization occurs, frequently leading to a substantial increase in local temperature which can cause the material to switch from a superconducting state to a normal (non-superconducting) state, a phenomenon known as a quench.
Flux leakage techniques – Magnetic particle inspection system based on flux leakage techniques is a well proven system but only suitable for cold billets. The magnetic sensors are deployed either to scan the surface directly or indirectly where a contacting tape transfers the magnetic image to a separate scanning head. In either case there is a temperature limit imposed on the billet to ensure a satisfactory test. Attempts have been made to utilize this form of inspection on continuous cast billet and the results are very disappointing. Continuous cast defects such as pinholes, transverse cracking and other defects with a transverse component can escape detection and in addition the level of spurious marking is very high. It is important to remember that the level of spurious marking generated by any inspection system is just as significant a feature as its detection efficiency.
Flux lines – These are imaginary lines which are used as a means of explaining the behaviour of magnetic and other fields. Their concept is based on the pattern of lines produced when magnetic particles are sprinkled over a permanent magnet. It is sometimes called magnetic lines of force.
Flux linkage – In a magnetic system, it is that part of the magnetic flux which passes through a given closed path, which can be a winding.
Fluxmeter – It is an instrument designed to measure changes in magnetic flux through a pickup or search coil, typically using an electronic integrator to calculate the net flux change. It acts as an advanced, specialized voltmeter or improved ballistic galvanometer, measuring the total charge flow induced by magnetic field changes.
Flux method – It is a high-temperature crystal growth technique where raw materials are dissolved in a molten solvent (flux) to create a saturated solution. Upon controlled cooling, the solute precipitates out to form high-quality single crystals, frequently used for materials which melt incongruently or need lower processing temperatures.
Fluxon – It is also called magnetic flux quantum (Wb). It is a localized, quantized bundle of magnetic flux which acts as a particle-like topological defect in a superconductor. Fluxons are important for superconducting electronics, particularly in Type-II superconductors and Josephson junctions.
Flux oxygen cutting – It is a non-standard term for chemical flux cutting.
Flux penetration – It is the process where magnetic flux lines (vortices) enter a Type-II superconductor, normally in the mixed state between critical fields Hc1 and Hc2. The magnetic field penetrates in quantized units (fluxons), forming a vortex lattice, and can be influenced by material defects or geometrical edge imperfections.
Flux pit – In porcelain enamel, it is a cone-like depression defect in the fired enamel surface, somewhat larger than a pinhole.
Flux rate – It is the rate of transfer of a quantity (mass, volume, energy, or particles) passing through or across a specific unit area per unit time. It acts as a 2D measure of flow intensity. It also refers to the velocity or volume of fluxing agent being applied or processed per unit of time.
Flux sensor – It is frequently referred to as a heat flux sensor or heat flux gauge. It is a specialized transducer designed to measure the rate of heat energy transfer per unit area across a surface. It converts the thermal energy passing through it into an electrical signal (voltage) which is directly proportional to the heat flux.
Flux staining – It occurs after galvanizing, when the crevices and overlaps, which are not sealed, can show signs of brown staining bleeding out of the crevices. This is the result of iron-rich flux residues being trapped in the crevices absorbing moisture.
Flux vector – It is a vector quantity which represents the rate of flow of a physical property (mass, heat, or particles) per unit area per unit time in a specific direction. It provides both the magnitude (how much is flowing) and the direction of the transport process.
Fly ash – It is a by-product which is generated during the burning of pulverized coal in a thermal power plant. Specifically, it is the unburned residue which is carried away from the burning zone in the boiler by the flue gases and then collected by electrostatic separators or by any other means. Fly ash is a pozzolanic material. It is normally finer than Portland cement and consists mostly of small spheres of glass of complex composition involving silica, ferric oxide, and alumina. The composition of fly ashes varies with the source of coal.
Fly ash blend – It is a mixture combining fly ash, a pozzolanic by-product of coal combustion, with materials like Portland cement, lime, or water to enhance concrete performance. It acts as a partial cement replacement (typically 15 % to 40 %) to improve durability, workability, and strength while reducing costs and environmental impact.
Fly ash carbon – It refers to the unburned, residual coal particles left in fly ash after coal combustion, measured by ‘loss on ignition’ (LOI). It is the carbonaceous residue from incomplete combustion, frequently including petrographically distinct forms like inertinite and coke (isotropic / anisotropic). Fly ash carbon is a critical quality indicator. High levels, typically active / activated, adversely affect concrete by adsorbing air-entraining agents, reducing durability and strength.
Fly ash concrete – It is a sustainable, high-performance building material created by replacing a portion of Portland cement with fly ash, a fine, pozzolanic by-product of pulverized coal combustion. It improves workability, reduces thermal cracking because of low heat of hydration, increases long-term strength, and improves durability by lowering permeability.
Fly-back converter – It is an isolated power converter which shares input voltage-current characteristics with buck-boost converters and provides input-output isolation, making it suitable for power factor correction (PFC) applications. It can output a voltage that is either higher or lower than the input voltage, although it may exhibit high di/dt noise and lower efficiency due to the use of a power transformer. It is a type of voltage converter which stores energy in an inductor.
Fly-back diode – It is also called freewheeling diode. It is a diode connected in parallel with an inductive load (e.g., relays, motors, solenoids) to eliminate sudden high-voltage spikes (flyback) which occur when the power is abruptly turned off. It protects sensitive switching components, like transistors, by allowing the inductor’s collapsing magnetic field to dissipate safely through a ‘freewheeling’ current path.
Fly-back transformer – It is a type of transformer which recovers energy stored in its own core. Historically it is used in the deflection circuits of cathode ray tube display systems.
Fly cutting – It is the cutting with a single-tooth milling cutter.
flyer plates – These are also called flier plates. These are thin, flat plates of material (normally metal) accelerated to high velocities to impact a target sample. This technique is used to generate high-pressure, high-strain-rate shock waves for material testing, explosive welding, or synthesis.
Flying capacitor inverter – It is a half-bridge three-level inverter topology which utilizes a floating capacitor instead of clamping diodes, enabling additional voltage levels while providing fault tolerance. It needs careful management of the capacitor voltage to prevent imbalances which can cause overvoltage and damage the inverter.
Flying flash – It can be a result of faults in die design, including inadequate gutters, incorrect flash land, or incorrect flash clearance. It is a hazard in forging and needs the use of protective equipment. Flash guards on the die and protective clothing are needed to minimize the danger to the operator. Movable shields placed in back of the hammer protect the passerby. Although such devices help to provide protection if flying flash occur, the problem can best be met by careful die construction and, if necessary, by correction in the die.
Flying shear – It is a machine for cutting continuous rolled products to length which does not need a halt in rolling, but rather moves along the runout table at the same speed as the product while performing the cutting, and then returns to the starting point in time to cut the next piece. It is a standard industrial equipment known for cutting a constant product at a determined length at line speed. Flying shears do not interrupt the primary production, ensuring maximized productivity.
Flying-shear cut-off machine – It is a high-speed, precision cutting unit used in sheet forming (roll forming, tube mills) to cut continuous material to length without stopping the production line. It accelerates to match the speed of the moving strip or tube, performs the cut, and returns to position, enabling continuous, high-efficiency manufacturing.
Flywheel – It is a mechanical device specifically designed to use the conservation of angular momentum so as to efficiently store rotational energy, which is a form of kinetic energy proportional to the product of its moment of inertia and the square of its rotational speed. In particular, if it is assumed that the flywheel’s moment of inertia is constant (i.e., a flywheel with fixed mass and second moment of area revolving about some fixed axis) then the stored (rotational) energy is directly associated with the square of its rotational speed.
Flywheel battery – It is a mechanical device which stores electricity in the form of rotational kinetic energy. It operates by accelerating a rotor (flywheel) to high speeds using an electric motor / generator during times of excess energy, and reversing the process to generate electricity when needed.
Flywheel diode – It is a diode connected in reverse parallel across an inductive load (e.g., relay, motor) to protect switching components. It creates a safe path for current to dissipate when the power is turned off, preventing high-voltage spikes, known as inductive kickback, from destroying transistors or switches.
Flywheel energy – It is the energy which is stored by the flywheel in the form of rotational kinetic energy (E = 1/2 I x w-square), where the stored energy is proportional to the moment of inertia (I) and the square of the angular velocity (w).
Flywheel energy storage – It is a method for storing electricity in the form of kinetic energy by spinning a flywheel at high speeds, which is facilitated by magnetic levitation in an evacuated chamber. This technology allows for efficient energy storage and retrieval, with a roundtrip efficiency of around 90 %.
Flywheel energy storage systems – These convert electrical energy into mechanical energy by using a motor to spin a rotor in a vacuum to high speeds, releasing it back to electricity through a generator when needed. Flywheel energy storage system (FESS) is an electro-mechanical device which stores electricity as rotational kinetic energy, using a motor / generator to accelerate a rotor (flywheel) within a vacuum. It provides high-power, rapid-response energy storage for grid stability, with lifetimes exceeding 20 years. Materials range from high-strength steel to advanced carbon-fibre composites.
Flywheel technology – It is a mechanical system which stores rotational energy in an accelerated rotor, allowing for rapid energy discharge mainly for frequency regulation in power grids. It is characterized by high peak power output, long cycle life, and responsiveness to frequency changes, though it has relatively low energy density and current efficiency.
FM dies – These are ‘free from Mannesmann effect’ dies. These are frequently utilized in forging and rolling. These are specialized tooling designed to prevent the formation of central cavities or internal fractures in metal billets, normally known as the Mannesmann effect. These dies reduce or eliminate the tensile stress state which develops at the centre of a work-piece during high-compression deformation, such as radial forging or skew rolling.
FML dies – These are ‘free of Mannesmann effect at lower press loads’ dies., These are specialized tools designed for open-die forging and industrial rolling processes to prevent the formation of internal voids or central cracking in work-pieces while minimizing the force needed. They are categorized as advanced tools that mitigate the Mannesmann effect, a phenomenon where tensile stresses at the centre of a material are generated by heavy compressive forces, causing damage in applications like cogging, rotary forging, or cross-wedge rolling.
Foam – It is a colloidal structure created by trapping a large volume of gas bubbles within a liquid or solid matrix, resulting in a lightweight, cellular material. Key properties include high strength-to-weight ratios, thermal insulation, and energy absorption, with structures classified as open-cell (pores connected) or closed-cell (sealed cells).
Foam blanket – It is an additive which forms a layer on the surface of electro-plating baths which have poor anode / cathode efficiency and prevents any mist or spray from escaping.
Foam cell – It is a single, solidified pocket of gas (bubble) trapped within a solid matrix, acting as the fundamental structural unit of solid foam materials. These cells are classified as closed-cell (isolated pockets, high strength / buoyancy) or open-cell (interconnected pores, porous / absorbent) and are engineered for insulation, packaging, and structural stability. Foam cells represent a ‘cellular solid’, where cell walls (made of polymer, metal, or ceramic) form a lattice structure. Closed cells look like small, dispersed bubbles (glass-like), while open cells are networked.
Foam control – It is the systematic management, prevention, and elimination of unwanted foam in industrial processes, such as fermentation, oil separation, and chemical production. It utilizes chemical (antifoams / defoamers) or mechanical techniques to prevent operational disruptions, ensure safety, and improve efficiency. Foam control manages gas-in-liquid dispersions to prevent overtopping vessels, reducing efficiency, or causing contamination.
Foam core – It is a low-density, cellular structural material (such as poly-vinyl chloride, poly-urethane, or poly-styrene) used as the central layer in sandwich-structured composites. It separates two stiff outer skins to maximize bending stiffness and strength-to-weight ratios, offering superior fatigue, impact resistance, and energy absorption for several applications. Foam core acts as the ‘muscle’ in sandwich panels, bearing shear loads and maintaining distance between outer skins to prevent buckling.
Foam density – It is the mass of a foam material per unit volume, typically measured in kilograms per cubic meter. It indicates the quantity of solid polymer structure relative to the air content, serving as a key metric for durability, support, and longevity.
Foam drilling – It is a specialized underbalanced drilling technique which uses a mixture of compressed air (or gas), water, and a foaming agent (surfactant) to create a stable, low-density foam fluid. It is used to improve cuttings transport, control fluid loss in fractured formations, minimize pay zone damage, and increase the rate of penetration.
Foamed bitumen – It is a hot asphalt binder (150 deg C to 180 deg C) temporarily converted into a foam by injecting water (1 % to 4 %) and compressed air, expanding it 20 times to 30 times its volume. This process lowers viscosity, allowing for uniform coating of cold, moist aggregates, frequently combined with reclaimed asphalt pavement (RAP) or recycled materials, in cold-mix, sustainable pavement construction.
Foamed concrete – It is a lightweight, cellular cementitious material, typically containing at least 20 % mechanically entrained air foam by volume in a slurry of cement and water (sometimes with fine sand). It has a low density (400 kilograms per cubic meter to 1,800 kilograms per cubic meter), excellent thermal / sound insulation, and high workability, making it ideal for geo-technical void-filling, insulation, and lightweight construction.
Foamed plastics – These are resins in sponge form, flexible or rigid, with cells closed or inter-connected and density over a range from that of the solid parent resin to 0.03 grams per cubic centimeters. Compressive strength of rigid foams is fair, making them useful as core materials for sandwich constructions. It is also a chemical cellular plastic, the structure of which is produced by gases generated from the chemical interaction of its constituents.
Foamers – These are chemical agents, specifically surfactants, used to generate and stabilize foam by reducing the surface tension of a liquid (normally water). Foamers are widely used to facilitate the creation of stable, uniform, and small bubbles which are dispersed within a liquid or solid continuous phase.
Foam fillers – These are lightweight, porous polymeric materials (typically poly-urethane, poly-styrene, or specialized syntactic compounds) used to fill gaps, cavities, or voids. They expand upon application to provide structural support, thermal insulation, sound-proofing, and sealing against air / water, particularly in construction, and mining applications.
Foam glass – It is also called cellular glass. It is a lightweight, rigid, and durable insulating material, engineered from crushed recycled glass and a foaming agent (like carbon) heated to form a closed-cell, porous structure. It is highly valued for having 90 % to 97 % air pores, providing superior non-combustible thermal insulation, 100 % resistance to water / moisture, and high compressive strength.
Foaming – It is the continuous formation of bubbles which have sufficiently high surface tension to remain as bubbles beyond the disengaging surface. Foaming is an important phenomenon which is normally encountered when gas is blown through a viscous liquid. It is beneficial in the steelmaking since it assists the refining process in different ways. It provides an increased surface area for the refining reactions and protects the liquid metal bath from the direct contact of the atmosphere. It improves the kinetics of the reactions, heat transfer, and energy efficiency of the process. It forms the medium for post-combustion and heat transfer. It protects the refractory lining from extreme combustion effects by providing a shield for the refractory and hence extends the life of the refractory lining. It acts as a sink for the oxides of impurities such as manganese, silicon, and phosphorus, which have been oxidized from the liquid bath. In addition, slag foaming prevents the liquid bath from oxidizing and enables control of its composition. It also acts as a thermal insulator between the hot bath and the surroundings and thus prevents major energy losses.
Foaming agent – It consists of chemicals added to plastics and rubbers which generate inert gases on heating, causing the resin to assume a cellular structure.
Foaming behaviour – It defines how a liquid or polymer, often containing surfactants or blowing agents, forms, stabilizes, and breaks down bubbles under mechanical action, pressure drops, or thermal decomposition. It is measured by foam capacity (volume of air incorporated) and stability (resistance to drainage and coalescence) over time, important for materials, processing, and chemical operations.
Foaming index – It is an important parameter for the slag foaming. It can be viewed as the time for the gas to pass through the slag. It is an indication of the extent of the foaming and is the ratio between the foam height and the superficial gas velocity. Hence, the unit of the foaming index is time which is normally in seconds. Hence, the foaming index can be interpreted as a measure of the time it takes for the process gases to vertically pass through the foam. The foaming index is related to the slag properties such as viscosity. The higher is the viscosity, the higher is the foaming index. The obvious consequence is that an increased viscosity automatically leads to an increased foam height. The foaming index decreases with increasing bubble size.
Foaming slag – It is a metallurgical process in steelmaking, mainly electric arc furnaces (EAF), where gas bubbles, normally carbon mono-oxide (CO), are trapped in molten slag, causing it to expand and foam. It is an important technique used to cover the arc, protect refractory linings, improve thermal efficiency, and improve energy consumption.
Foaming slag control system – For automated foaming slag operation, several approaches exist which use sound measurements. Foaming slag control system is a sensor system. It is based on structure-born noise and is an approach to evaluate the quantity of foaming slag in the electric arc furnace. In regards to trends and reproducibility, this method has proved to successfully follow the real foaming slag situation in the arc furnace.
Foam inhibitor – It is a surface-active chemical compound which is used in minute quantities to prevent or reduce foaming. Silicone fluids are frequently used as foam inhibitors.
Foam-in-place – It refers to the deposition of foams when the foaming machine must be brought to the work that is ‘in place’ as opposed to bringing the work to the foaming machine. It is also, foam mixed in a container and poured into a mould, where it rises to fill the cavity.
Foam, metal – It is a cellular, porous structure comprising a metal matrix (frequently aluminum) with a large volume fraction of gas-filled pores, creating an ultralight material with high strength-to-weight ratios. Typically produced through liquid foaming or powder metallurgy, it features open or closed cells used for energy absorption, heat exchange, and sound damping.
Foam quality – It is the volumetric ratio of gas to the total volume of foam (gas + liquid), typically expressed as a percentage, normally ranging from 52 % to 95 % for stable foams. It measures the dryness of the foam, with higher percentages indicating more gas (drier) and lower percentages indicating more liquid (wetter), directly affecting flow behaviour and stability.
Foam sensor – It is a device which detects, measures, or controls foam formation within industrial processes or liquid systems, typically by measuring electrical conductivity or capacitance changes. These sensors provide signals to trigger antifoam agents, preventing overspill, or, in the case of conductive foam, act as flexible pressure / strain sensors.
Foam stability – It is the ability of a dispersed gas-in-liquid system to maintain its structure, resisting collapse, drainage, and coalescence over time. Although thermodynamically unstable, stable foams are to persist for specific applications by managing surface tension, viscosity, and bubble size.
Foam system – It is a fire suppression mechanism which mixes water, foam concentrate, and air to create a stable, low-density blanket which extinguishes flammable liquid (class B) fires. It works by covering the fuel to smother flames, cooling the surface, and preventing vapour-air mixture formation to stop re-ignition.
Foam tape – It is a pressure-sensitive adhesive (PSA) tape featuring a cellular foam backing (poly-ethylene, acrylic, poly-urethane, ethylene propylene diene monomer) which provides sealing, cushioning, insulation, and bonding. It offers high tensile strength and visco-elastic properties to fill gaps, dampen vibration, and replace mechanical fasteners in demanding structural, automotive, and electrical applications.
Foam viscosity – it is the measure of a foam’s internal resistance to flow and deformation, functioning as a non-Newtonian, shear-thinning (pseudo-plastic) fluid. It is defined as the apparent viscosity, which is a function of foam quality (gas volume fraction), shear rate, and temperature, rather than a single material constant. Foam viscosity represents the stiffness of the foam, which increases with higher gas bubble density and stabilizers. It is frequently modelled using a power law (or Herschel-Bulkley) model, which links shear stress to the shear rate, normally displaying lower viscosity as flow velocity / shear increases (shear-thinning).
Foamy slag – It is at the heart of modern steelmaking in electric arc furnace (EAF) process. The foaming helps to shield refractories from arc plasma, stabilizes the arc and helps to increase the power input and energy efficiency, reduces nitrogen pick-up, improves productivity, and chromium recovery in stainless steel melting. Foaming of slag takes place because of carbon mono-oxide bubbles generated by the reaction of bath carbon with the injected oxygen gas.
Foamy slag practice – In electric arc furnace steelmaking, progressive melting of scrap increases the irradiative heat transfer from arc to the side walls of the furnace. By covering the arc in a layer of slag, the arc is shielded and more energy is transferred to the bath. The foaming slag during this period is beneficial. The effectiveness of slag foaming depends on slag basicities, ferrous oxide (FeO) content of slag, slag temperature and availability of carbon to react with either oxygen or ferrous oxide of slag. A foaming slag reduces refractory damage and heat loss from the arc region. The net energy savings are estimated at 6 to 8 kilowatt-hour per ton of steel.
Focal document – It is a primary, foundational document used as the baseline for comparing, evaluating, or auditing against other documents, systems, or standards. A focal document serves as the authoritative reference point to ensure consistency, compliance, or interoperability, especially when mapping between different standards.
Focal length – It is the distance from the second principal point to the point on the axis at which parallel rays entering the lens converges or focuses.
Focal plane – It is the plane perpendicular to the optical axis of a lens or mirror which passes through the focus. It is the specific surface where light rays from an object converge to create a sharp, in-focus image, important for the placement of imaging sensors or film in engineering systems. Focal plane is situated in the object or image space, perpendicular to the principal axis at the focal point. It is the position where incoming light is brought to focus, placing a sensor (like in a camera or telescope) here ensures maximum sharpness.
Focal point – It is the specific, precise location on the optical axis where parallel light rays converge (focus) or appear to diverge from after passing through a lens or reflecting off a mirror. It is a fundamental parameter in optics for designing imaging systems, laser devices, and telescopes, defining where the maximum beam intensity or image sharpness is achieved.
Focal point position – It is the precise spatial location where rays (light, laser, or sound) converge or appear to diverge after passing through an optical element, such as a lens or mirror. It is defined by the distance from the optical system’s principal plane, with the focal length determining this distance for objects at infinity. It is the location where the sensor is placed, determined by the lens curvature and focal length, ensuring light from distant objects converges for a sharp image.
Focal position – It is the specific axial location where light rays (or energy) converge to a point of maximum intensity after passing through a lens or reflecting off a mirror. It defines the distance from the optical element to the point of minimum spot size, crucial for focus, imaging, and material interaction. It is the point where parallel incoming rays converge, normally denoted on the principal axis.
Focal spot – It is that area on the target of an X-ray tube which is bombarded by electrons.
Focal surface – It is defined as the locus of the centres of principal curvature (or focal points) of a given surface. It is basically the envelope of the normals to a surface, frequently representing the evolute or surface of centres. Focal surfaces are extensively used for surface modeling, quality analysis, and optical system design to determine how a surface twists and bends.
Focus – It is a point at which rays originating from a point in the object converge or from which they diverge or appear to diverge under the influence of a lens or diffracting system.
Focus blur – It refers to a type of blurring which occurs when parts of a scene are out of focus during the capture of a 3D image to a 2D image. This results in a reduction of clarity in the image.
Focus depth – It is also called depth of focus (DOF). It is the allowable tolerance of placement of the image-capturing plane (sensor or film) along the optical axis, without the image appearing blurred. It measures how much the image sensor can be moved toward or away from the lens while maintaining an acceptable level of sharpness.
Focused image – It is the image formed at a specific distance behind the second principal plane of a lens, where the detector array senses the image sharply without defocus blur, corresponding to the object’s distance from the first principal plane of the lens.
Focused improvement – It refers to a structured, team-based approach aimed at eliminating specific, high-priority losses (such as defects, downtime, or inefficiencies) in equipment, processes, or production lines to achieve zero-loss operations. It is an improvement strategy based on the theory of constraints. Attention is focused on addressing one limiting factor, called a constraint, at a time in order to optimize a system. Each constraint is improved until it no longer limits the system’s performance. As a core pillar of ‘total productive maintenance’ (TPM), frequently referred to as Kobetsu Kaizen, it involves using data-driven tools like 5-why Analysis and PM (phenomenon-mechanism) analysis to identify and remove root causes of metallurgical process variability.
Focused ion beam – It is a maskless, high-precision instrument used for micro / nano-machining, imaging, and deposition. It works by accelerating a focused ion beam, typically gallium (Ga+), to sputter (remove) or deposit materials on a sample surface, allowing for site-specific editing and cross-section analysis at the nano-scale.
Focused ion beam (FIB) technology – It is a scientific technique which uses a focused, high-energy beam of ions, normally gallium (Ga+), to perform site-specific ablation (milling), deposition, and imaging of materials at the nano-scale. Operating as a vacuum-based, destructive, and ultra-precise tool, focused ion beam is mainly used for failure analysis, cross-sectioning, and circuit modification in semiconductors, as well as TEM (transmission electron microscopy) sample preparation.
Focused laser beam – It is a highly concentrated, coherent, and monochromatic light beam reduced to its minimum diameter (spot size) using optics, producing maximum power density at the focal point. It is important for precision engineering tasks like cutting, welding, and marking by concentrating energy, frequently to a spot size comparable to the wave-length of the light.
Focused observation – It is a systematic, goal-oriented process of watching and documenting specific activities, behaviours, or technical processes to assess performance, verify compliance with standards, or identify improvement opportunities. Unlike general observation, this technique concentrates on a pre-identified high-risk, high-frequency, or critical area to collect actionable, often quantitative, data.
Focused programme – It involves strategically coordinating related projects to achieve overarching organizational goals. It defines clear objectives, maps dependencies, and aligns stakeholder expectations to ensure collective project outputs generate superior value compared to individual management. This structure boosts efficiency, mitigates risks, and drives long-term strategic transformation. It ensures all projects align with organizational goals and objectives, delivering high-level benefits rather than just individual project outputs.
Focused spot size – It refers to the minimum diameter (d) a laser beam or wave reaches at the focal plane (beam waist), where energy is highly concentrated. It is typically defined as the diameter containing 86.5 % (1/e-square) of the total beam power. 1/e-square describes the width where intensity drops to (around 13.5 %) of the peak intensity, encompassing 86.5 % of total power.
Focused testing – It is a targeted, frequently gray-box methodology that assesses specific components or functionalities based on technical requirements and internal knowledge. It isolates modules to verify correct operation, such as user workflows, API (application programming interface) calls, or specific code units, ensuring high-quality deliverables by limiting scope to key requirements, rather than the entire system.
Focus function – It is also called focus measure. It is an algorithm or criterion used in automated imaging systems to determine the optimal image sharpness by calculating gradients or statistical measures from image data. It evaluates the image quality, frequently using edge gradient methods to find the maximum contrast, allowing autofocus systems to adjust lens position for maximum sharpness. It is a numerical measure of the ‘sharpness’ or focus quality of a digital image or optical system, typically peaking when the image is in sharp focus.
Focusing (X-rays) – It is the operation of producing a convergent beam in which all rays meet in a point or line.
Focusing attention – It is the process of scheduling the activation of information sources, both external and internal, to concentrate on specific goals, such as updating beliefs about target hypotheses. This process economizes data acquisition and allows reasoning activities to be limited to a manageable subset of knowledge, hence optimizing computational efficiency.
Focusing device (electrons) – It is a device which effectively increases the angular aperture of the electron beam illuminating the object, rendering the focusing more critical.
Focus-to-object distance (FOD) – In optical systems, it refers to the distance between the point where light converges (the focus) and the object being imaged. It is also sometimes referred to as the source-
to-object distance (SOD) in the context of X-ray imaging. Essentially, it is the distance at which an object needs to be placed relative to a lens or mirror to be sharply focused.
Fog – It is a collection of water droplets or ice crystals suspended in the air at or near the earth’s surface. While fog is a type of a cloud, the term ‘fog’ is typically distinguished from the more generic term ‘cloud’ in that fog is low-lying and the moisture in the fog is frequently generated locally (such as from a nearby body of water).
Fog computing – It is a decentralized infrastructure which extends cloud computing to the network edge, distributing computing, storage, and networking services closer to data sources. It acts as an intermediate layer between IoT (internet of things) devices and the cloud, reducing latency, improving security, and optimizing bandwidth for real-time applications.
Fog level – It defines the density of condensed water droplets or ice crystals suspended in the air near the ground, specifically measured to assess its impact on visibility and driving safety.
Fog quenching – It is also known as mist quenching or spray quenching. It is a specialized heat treatment process where a heated metal work-piece is cooled using a finely atomized mixture of water droplets and high-velocity air (or other gases). This method provides a cooling rate which is intermediate between oil quenching and air cooling, offering a high degree of control over the cooling process to minimize distortion and cracking while achieving high strength.
Foil – It is a very thin, flexible sheet of metal produced by rolling or hammering, typically with a thickness of less than 0.15 millimeter thick. Foils are made from malleable metals, very frequently aluminum, copper, or tin, and are used extensively for packaging, industrial insulation, and electrical applications because of their, light weight, and, in some cases, reflective properties.
Foil, annealed It is that foil which has been completely softened by thermal treatment.
Foil bearing – It is a bearing in which the housing is replaced by a flexible foil held under tension against a partition of the journal periphery, lubricant being retained between the journal and the foil.
Foil, bright two sides – It is the foil which is having a uniform bright specular finish on both sides.
Foil butt-seam welding – It is a resistance welding technique where a narrow metal foil strip is fed on one or both sides of two butt-jointed sheets as they pass between rotating electrode wheels. The foil acts as a filler and current conductor, producing a flush, high-strength seam, frequently used for coating-preserving, thin-gauge, large-panel fabrication.
Foil, chemically cleaned – It is the foil which is chemically washed to remove lubricant and foreign material.
Foil, embossed – It is the foil on which a pattern has been impressed by means of an engraved roll or plate.
Foil, etched – It is the foil which has been roughened chemically or electro-chemically to provide an increased surface area.
Foil, hard – It is the foil which has been fully work hardened by rolling.
Foil, intermediate temper – It is the foil which is intermediate in temper between annealed foil and hard foil.
Foil (film) lamination – It is an industrial process in which decorative foils are bonded to substrate materials in order to improve their appearance and feel.
Foil, matte one side (M1S) – It is the foil with a diffuse reflecting finish on one side and a bright specular finish on the other.
Foil, mechanically grained – It is the foil which has been mechanically roughened for such applications as lithography.
Foil, mill finish (MF) – It is the foil which is having a non-uniform finish which can vary from coil to coil and within a coil.
Foil, scratch brushed – It is the foil which is abraded, normally with wire brushes, to produce a roughened surface.
Foil stock – It is a semi-finished rolled product of rectangular cross section in coiled form suitable for further rolling.
Foil thickness – It is normally defined as a thin-rolled metal sheet, typically aluminum, with a thickness of 0.2 millimeters or less. It is defined by its minimal gauge, normally ranging from 0.006 millimeters to 0.15 millimeters, and serves as a barrier to light, moisture, and gases.
Fokker bond tester – It is a widely used industrial non-destructive testing (NDT) instrument which uses low-frequency ultrasonic resonance (30 kilo-hertz to 1,000 kilo-hertz) to detect voids, disbonds, and evaluate the cohesive quality of adhesive joints. It operates by analyzing shifts in resonant frequency and amplitude, and it is capable of measuring adhesive bond strength, particularly in composite structures.
Fokker-Planck equation – It is a linear partial differential equation (PDE) which describes the time evolution of the probability density function of a system’s position or velocity under the influence of deterministic drag (drift) and random forces (diffusion), normally modeling Brownian motion and Markov processes. It is widely used to calculate how the statistical properties of a stochastically forced system change over time.
Fold – It is a defect in metal, normally on or near the surface, caused by continued fabrication of overlapping surfaces. It is a forging defect caused by folding metal back onto its own surface during its flow in the die cavity. In mining, fold is the bending or wrinkling of rock strata.
Fold axis – It is a theoretical line that, when moved parallel to itself, generates the shape of a folded rock layer. It represents the line of maximum curvature and serves as the hinge line around which folding occurs. In geology, it is used to define fold orientation, plunge, and structural trends for stability analysis.
Foldback current limiting – It is a protection technique in power supplies which reduces both output current and voltage simultaneously when an overload or short circuit occurs. It protects the series pass transistor from overheating by minimizing power dissipation during faults, reducing the current to a safer, lower level than the maximum output.
Fold defect – It is a surface discontinuity which occurs when metal surfaces overlap and unite, but do not weld together during forging, casting, or rolling processes. Frequently caused by uneven metal flow, it manifests as a ‘cold shut’ or crease, frequently trapping oxide scale, reducing surface quality and structural integrity.
Folding frequency – It is also called Nyquist frequency. It is defined as half the sampling rate (fs/2) of a discrete system. It represents the maximum frequency a sampled system can reproduce without aliasing (error). Frequencies above this point ’fold’ back and appear as lower-frequency aliases in the spectrum.
Folding mirror – It is a planar (flat) mirror used in optical engineering to redirect light paths, allowing long optical paths to fit within compact, smaller physical volumes. Frequently set at 45-degree to redirect light by 90-degree, they are normal in systems like Newtonian telescopes, periscopes, and infrared imaging.
Folding operation – It is a shaping process which involves applying a bending force to a flat sheet (typically metal, paper, or plastic) to create a permanent crease, angle, or complex structural shape along a defined line. It is a form of plastic deformation which changes the shape of a material into a folded configuration.
Folias factor – It is a parameter used to account for the effects of defect geometry on the stress concentration in pipes, calculated using specific equations that relate the defect length and wall thickness.
Follow board – In foundry practice, it is a board contoured to a pattern to facilitate the making of a sand mould.
Follow die – It is a progressive die consisting of two or more parts in a single holder. It is used with a separate lower die to perform more than one operation (such as piercing and blanking) on a part in two or more stations.
Follower – It is an extension used between the pile and the hammer which transmits blows to the pile when the pile head is either below the reach of the hammer (below the guides / leads) or under water. A follower is normally a section of pipe or ‘H’ pile with connections which match both the pile hammer and the pile.
Follower load – It is a force which changes its direction and / or magnitude as the structure deforms, always remaining tangent to the deformation curve or perpendicular to a moving surface. Unlike fixed loads, it acts as a ‘deformation-dependent’ load. In finite element analysis (FEA), this is achieved by selecting ‘follow nodal rotation’, where the load rotates with the node.
Follower plate – It is a plate fitted to the top surface of a grease dispenser.
Font – It is a digital data file containing a set of graphically styled characters, letters, numbers, symbols, and glyphs, used to display text. It defines the specific typeface, weight (e.g., bold), and size of text, allowing users to alter the appearance of documents. Common formats include TrueType and PostScript, enabling scalable text display.
Font size – It is the vertical measurement of characters (typically points, 0.35 millimeters) displayed on screen or printed, defining how large text appears. It is used to adjust readability and visual hierarchy in documents, web design, and system interfaces, normally adjusted through settings for accessibility or design.
Food-to-micro-organism (F/M) ratio – In the waste-water treatment, it is a key parameter representing the quantity of food (measured as bio-chemical oxygen demand, chemical oxygen demand, or total organic carbon) relative to the mass of micro-organisms (typically measured as mixed liquor suspended solids, or mixed liquor volatile suspended solids) in an activated sludge system. It essentially indicates how much ‘food’ is available for the micro-organisms to consume in a given time.
Footbridge – It is a specialized structure designed for pedestrian and cyclist traffic, enabling them to safely cross obstacles like highways, railways, or waterways. Engineered with a focus on human-induced dynamic loads rather than heavy vehicle traffic, these structures need analysis of vibration, stiffness, and structural, aesthetic, or material innovation.
Footprint – It normally refers to the environmental impact, resource consumption, or physical space occupied by metallurgical processes (extraction, refining, alloying) and the resulting products. It is normally used to quantify sustainability, covering the entire lifecycle from raw material extraction to final production. Key types of footprints are carbon footprint, water footprint, material footprint, energy footprint, and pollution / chemical footprint.
Footprint family – It refers to a complex system of different sustainability metrics, including carbon, ecological, water, energy, land, nitrogen, and material footprints, which collectively address a wide range of sustainability issues but cannot fully capture the complexity of the entire family.
Foot control – It is a foot-operated mechanism designed to activate, control, or modulate industrial machinery, allowing the operator to keep their hands free for manipulating the work-piece. It is frequently used in welding, cutting, press operating, and shearing to improve efficiency and safety.
Foot correction – The sample is placed in the grips and is secured by closing the grips. If preload is to be removed before the test is started, it is to be physically unloaded by moving the loading mechanism. The zero adjustment is never to be used for this purpose. In some cases, preload can be desirable and can be deliberately introduced. For materials for which the initial portion of the curve is linear, the strain zero can be corrected for preload by extending the initial straight portion of the stress-strain curve to zero load and measuring strain from that point. The strain valve at the zero-load intercept is normally called the ‘foot correction’ and is subtracted from readings taken from strain scale.
Foot pedal – It is a foot-operated lever or switch used to control machinery, allowing the operator to keep both hands free for maneuvering, holding, or positioning the work-piece. Foot pedals are important components in industrial processes such as welding, bending, shearing, and punching. They provide a safe and ergonomic method for controlling machinery, frequently offering variable control over speed, power, or pressure depending on how far the pedal is depressed.
Foot step bearing – It is also known as pivot bearing. In this bearing the bearing pressure is exerted parallel to the shaft whose axis is vertical. It is to be noted that in this case the end of the shaft rests within the bearing.
Foot switch – It is normally an electrical switch. It is simply a device which opens or closes an electrical circuit. It is operated by an operator by stepping on the actuator, which is typically a push-button or a pedal. The advantage of using a foot switch is simply that it frees up the operator’s hands for other work while still allowing the operator’s full control over switching. It is a rugged, pedal-operated electrical controller used to initiate machinery processes, such as pressing, shearing, or welding, while allowing the operator to keep both hands free for material handling. They act as a ‘dead man’s switch’ in forming and metalworking, improving safety by needing continuous pressure or acting as an emergency stop.
Foot valve – – It is also known as a bottom valve. It is a specialized type of non-return check valve installed at the intake end (or ‘foot’) of a pump suction pipe, typically submerged in a tank, well, lake, or pit. It plays an important role in preventing backflow when the pump is turned off, ensuring the suction pipe remains filled with liquid, which keeps the pump primed and ready for immediate restart.
Footwall – It is the rock which is on the underside of a vein or ore structure.
Force – It is an influence which can push or pull an object to change its motion. A force can cause an object with mass to change its velocity (e.g., moving from a state of rest), i.e., to accelerate. A force has both magnitude and direction, making it a vector quantity. It is also the male half of the mould which enters the cavity, exerting pressure on the resin and causing it to flow. It is also called punch. It is an external agent or interaction applied to a metallic body which causes a change in its state of rest, motion, or deformation. In the context of metal processing, forces are necessary for changing the material’s shape, size, or internal structure, typically through methods such as compression, tension, or shear.
Force balance principle – It is a mechanism where an imbalance in input forces (such as pressure) is countered by a feedback force, establishing an equilibrium which keeps a system stable, normally used in pneumatic controllers and pressure regulators to maintain precise output. It ensures that the output is directly proportional to the input, allowing automatic adjustments.
Force boundary conditions – These refer to the constraints applied to a material that involve surface traction and loads, which can be either distributed or concentrated, influencing the stress development during processes such as forging. These conditions are necessary for modeling the interaction between external forces and the material’s response, particularly in scenarios involving volumetric changes.
Force coefficient – It is a dimensionless number which quantifies the force exerted on an object (such as drag or lift) relative to dynamic pressure and a reference area. It measures the efficiency of an object’s shape in a fluid flow, defined as ‘C = F/(P x A)’, where ‘F’ is the force, ‘P’ is dynamic pressure, and ‘A’ is area.
Force control – It is a technology used in automated processes, such as welding, grinding, or polishing, to regulate the quantity of downward or lateral force applied by a tool, rather than solely controlling its position. It allows a machine, frequently a robot, to adapt in real-time to material inconsistencies or complex, curved geometries.
Forced-air quench – It is a quench utilizing blasts of compressed air against relatively small parts such as a gear.
Forced / assisted circulation boiler – The density difference between the saturated liquid and saturated vapour starts diminishing at 18 MPa or higher fluid pressure, hence, it is difficult to maintain natural circulation of fluid flow in boiler tubes. In such cases fluid flow is ensured with the help of forced / assisted circulation using pumps. The forced / assisted circulation principle applies equally in both super-critical and sub-critical ranges.
Forced cavity – It is frequently referred to as a die cavity or mould cavity. It is a recessed or hollow shape within a die or mould, into which material is forced under high pressure to form a specific, intricate part. This technique is used to create the desired final shape of a product, particularly in die casting, forging, and powder metallurgy.
Forced circulation – It is the circulation of water in a boiler by mechanical means external to the boiler.
Forced circulation boiler – It is a type of boiler where a pump is used to circulate water through the heating tubes. This contrasts with natural circulation boilers, which rely on density differences created by heating the water to circulate it. The pump ensures a constant and controlled flow of water, which can be beneficial in several applications.
Forced continuous mode – It is also called forced continuous conduction mode (FCCM). It is a technique which forces a switching converter (like a buck or boost regulator) to operate in continuous conduction mode (CCM) regardless of the load current. Unlike natural continuous conduction mode, which transitions to discontinuous conduction mode (DCM) under light loads, forced continuous conduction mode forces the inductor current to continue flowing, even if it becomes negative, to maintain a fixed switching frequency and reduce output ripple.
Forced continuous conduction mode – It is a power supply operating mode where the inductor current is forced to flow continuously, never falling to zero, even under light loads. Unlike standard continuous conduction mode (CCM), forced continuous conduction mode (FCCM) allows the current to become negative, re-injecting energy into the input to maintain a fixed switching frequency and reduce output voltage ripple.
Forced convection – It is a heat transfer mechanism where an external agent, such as a fan, pump, or blower, artificially moves a fluid (gas or liquid) over a metal surface to accelerate heating or cooling rates. This technique is necessary in controlling heat treatment, quenching, and annealing processes, providing higher heat transfer coefficients than natural convection.
Forced convection heat transfer – It is the process of moving a fluid (gas or liquid) over a metal surface using external means, fans, blowers, or pumps, to rapidly transfer heat. This technique considerably increases the cooling or heating rate of metals compared to natural convection, important for high-speed quenching, annealing, and heat treating to achieve specific microstructures.
Forced-draft burners – These are the burners in which the oxidizer is supplied to the burner under pressure. As an example, in a forced-draft air burner, the air used for combustion is supplied to the burner by a blower. Forced draft burners can control the combustion of all gaseous fuels and liquid fuels. There are burners which use only one family of fuel (liquid or gaseous) and while there are also burners which can use both the fuels. Such burners are called ‘dual fuel’ (double fuel) burners. Hence, there are three classes of burner. Forced draft burners can also be classified according to the type of construction, namely (i) monobloc burners, and (ii) separate fired burners. In monobloc burners, the fan and pump are an integral part of the burner forming a single body. In separate fired burners, the fan, pump and / or other fundamental parts of the burner are separate from the main body (head). Monobloc burners are those burners which are normally used in output ranges varying from tens of kilowatts to several megawatts output. For higher outputs, or for special industrial processes, separate burners are used.
Forced-draft cooling tower – It is a mechanical draft cooling system which uses a blower fan located at the air intake (bottom or side) to push air into the tower. This pressurized air travels upward through the fill media, improving evaporation and heat transfer before exiting at the top.
Forced draft fan – It is a centrifugal blower which pushes fresh air into a combustion chamber (like a boiler or furnace) to provide the necessary oxygen for fuel combustion. Positioned at the inlet, they create positive pressure to ensure efficient, consistent burning, frequently used for furnace draft, industrial ventilation, and drying systems.
Force decay – It refers to the gradual loss of force, tension, or repulsive strength in a material or system over time, frequently because of the stress relaxation or environmental degradation.
Force delivery – It refers to the mechanism, path, or method by which a specific load, action, or energy is transferred, applied, or transmitted to a component or system.
Force density method – It is a structural engineering technique used to determine the equilibrium shape of cable nets, membrane structures, and grid-shells. By setting the ratio of tensile force to length (q = F/L) for each element, it transforms non-linear equilibrium equations into a linear system, making the finding of complex, bending-free shapes computationally efficient and robust.
Forced expression – It refers to something which is produced with substantial effort, strain, or pressure, resulting in an unnatural, insincere, or artificial appearance or sound. It is a display of emotion, such as a smile, laugh, or tone of voice, which does not happen naturally, spontaneity, or genuinely.
Forced oscillations – These are vibrations which occur when an external, periodic driving force acts on a system, compelling it to vibrate at the frequency of that force rather than its own natural frequency. These oscillations maintain a constant amplitude by offsetting damping forces with continuous external energy input.
Forced vibration – It is the oscillation of a system, such as a bridge, machine, or building, caused by an external periodic force applied continuously. Unlike free vibration, the system vibrates at the frequency of the external force, not its own natural frequency.
Forced vortex – It is a type of fluid flow where the entire fluid mass rotates at a constant angular velocity, similar to a rotating solid body, driven by an external torque. Unlike a free vortex, tangential velocity in a forced vortex increases linearly with radius, with maximum velocity at the periphery.
Force-feed lubrication – It is a system of lubrication in which the lubricant is supplied to the bearing under pressure.
Force generation – It is the process of creating, applying, or transmitting an intentional mechanical action (push or pull) to cause, change, or stop motion, or to deform an object. It is a vector quantity defined by magnitude and direction, frequently involving mechanisms which convert energy into useful mechanical output.
Force generator – It is a device or mechanism designed to produce a specific force or torque, frequently independent of the movement of the system it acts upon. Common examples include electromagnetic transducers (e.g., actuators, moving-coil devices) where force is generated by the interaction of current and a magnetic field.
Force law – It refers to the mathematical relationships which describe the forces acting on a particle, which can be calculated based on the properties of the particle and its environment, including laws such as gravity and empirical laws for solids and fluids.
Force loop – It is a closed-loop control mechanism which maintains a desired force or torque output by continuously measuring actual load using sensors and calculating a correction signal to eliminate errors. It is frequently used for control-loading in actuators and robotics to regulate precise physical interactions.
Force majeure – It is a common clause in contracts which essentially frees both parties from liability or obligation when an extraordinary event or circumstance beyond the control of the parties, such as a war, strike, riot, crime, epidemic, or sudden legal change prevents one or both parties from fulfilling their obligations under the contract. Force majeure frequently includes events described as an act of God, though such events remain legally distinct from the clause itself. In practice, most force majeure clauses do not entirely excuse a party’s non-performance but suspend it for the duration of the force majeure.
Force method – It is also called flexibility method. It is a structural analysis technique used to solve statically indeterminate structures by identifying redundant forces. It breaks the structure into a stable, determinate ‘primary structure’ and uses compatibility equations to ensure deflections match the original structure, making it ideal when degrees of freedom are low.
Force model – It defines the interaction between objects as a push or pull, acting as an external agent which causes mass to accelerate, deform, or change motion. Modeled as a vector quantity, it has magnitude, direction, and a specific point of application, typically represented by Newton’s second law (F = m x a).
Forces and fluxes – These refer to the relationship between the movement of materials (flux) and the net forces driving this movement, with flux being defined as the flow of material per unit area which varies linearly with the applied force. This concept applies to different types of transport, including heat, electrical current, and solute diffusion.
Forces applied during bending – These forces are in opposite directions, just as in cutting of sheet metal. The bending forces, however, are spread farther apart, resulting in plastic distortion of metal without failure.
Forces between colloidal particles – These refer to the interaction forces which influence the stability, rheology, and overall behaviour of suspensions and emulsions, depending on factors such as surface charge properties and the dispersing medium. These forces are important in determining material properties and are studied through different theoretical and experimental methods.
Force sensitivity – It defines a sensor’s ability to detect and quantify mechanical loads (pressure, tension, or compression) by converting them into electrical signals. It represents the ratio of electrical output change (e.g., resistance) to input force, typically utilizing piezo-resistive, strain gauge, or piezo-electric effects to monitor, control, or measure physical interaction. It is frequently quantified as the change in resistance (dR) relative to the initial resistance (Ri) or the sensitivity coefficient, where a higher ratio indicates higher sensitivity.
Force sensor – It measures the force at the tool and provides feedback to the controller to make adjustments. Example is a six-axis force / torque sensor.
Force signal – It is a time-varying, measurable quantity (normally an electrical voltage or current) which represents the magnitude, direction, and dynamics of a physical push or pull applied to an object. It serves as an important data stream for monitoring mechanical interactions, such as stress, cutting forces, torque, or vibration, in processes like machining, and structural testing. Force signals convert physical forces (tensile, compressive, shear, or torsional) into data which can be analyzed to evaluate the state of a system, such as tool wear in machining or structural integrity.
Force transducer – It is a sensor which converts mechanical input, such as tension, compression, load, or torque, into a proportional, measurable electrical signal. It utilizes internal elements like strain gauges or piezo-electric materials to detect deformation or stress, translating it into voltage or resistance changes for accurate force quantification.
Force transmissibility – It is the ratio of the amplitude of force transmitted to a supporting foundation (Ft) to the amplitude of the exciting force (Fo) applied to a system. It is an important, dimensionless parameter in mechanical engineering vibration isolation measuring how much vibrational energy passes through an isolator to the structure. Force transmissibility evaluates the effectiveness of vibration isolation mounts, such as rubber or springs, in protecting supporting structures from machine vibration.
Force transmission – It refers to the process where a force, torque, or power generated at one point is conveyed to another point within a system, frequently involving mechanical, hydraulic, or pneumatic components. It encompasses how loads are transferred through structures, machines, or materials. It is governed by Newton’s laws of motion, where internal forces (stress) propagate through deformable bodies.
Force variation – It refers to the periodic fluctuations in force, torque, or moments acting on a component, typically a rotating tyre / wheel assembly, caused by structural, material, or manufacturing irregularities. These variations, frequently measured as radial (up / down) or lateral (side / side) forces, lead to ride disturbances, vibrations, and diminished performance.
Force vector – It is a mathematical representation of a force, defined by both magnitude (strength) and direction in space, important for analyzing loads on structures in engineering mechanics. It is represented as a vector ‘F’ with components, most commonly in Cartesian coordinates as Fx, Fy, Fz, frequently measured in Newtons.
Force-velocity relationship – It is an engineering and physiological principle stating an inverse, curvilinear relationship where higher contraction velocities limit muscle force production, while lower velocities allow maximum force output. Characterized by Hill’s equation, this trade-off is important for modeling actuator performance, robotic design, and human motion optimization.
Forchheimer equation – It is a mathematical representation which relates flow rates in porous media to pressure differentials, incorporating both Darcy’s law and non-Darcy flow effects. It can be expressed in terms of empirical constants and reservoir parameters, facilitating the estimation of flow characteristics within a reservoir.
Forchheimer law – It is an equation which describes fluid flow through porous media at high velocities, where inertial forces become substantial. It extends Darcy’s law by adding a quadratic velocity term to account for non-linear pressure drops caused by turbulence or inertia, important for modeling flow in porous materials, high-rate filtration, and reservoir engineering.
Forcing amplitude – It defines the maximum strength of an external periodic force applied to an oscillating system, governing the magnitude of forced vibrations. It directly dictates how far the system moves from equilibrium, where higher forcing amplitude results in higher oscillation displacement, provided damping is low.
Forcing frequency – It is the rate (hertz) at which an external periodic force or vibration is applied to a mechanical system, forcing it to oscillate at that specific rate rather than its natural frequency. It is an important concept used for analyzing vibrations, designing structures to avoid resonance, and managing machinery load.
Forcing function – It is a design feature or constraint which prevents unintended actions by needing a specific, conscious action before proceeding. It enforces safety, compliance, or correct process flow, frequently preventing human error by breaking the automation of dangerous or incorrect behaviours.
Forecast – It is the definite statement or statistical estimate of the likely occurrence of a future event or conditions for a specific area. It is a prediction or estimation of future product demand in the market based on available information.
Forecasting network – It is the process of predicting future system conditions (e.g., traffic, energy load) by analyzing historical data, flow, and utilization metrics, typically using machine learning or statistical methods. It enables proactive management of network performance and resource optimization. It consists of active monitoring and anticipation of future network states, such as node popularity, link formation, and traffic congestion, to improve ’quality of service’ (QoS). It is mainly used for capacity planning, energy load balancing, and optimizing operational resources in dynamic environments.
Foreground detection – It is a fundamental computer vision and video processing task which identifies and extracts moving objects (foreground) from a static or dynamic background in a sequence of images. It acts as a primary preprocessing step for high-level tasks such as object tracking, recognition, and surveillance, and is mainly achieved through background subtraction techniques. Foreground detection aims to classify pixels into either foreground (moving objects) or background (static scene). Engineering-wise, this is normally accomplished through a multi-stage approach:
Foreground object – It involves identifying, extracting, and modeling meaningful visual data (objects, people, or motion) which differs from the static background. It utilizes techniques like background subtraction, thresholding, and morphological operations (opening / closing) to distinguish subjects from scenes, important for surveillance, tracking, and video compression. Foreground objects are the main, frequently moving, subjects in a scene which capture attention, distinct from the stationary or back-ground elements.
Fore-hand welding – It is a welding technique in which the welding torch or gun is directed toward the progress of welding.
Forehearth – It is a specialized, forward-extended section of a smelter hearth which serves as a reservoir for molten metal or slag. It acts as a transitional, accessible chamber, frequently located under the tymp-arch, allowing for continuous separation, sampling, and tapping of liquid products from the furnace. It holds molten materials (iron or slag) to allow for separation of materials and facilitates the removal of refined molten metal from the main furnace body. In a glass melting furnace, forehearth is a component of the melting furnace which facilitates the controlled flow and cooling of molten glass from the furnace to the forming area, allowing for the consistent processing of glass.
Foreign body – It refers to any unwanted, non-homogeneous inclusion, particle, or contaminants (such as ceramic, dirt, or different metal) present within a metal alloy or on its surface. These impurities originate from external sources during manufacturing, processing, or casting, and they can considerably weaken the metal’s structure, causing stress concentrations or failures. Foreign bodies enter the material during smelting, pouring, or casting (e.g., refractory lining debris, tool fragments, oxide inclusions).
Foreign material – It refers to an unwanted substance or object not part of the intended metal composition, introduced during melting, casting, or processing. These contaminants, such as refractory debris, slag, metallic fragments, or tooling debris, impair structural integrity and cause foreign object damage (FOD).
Foreign object damage – It refers to the physical damage, deformation, or material degradation of components caused by the impact of, or ingestion of, extraneous material (foreign object debris). It manifests as denting, cracking, or surface disruption resulting from debris colliding with metal surfaces.
Foreign structure – It is a metallic structure which is not intended as part of a cathodic protection system of interest.
Foreign substrate – It is a base material upon which a thin film or coating is deposited, which differs in chemical composition and / or crystal structure from the material being grown. Unlike native substrates (where the substrate and growing layer are the same material), foreign substrates are used for heteroepitaxy to reduce costs, increase size, or add functionality.
Foreman – Foreman is a person in charge of a particular department, group of workers, etc., as in a factory or the like. Foreman is a skilled person with experience who is in charge of and supervises over a group of workers.
Foreman equation – It is a mathematical model in fracture mechanics and metallurgy used to predict the rate of fatigue crack growth (da/dN) in materials, particularly when the stress intensity factor range (delta K) approaches the material’s fracture toughness (Kc). It improves upon the Paris law by accounting for the accelerating crack growth rate caused by higher stress ratios (R) and the proximity to critical fracture toughness.
Forensic metrology – Forensic metrology is the application of measurements and hence measurement standards to the solution and prevention of crime. It is practiced within the laboratories of law enforcement agencies throughout the world.
Foreseeable future – It is the period of time which a project can make a reasonable projection of the occurrence of future conditions, events, or other factors which determine the environmental-socio-economic viability or technical feasibility of the project.
Forest – It consists of a dense growth of trees and underbrush covering a large tract. It is an ecosystem characterized by a dense community of trees.
Forest land – It refers to land mainly covered by trees and other vegetation, frequently with a dense growth of trees and undergrowth. It encompasses several types of forested areas. It can range from dense, old-growth forests to more open woodlands.
Forest products laboratory (FPL) etch – It is a widely used chemical surface treatment for aluminum to prepare it for adhesive bonding. It utilizes a solution of sulphuric acid, sodium di-chromate, and water, typically at 71 deg C for 10 minutes to 30 minutes, to clean and create a durable, receptive oxide layer for bonding. It is used to remove surface contaminants and create a porous, high-surface-area oxide layer, which considerably improves the strength and durability of adhesively bonded aluminum joints.
Forgeability – It is the term used to describe the relative ability of material to deform without fracture. It also describes the resistance to flow from deformation.
Forgeability ratings – These define the relative ease with which a metal or alloy can be shaped through compressive forces, such as hammering, pressing, or rolling, without developing cracks, surface defects, or internal fractures. It is a critical manufacturing property that indicates a material’s plasticity and deformation behaviour under specific temperature and strain rate conditions.
Forgeability tests – These tests measure a metal’s ability to undergo plastic deformation under compression (forging) without cracking or creating surface / internal defects. These tests determine optimal temperature ranges, strain rates, and pressure limits for forming alloys, frequently evaluated by measuring deformation limits before failure. Key forgeability test methods are upsetting test (compressive test), hot twist test, hot-impact tensile test, and hot compression test (Gleeble simulation).
Forge bonding – It is a solid-state joining process which unites two metal pieces by applying heavy pressure and frictional heat, without melting the materials into a liquid state. Frequently classified as a type of friction welding, it works by plastically deforming (softening) the metals at the interface to create a high-strength bond that is typically stronger than the base materials themselves.
Forge casting – it is also known as liquid metal forging or squeeze casting. It is a casting process by which molten metal (ferrous or nonferrous) solidifies under pressure within closed dies positioned between the plates of a hydraulic press.
Forged components – These are metal parts manufactured by shaping solid metal (billets or ingots) through localized compressive forces, typically using hammers, presses, or dies. This process improves structural integrity by refining the metal’s internal grain structure to match the part’s contour, resulting in superior strength, toughness, and fatigue resistance compared to casting or machining.
Forged rib – It is a thin, wall-like, or brace-like projection which projects outward from a web (a relatively flat part) of a forged component. They are integral features formed during the closed-die forging process, normally to provide structural rigidity, strength, or to act as fastening points.
Forged rolls – These are high-performance cylindrical tools used in rolling mills, manufactured by shaping alloy steel ingots through intensive compressive force, typically through hydraulic presses or hammer forging. Unlike cast rolls, forged rolls are worked in a solid or semi-plastic state, which eliminates internal voids and segregations, resulting in a refined, dense grain structure with superior toughness, fatigue resistance, and wear resistance.
Forged roll Scleroscope hardness number (HFRSc or HFRSd) – It is a number related to the height of rebound of a diamond-tipped hammer dropped on a forged steel roll. It is measured on a scale determined by dividing into 100 units the average rebound of a hammer from a forged steel roll of accepted maximum hardness.
Forged steel rolls – These rolls are made by forging. The forged steel rolls contain less carbon compared to cast steel rolls since high carbon content can cause cracks during the forging process. The structure of the forged steel rolls is denser than that of cast steel rolls and hence is tougher and can take more loads. However, because of the lower carbon content the hardness is low and more prone to wear than cast steel rolls. These rolls are primarily used where they have to withstand high loads as in blooming mills or in heavy section mills. Forged and hardened rolls are also used as back-up rolls in 4-high mills although normally alloy cast steel rolls are used for back-up.
Forged structure – It is the macro-structure through a suitable section of a forging which reveals direction of working.
Forge rolling – It is also called roll forging. It is a longitudinal hot-metal process which reduces the cross-sectional area of heated bars or billets using specially designed rotating roll segments. Frequently called reducer rolling, it uses notched rolls to shape metal, mainly as a high-efficiency preforming step to create tapered or varied cross-sections before final die forging.
Forge welding – It is solid-state welding in which metals are heated in a forge (in air) and then welded together by applying pressure or blows sufficient to cause permanent deformation at the interface.
Forging – It is the process of working metal to a desired shape by impact or pressure in hammers, forging machines (upsetters), presses, rolls, and related forming equipment. Forging hammers, counter-blow equipment, and high-energy-rate forging machines apply impact to the work-piece, while majority of the other types of forging equipment apply squeeze pressure in shaping the stock. Some metals can be forged at room temperature, but majority are made more plastic for forging by heating. Specific forging processes include closed-die forging, high-energy-rate forging, hot upset forging, isothermal forging, open-die forging, powder forging, precision forging, radial forging, ring rolling, roll forging, rotary forging, and rotary swaging. In powder metallurgy, forging is the process of placing a powder in a container, removing the air from the container, and sealing it. This is followed by conventional forging of the powder and container to the desired shape.
Forging alloys – These are metals (such as steel, aluminum, titanium, or copper) combined with other elements, shaped through localized compressive forces, hammering or pressing, to achieve high-strength, durable components with refined, oriented grain flow. Typically done hot, this process eliminates porosity and improves mechanical properties compared to casting.
Forging billet – It is a wrought metal slug used as forging stock.
Forging, blocker-type – It is a forging made in a single set of impressions to the general contour of a finished part.
Forging, cold-coined – It is a forging which has been restruck cold to get closer dimensions, to sharpen comers or outlines, and in non-heat-treatable alloys, to increase hardness.
Forging defects – These are structural or surface imperfections in metal components which arise during plastic deformation, rendering them substandard because of improper heating, poor die design, or improper cooling. Key defects include cracks, unfilled sections, laps, die shifts, and internal flakes.
Forging design – It is the process of creating detailed specifications for metal components shaped through compressive force (hammering or pressing), normally while heated. It focuses on optimizing the part’s geometry, incorporating draft angles, parting lines, and fillet radii, to ensure proper material flow, superior grain structure strength, and manufacturability.
Forging dies – These are forms for making forgings. They normally consist of a top and bottom die. The simplest is which forms a completed forging in a single impression. The most complex, consisting of several die inserts, can have a number of impressions for the progressive working of complicated shapes. Forging dies are normally in pairs, with part of the impression in one of the blocks and the rest of theimpression in the other block.
Forging difficulty – It is frequently quantified as a complexity factor or forgeability rating. It refers to the measure of effort, needed force, and metallurgical challenges involved in shaping a specific material into a desired form without producing defects. It is not a single property, but a composite evaluation involving material properties (plasticity, flow stress), part geometry (intricacy, thin sections), and process parameters (temperature, friction).
Forging, draft-less – It is a forging with zero draft on vertical walls.
Forging envelope – It is the quantity of excess metal surrounding the intended final configuration of a formed part. It is sometimes called forging envelope, machining allowance, or cleanup allowance. It is also the quantity of stock left on the surface of a casting for machining.
Forging equipment – It comprises industrial machinery and tools used to plastically deform metal into specific shapes through localized compressive forces, typically using hammers, presses, or rolling machines. Engineered to improve grain flow and structural integrity, this equipment handles materials, normally steel or alloys, at high hot-forging temperatures or room-temperature cold forging, frequently including heating furnaces and dies.
Forging, flash-less – It is a closed-die forging made in dies constructed and operated to eliminate, in pre-determined areas, the formation of flash.
Forging force – It is the compressive force, pressure, or impact applied to a metal work-piece to plastically deform it into a desired shape. It is exerted by tools like hammers, presses, or upsetters to refine the material’s microstructure, improving strength and durability. The force needed is influenced by material temperature, deformation speed, and friction.
Forging-grade billet or bar stock – It refers to high-quality, semi-finished solid metal forms (typically steel, aluminum, or titanium) specially produced for subsequent hot or cold forging. These materials are designed to be malleable when heated and have low defect levels, allowing them to be shaped under high-compressive forces into high-strength, fatigue-resistant finished parts.
Forging hammers – These are industrial machines which utilize high-energy, rapid impact blows, rather than sustained pressure, to deform and shape heated metal (hot forging) or, less commonly, cold metal. They consist of a ram, anvil, and die, delivering, typically 1 meter per second to 1.5 meters per second, to force metal into a die cavity. Common types include gravity drop, steam, and pneumatic power hammers.
Forging, hand – It is a forging which has been worked between flat or simply shaped dies by repeated blows. It is a manual, specialized form of forging process where a blacksmith uses hand tools, such as hammers and anvils, to shape heated metal.
Forging heat – It refers to the high temperatures, typically 50 % to 75 % of a metal’s melting point, used in hot forging to make material plastic and pliable for shaping. It exceeds the material’s recrystallization point (frequently up to 1,250 deg C for steel), allowing for lower shaping forces, improved ductility, and grain structure refinement.
Forging ingot – It is a cast metal slug used as forging stock.
Forging-limit diagrams – These diagrams are frequently referred to in the context of forging limit criteria. These are graphical tools used to determine the maximum quantity of deformation a metal can withstand during a forging process before failure, typically in the form of cracking or fracturing. They are important for designing dies and selecting process parameters to prevent defects like internal cracks or flash line cracks.
Forging lubricants – These are specialized chemical compounds applied to dies and work-pieces to reduce friction, wear, and heat transfer during the shaping of metal under high compressive forces. They are important to the forging process as they ensure smooth metal flow, improve surface quality, prevent sticking (parting agent), and extend the lifespan of expensive forging dies.
Forging, no-draft – It is a forging with zero draft on vertical walls.
Forging machine (upsetter or header) – It is a type of forging equipment, related to the mechanical press, in which the main forming energy is applied horizontally to the work-piece, which is gripped and held by prior action of the dies.
Forging-machine dies – These are specialized, high-strength tool steel moulds used in industrial forging to shape metal blanks (billets) into specific components under high compressive forces. These dies, either open (flat) or closed (impressed cavity), control metal flow to refine microstructure, improve grain structure alignment, and enhance strength.
Forging machines – These are industrial equipment used to plastically deform metal into specific shapes using compressive forces, such as hammers, presses, and upsetters. These machines apply high-pressure, localized forces, frequently with heated metal, to improve grain structure, increase strength, and produce durable, high-reliability components.
Forging materials – These are ductile metals and alloys shaped into high-strength, durable components using compressive forces like hammering, pressing, or rolling. These materials, typically heated (hot forging) or worked at room temperature (cold forging), have their grain structure aligned to the part’s shape, improving toughness, ductility, and resistance to fatigue.
Forging methods – These methods range from manual smith-forging to industrial techniques like open-die, closed-die, and roll forging, performed hot or cold.
Forging mode – It refers to the specific technique, temperature, and equipment used to apply compressive force to a metal blank (billet or ingot) to plastically deform it into a desired shape. The choice of forging mode dictates the part’s final properties, including grain structure, strength, and dimensional precision. Forging modes are mainly classified by temperature, die usage, and equipment.
Forging of rings – it is also called ring forging. it is a process which shapes metal into hollow circular or cylindrical forms using localized compressive forces. This manufacturing technique is designed to produce high-strength, durable, and reliable parts, with a particular emphasis on creating a continuous, superior grain structure. Forging of rings involves manipulating heated metal into a ring shape through hammering, pressing, or rolling. The process is frequently performed hot (at or near recrystallization temperatures). The process typically begins with upsetting a billet to improve structural integrity, followed by piercing a hole in the centre to create a donut-shaped blank, and finally, ring rolling or expanding.
Forging parameters – These are the controllable variables which dictate material deformation, micro-structure, and component quality. Key parameters include forging temperature (hot, warm, cold), strain rate, forging force and pressure, friction and lubrication, die design and pre-heat, and material properties. These factors determine forgeability, metal flow, and the prevention of defects like cracks.
Forging plane – It is a reference plane or planes normal to the direction of applied force from which all draft angles are measured. It is the plane which includes the main die face and which is perpendicular to the direction of ram travel. When parting surfaces of the dies are flat, the forging plane coincides with the parting line.
Forging, precision – It is a forging produced to tolerances closer than standard.
Forging, press – It is a die forging produced by pressure applied in a forging press.
Forging pressure – It is the compressive force, either exerted gradually by a press or through repeated impact by a hammer, applied to a metal work-piece to plastically deform it into a desired shape. It forces the material to fill die cavities (closed die) or flow (open die), increasing strength, density, and grain refinement.
Forging process – It is a fundamental manufacturing process which shapes metal using localized compressive forces, applied through hammers, presses, or rolling machines. It is a process which transforms raw material (billets or ingots) into durable, high-strength components by refining the metal’s internal grain structure to follow the shape of the part. Different forging processes are closed die forging, open die forging, hot forging, cold forging, upset forging, isothermal forging, precision forging, drop forging, ring forging, and roll forging.
Forging process variables – These are the controllable parameters, including material characteristics, temperature, tooling, friction, and deformation rates, which dictate the final geometry, microstructure, mechanical properties, and quality of a metal component. Forging involves controlling plastic deformation through pressure or impact to rearrange the metal’s internal grain structure.
Forging quality – Forging quality of a metal or an alloy means that the metal or alloy has a good ‘forgeability’. The term ‘forgeability’ is defined here as the tolerance of a metal or alloy for deformation without failure, regardless of forging-pressure requirements. Majority of the metals and alloys can be classified into one of three groups namely (i) showing good forgeability, (ii) showing poor forgeability, and (iii) showing variable forgeability. All metals and metal alloys, with very few exceptions, are suitable are suitable for forging.
Forging quality stainless steel – It is a corrosion-resistant iron-based alloy with 10.5 % chromium and above, specifically produced with high purity to withstand compressive shaping at high temperatures (1,035 deg C to 1,260 deg C) without cracking. It offers improved structural integrity, refined grain flow, and superior strength compared to casting, ideal for high-pressure components.
Forging quality steel – It is a high-purity, specialized grade of carbon or alloy steel designed to withstand intense, compressive plastic deformation (hot or cold working) without cracking or creating internal defects. It features precise chemical composition control, high toughness, superior structural integrity, and reduced internal flaws like pipe or segregation. These steels have a good ‘forgeability’. These are the steels which are used for open forging, die forging and upsetting operations. In these steels, gas content and inclusions are controlled.
Forging range – It is the temperature range in which a metal can be forged successfully.
Forging reduction ratio – It is also called forging ratio. It is a measure of plastic deformation intensity, defined as the ratio of the initial cross-sectional area to the final cross-sectional area of a workpiece. It is used to calculate grain refinement, density increase, and defect removal, typically calculated as initial cross-sectional area / final cross-sectional area or final length /initial length.
Forging, rolled ring – It is a cylindrical product of relatively short height, circumferentially rolled from a hollow section.
Forging rolls – These are power-driven rolls which are used in pre-forming bar or billet stock which have shaped contours and notches for introduction of the work.
Forgings – These are metal components shaped through localized compressive forces, hammering, pressing, or rolling, normally while heated (hot forging), though sometimes done cold. This process refines the metal’s grain structure, increasing strength, density, and fatigue resistance compared to cast or machined parts. Common products include gears, shafts, and fasteners.
Forging schedule – It is frequently termed a ‘pass schedule’ or forging sequence’. It is a structured, step-by-step plan which outlines the sequential deformation process, heating parameters, and manipulation techniques used to shape a metal billet into a final, high-strength component. It bridges metallurgical design with operational execution, focusing on achieving precise geometry, grain flow refinement, and desired mechanical properties while managing energy consumption and material limits.
Forging schedule development – It is the strategic planning process which defines the specific sequence of operations, heating, deformation, and cooling, needed to transform a metal blank into a high-strength finished part with needed grain structure, dimensional accuracy, and mechanical properties. This process is critical for producing durable components in industries such as aerospace, automotive, and heavy equipment.
Forging sequencing – It is the planned, progressive series of deformation steps (forming strokes or blows) used to transform a raw material, such as a billet or ingot, into a final complex shape. It is an important aspect of closed-die and open-die forging which optimizes material flow, ensures complete die filling, minimizes defects, and controls grain structure.
Forgings, hammer – These are forgings produced by repeated blows in a forging hammer.
Forging simulation – It is a computer-aided engineering (CAE) technique which uses numerical methods, mainly finite element method’ (FEM), to virtually model, visualize, and predict the behaviour of a metal work-piece during forging operations. It enables engineers to simulate thermo-mechanical phenomena, such as deformation, stress, temperature distribution, and microstructural changes, to optimize tool design and process parameters before physical production.
Forging stock – It is a wrought rod, bar, or other section suitable which is for subsequent change in cross section by forging.
Forging temperatures – These temperatures define the specific range at which a metal becomes soft and malleable, typically 70 % to 90 % of its absolute melting point, allowing shaping without cracking. Hot forging occurs above the recrystallization temperature (around 0.6 of melting point), while cold forging happens below this threshold.
Forging temperature ranges – These temperatures are defined based on the metal’s recrystallization temperature, which dictates its ability to deform plastically without cracking. Hot forging, the most common type, occurs above the recrystallization temperature (typically 0.6 times to 0.9 times the melting point in Kelvin), making the metal soft and malleable, while cold forging occurs at or near room temperature. Forging temperatures are classified in three ranges. In hot forging, material is heated above recrystallization temperature to reduce deformation resistance and improve ductility. Typically, these temperatures are in the range of 650 deg C to 1,300 deg C depending on the alloy. Warm forging is performed at intermediate temperatures, frequently 0.3 times to 0.5 times the melting point. Typically, these temperatures are in the range of 600 deg C to 900 deg C for steel, offering a balance between ductility and precision. Cold forging ids performed at or near room temperature (below 0.3 times the melting point), relying on high pressure, frequently resulting in strain hardening.
Forging tolerances – These are the permissible variations in dimensions, shape, and weight of a forged component relative to its design specification. They represent the maximum allowable deviation from the nominal size, necessitated by process variables like metal shrinkage, die wear, and forging equipment limitations. These tolerances ensure that parts fit securely in assemblies, maintain functionality, and allow for efficient machining.
Forging tool – It is equipment used to plastically deform heated or cold metal into specific shapes using compressive forces. These tools, including dies, hammers, and presses, operate under high thermal and mechanical loads to improve material strength, toughness, and grain structure.
Forging, upset – It is a forging which is having part or all of its cross section higher than that of the stock.
Forging with advanced titanium materials – It is a sophisticated manufacturing process that uses high-temperature, compressive forces to shape high-performance titanium-aluminum-vanadium alloys, such as Ti-6Al-4V, Ti-6Al-4V ELI (extra low interstitials), and beta alloys, into complex, high-strength components. This metallurgical process aims to refine the material’s grain structure to improve fatigue resistance and structural integrity for critical applications, frequently achieving superior strength-to-weight ratios compared to steel.
Forklift trucks – These are material handling equipments. They are the most commonly used industrial lift trucks. It is a powered industrial lift truck equipped with lifting media made up of a mast and elevating load carriage. It is a vehicle drawn or propelled by mechanical, or electrical power, designed incorporating a powered lift principally to lift, carry or stack goods by means of (i) a fork consisting of one or more arms which support the load, (ii) a platform, or (iii) any attachment or other mechanism. Forklift truck consists of variety of components needed to handle the task effectively. These components range from truck frame, power source to counterweight and are essential for the forklift to function efficiently. Forklift trucks are the workhorses of material handling because of their flexibility which include (i) indoor / outdoor operation over a variety of different surfaces, (ii) availability with a variety of load capacities, and (iii) availability with a variety of attachments.
Formability – It is the ease with which a metal can be shaped through plastic deformation. Evaluation of the formability of a metal involves measurement of strength, ductility, and the quantity of deformation needed for causing fracture. The term workability is used interchangeably with formability, however, formability refers to the shaping of sheet metal, while workability refers to shaping materials by bulk forming.
Formability analysis – It is the systematic evaluation of a material’s capability to be deformed into a desired shape without failure (tearing or wrinkling). It quantifies safe operating zones using parameters like ‘forming limit diagrams’ (FLD), strain hardening, and anisotropy to predict defects in stamping or deep drawing processes.
Formability limit – It defines the maximum strain (stretching or drawing) a metal sheet can undergo without failing by localized necking or tearing. Mainly represented by ‘forming limit curves’ (FLCs), it maps the boundary between safe, uniform deformation and failure (fracture or necking) under varying stress conditions like biaxial tension.
Formability testing of sheet metals – It defines the capability of a metal sheet to undergo plastic deformation, such as stretching, drawing, or bending, into a desired 3D shape without cracking, tearing, or excessive thinning. These tests establish ‘forming limit diagrams’/ ‘forming limit curves’ (FLC / FLD) to optimize manufacturing, reduce defects, and select materials.
Formaldehyde – It is an organic compound with the chemical formula CH2O and structure H−CHO, more precisely H2C=O. The compound is a pungent, colourless gas that polymerizes spontaneously into paraformaldehyde. It is stored as aqueous solutions, which consists mainly of the hydrate CH2(OH)2. It is a colourless chemical with a strong pickle-like odour which is normally used in several manufacturing processes. It easily becomes a gas at room temperature, which makes it part of a larger group of chemicals known as volatile organic compounds (VOCs).
Formaldehyde emission – It refers to the release of formaldehyde gas (CH2O) into the atmosphere during specific metallurgical processes, particularly those involving binders, resins, or high-temperature processing of metals. It is a colourless, pungent, and carcinogenic gas generated either directly from materials or as a by-product of incomplete combustion and chemical reactions.
Formaldehyde levels – These levels refer to the concentration of formaldehyde gas (CH2O) released during industrial metalworking processes, particularly when using specific types of binders, lubricants, or coatings that contain phenolic or urea-based resins. It is often released during high-temperature operations, such as casting or welding, acting as a volatile organic compound (VOC).
Formaldehyde removal – It refers to the separation, adsorption, or catalytic destruction of formaldehyde (HCHO) gas from emission streams to meet environmental regulations, protect workers, and manage toxic, flammable by-products generated by industrial processes. Common applications involve treating air pollution, cleaning gas streams in manufacturing, and managing waste streams produced during chemical processes, such as in the creation of binders for foundry sands.
Formaldehyde resins – These are synthetic thermosetting polymers, mainly phenol-formaldehyde (PF) or urea-formaldehyde (UF), created by condensing formaldehyde with phenol, urea, or melamine. These resins are used as high-strength, heat-resistant binders for sand casting, mould making, and producing foundry cores because of their superior bonding and thermal stability. These are utilized in the ‘shell mould’ process, where they bind sand particles to create precise moulds for casting metal components.
Formal communication – It is the official, structured exchange of information within an organization, following predefined channels and protocols, such as vertical hierarchies. It prioritizes accuracy, authority, and documentation, using professional language for tasks like memos, reports, and meetings, ensuring accountability and preventing misunderstandings.
Formal methods – These are mathematically rigorous techniques used in system engineering for the specification, design, and verification of software and hardware systems. These methods apply mathematical modeling, frequently using predicate calculus and set theory, to define and verify that system requirements are unambiguous, correct, and consistent. By proving correctness at every stage, these methods provide a formal, systematic alternative to ad-hoc, test-based development, mitigating risks in safety-critical systems.
Formal report – It is a structured document which presents the findings of a study, including sections such as a cover page, executive summary, table of contents, methodology, and findings, aimed at conveying information clearly and effectively to a specified audience. It is an official document which analyzes complex technical information, research, or design projects to inform decision-making. It uses an objective tone, standardized formatting, and detailed evidence (data, charts, calculations) to address specific problems for stake-holders.
Formal safety assessment – It is a structured, systematic, and proactive methodology used to evaluate risks, improve safety, and ensure regulatory compliance. Mainly used in high-risk industries, it combines hazard identification, risk analysis, and cost-benefit analysis to make informed decisions.
Formal standards – These standards are published by the national standardization organizations, regional standardization organizations (e.g. CEN, CENELEC etc.), and international standardization organizations (e.g. ISO, IEC etc.). There are around 160 national standardization organizations which are members of ISO (the International Organization for Standardization).
Formal technical review – It is a structured software quality assurance activity where technical staff examine software artifacts, such as requirements, design, or code, to detect errors, verify compliance with standards, and ensure quality. It is a planned meeting designed to identify functional / logical issues early, improving product consistency and reducing later-stage defects.
Formal training – It refers to a structured, planned, and methodical educational process designed to impart specific technical competencies, theoretical knowledge, and practical skills. It is typically conducted by qualified trainers within institutions or through organization-led programmes, characterized by predefined curricula, assessments, and certifications.
Formation compressibility (Cf) – It is a reservoir property defined as the fractional change in a formation’s pore volume (Vp) per unit change in pressure (P), expressed as Cf = 1/Vp (dVp/dP). It represents how rock porosity and volume contract as production reduces pressure. Formation compressibility measures the relative change in pore volume divided by the change in reservoir pressure.
Formation energy – It is the energy difference between a compound or defect and its constituent elements in their most stable, reference states. It is a critical engineering metric used to predict thermodynamic stability (lower / negative values mean higher stability) and is frequently calculated in density functional theory (DFT) studies.
Formation factor – It is a dimensionless parameter defined as the ratio of the electrical resistivity of a porous material (like concrete or rock) saturated with a conductive fluid to the resistivity of the pore solution itself. It quantifies the microstructure’s pore network, specifically its connectivity and tortuosity, independent of the fluid’s resistivity.’
Formation fluids – These are naturally occurring liquids (oil, water) or gases (methane, carbon di-oxide) contained within the pore spaces of underground geological formations. They are distinct from drilling fluids (mud) introduced during well construction and are defined by their pressure, density, and viscosity, which dictate flow behaviour during drilling, testing, and production.
Formation linear flow – It is a reservoir flow regime where fluid streamlines are parallel and orthogonal to a hydraulic fracture or linear boundary, causing pressure derivative plots to show a + 1/2 slope. Normal in unconventional, fractured reservoirs, it indicates flow from the matrix towards a fracture or along a channel.
Formation material – It refers to naturally occurring, solid materials, such as sand, silt, clay, or rock fragments, generated during drilling processes, rather than in a dissolved state. It represents the native geological substance, such as in soil formation (parent material) or oil / gas production, where it forms distinct, mappable rock layers.
Formation permeability – It is the capability of a porous rock layer to transmit fluids (such as oil, gas, or water), representing the ease with which fluids pass through interconnected pores. It is an intensive property measured in Darcy (D) or millidarcy (mD), influenced by pore structure, connectivity, and whether the rock is fractured.
Formation pore pressure – It is the pressure exerted by fluids (water, oil, or gas) contained within the pore spaces of subsurface rock formations. It is an important parameter in drilling engineering which supports part of the overburden stress and is to be managed to ensure wellbore stability.
Formation pressure – It is the pressure exerted by fluids (water, oil, or gas) contained within the pore spaces of subsurface rock formations. It is an important parameter in drilling engineering, frequently measured as the shut-in bottom-hole pressure. Formation pressure supports part of the rock’s overburden stress.
Formation resistivity factor (F) – It is the ratio of a porous rock’s electrical resistivity when fully saturated with a conductive fluid (Ro) to the resistivity of that fluid (Rw). It is a dimensionless parameter mainly representing the influence of pore structure, tortuosity, and porosity on conductivity, independent of the brine conductivity. It is an intrinsic property of a porous medium which indicates the efficiency of electrolyte-filled paths to conduct electrical current, calculated as the ratio of the resistivity of brine-saturated rock to that of saturated brine. It is influenced by factors such as rock porosity, pore structure, and pore size distribution, with values always higher than 1.
Formation temperature – It is the undisturbed temperature of rock and fluids (oil, gas, water) within a subsurface reservoir, important for petroleum engineering, logging, and heat flow studies. It is normally calculated based on depth and geothermal gradient, typically rising as depth increases, and is frequently estimated from maximum borehole temperatures. It dictates reservoir fluid properties, fracture pressure, and chemical reaction rates (e.g., in polar / non-polar compound studies).
Formation volume factor – It is the ratio of the volume occupied by a fluid phase at reservoir conditions to the volume occupied by the same fluid phase at surface conditions, with variations influenced by changes in pressure, temperature, and composition.
Formation water – It is the naturally occurring water trapped within the pore spaces of sedimentary rocks. It is found in subterranean geological formations, frequently in close association with oil and gas, and is typically highly saline brine, distinguished from surface water. When brought to the surface during petroleum extraction, it is referred to as produced water
Form block – It is the tooling, normally the male part, which is used for forming sheet metal contours. It is normally used in rubber-pad forming.
Form cutter – It is a cutter which is profile sharpened or cam relieved, shaped to produce a specified form on the work.
Form, crystals – Crystals are composed of molecules, atoms, or ions arranged in an orderly, repetitive, three-dimensional array or space lattice. The distances between constituent units within crystals of a given substance are fixed and characteristic of that material. Under ideal growth conditions, this gives rise to reproducible and well-defined crystal shapes. Crystals forming freely from solution appear as polyhedrons bounded by planar faces. For a given material, although the angles between the crystal faces remain constant, the space lattice allows for variation in the relative sizes of the faces. Hence, variation in crystal habit can be observed between individual crystals of a particular substance.
Form defects – These are incomplete / improper macroscopic metal flow leading to improper shape / size of the defects. They are mostly macroscopic with both of process related origin and metallurgical origin.
Form dies – These are dies which are used to change the shape of a sheet metal blank with minimal plastic flow.
Form-drag – It is also known as pressure drag. It is the aerodynamic or hydrodynamic resistance force caused by the shape of an object moving through a fluid. It arises from a pressure difference between the high-pressure front and low-pressure wake (flow separation) behind the body. It is heavily dependent on shape (bluntness) and is reduced by streamlining. It is caused by the separation of the fluid’s boundary layer from the object’s surface, creating a wake of low pressure and reduced flow.
Form-drag coefficient (Cd) – It is a dimensionless number which quantifies the resistance an object experiences because of its shape and size when moving through a fluid. It specifically represents the pressure differential between the front and rear of the body caused by flow separation. It is defined in the drag equation as ‘Cd = 2Fd/(D x v-square x A), relating drag force (Fd) to fluid density (D), velocity (v), and reference area (A).
Formed austenite – It is the austenite formed because of the phase transformation of iron into austenite (gamma phase) during heating processes, characterized by carbon concentration which can exceed equilibrium levels, particularly occurring at ferrite / cementite interfaces or within pearlite colonies. Its formation is influenced by diffusion mechanisms and the carbon content, which is critical for determining the transformation start temperature.
Formed member – It refers to a structural component created by shaping metal (normally steel) at room temperature, known as cold-formed, or through specialized molding processes. These members are characterized by their thin-walled, lightweight nature, high strength-to-weight ratio, and precise dimensional flexibility, making them ideal for modern construction.
Formed refractories – These are those refractories which are manufactured by firing or chemical bonding methods. The fired refractory material is formed by heating the refractory material to a high temperature in a kiln to form a ceramic bond. This process makes the raw material fire-resistant. Chemically bonded refractory bricks are formed with the help of selected additives which solidify at room temperature and provide structural integrity without the need for high-temperature sintering. By eliminating the need for high-temperature processing, considerable energy savings can be achieved. In addition, several methods of changing chemical bonds can develop new compositions to withstand the harsh environments found in several industrial processes.
Formed steel – It is the cold-formed steel (CFS) which is a structural material manufactured by bending thin-gauge steel sheets, strips, or plates at ambient temperatures (cold working) using roll-forming machines or press brakes. Cold-formed steel products are normally thin-walled, lightweight, and durable, normally used for structural framing, joists, and decking in construction. Unlike hot-rolled steel, cold-formed steel is formed without heat. This allows for higher precision, tighter tolerances, and improved strength through strain hardening (work hardening).
Formed steel structural members – These are cold-formed steel (CFS) structural members which are thin-walled, high-strength building components manufactured by bending flat steel sheets, plates, or strips at room temperature using press-braking or roll-forming. These versatile members provide a high strength-to-weight ratio for applications like studs, joists, and decking.
Formed steel structures – These are specifically cold-formed steel (CFS) which are construction frameworks created by bending thin steel sheets or coils into shapes (C, Z, or decks) at ambient temperatures. They are lightweight, high-strength members used mainly for wall studs, floor joists, and trusses.
Form expression – It defines a mathematical statement, equation, or logical rule used to model relationships between variables, calculate values, or represent system behaviour. These expressions combine constants and variables (x, y, t) using operations like addition, multiplication, or division to represent physical quantities.
Form grinding – It is the grinding with a wheel having a contour on its cutting face which is a mating fit to the desired form.
Formic acid (HCOOH) – It is a colourless, fuming liquid (methanoic acid) with a strong odour, functioning as a key chemical reagent. It is the simplest carboxylic acid, acting as a strong reducing agent and acid used in metallurgy for surface treatment, specifically in electroplating as a component of electrolyte solutions, and in chemical cleaning for removing metal oxide deposits. It helps in depositing metal coatings and in descaling mineral deposits.
Formic acid corrosion – It refers to the degradation of metals and alloys, particularly stainless steels, copper, and nickel-based alloys, caused by exposure to formic acid (HCOOH). As the simplest carboxylic acid, it is a highly corrosive and reducing organic acid which causes substantial uniform corrosion, especially in concentrated forms (above 50 %) and at high temperatures.
Forming – It is making a change, with the exception of shearing or blanking, in the shape or contour of a metal part without intentionally altering its thickness. It is also the plastic deformation of a billet or a blanked sheet between tools (dies) to get the final configuration. Metal-forming processes are typically classified as bulk forming and sheet forming. It is also being referred to as metal-working. Forming is also a process in which the shape of plastic pieces such as sheets, rods, or tubes is changed to a desired configuration. The use of the term forming in plastics technology does not include such operations as moulding, casting, or extrusion, in which shapes or pieces are made from moulding materials or liquids. In powder metallurgy, forming is a generic term describing the first step in changing a loose powder into a solid of specific configuration.
Forming alloying elements -These are metallic or non-metallic elements intentionally added to a base metal to improve its properties, such as strength, hardness, corrosion resistance, or toughness. These elements (e.g., carbon, chromium, and nickel) modify the base metal’s microstructure through solid solution strengthening or forming new phases.
Forming die – It consists of a pair of mating members (punch and die) which deform a material, typically sheet metal, using pressure applied by a press ram. Forming dies are specialized, high-precision tools used in press working to permanently reshape sheet metal through plastic deformation (bending, stretching, or drawing) without removing material. They are important for shaping metal sheets into 3D, complex, or contoured parts by utilizing the material’s ductility.
Forming direction – It refers to the specific orientation along which a metal work-piece is shaped, stretched, or compressed during manufacturing processes such as rolling, forging, or extrusion. It is a critical aspect of metalworking because the plastic deformation process induces anisotropy, meaning the metal’s mechanical properties, such as tensile strength and ductility, become directional rather than uniform throughout the material.
Forming gas anneal – It is a specialized heat treatment where metal or electronic components are heated in a mixture of hydrogen (H2) and nitrogen (N2), typically around 5 %, to prevent surface oxidation while reducing existing oxides. It creates a bright, corrosion-free finish, removes impurities, and aids in passivating surface defects in semi-conductors.
Forming limit curve – It is a graphical representation of the maximum quantity of deformation a sheet metal can withstand before it starts to fracture or neck (a localized thinning) during a forming process. It essentially defines the boundary between safe and failure regions in a forming operation.
Forming limit diagram – It is a diagram in which the major strains at the onset of necking in sheet metal are plotted vertically and the corresponding minor strains are plotted horizontally. The onset-of-failure line divides all possible strain combinations into two zones namely the safe zone (in which failure during forming is not expected) and the failure zone (in which failure during forming is expected).
Forming machine – It is a specialized piece of industrial equipment which shapes metal work-pieces through plastic deformation, a permanent change in shape, without adding or removing material (i.e., no chips are produced). These machines apply controlled mechanical, hydraulic, or pneumatic force to exceed the yield strength of the metal, altering its shape while maintaining its total mass.
Forming method – It is a manufacturing process which shapes a solid body (normally metal) through plastic deformation without adding or removing material, keeping the overall mass consistent. It involves applying external force (tensile, compressive, bending, or shearing) to exceed the material’s yield strength.
Forming of steel strip in multiple-slide machines – It is a process in which the work-piece is progressively formed in a combination of units which can be used in different ways for the automated fabrication of a large variety of simple and intricately shaped parts from coil stock or wire. It is an automated, high-speed process which progressively shapes steel strip or wire into complex parts using a central post and four slides. It combines straightening, blanking, embossing, and bending into one cycle, ideal for complex, high-volume production of parts up to around 200 milli-meters wide.
Forming of stainless-steel sheet – It is the process of shaping thin, flat pieces of stainless steel (typically 0.5 milli-meters to 6 milli-meters thick) into desired shapes through mechanical deformation at room temperature (cold forming) or high temperature. Forming of stainless-steel sheet frequently needs higher force than carbon steel because of stainless steel’s high strength, work-hardening, and spring-back characteristics. Common techniques include bending, deep drawing, and rolling, utilizing techniques like press brake bending and stamped dies to produce durable, corrosion-resistant components like kitchen sinks and auto panels.
Forming of titanium and titanium alloy sheet – It is the process of shaping metal sheets into components, mainly using hot forming (up to 925 deg C) to improve ductility, manage severe spring-back, and prevent cracking because of the metal’s high notch sensitivity. It involves processes like bending, drawing, and superplastic forming. Titanium and its alloys can be formed in standard machines to tolerances similar to those obtained in the forming of stainless steel. However, to reduce the effect of spring-back variation, improve accuracy, and to gain the advantage of increased ductility, the great majority of formed titanium parts are made by hot forming or by cold preforming and then hot sizing.
Forming of wire – It is a metal fabrication process which shapes metal wire (from coils or blanks) into custom components like clips, springs, and hooks using bending, cutting, and coiling, mainly through CNC (computer numerical control) machines. It is a cold-working process, frequently distinguished from wire drawing, used to create complex, precise 3D shapes for different industries.
Forming polymers – It refers to the processes used to shape, mould, or structure polymer materials (plastics, rubbers, resins) into final products. It involves transforming raw polymer resin, frequently using heat or chemical reactions, into functional shapes through methods like extrusion, injection moulding, or compression moulding, tailoring the material’s properties for specific applications.
Forming process – It is a manufacturing process which shapes metal parts through mechanical deformation (plastic deformation) rather than removing material (machining). It involves applying forces, such as compression or tension, which exceed the material’s yield strength, forcing it to take the shape of a tool or die while keeping its total mass constant.
Forming processes – Among all manufacturing processes, metal forming processes have a special place since it helps to produce parts of superior mechanical properties with minimum waste of material. In metal forming, the starting material has a relatively simple geometry. The material is plastically deformed in one or more operations into a product of relatively complex configuration. Forming to near-net or to net-shape dimensions drastically reduces metal removal requirements, resulting in considerable material and energy savings. Key processes include deep drawing, stretch forming, and incremental sheet forming (ISF), where the material is subjected to plastic deformation while maintaining its mass. Metal forming processes are normally classified as per two broad categories namely (i) bulk, or massive, forming operations, and (ii) sheet-forming operations. In the broadest and most accepted sense, however, the term forming is used to describe bulk forming as well as sheet-forming processes. In both types of processes, the surfaces of the deforming metal and the tools are in contact, and friction between them can have a major influence on material flow. In bulk forming, the input material is in billet, rod, or slab form, and the surface-to-volume ratio in the formed part increases considerably under the action of largely compressive loading. In sheet forming, on the other hand, a piece of sheet metal is plastically deformed by tensile loads into a three-dimensional shape, frequently without considerably changes in sheet thickness or surface characteristic.
Forming processes for sheet, strip, and plate – These forming processes involve shaping or cutting metal sheets, strips, or plates (typically below 6 milli-meters thick) using tools like punches and dies, frequently in a press. These methods include bending, deep drawing, and shearing to create precise, frequently complex, parts from metal which retains a constant thickness.
Forming processes of superplastic sheet – Superplastic forming (SPF) is a specialized sheet forming process, frequently using titanium or aluminum, where material is heated to a high temperature (above 500 deg C) and slowly shaped into complex geometries using gas pressure, achieving over 500 % elongation. It is widely used in several industries to produce low-volume, high-precision, lightweight panels with minimal spring-back.
Forming processes, statistical analysis – Statistical analysis is heavily utilized in the field of forming processes, focusing on ‘statistical process control’ (SPC) to monitor consistency and prevent defects like tearing and wrinkling, particularly in high-volume production.
Forming sequence – It refers to a planned, chronological series of manufacturing steps, such as in forging, rolling, or bending, designed to transform a raw material into a final component. It optimizes technical and economic factors like material flow, energy consumption, and tool life while ensuring volume consistency. It consists of the systematic arrangement of individual forming processes to produce a high-quality part efficiently, frequently involving modeling and simulation to optimize the process chain. In forging, this sequence includes steps like preforming, blocking, and finishing, intended to maintain volume constancy and achieve the desired shape.
Forming species – It refers to the particles, including neutral atoms, ions, and reactive gas molecules, which contribute to the deposition of films during processes such as sputtering. Their energy and composition considerably influence the properties of the resulting films.
Forming speed – It describes the rate or velocity at which a piece of metal is deformed (reshaped) during processing. It is a key factor in determining the quality and efficiency of the forming operation. Frequently defined as the speed of the ram in a press or die, it is normally expressed in units like per second (strain rate) or velocity units. High forming speeds (high strain rates) normally increase the flow stress (higher resistance to deformation) and can cause adiabatic heating (local temperature rise).
Forming surface – It refers to the precise specification, design, and generation of a component’s outer boundary through plastic deformation processes, such as bending, drawing, or stamping. These processes aim to produce specific shapes without removing or adding material, frequently needing comprehensive knowledge of material properties to ensure accuracy and functionality.
Forming technology – It is a manufacturing process which reshapes solid materials, mainly metals, using compressive, tensile, or bending forces to create desired shapes without removing material (maintaining mass). It uses plastic deformation, frequently through tools like dies and presses, to alter geometry, improve structural strength, and refine material properties, encompassing bulk forming and sheet metal forming.
Forming temperature – It refers to the temperature at which a metal is deformed, directly impacting its ductility, flow stress (strength), and workability. It determines whether the process is classified as hot, warm, or cold, primarily based on the metal’s recrystallization temperature (Tr), which normally ranges between 0.3 Tm and 0.6 Tm (where Tm is the melting point).
Forming tool – It is a device (punch, die, or mould) used to plastically deform materials, mainly metals, into a desired shape by applying pressure without cutting away material. Forming tools are important in manufacturing to create 3D forms, contours, or bends in sheet metal, typically leaving the shape of the die / punch on the work-piece.
Forming zone – It is also called deformation zone. It is the specific, localized region within a work-piece where material undergoes permanent plastic deformation during manufacturing processes like rolling, extrusion, or drawing. It is the critical area where applied forces, such as compression or tension, change the material’s shape without material removal.
Form parameter – It involves selecting and quantifying specific variables (e.g., dimensions, material properties, process settings) which dictate the performance and characteristics of a product, system, or model. These parameters are crucial for optimizing output, controlling quality, and ensuring stability. These are frequently defined in Computer-aided design (CAD) / finite element method (FEM) models for simulation or as operational settings, such as machining speeds or tolerances.
Form poly-silicon – It refers to the process of producing polysilicon granules from silane gas (SiH4) in a fluidized bed reactor (FBR), where the silane is dissociated and deposited onto seed particles, resulting in the growth of larger poly-crystalline structures suitable for silicon crystal manufacturing.
Form-relieved cutter – It is a cutter so relieved that by grinding only the tooth face of the original form is maintained throughout its life.
Form resistance – It is the component of total viscous resistance caused by the shape (form) of a body, specifically because of the pressure difference between the fore and aft sections. It arises from flow separation and vortex generation around curved or blunt shapes, which prevents pressure recovery at the stern, thus increasing drag beyond simple skin friction. It is part of the “viscous pressure resistance,” representing energy lost to eddies and vortices rather than skin friction.
Form rolling – It is the hot rolling to produce bars having contoured cross sections. It is not to be confused with roll forming of sheet metal or with roll forging.
Form tolerance – It is a ‘geometric dimensioning and tolerancing’ (GD&T) concept which defines the allowable deviation of a feature’s shape from its theoretically perfect geometry (e.g., straightness, flatness, roundness). It controls individual features without needing datums. Key types include flatness, straightness, circularity, and cylindricity, ensuring parts fit and function properly, particularly for assembly.
Formula – It is a mathematical rule or expression relating variables to quantify physical systems and solve technical challenges. These equations model relationships to evaluate designs, ensure safety, and predict performance in disciplines like mechanics and structural analysis. Formulas provide a consistent method for calculating unknown values from known parameters, transforming theoretical concepts into practical, actionable data.
Form voids – These refer to defects within a crystal which occupy a volume, typically arising from the clustering of vacancies, gas bubbles, or cavities because of the processes such as heat-treatment, irradiation, or deformation. These voids are characterized by their non-spherical shapes and specific crystallographic boundaries, with their formation being influenced by factors like quenching rates and the presence of gas in solid solution.
Form tool – It is a single-edge, non-rotating cutting tool, circular or flat, which produces its inverse or reverse form counter-part upon a work-piece.
Formula bar– It is a user interface element in spreadsheet software (like MS Excel or Google sheets) located above the worksheet grid. It displays and allows editing of data, text, or complex formulas for the active cell, ensuring precision in data manipulation, cell referencing, and formula auditing.
Formulas – These are standardized mathematical relationships, equations, used by professionals to quantify, analyze, and design physical systems. They represent laws, theories, or empirical data to convert known parameters (inputs) into necessary design data, such as strength, efficiency, or dimensions.
Formulas for sheet forming – Sheet metal forming formulas calculate blank size, forces, and bending allowances to ensure accurate, crack-free parts. Key calculations include bend deduction, bending force and blank diameter for drawing, ensuring precise tool setup, blanking, and spring-back management. Bend allowance (BA) nis the length of the neutral axis between bend tangent points ‘BA = Pi/180 x A x (R + K x T)’, Where ‘A’ is angle, ‘R’ is inside radius, ‘T’ is thickness, and ‘K’ is K-factor. Bend deduction (BD): is the quantity to subtract from the flat length to account for material stretching ‘BD = 2 x OSSB – BA’, where OSSB is outside setback. The formula for OSSB is ‘OSSB = tan (A/2) x (R + T). The formula for bending force is ‘F = (k x S x L x T-square)/W’ where ‘k’ is constant (1.33 for V-die), ‘S’ is tensile strength, ‘L’ is length, ‘T’ is thickness, and ‘W’ is die-opening. The formula for blanking / punching force (F) is ‘F = S x P x T’, where ‘S’ is shear-strength, ‘P’ is perimeter, and ‘T’ is thickness. The formula for blank diameter (Db) for cup is ‘Db = root (d-square + 4dh), where ‘d’ is punch-diameter, and ‘h’ is cup height. The formula for drawing force (F) is ‘F = pi x D x T x TS x (Db/d – 0.7), where ‘TS’ is tensile strength. Strain hardening exponent (n) affects formability. Higher ‘n’ (e.g., 0.3) allows better stretching than lower (e.g., 0.15). Formula for spring-back calculation is ‘Ri/Rf = 1 – 3[(Sy x Ri) / (E x T)]’ where ‘Ri’, ‘Rf’ are initial, final radii, ‘Sy’ is yield strength, and ‘E’ is young’s modulus. K-factor is the ratio of the location of the neutral axis to the material thickness (0.33 to 0.5 typical)
Formula, score – It refers to a mathematical model used to evaluate an organization’s financial health and likelihood of bankruptcy, such as the Altman Z score, which incorporates different financial ratios to determine the stability and risk associated with an organization.
Formula weight – It is a synonym for molar mass and molecular weight, frequently used for non-molecular compounds such as ionic salts.
Formvar – It is a plastic material used for the preparation of replicas or for sample-supporting membranes.
Formvar replica – It is a reproduction of a surface in a plastic Formvar film (used for the preparation of replicas or for sample-supporting membranes).
Formwork -It consists of moulds into which concrete or similar materials are either precast or cast-in-place. In the context of concrete construction, the falsework supports the shuttering moulds. In specialty applications formwork can be permanently incorporated into the final structure, adding insulation or helping reinforce the finished structure.
Forsterite -It is magnesium ortho-silicate, which is frequently naturally occurring, with a chemical composition suitable for use as a refractory raw material.
Forsterite refractory – It is a refractory composed predominantly of forsterite and containing greater than 40 % by mass of magnesium oxide.
Forster resonance energy transfer – It is a non-radiative, dipole-dipole energy transfer mechanism between an excited donor molecule and an acceptor molecule. Used mainly to measure nano-meter-scale (1 nano-meter to 10 nano-meters) distances and molecular interactions, Forster resonance energy transfer (FRET) efficiency is inversely proportional to the sixth power of the distance between the molecules, acting as a sensitive ‘spectroscopic ruler’.
Fortin barometer – It is a high-precision mercurial cistern barometer featuring an adjustable leather diaphragm base, allowing the cistern’s mercury level to be set to a zero-point (ivory pointer) before measurement. Designed for accuracy, it uses a vernier scale to measure local atmospheric pressure with precision, typically used in laboratories.
Forward and backward extrusions – These are metal-forming processes where a ram forces a billet through a die to create shapes. Forward (direct) extrusion moves the metal in the same direction as the ram, creating solid or hollow sections, while backward (indirect) extrusion forces metal to flow through a hollow ram in the opposite direction, eliminating friction.
Forward approach – It normally refers to a proactive, step-by-step method which begins with current knowledge, data, or foundational principles to move toward a desired goal or predict an outcome. It is commonly used in engineering, problem-solving, and business strategy to mean starting from the beginning and working forward through the process. A forward approach (frequently called ‘white-box’ modeling) involves building a model based on physical principles (e.g., thermodynamic equations, physical envelope parameters like thickness and thermal conductivity) to predict performance. It is frequently described as a bottom-up pattern where parameters are calculated rather than fitted from data. It involves defining the current situation and planning step-by-step toward the future or a goal. It emphasizes flexibility, allowing for adjustments based on immediate challenges as they arise.
Forward bias – It is an electrical configuration applied to a p-n junction diode (semi-conductor material) where the positive terminal connects to the p-type side and the negative terminal to the n-type side. This lowers the potential barrier, reduces the depletion region width, and allows substantial current to flow, making it conductive.
Forward combustion – It is an in-situ combustion technique used in improved oil recovery where the fire front moves in the same direction as the injected air, from the injection well toward the production well. It is a form of fire flooding which creates a high-temperature zone that heats and drives oil toward production wells.
Forward contract – It is a customized, private agreement between two parties to buy or sell an asset at a set price on a specific future date. Traded over-the-counter (OTC) rather than on exchanges, they are mainly used to hedge risk against price volatility in commodities, currencies, or interest rates. It is the sale or purchase of a commodity for delivery at a specified future date.
Forward converter – It is a type of voltage converter which relies on transformer action to couple energy to its output circuit.
Forward curved fans – These fans are with forward curved blades can move high air volumes against relatively low pressure and are of relatively small size. These fans have low noise level (because of low speed) and are well suited for residential heating, ventilation, and air conditioning (HVAC) applications. They are only suitable for clean service applications but not for high pressure and harsh services. The fan output is difficult to adjust accurately. In these fans, driver is to be selected carefully to avoid motor overload since power curve increases steadily with airflow. These fans have relatively low energy efficiency (55 % to 65 %).
Forward elimination – It is the initial phase of Gaussian elimination in engineering, used to transform a system of linear equations (represented as an augmented matrix) into upper triangular form. It systematically uses elementary row operations (EROs) to eliminate variables below the diagonal (pivots), creating zeros to facilitate final solving via back substitution.
Forward engineering – It is the traditional process of moving from high-level conceptual designs, requirements, and models to the creation of a new physical system, software application, or database. It involves a structured development lifecycle (analysis, design, implementation) to build, rather than deconstruct, systems.
Forward equation – It is frequently known as the Kolmogorov forward equation or the Fokker–Planck equation, is a differential equation which describes how the probability density function (or probability distribution) of a stochastic process evolves over time. It is used to ‘push’ initial distributions forward, predicting future state probabilities.
Forwarder – A forwarder is an intermediary agent or entity which organizes, manages, and executes the transportation of goods, acting as a logistics specialist rather than a physical carrier. They act as a ‘travel agent’ for freight, optimizing logistics networks through road, air, sea, and rail to transport goods globally, optimizing for cost, safety, and compliance.
Forward error correction – It is a digital signal processing technique which improves data reliability by adding redundant bits to transmitted data, allowing the receiver to detect and correct errors without requesting retransmission. It operates at the physical or data link layer, creating a robust, one-way communication channel suited for high-noise or high-latency environments.
Forward Euler – It is the simplest numerical integrator, where the next value is calculated by adding the product of the function’s value and a time step to the current value, although it can become numerically unstable for stiff equations and need small time steps for accuracy.
Forward extrusion – It is the extrusion in which the die and ram are at opposite ends of the extrusion stock, and the product and ram travel in the same direction. Also, there is relative motion between the extrusion stock and the die.
Forward flow forming – It is a metalworking process where a cylindrical preform is rotated on a mandrel while rollers apply pressure, forcing the material to flow longitudinally in the same direction as the roller movement (tailstock to headstock). Used for closed-bottom parts, it reduces wall thickness and increases tensile strength, creating precise, high-strength tubular components.
Forward integration – It is a form of vertical integration in which the organization moves further in the direction of controlling the distribution of its products or services. In forward integration the organization integrates its operational activities toward the end customer. Forward integration is a strategic process which helps the organization to improve its efficiency and increase profits. By implementing forward integration, the organization gains more control over its product and its delivery to the consumers.
Forward kinematics – it is the mathematical process of determining the end-effector’s position and orientation (Cartesian coordinates) of a robot manipulator or articulated structure, based on known joint variables (angles for revolute joints, extensions for prismatic joints). It calculates the robot’s pose from its joint configuration.
Forward looking infrared – It is a thermal imaging technology which detects and measures infrared radiation (3 micro-meters to 12 micro-meters range) to create real-time, 2D visual images based on temperature differences. It uses sensors (frequently uncooled bolometers) to map thermal energy, rather than visible light, for detection in low-light, obscured, or night environments, acting as a ‘forward-looking’ passive sensor, distinct from scanning ‘push-broom’ systems.
Forward market – It is an informal, over-the-counter (OTC) financial market where customized contracts are negotiated between two parties to buy or sell assets, such as commodities, at a fixed price on a specific future date. It is used for hedging risk, reducing price uncertainty, and speculation.
Forward methods – These methods normally refer to the sequential, downstream processing stages, from ore to metal, or specific industrial techniques like forward extrusion.
Forward model – It is a computational or mathematical simulation which predicts the behaviour, output, or emergent properties of a physical system based on known input parameters and system components. It flows from causes to effects, e.g., simulating energy consumption from building design or calculating seismic data from reservoir properties, used to analyze how system changes impact performance.
Forward osmosis – It is a membrane separation process which uses the natural osmotic pressure difference between a low-concentration feed solution and a high-concentration draw solution to transport water across a semipermeable membrane. Unlike reverse osmosis (RO), it needs little to no hydraulic pressure, resulting in lower fouling and higher selectivity.
Forward osmosis membrane bio-reactor – It is an advanced wastewater treatment technology combining biological degradation (activated sludge) with low-fouling forward osmosis membrane filtration. It uses an osmotic pressure gradient, rather than high hydraulic pressure, to draw clean water across a semi-permeable membrane into a highly concentrated draw solution (DS).
Forward pass – It is the process of moving through the project from start to finish time determining the earliest start and finish times for the activities of the project.
Forward path – It is the direct sequence of components and signals from the input node to the output node, without traversing any node more than once. It defines the main signal flow, where the forward path gain is the product of all branch gains along this route, determining how the input drives the output.
Forward path gain – It is the product of all branch gains along a path starting from the input node and ending at the output node. It represents the direct, non-reversed signal amplification or attenuation through the system without traversing any node more than once.
Forward path transfer function – It is the mathematical relationship (ratio of Laplace transforms) between the output and the input of the main forward path in a control system, assuming zero initial conditions. It represents the combined gain of elements (controllers, actuators, processes) located directly between the error signal and the output.
Forward prediction – It is a methodology which establishes a correlation between system inputs (such as material allocation, design parameters, or past signal data) and the resulting system outputs (physical behaviors, performance metrics, or future data points). It is normally used for simulating the behaviour of a system based on its configuration, often serving as the counterpart to ‘inverse design’ (which works backward from desired performance to determine inputs).
Forward projection – It is the computational modeling process of simulating 2D data (like an X-ray image) from a known 3D object or model, acting as the forward operator in image reconstruction. It maps physical properties (e.g., density, attenuation) into projection space, representing the ‘gather’ operation of summing voxel values along ray paths, normal in computer vision, and graphics.
Forward reaction – It refers to the process in which reactants are converted into products, moving to the right in a chemical equation (A + B = C + D).
Forward signal – It refers to a signal which propagates in the intended direction of transmission, from the source, transmitter, or controller to the destination, load, or process. In control systems, this frequently forms a ‘forward path’ where information travels directly to affect an output, distinguishing it from feedback, which returns information to the input.
Forward simulation – In the context of modeling and simulation, it refers to a process where a model is used to predict the outcome or behaviour of a system based on a set of inputs or parameters. Essentially, it involves starting with known initial conditions and using a defined set of rules or equations to project how the system is going to evolve over time or under different conditions. This is in contrast to inverse modeling, where one tries to determine the underlying parameters of a system based on observed data.
Forward slip – It refers to the difference in speed between the rolled material (strip) exiting the roll bite and the surface speed of the rolls themselves. Specifically, it is the quantity the strip’s exit speed exceeds the roll’s surface speed. This difference is normally expressed as a percentage or ratio of the roll’s surface speed.
Forward solution – it derives the measurable strains (compliance functions) which develop from introducing a successively deeper slot into a part containing an arbitrary known stress distribution.
Forward solver – It is a mathematical or numerical tool which predicts the system’s output (response / state) by calculating forward in time or logic, based on known parameters, initial conditions, and mathematical models. It simulates how a system behaves, frequently using approaches like the forward Euler method, finite element analysis (FEM), or kinematic calculations to determine future values.
Forward stagnation point – It is a specific location on a submerged body’s leading edge where local fluid flow velocity becomes zero, dividing the flow to travel over or under the object. It is characterized by maximum static pressure, frequently referred to as the stagnation pressure, and represents a point of maximum heat transfer in aerodynamic and thermodynamic applications.
Forward transfer function (Gs) – It represents the forward path component ‘Gs’ in a control system diagram (frequently a block diagram) where the output ‘Cs’ is the product of input and ‘Gs’. It is the mathematical model (Laplace domain) describing the relationship between the input and output of the main, open-loop path in a control system. It represents the combined action of controllers, actuators, and processes, specifically mapping the error signal to the output.
Forward velocity – It is the component of an object’s total velocity vector oriented parallel to its direction of motion or longitudinal axis (e.g., front-to-back in a vehicle). It is defined as the rate of change of displacement in this forward direction and is typically measured in meters per second or equivalent units.
Forward voltage (Vf) – It is the minimum voltage drop needed across a diode or semi-conductor junction to allow substantial current to flow in the forward direction. It represents the potential barrier which is to be overcome for electrons to cross the p-n junction, normally ranging from 0.3 volts to 0.7 volts for silicon diodes to 1.6 volts to 4 volts for light emitting diodes (LEDs).
Forward voltage drop – It is the voltage decrease across a diode when a forward current flows from anode to cathode, resulting from contributions related to the diode’s materials and an ohmic term proportional to the current.
Forward wave – It is a wave propagating in the direction of increasing spatial coordinates (down-stream or away from the source), characterized by phase and group velocities acting in the same direction. It moves energy away from the source, normal in traffic flow, electro-magnetic wave-guides, and structural vibration analysis. Forward wave (FW) is typically defined where the phase velocity (phase direction) and group velocity (energy propagation) are in the same direction.
Fossil alternative fuels – These are non-conventional, low-carbon materials used to substitute petroleum-based fuels (gasoline, diesel) to reduce greenhouse gases. These include biofuels (biodiesel, bioethanol), hydrogen, synthetic fuels, electricity, and natural gas derivatives, frequently designed to work with minimal modifications to existing equipment.
Fossil energy ratio – It is the ratio of final energy output (usable fuel) to the total fossil energy input needed to produce, process, and distribute that fuel, frequently expressed as a life-cycle assessment (LCA) metric. A ratio above 1 indicates positive net energy, while a declining ratio shows diminishing returns.
Fossil fuel – It is a flammable carbon compound- or hydrocarbon-containing material formed naturally in the earth’s crust from the buried remains of pre-historic organisms, a process which occurs within geological formations. Fossil fuels are non-renewable energy sources.
Fossil fuel burner – It is a device designed to mix fuel (coal, oil, or natural gas) with air and initiate combustion to generate high-temperature thermal energy. It acts as the final conveyance system for fuel or air-fuel mixtures, injecting them into a furnace or combustion chamber to create a stable flame for heat generation.
Fossil fuel combustion – It is a chemical reaction where hydrocarbon fuels (coal, oil, natural gas) react with oxygen, releasing high-temperature heat energy. This exothermic process converts chemical energy into mechanical or electrical energy, emitting carbon di-oxide (CO2), water (H2), and pollutants. It typically involves complete or incomplete combustion, important for industrial heat, power generation, and transportation.
Fossil fuel deposits – These are natural, combustible geological concentrations of hydrocarbons, mainly coal, petroleum (oil), and natural gas, formed over millions of years from the buried, decomposed remains of prehistoric plants and animals. These non-renewable, energy-rich resources are trapped within the earth’s crust and extracted for heating, electricity generation, and transportation fuel. Engineering focuses on identifying, quantifying, and extracting these non-renewable resources, typically found in sedimentary rock basins, using geological modeling, drilling, and stimulation.
Fossil fuel energy – It is a non-renewable energy source produced by burning carbon-based materials, coal, oil, and natural gas, formed deep within the earth over millions of years from decayed plants and animals. These hydrocarbons are extracted and burned to generate heat and electricity, powering transportation and industrial processes.
Fossil fuel-fired boiler– It is a boiler which heats water to produce steam by burning a fossil fuel like coal, oil, or natural gas. The generated steam can be used for several purposes, including heating buildings, generating electricity, or industrial processes.
Fossil-fuel phase-out – It is a plan to replace coal, oil, or natural gas fuel with other sources to produce electrical energy.
Fossil-fuel power plant – It is a thermal station which generates electricity by burning combustible fuels, coal, natural gas, or oil, to heat water, producing high-pressure steam which spins turbines connected to electrical generators. These plants convert chemical energy into thermal, mechanical, and finally electrical energy.
Fossil-fuel power station – It is a power plant which uses coal, oil, or natural gas fuel.
Fossil hydro-carbons – These are naturally occurring organic compounds consisting mainly of carbon and hydrogen, formed over millions of years from compressed, decayed prehistoric biological matter (plants and plankton). These non-renewable substances, mainly coal, petroleum, and natural gas, are extracted from the earth’s crust to serve as the world’s main energy source.
Fossil natural gas – It is a non-renewable hydro-carbon mixture, mainly methane (CH4), formed underground over millions of years from decomposed organic matter. It is a fossil fuel extracted from geological formations, frequently associated with oil or coal beds. Used for heating, electricity, and industrial processes, it is nicknamed ‘fossil gas’ or ‘methane gas’.
Fossil resources – These are non-renewable, hydro-carbon-based energy and chemical materials, mainly coal, petroleum (oil), and natural gas, formed from buried ancient organic matter (plants and animals) subjected to high heat and pressure over millions of years. They are finite, non-renewable, and serve as the foundation for global electricity, transportation, heating, and industrial chemical production.
Fotonic sensor – It is a high-resolution, non-contact, fibre-optic device which measures displacement, position, and vibration by detecting changes in light intensity reflected from a target surface. It works by transmitting light through fibre optics, reflecting it off a surface, and measuring the reflected light, which corresponds linearly to the gap size.
Fouled condition – It refers to the unwanted accumulation of deposits, such as scale, rust, organic matter, or sludge, on industrial surfaces, especially heat exchangers and membranes, which decreases efficiency and increases hydraulic pressure. It indicates a degraded state where equipment performance is impaired by material build-up.
Fouling – It is an accumulation of deposits. This term includes accumulation and growth of marine organisms on a submerged metal surface and also includes the accumulation of deposits (normally inorganic) on heat exchanger tubing. It is also the accumulation of refuse in gas passages or on heat absorbing surfaces which results in undesirable restriction to the flow of gas or heat.
Fouling behaviour – It refers to the undesirable accumulation of materials (such as solids, microbial species, or chemical precipitates) on the surface, within the pores, or in the matrix of a component, very frequently membranes or heat transfer surfaces. It is characterized by the time-dependent degradation of system performance, specifically a reduction in permeability (flux decline) and thermal efficiency, alongside increased resistance to flow.
Fouling deposits – These are the accumulation of unwanted materials, such as scale, suspended solids, corrosion products, or biological growth, on heat transfer surfaces, pipes, or membranes. These deposits reduce operational efficiency by acting as an insulating layer, lowering heat transfer, and increasing pressure drops (flow resistance) in industrial equipment.
Fouling factor – It is a numerical measure of the additional thermal resistance caused by accumulated deposits, such as scale, corrosion, or biological growth, on heat exchanger surfaces. It represents the decrease in efficiency over time, and is used to ensure equipment operates effectively between cleanings. It helps designers compensate for future performance drops because of the dirt buildup, ensuring the heat exchanger works even when dirty. It consists of two main parts namely fouling on the internal tube surface and fouling on the external tube surface.
Fouling layer – It is an accumulation of unwanted substances, organic, inorganic, or biological, on a surface, typically reducing performance in membrane filtration or heat exchanger systems. It causes increased hydraulic resistance, reduced heat transfer, and pressure drops by blocking surfaces and pores.
Fouling mechanism – It is the process by which unwanted materials (solid particles, bio-organisms, or chemical compounds) deposit, build up, or adhere to a heat transfer or membrane surface. It acts as a barrier, reducing the thermal efficiency, hydraulic performance, and overall operational efficiency of equipment.
Fouling monitoring – It is the process of detecting, measuring, and analyzing the accumulation of unwanted materials (such as scale, sludge, or bio-films) on industrial surfaces, particularly heat exchangers and filters. It tracks, in real-time, the decline in thermal and hydraulic performance, such as reduced heat transfer efficiency or increased pressure drop, to optimize cleaning schedules and prevent equipment failure.
Fouling organism -It is an aquatic organism with a sessile adult stage which attaches to and fouls under-water structures of ships.
Fouling resistance – It is a measure of the added thermal resistance created by unwanted material deposits (like scale, algae, or sediment) on heat transfer surfaces. Defined as the ratio of deposit thickness to the foulant’s thermal conductivity, it represents the insulating barrier which reduces heat exchanger efficiency.
Fouling surface – It is a solid interface (normally in heat exchangers, pipes, or membrane systems) subjected to the undesirable accumulation of materials, such as liquids, gases, particles, micro-organisms, or chemical deposits. This unwanted deposit acts as an insulating layer, reducing heat transfer efficiency, restricting flow, and increasing pressure drop.
Foul release coatings – These are defined as low surface energy coatings designed to prevent the adhesion of fouling organisms on surfaces, thereby facilitating easier cleaning and maintenance. These coatings are characterized by their smoothness and effectiveness, particularly in applications like propeller blades.
Foundation analysis and design – Every foundation is analyzed for its dynamic response and checked for strength and stability. Using the equipment, soil and foundation parameters, amplitudes of vibration are computed at the equipment as well as the foundation level. In addition, foundation is designed for its strength and stability to withstand applicable static and dynamic forces. For this, the dynamic forces of the equipment are translated into equivalent static forces on the foundation. Strength check of the foundation is also done for forces because of the environmental effects like wind and earthquake etc. If the strength analysis indicates that there is a need for change in the foundation size, a recheck on the dynamic analysis with the revised foundation size is a necessity. Typical foundation parameters needed for design of equipment foundation system are (i) foundation geometry, (ii) material properties i.e., mass density, dynamic modulus of elasticity, Poisson’s ratio, and coefficient of thermal expansion etc., (iii) strength parameters i.e., yield strength, ultimate tensile strength, allowable strength in compression, tension, bending, and shear etc.
Foundation and equipment load – Foundations supporting different types of equipments are to withstand all the forces which can be imposed on them during their service life. Equipment foundations are unique since they can be subjected to considerable dynamic loads during operation in addition to normal design loads of gravity, wind, and earthquake. The magnitude and the characteristics of the operating loads depend on the type, size, speed, and layout of the equipments. There are two types of loads on the equipment foundations. These are static loads, and dynamic loads. Static loads are (i) dead loads, (ii) live loads, (iii) wind loads, (iv) seismic loads, (v) static operating loads, (vi) special loads for elevated-type foundations, (vii) erection and maintenance loads, and (viii) thermal loads. Dynamic loads are (i) rotating equipment load, (ii) reciprocating equipment load, (iii) impulsive equipment load, (iv) loading conditions, and (v) load combinations.
Foundation, block – It is a solid, massive concrete block designed to support heavy, vibrating, or rotating industrial machinery, directly anchoring it to the soil or piles. These foundations resist dynamic forces, minimize vibrations, and provide high bending / torsional stiffness to machinery like compressors and engines.
Foundation design precautions – The precautions needed for foundation design are (i) foundation is to be designed to transmit combined dead load, imposed load, and wind load to the ground, (ii) net loading intensity of pressure coming on the soil is not to exceed the safe bearing capacity, (iii) foundation is to be designed in such a way that settlement to the ground is limited and uniform to avoid damage to the structure, and (iv) design of the foundation, super-structure, and characteristics of the ground are to be studied to get the overall economy.
Foundation engineering – It is the application of soil mechanics, rock mechanics, and structural engineering principles to design and construct the substructure elements which safely transfer building loads (weight, wind, seismic) to the ground. It ensures structural stability by preventing excessive settlement or shear failure of the soil.
Foundation, equipment – It is a support system for heavy equipments with reciprocating, impacting, or rotating masses. It can resist dynamic forces and the resulting vibrations. When excessive, such vibrations can be detrimental to the equipments, its support system, and any operating personnel subjected to them. The super-structure of vibrating and rotating equipments is known as equipment foundation. It essentially consists of a mass of reinforced concrete. Design of equipment foundation involves consideration of static and dynamic loads.
Foundation materials – Plain concrete, brick, reinforced cement concrete (RCC), pre-stressed concrete, and steel are the materials used for the construction of the equipment foundation. Foundations using steel structures have also been used for frame foundations.
Foundation, pile – It is a deep, slender structural element (concrete, steel, or timber) driven or bored into the ground to transfer structural loads to deeper, stronger soil or rock strata. They are necessary for heavy loads, high water tables, or poor surface soil conditions. Piling equipment includes diesel / hydraulic hammers, vibratory drivers, and rotary augers.
Foundation plan drawing – A foundation plan drawing shows the top view of the footings or foundation walls, and shows their area and their location by distances between centre-lines and by distances from reference lines or boundary lines. Actually, it is a horizontal section view cut through the walls for the foundation showing beams, girders, piers or columns, and openings, along with dimensions and internal composition. The foundation plan is used primarily by the people who construct the foundation of the proposed structure. A foundation plan drawing can be made for any floor of a plant facility. The purpose of making this drawing is to convey the dimensions, sizes, shapes, and every single configuration of a floor. Footings are also a necessary part of a foundation plan drawing.
Foundation materials – Plain concrete, brick, reinforced cement concrete (RCC), pre-stressed concrete, and steel are the materials used for the construction of the equipment foundation. Foundations using steel structures have also been used for frame foundations. The sizes of structural members in steel foundations are less than those for reinforced cement concrete foundations and hence the space requirement is much less. As regards vibration, steel structures undoubtedly involve higher risk. Natural frequencies are low and the foundation is deeply under-tuned. The resistance to fire of a steel structure is lower than that of reinforced cement concrete structure. Majority of the high tuned foundations are built of reinforced concrete. Vibration amplitudes are reduced because of the relatively higher damping present in the concrete.
Foundations -They provide support to the structure and transfer the loads from the structure to the soil. But the layer at which the foundation transfers the load is required to have an adequate bearing capacity and suitable settlement characteristics. There are several types of foundations depending on different considerations such as total load from the super-structure, soil conditions, water level, noise and vibrations sensitivity, available resources, time-frame of the project, and cost. Broadly speaking, foundations can be classified as (i) shallow foundations, and (ii) deep foundations.
Founded structure – It is also called bottom-founded structure, It is an engineering construction, frequently made of steel or concrete, which rests on the seabed to support equipment and resist environmental loads like wind and waves. It acts as a permanent base designed for heavy-duty stability, normally used in offshore oil, gas, and renewable energy industries.
Founding – It is the manufacturing process of producing metal parts by melting metal into a liquid state, pouring it into a mould, and allowing it to solidify to take the shape of the mould cavity. It is a key method for shaping metals into intricate or large forms that would be difficult or costly to achieve through other manufacturing methods like machining or forging.
Foundry – It is a commercial establishment or building where metal castings are produced.
Foundry grade pig iron – This type of pig iron is being used in iron foundries and contains higher silicon. Different standards specify composition limits for silicon and manganese for different grades of this type of pig iron. Silicon content in foundry grade pig iron is much higher and is normally in the range of 1.5 % to 3.5 %. It can be as high as 4.25 %.
Foundry ladle – It is a heat-resistant, refractory-lined vessel used to transport, hold, and pour molten metal from furnaces into casting moulds. Ranging from small hand-held tools to large 300-ton crane-operated containers, they are typically made of steel and designed to prevent premature metal solidification during casting. These ladles are needed to safely transport molten metal (iron, steel, aluminum) and pour it into moulds.
Foundry practice – It refers to the comprehensive industrial process of producing metal castings, involving the melting, pouring, and solidification of metal inside a prepared mould. It is an important manufacturing technique used to transform raw metals, typically iron, aluminum, steel, bronze, or brass, into complex shapes which are difficult or uneconomical to produce through other methods.
Foundry products – These are metal components created by melting metal, pouring it into a mould, and allowing it to solidify, a process known as casting. Foundries produce complex, durable shapes from materials like cast iron, steel, aluminum, and brass, serving industries from automotive to machinery. These products are versatile, ranging from engine components to artistic castings.
Foundry returns – It is the metal in the form of gates, sprues, runners, risers, and scrapped castings of known composition returned to the furnace for remelting.
Foundry sand – It is a specialized, high-quality silica sand (or sometimes synthetic sand) used to create moulds and cores for shaping molten metal, particularly in sand casting. It is composed of sand grains, binding agents (clay or chemical), and additives that allow it to hold its shape under high temperatures, withstand the thermal shock of molten metal, and produce precise casting details. It mainly consists of high-quality silica sand (85 % to 95 %) coated with a thin film of burnt carbon, residual binders, and dust.
Four-bar mechanism – It is the simplest closed-loop planar linkage, consisting of four rigid bodies (links) connected by four joints to convert input motion (normally rotation) into a specific output motion. It typically includes a fixed frame, an input link, a coupler, and an output link.
Four-column press – It is an industrial machine with four vertical pillars, a top beam, and a base (platen) to provide exceptional stability, rigidity, and parallelism for high-tonnage shaping. Mainly hydraulic-driven, this design utilizes Pascal’s law to distribute force uniformly, making it ideal for precision stamping, drawing, and forging operations.
Fourdrinier machine – It is the foundational industrial machine for continuous papermaking, utilizing a horizontal, moving, fine-mesh conveyor belt (wire) to form a paper web from pulp slurry. It transforms diluted pulp into a continuous sheet through forming, pressing, and drying, largely replacing manual sheet moulding.
4G (fourth-generation) wireless – It is the mobile network standard succeeding third-generation (3G) of cellular network technology, offering high-speed data, low latency, and all-IP packet switching. It delivers mobile broadband internet with speeds up to 100 Mbps (mega-bits per second) or more, enabling HD (high-definition) streaming, video conferencing, and fast app downloads. Key technologies include LTE (long-term evolution), which provides reliable connectivity.
4G LTE – Its full form is ‘fourth generation long term evolution’. It is a high-speed wireless broadband technology for mobile devices, offering considerably faster data speeds than 3G for browsing, streaming, and downloads. It provides improved capacity and lower latency, enabling smooth HD (high-definition) video conferencing and faster file transfers, often achieving speeds over 100 Mbps (mega-bits per second).
Four-high flattener – In this flattener, the work rolls are backed-up by a set of backup rolls. Four-high flattener allows the use of small-diameter work rolls since work-roll deflection is restrained by backup rolls. These flatteners are typically self-driven and have seven to thirteen work rolls.
Four-high mill – It is a type of rolling mill, normally used for flat-rolled mill products, in which two large-diameter backup rolls are used to reinforce two smaller diameter work rolls, which are in contact with the product. Either the work rolls or the back-up rolls can be driven.
Four-high mill roll configuration – In this type of roll configuration, there are four horizontal rolls, mounted in a single vertical plane. Two rolls (inner) are work rolls and two rolls (outer) are back-up rolls. Significance of the back-up rolls consists in a chance of using higher roll forces and decrease in bending (deflection) of work rolls. Small diameters of work roll also permit (except for greater elongation of the rolling stock) a possibility of achieving of more favourable dimensional thickness deviations. The work rolls of the four-high mill are driven while the back-up rolls are normally friction driven. The four-high roll configuration is used for rolling of plates and for hot rolling and cold rolling of steel strip. It is used both in the non-reversing and reversing rolling mills.
Four-high roller leveller – It is normally simply referred to as a leveller. It is similar to a four-high flattener in that the design involves four-high small diameter work rolls. Unlike the four-high flattener, however, each work roll in the leveller is supported by a number of narrow backup rolls, instead of straight solid backup rolls. This arrangement allows small work rolls and a close work roll spacing in the leveller for more capability in shape correction.
Fourier amplitude spectrum – It is a graphical representation displaying the magnitude (amplitude) of frequency components within a signal, plotted against frequency. It represents the square root of the sum of the squares of the real and imaginary parts of a signal’s Fourier transform, revealing how signal intensity is distributed across frequencies.
Fourier coefficients – These are scalar values (an, bn) derived from the Fourier series representation of periodic or quasi-periodic signals, such as X-ray diffraction patterns, micro-structural boundary shapes, or heat flow data. They quantify the amplitude and phase of specific harmonic frequencies (sine and cosine components) which comprise the overall signal.
Fourier component – It is a single, fundamental sinusoidal wave, defined by specific amplitude, frequency, and phase, which contributes to a larger, complex signal or shape, normally representing a single harmonic in a Fourier series or a specific frequency in a Fourier transform. These components break down periodic signals into simple, additive sine / cosine waves.
Fourier cosine series – It is an expansion of an even function ‘fx’ into a sum of constant and cosine terms, used in engineering to simplify signals or solve partial differential equations (e.g., heat conduction) where Neumann boundary conditions exist. It uses only cosine functions since the function is modelled as even, causing all sine coefficients to vanish.
Fourier decomposition – It is the process of breaking down a signal into a series of harmonically related sinusoids, allowing for the analysis and reconstruction of periodic and aperiodic signals in both time and frequency domains.
Fourier descriptors – These are mathematical coefficients that define the shape of an object’s boundary in an image by applying a 1D ‘discrete Fourier transform’ (DFT) to the sequence of coordinate points (x, y) mapped as complex numbers [s(k) = x(k) + jy(k)]. They provide rotation, scaling, and translation invariance, making them ideal for object recognition, classification, and contour simplification in image processing.
Fourier features – These refer to the characteristics extracted from the frequency spectrum of a signal or image, which can reveal defects in materials such as textiles by highlighting changes in the fabric’s regular structure. These features are utilized in various methods, including ‘discrete Fourier transform’ (DFT) and ‘windowed Fourier transform’ (WFT), to effectively analyze periodic patterns and detect defects.
Fourier method – It is also called Fourier transform. It is a mathematical technique which decomposes a function or signal, frequently representing time or space, into its constituent frequencies, transforming it into the frequency domain. It represents complex signals as sums of simple sines and cosines, important for analysis
Fourier number (Fo) – It is a dimensionless parameter representing the ratio of heat conduction rate to the rate of thermal energy storage in a material. Defined as Fo = (a x t)/Lc-square (where ‘a’ is thermal diffusivity, ‘t’ is time, and ‘Lc’ is characteristic length), it serves as dimensionless time, important for predicting transient cooling / heating rates during processing.
Fourier series – It is a set of coefficients of sine and cosine waves. This can represent a time function as a function of frequency.
Fourier series coefficients – These coefficients are scalar values which define the weights of the individual sine and cosine (or complex exponential) functions comprising a periodic signal’s representation in the frequency domain. These coefficients measure the amplitude of a specific harmonic frequency, calculated through integration of the function over one period.
Fourier’s law – It states that the rate of heat conduction through a material is directly proportional to the area normal to the heat flow and to the temperature gradient. It quantifies heat transfer through metals during casting, forging, and welding, where heat moves from hotter to colder regions.
Fourier’s law of heat conduction – It states that the rate of heat transfer through a material is directly proportional to the negative temperature gradient and the cross-sectional area through which heat flows. It is expressed as ‘q = -k x A x dT/dx’, where ‘q’ is the heat flow rate, ‘k’ is thermal conductivity, ‘A’ is area, and dT/dx is the temperature gradient. The negative sign indicates that heat flows from higher temperature to lower temperature (down the gradient).
Fourier space – It is also called frequency domain. It is the mathematical domain where a function is represented by its Fourier transform, mapping signals from the time / spatial domain to their constituent frequencies. It describes how much of each frequency exists in a signal, with large-scale structures appearing at low ‘q’ (small wave vectors) and small-scale structures at high ‘q’.
Fourier spectrum – It refers to the frequency-domain representation of a signal generated from metallic materials, typically derived by applying a Fourier transform (such as ‘fast Fourier transform,’ FFT) to raw time-domain or spatial-domain data (e.g., ultrasonic waves, electron diffraction patterns, or surface roughness measurements). It breaks down complex structural or process data into individual frequency components, identifying the amplitudes and phases of signals present in the material, which allows for the analysis of microstructural features, defects, or vibration in manufacturing.
Fourier symbol – It is the representation of a spatial discretization operator in the frequency domain, capturing the behaviour of a finite-difference solution and allowing for the analysis of numerical scheme stability through the evolution of a single Fourier mode.
Fourier transform – It is an algorithm for converting a continuous wave-form in the time domain into an equivalent set of spectral components in the frequency domain.
Fourier transform design – It is a mathematical approach which applies Fourier analysis to decompose complex signals or data into fundamental sinusoidal components, enabling manipulation, filtering, and reconstruction in the frequency domain. It is widely used to analyze, design, and optimize systems by mapping time-domain data (like audio) or spatial data (like images) to their frequency components.
Fourier transform infrared (FT-IR) spectrometer – It is an analytical instrument which measures the infrared absorption or emission of solids, liquids, or gases to identify chemical compounds. It uses an interferometer to measure all wavelengths simultaneously, applying a Fourier transform (a mathematical calculation) to convert raw interferometer data into a unique molecular ‘fingerprint’ spectrum.
Fourier transform infrared (FT-IR) spectrometry – It is a form of infra-red spectrometry in which data are obtained as an interferogram, which is then Fourier transformed to get an amplitude against wave-number (or wave-length) spectrum.
Fourier transform infrared (FT-IR) spectroscope – It is an analytical instrument which measures the energy of infrared radiation passing through a substance, allowing for the qualitative determination of individual bond types in a sample by analyzing the resulting IR (infrared) spectrum. It utilizes Fourier transform to process the collected data, enabling improved spectral quality and faster data acquisition.
Fourier transform infrared (FT-IR) spectroscopy – It is a non-destructive analytical technique used to identify organic compounds, surface contamination, and corrosion products on metal surfaces. It measures infrared absorption, acting as a ‘molecular fingerprint’ to determine chemical composition and evaluate surface coatings or residue. Fourier transform infrared spectroscopy is highly effective for identifying organic contaminants (oils, lubricants, cleaning agents) and inorganic corrosion products on metal substrates.
Fourier transform method – It is a mathematical technique which converts a time or space-domain signal into its frequency-domain representation. It decomposes complex, non-periodic, or periodic signals into a sum of simple sinusoidal components (sines and cosines) to identify the amplitude and phase of each frequency.
Fourier transform near-infrared (FT-NIR) spectroscopy – It is a non-destructive analytical technique used to identify and quantify chemical compositions in metals and inorganic materials by measuring how they absorb or reflect light in the near-infrared range (typically 750 nano-meters to 2,500 nano-meters). It utilizes a Fourier transform mathematical process to convert an interference pattern (interferogram) from a Michelson interferometer into a readable spectrum.
Fourier-transform spectrometer – It is an analytical instrument used to identify and characterize surface compounds, impurities, and inorganic materials by measuring the absorption or reflection of infrared radiation. Unlike dispersive spectrometers, it uses a Michelson interferometer to collect high-resolution data over a wide spectral range simultaneously (the ‘Fellgett advantage’), allowing for rapid and precise analysis. A Fourier transform (mathematical algorithm) then converts this raw interference signal (interferogram) into a readable spectrum.
Fourier-transform spectroscopy – It is a measurement technique whereby spectra are collected based on measurements of the coherence of a radiative source, using time-domain or space-domain measurements of the radiation, electromagnetic or not. It can be applied to a variety of types of spectroscopies including optical spectroscopy, infrared spectroscopy (Fourier transform infrared spectroscopy, FT-IRS, Fourier transform near-infrared spectroscopy, FT-NIRS), nuclear magnetic resonance (NMR) and magnetic resonance spectroscopic imaging (MRSI), mass spectrometry and electron spin resonance spectroscopy.
Fourier transform spectrograph – It is an analytical technique used to determine the molecular composition, structure, and functional groups of inorganic materials by measuring the absorption or reflection of infrared radiation. It is particularly effective for identifying surface contaminants, oxides, coatings, and corrosion products, providing a ‘molecular fingerprint’ which helps engineers evaluate material quality and purity.
Four-mandrel mechanical table mills – These mills have been used extensively in the production of anti-friction bearing races. In these mills, the undriven mandrels are supported only at their lower ends, where they are mounted in a rotating table. The driven main roll is set inside the annular table, with its centre offset from that of the table. The blank is loaded at position 1, where the eccentricity of the table and main roll centres provides a suitable clearance between the mandrel and the main roll. The table is then rotated by electrical drive, and the gap between the mandrel and the main roll decreases until the ring blank is contacted (position 2). As the table continues to rotate (at much slower angular velocity than the main roll), the gap between the mandrel and the main roll decreases to a minimum (position 3), causing the rapidly rotating ring to be reduced in wall thickness and to increase in diameter. The table rotates to position 4, and the ring is unloaded. The height of the ring is controlled by a closed pass between the main roll and mandrel.
Four-piece die – It normally refers to a specialized tool set composed of four distinct working components, typically an upper die, a lower die, and two side dies, which move in coordination, normally from four orthogonal directions, to shape a metal work-piece. This setup is frequently used in four-slide / multi-slide manufacturing or four-die forging devices to create complex, high-precision shapes in a single, efficient operation.
Four-point bending test – It is a mechanical testing method used to determine the flexural strength, stiffness (modulus), and deformation behaviour of a material. It involves placing a sample (frequently rectangular) on two outer supports and applying a load through two inner loading pins. The defining characteristic of this test is that the region between the two inner loading points experiences pure bending, a constant maximum bending moment, with zero shear forces.
Four-point flexural test provides values for the modulus of elasticity in bending, flexural stress, flexural strain, and the flexural stress-strain response of the material. This test is very similar to the three-point bending flexural test. The major difference being that with the addition of a fourth bearing the portion of the beam between the two loading points is put under maximum stress, as opposed to only the material right under the central bearing in the case of three-point bending.
Four-point press – It is a press whose slide is actuated by four connections and four cranks, eccentrics, or cylinders, the main merit being to equalize the pressure at the corners of the slides.
Four-point test – It is a mechanical method used to determine the flexural strength, stiffness, and modulus of elasticity of materials by applying load at two points, while supported at two outer points. It produces a uniform bending moment and constant maximum stress between the inner loading points, reducing localized stress concentration.
Four-stroke cycle – It is a sequence of four distinct piston movements in an engine, comprising the intake, compression, power, and exhaust strokes, which collectively complete one cycle of operation. Each cycle involves two upward strokes (compression and exhaust) and two downward strokes (intake and power) of the piston.
Fourth generation (4G) – It refers to the fourth iteration in a technological evolution, normally characterized by microprocessors (computers), 4G LTE (long-term evolution) wireless networks, or high-level, domain-specific programming languages. It refers to problem-oriented languages mainly used in commercial data processing for tasks such as report generation and data analysis. These languages include statistical analysis packages and are gradually spreading into other domains. It indicates advancements toward faster speeds, higher efficiency, and higher accessibility.
Fourth-order tensor – It is a mathematical object with four indices (Tijkl) which normally acts as a linear mapping between second-order tensors (matrices), producing another second-order tensor. In 3D continuum mechanics, it contains ‘3 to the power 4 = 81’ components and is frequently used to define constitutive relations like the elasticity or compliance tensors.
Fourth-party logistics (4PL) – It is an operational model in which an organization outsources its entire supply chain management and logistics to one external service provider. Unlike a third-party (3PL) provider, which oversees part of supply chain operations for a business, a fourth-party logistics provider is normally the single point of contact for supply chain management. This provider has a broader scope of responsibilities which include managing resources, technology and infrastructure and providing strategic insights and management.
Fourth quadrant – It is one of the four sections (or ‘quarters’) that a graph paper is divided into by two main lines called the x-axis and y-axis. It consists of positive x-values and negative y-values, and is shown in the bottom right corner of the plane.
Four-way machine – It is a specialized, automated mechanical device designed to perform operations (typically cutting) on four work-pieces simultaneously. It is designed to increase productivity and efficiency in manufacturing settings, such as machine shops, by reducing idle time and human effort compared to traditional single-piece machines.
Four-wheel drive – It is a vehicle configuration in which the engine’s power is distributed to all four wheels, allowing for better traction and stability by preventing any individual wheel from exceeding its limiting traction force before skidding occurs. This system improves safety during driving, especially in conditions where traction can be compromised.
Four-wire system – It is an electrical distribution method containing three phase conductors and a neutral wire, used mainly to deliver both single-phase (e.g., 220 volts to 240 volts) and three-phase (400 volts to 440 volts) power simultaneously. It acts as a star (Y) connected configuration allowing for unbalanced loading in industrial applications.
Fowler-Nordheim tunneling – It refers to a quantum mechanical tunneling process that occurs at higher bias in a material, characterized by the transition from direct tunneling at lower bias. It is a conduction mechanism observed in structures such as self-assembled mono-layers where the current-voltage characteristics display a dependence on the applied bias range.
Fox equation – It is a mathematical expression used to predict the glass transition temperature (Tg) of binary blends of materials, formulated as ‘1/Tg = w1/Tg1 + w2/Tg2’, where weights ‘w1’ and ‘w2’ correspond to the proportions of the components in the blend.
FP fibre – It consists of poly-crystalline alumina (Al2O3) fibre developed by DuPont. It is a ceramic fibre useful for high-temperature (1,370 deg C to 1,650 deg C) composites.
Fraass breaking point – It is the temperature at which a thin film of bituminous binder, applied to a flat steel plaque, first cracks when cooled and subjected to bending, indicating its brittle behaviour at low temperatures. It defines the transition from a flexible state to a brittle state, typically testing bituminous materials.
Fracking – It is also known as hydraulic fracturing, fracing, hydro-fracturing, or hydro-fracking. It is a well stimulation technique involving the fracturing of formations in bedrock by a pressurized liquid. The process involves the high-pressure injection of ‘fracking fluid’ (mainly water, containing sand or other proppants suspended with the aid of thickening agents) into a well-bore to create cracks in the deep-rock formations through which natural gas, petroleum, and brine flow more freely. When the hydraulic pressure is removed from the well, small grains of hydraulic fracturing proppants (either sand or aluminum oxide) hold the fractures open.
Fracking fluid – It is also called fracturing fluid. It is a specially engineered mixture, typically 99.5 % water and proppant (sand), with 0.5 % chemical additives, pumped at high pressure into subterranean rock formations to initiate or extend fractures, allowing for the increased extraction of oil and natural gas. Fracking fluid is designed to interact specifically with the geological, petrophysical, and mechanical properties of the reservoir, while also managing chemical interactions with metal downhole components.
Fractal description – It refers to the representation of objects or structures which show an indefinite broken geometry, characterized by self-similarity and scale invariance, where smaller sections resemble the whole and maintain statistical properties across different scales.
Fractal dimension (Df) – It is a quantitative, non-integer measure of an object’s complexity, roughness, or space-filling capacity, often characterizing self-similar structures. Unlike Euclidean dimensions (1D, 2D, 3D), ‘Df’ quantifies how detail increases with smaller measurement scales, used extensively to analyze chaotic signals, irregular surfaces, and network structures.
Fractal geometry – it is the mathematical study and application of self-similar, irregular, and complex shapes which show similar patterns at different magnification scales. It uses fractional dimensions to quantify complex structures which cannot be properly defined by traditional Euclidean geometry, enabling optimized design in structures, antennas, and material science.
Fractal model – It is a mathematical or simulation approach which describes complex, irregular structures (like porous media, rough surfaces, or jagged coastlines) which show self-similarity across different scales. These models, frequently created by repeating simple recursive processes, allow engineers to analyze chaotic or disordered systems, where Euclidean geometry fails, using a fractional, rather than integer, dimension.
Fractalness – It is the quantitative measure of how closely a structure, surface, or process mimics a mathematical fractal, characterized by self-similarity across multiple scales and non-integer dimensions. Unlike smooth Euclidean shapes, fractalness describes irregular, complex, or fractured forms, such as fracture surfaces, porous media, or branching networks, which maintain statistical properties regardless of the magnification.
Fractal parameters – These are quantitative metrics, such as fractal dimension (D) and scale coefficients, which characterize complex, irregular, or self-similar structures across multiple scales. Unlike Euclidean geometry, these parameters define roughness, fragmentation, and spatial distribution in natural systems (e.g., surface topography, porous media, soil) to analyze variability and behaviour.
Fractal set – It is a complex, irregular geometric shape characterized by self-similarity across different scales, where its Hausdorff-Besicovitch dimension (Dh) strictly exceeds its topological dimension (Dt). These sets are generated by iterative, recursive processes, and are used to model, analyze, or optimize irregular structures, material surfaces, and chaotic systems, often providing more accurate descriptions than traditional Euclidean geometry.
Fractal signal – It is a type of signal characterized by self-similarity across multiple scales, meaning its structural pattern repeats regardless of the magnification level. These signals frequently have a non-integer, or fractional, dimension, allowing for the analysis of complex, non-linear data in fields like telecommunications, and finance.
Fractal surface – It is a rough, irregular surface which shows self-similarity (the same structure appears at different magnifications) across multiple scales. Unlike Euclidean surfaces (smooth, flat), fractal surfaces are used to model complex, natural, or engineered phenomena where roughness affects performance. These are quantified by their fractional dimension.
Fractile – It is also known as a quantile. It is a specific data point which divides an ordered dataset into equal, ordered parts, representing a threshold value below which a specified fraction of values falls. Frequently used for risk assessment, structural reliability, and quality control, it dictates how much probability exists in the lower or upper ‘tails’ of a distribution (e.g., 5th percentile).
Fraction – It represents a part of a whole, where the whole can be a single object or a group of objects. It is written as ‘p/q’, where ‘p’ is the numerator (the number of parts taken) and ‘q’ is the denominator (the total number of equal parts the whole is divided into). Fractions are used to express quantities that are not whole numbers. A fraction is a numerical value which represents a part or portion of a whole, which can be any number, value, or object. It is also that portion of a powder sample which lies between two stated particle sizes.
Fractional bandwidth (FBW) – It is a engineering metric defined as the absolute bandwidth (delta f) divided by the centre frequency (fc) of a system, normally expressed as a percentage. It measures how spread out a signal’s frequency content is, calculated as ‘FBW = [(fh – fl)/fc] x 100 %’, where ‘fh’ and ‘fl’ are the upper and lower frequency limits.
Fractional Brownian motion – It is a continuous-time Gaussian process, generalizing standard Brownian motion (H = 0.5) to model processes with self-similarity and long-range dependence. It is defined by its Hurst exponent (H), controlling memory normally H = above 0.5 (persistence), H = below 0.5 (anti-persistence), with stationary increments and zero mean. It is a generalization of ordinary Brownian motion which incorporates self-similarity, allowing for the generation of curves and surfaces with varying fractal dimensions. It is used to simulate fractal patterns and is characterized by long-range dependence in its time series.
Fractional Brownian motion process – It is a stochastic process which describes an isotropic fractional Brownian motion surface, characterized by its increment process, which satisfies specific probabilistic relations involving the Hurst coefficient and surface incremental standard deviation. It shows self-affinity and has a fractal dimension determined by the Hurst exponent.
Fractional change – It is the ratio of a quantity’s change (dX = X-final – X-initial) to its original value (X-initial), defined as dX/X-initial. It measures the relative alteration of a system property (e.g., strain, resistance change). It is dimensionless, used for sensitivity analysis, and differs from percentage change by not multiplying by 100.
Fractional conversion – It is the ratio of the moles of a specific reactant consumed to the initial moles of that reactant fed into a reactor. It measures how far a reaction has progressed, normally focusing on the limiting reactant, with a value ranging from 0 (no reaction) to 1 (complete conversion).
Fractional coverage – It defines the proportion of a surface, area, or material occupied by a specific substance, feature, or component, expressed as a ratio between 0 and 1 (or 0 % to 100 %). It measures spatial density or adsorption, such as lubrication films on asperities, vegetation density in remote sensing, or molecules on a catalyst.
Fractional derivative – It is a generalization of integer-order calculus to non-integer or arbitrary orders, representing derivatives of any fractional, real, or complex order. It serves as a powerful mathematical tool to model non-local, memory-dependent systems, where the current state depends on its entire history, such as viscoelastic materials, electrochemistry, and signal processing.
Fractional diffusion equation – It is a type of differential equation which incorporates fractional derivatives to describe diffusion processes, frequently needing approximate or numerical solutions because of the lack of exact solutions.
Fractional distillation – It is the fractionation of a mixture of liquids into its component parts, or fractions, by the process of distillation, typically by using a long vertical column attached to the distillation vessel and filled with glass beads. The mixture is heated to a temperature at which one or more of the component compounds vapourizes. The vapour rises up the column until it condenses and runs back into the vessel, creating a temperature and volatility gradient and permitting different fractions to be drawn off at different points along the length of the column. The technique is sensitive enough to separate compounds which have boiling points which differ by less than 25 deg C from each other at standard pressure.
Fractional factorial design – It is a ‘design of experiments’ (DOE) technique used in engineering to efficiently identify significant factors by running a subset (1/2, 1/4, etc.) of a full factorial design. It reduces experimental costs and time while allowing investigation of several variables, focusing on main effects and key interactions.
Fractional factorial experiment – It is a designed experiment which investigates the influence of multiple processing factors (e.g., temperature, composition, pressure, and cooling rate) on a metallurgical property (e.g., hardness, tensile strength, or corrosion resistance) by running only a carefully selected subset, or fraction, of the total possible factor combinations. Fractional factorial experiment is used for screening, aiming to identify which of several factors have the largest influence on the material’s properties, effectively reducing the number of runs needed. Instead of testing all possible combinations (full factorial), fractional factorial experiment reduces resource consumption (time, raw materials, energy for furnaces) while still providing important information on main effects and low-order interactions, assuming higher-order interactions are negligible (sparsity of effects principle).
Fractional horse-power motor – It is an electric motor designed for a rated output of less than 1 horse-power (746 Watts). Engineered for smaller-scale applications, these motors normally operate at 115 volts / 230 volts AC (alternating current) or low-voltage DC (direct current). They are typically defined by their compact frame size and are normally used in HVAC (heating, ventilation, and air conditioning) systems, and industrial automation where precise, low-power motion is needed.
Fractional method – It typically refers to fractional calculus, a branch of mathematics using non-integer (arbitrary) order derivatives / integrals to model complex dynamic systems more accurately than integer-order derivatives. These methods, such as Riemann-Liouville or Caputo derivatives, incorporate memory effects (non-locality) to better represent visco-elasticity, signal processing, and control system behaviours.
Fractional-order – It is the generalization of traditional integer-order derivatives and integrals to non-integer, real, or complex orders. It uses fractional calculus, such as Riemann–Liouville or Caputo definitions, to model complex systems characterized by power-law nonlocality, memory effects, and hereditary properties more accurately than standard models.
Fractional-order controller – It is a generalized feedback mechanism utilizing fractional calculus to extend traditional integer-order controllers (like proportional-integral-derivative controllers) to non-integer, arbitrary order for improved tuning flexibility, increased system robustness, better disturbance rejection, and faster dynamic response in complex, nonlinear control systems.
Fractional-order systems – These refer to control systems characterized by transfer functions of arbitrary real order, which can better describe system dynamics than traditional integer-order models. These are dynamical systems modeled by differential equations using non-integer (fractional) order derivatives and integrals, rather than traditional integer-order derivatives. These systems better describe memory effects, complex materials, and material hereditary properties.
Fractional part – Fractional part of a real number is the non-integer component remaining after removing the integer part. It represents the decimal portion sed in computing, signal processing, and numerical analysis for precision mapping. It refers to the decimal portion of a number, typically displayed after the decimal point. It can be represented as values such as ‘.00’, ‘.25’, ‘.50’, ‘.75’, based on the binary representation of the number.
Fractional porosity – It is the ratio of void space volume to the total bulk volume of a material, representing the empty space in a solid. It is expressed as a fraction between 0 and 1 (or 0 % to 100 %) and is defined by the equation ‘P = Vvoid/Vtotal.
Fractional recovery – It is the ratio of the quantity of a specific component or material successfully separated and collected in a process (e.g., in a concentrate, distillate, or product stream) to the total quantity of that component present in the original feed stream. It represents the efficiency of separation, normally expressed as a fraction or percentage.
Fractional saturation – It refers to the ratio of a specific component’s current concentration or volume to its maximum potential (saturation) value under given conditions. Ranging from 0 to 1, it measures the extent of saturation, widely applied in fluid dynamics, reservoir engineering, and chemical process engineering to calculate binding, phase changes, or moisture content.
Fractional spurs – These are unwanted, periodic spurious tones (noise) in the output spectrum of a fractional-N ‘phase-locked loop’ (PLL) frequency synthesizer, occurring at frequency offsets related to the channel spacing or the fractional part of the division ratio. These are caused by the systematic switching between integer division ratios and charge pump non-linearities.
Fractional step method – It is a computational fluid dynamics (CFD) technique used to solve complex, coupled partial differential equations, very frequently the Navier-Stokes equations, by breaking them into simpler, sequential sub-steps. This approach reduces computational memory needs and increases calculation speed by treating physical processes (like advection and diffusion) or velocity and pressure independently.
Fractionating column – It is a vertical cylindrical vessel used to separate liquid mixtures into component parts (fractions) based on differences in boiling points and vapour pressure. It works through fractional distillation, utilizing internal packing or trays to provide surface area for multiple condensation-vapourization cycles which purify liquids.
Fractionation – It is a separation process in which a particular quantity of a mixture is divided during a phase transition into a number of smaller quantities, known as fractions, for which the chemical composition varies according to a gradient. Fractionation exploits subtle differences in some specific property (e.g., mass, boiling point, solubility, etc.) between the mixture’s component compounds, making it possible to isolate more than two components of a mixture at the same time. There are several varieties of fractionation employed in many branches of science and technology.
Fractionation column – It is a vertical apparatus designed to separate liquid mixtures into component parts (fractions) based on differing boiling points and vapour pressures. Utilizing packed or trayed interiors, it creates continuous, counter-current contact between rising vapours and descending liquid, achieving multiple, sequential vapourization-condensation cycles to provide precise separation of high-purity chemicals, petroleum, or gas components.
Fractionation tower – It is also called fractionation column. It is a vertical, cylindrical pressure vessel used to separate liquid mixtures into components based on boiling point differences. By facilitating multi-stage vapour-liquid equilibrium, lighter compounds rise and condense at the top while heavier compounds exit at the bottom.
Fractography – It is the descriptive treatment of fracture of materials, with specific reference to photographs of the fracture surface. Macro-fractography involves photographs at low magnification (less than 25×), while the micro-fractography involves photographs at high magnification (higher than 25×).
Fracture – It is the irregular surface produced when a piece of metal is broken. Fracture can be defined as the mechanical separation of a solid owing to the application of stress. In composites, it is the separation of a body, which is defined both as rupture of the surface without complete separation of the laminate and as complete separation of a body because of external or internal forces. Fractures in continuous-fibre-reinforced composites can be divided into three basic fracture types namely intra-laminar, inter-laminar, and trans-laminar. Trans-laminar fractures are those oriented transverse to the laminated plane in which conditions of fibre fracture are generated. Inter-laminar fracture, on the other hand, describes failures oriented between plies, whereas intralaminar fractures are those located internally within a ply. Fractures of engineering materials are broadly categorized as ductile or brittle, and fracture toughness is related to the quantity of energy needed to create fracture surfaces. In mining, fracture is a break in the rock, the opening of which allows mineral-bearing solutions to enter. A ‘cross-fracture’ is a minor break extending at more-or-less right angles to the direction of the main fractures.
Fracture analysis – It is an investigation technique used to determine the cause of material failure by examining fractured surfaces to understand crack origin, propagation, and stress mechanisms. It combines microscopic / macroscopic inspection (fractography) with stress calculation, covering failure types like brittle, ductile, and fatigue in metals, plastics, and structures.
Fracture angle – It is defined as the inclination of the fracture surface, or the crack propagation path, relative to a reference axis, normally the direction of applied tensile stress or the horizontal axis of the sample. This geometric parameter indicates how a material separates under stress.
Fracture aperture – In materials science, particularly when analyzing fractures in brittle materials (like ceramics) or geological materials (similar to rock mechanics), it is defined as the perpendicular distance separating the two opposing walls of an open crack or fracture. It represents the width of the void space within a fracture.
Fracture appearance transition temperature – It is the temperature at which a material shows a 50 % ductile and 50 % brittle fracture appearance when subjected to a fracture test, typically the Charpy impact test. It is a key parameter in understanding a material’s fracture behaviour at different temperatures, particularly in materials which show a ductile-to-brittle transition.
Fracture behaviour – It describes how a material responds to applied stress through crack initiation, propagation, and final separation. It is categorized by the degree of plastic deformation, either ductile (large deformation, slow propagation) or brittle (little deformation, fast / catastrophic propagation), and is influenced by micro-structure, temperature, loading rate, and environment.
Fracture closure – It is normally referred to as crack closure in fatigue. It is a phenomenon where the opposite faces of a crack (or fracture) come into contact during the unloading portion of a load cycle, even while the external load is still in tension. This phenomenon means the crack remains closed for a portion of the loading cycle, reducing the effective stress range which drives crack growth.
Fracture criterion – It is a defined condition, typically based on critical stress, strain, or energy, which predicts when a material is going to crack or fail under load. These criteria allow engineers to determine if a component with a specific flaw size will undergo brittle failure, ductile tearing, or stable crack growth, essential for designing safe structures.
Fracture critical member – It is a steel tension component in a structure, mainly bridges, whose failure is likely to cause a partial or total collapse. These members are defined by having no redundancy, meaning no alternative load paths exist if the member fails. These members need intense inspection and high toughness standards to prevent brittle fracture.
Fracture deformation – It is the separation of a metal component into two or more parts because of the applied stress, frequently following structural damage. It is classified into ductile fracture (extensive plastic deformation / necking) or brittle fracture (rapid propagation with little to no deformation). It is the ultimate failure of materials.
Fractured reservoir – It is a geological formation where natural fractures (discontinuities) create important networks which considerably improve permeability and porosity, facilitating commercial oil and gas flow in otherwise low-permeability rock. These reservoirs frequently feature a ‘dual-porosity’, where matrix blocks hold the bulk volume, while the fractures act as the main conduit for fluid production.
Fractured rock mass – It is a geological formation containing discontinuities like joints, fissures, and faults which disrupt its integrity, considerably affecting its strength, permeability, and deformation behaviour. These rock bodies are broken by brittle deformation, reducing overall stability and facilitating fluid movement.
Fracture elongation – It is the elongation at break. It is a key measure of a material’s ductility, defined as the percentage increase in length a test sample undergoes before breaking. It calculates the difference between the final fractured gauge length and initial gauge length, representing the total plastic deformation.
Fracture energy – It is the total energy per unit area dissipated to create a new fracture surface, representing a material’s resistance to crack propagation. It includes energy for atomic separation, localized plastic deformation, and micro-cracking, and is typically determined through notched sample tests to measure toughness. Fracture energy is the work done per unit area of fracture surface.
Fracture face – It is also called fracture surface. It refers to the newly created surfaces formed when a metallic material separates into two or more parts under stress. Examination of this surface through fractography is a critical failure analysis technique used to determine the cause, mechanism, and origin of a failure by analyzing the topography, pattern, and shape of the broken surface. The appearance of a fracture face reveals how the material behaved during the failure:
Fracture failure – It is the separation of a metal component into two or more pieces, resulting from crack initiation and propagation when stresses exceed the material’s strength. This catastrophic failure can be caused by excessive static load, fatigue, or environmental factors, frequently occurring at pre-existing defects.
Fracture flow – It refers to the movement of fluids through fractures in geological formations, which can be modeled using either a single fracture approach or fracture networks, with substantial challenges in accurately representing the complex physics and roughness of fractures in mathematical models.
Fracture forming limit curve – It is also called ‘fracture forming limit line’. It is a graphical representation in principal strain space which defines the threshold of final rupture in sheet metal, extending beyond the conventional forming limit curve (FLC). While the traditional forming limit curve indicates the onset of localized necking, the fracture forming limit curve (FFLC) represents the strain levels at which actual separation or fracturing occurs.
Fracture Forming Limit Line – It is frequently referred to as the fracture forming limit curve (FFLC). It is a material-specific failure threshold in sheet metal forming which defines the onset of actual crack initiation or material separation. Unlike the standard forming limit curve (FLC), which predicts localized necking, the fracture forming limit line represents the strain states where the material completely fails, frequently allowing for higher deformation levels than the forming limit curve.
Fracture frequency – It is the number of natural fractures or discontinuities encountered per unit length of material, normally measured along a drilled core sample or a scanline. It is an important parameter for assessing the quality and structural integrity of materials, such as rock masses, and is frequently expressed in fractures per meter.
Fracture geometry – It refers to the quantitative description of the shape, topography, size, and orientation of a fractured surface, as well as the crack path through the material micro-structure. It is a key element of fractography, which uses this geometry to identify the failure mode (ductile against brittle), the site of crack initiation, and the direction of propagation.
Fracture gradient – It is the pressure needed to induce fractures in a geological formation at a given depth, expressed as a pressure-to-depth ratio. It represents the maximum pressure that a formation can withstand from a wellbore fluid (e.g., drilling mud) before tensile fractures occur, often measured in units such as kilopascals per meter or kilograms per cubic meter.
Fracture grain size – It is the grain size which is determined by comparing a fracture of a sample with a set of standard fractures. For steel, a fully martensitic sample is normally used, and the depth of hardening and the prior austenitic grain size are determined.
Fracture half-length – It is the length of a hydraulic fracture on each side of the wellbore, typically extending in the direction of least resistance. It can be categorized into hydraulic fracture half-length, propped fracture half-length, and effective fracture half-length, each representing varying contributions to flow within the reservoir. Fracture half-length is the distance from the wellbore to the outer tip of a hydraulic fracture wing. In hydraulic fracturing, it is typically assumed that fractures propagate in two symmetrical ‘wings’ or ‘bi-wings’ from the wellbore in the direction of least resistance. Hence, the total fracture length is twice the fracture half-length.
Fracture half-width – It is the distance from the centre-line of a fracture to its outer edge, which is influenced by factors such as fluid pressure and leak-off velocity during fracture propagation in permeable rock.
Fracture, horizontal – It is normally referred to as a transverse fracture or a type of tensile / cleavage fracture. It is a break which propagates perpendicular to the direction of the applied tensile stress. It is a separation of the material into two pieces where the fracture plane is oriented ‘horizontally’ relative to the vertical force applied to it.
Fracture initiation – It is the initial formation of a microscopic crack or void within a material, marking the transition from stable damage accumulation to the creation of a distinct, separable surface. It is the first stage in the overall fracture process, followed by crack propagation and, ultimately, final failure.
Fracture length – It refers to the physical size of a crack, flaw, or discontinuity within a metal component which has been subjected to stress. It is a critical parameter used to calculate the stress intensity factor and determine if a material is going to fail under load.
Fracture limit lines – These are also called fracture forming limit curves (FFLC). These lines are graphical representations in principal strain space (e1, e2) which define the onset of cracking or rupture in a material. Unlike the ‘forming limit curve’ (FLC), which marks the start of localized necking, the fracture limit line indicates the boundary where the material fails completely due to excessive straining.
Fracture limit locus – It refers to a graphical representation, typically in principal strain space (e1, e2), which defines the specific combinations of deformation (strains) at which a metal will fracture. Unlike the ‘forming limit curve’ (FLC), which marks the onset of necking, the fracture locus marks the actual onset of crack initiation and propagation. Fracture limit locus is the ‘geometric place’ (locus) of strain pairs (e1, e2) at the onset of fracture, separating safe forming conditions from failure conditions. Fracture loci in sheet metal are normally divided into two main categories namely fracture forming limit line (FFL) and shear fracture forming limit line (SFFL).
Fracture linear flow – It is an early-time flow regime in hydraulically fractured wells, characterized by fluid traveling perpendicular to the fracture face toward the fracture, or along the fracture to the wellbore. It appears as a half-slope (1/2) on a log-log diagnostic plot of pressure derivatives, signaling high conductivity or early-time fracture linear-flow behaviour.
Fracture load – It is the maximum force applied to a material or structure before it breaks or experiences catastrophic failure. It measures resistance to cracking under stress, often measured in newtons (N) or kilo-newtons (kN).
Fracture mechanics – Fracture mechanics is the field of mechanics concerned with the study of the propagation of cracks in materials. It uses methods of analytical solid mechanics to calculate the driving force on a crack and those of experimental solid mechanics to characterize the material’s resistance to fracture. It is a quantitative analysis for evaluating structural behaviour in terms of applied stress, crack length, and sample or machine component geometry.
Fracture mechanics-based model – It is a computational approach, e.g., finite element method (FEM), extended finite element method (XFEM), which uses physics-based principles to simulate crack propagation, material failure, and damage tolerance under various loading conditions. These models, also known as fracture analysis methods or failure mechanics models, rely on parameters like stress intensity factors or energy release rates to predict structural life.
Fracture mechanics research – It is the study of how cracks and flaws initiate, propagate, and cause failure in materials under stress. It develops methods to analyze stress intensity factors, material toughness, and crack tip plasticity to predict failure conditions, aiming to ensure structural integrity in design and evaluate defects.
Fracture mechanics sample – It is a specifically configured, notched material piece used to quantify how a material resists crack growth under load, frequently to assess material toughness or fatigue life. These samples, such as compact tension (CT) or single-edge notch bending (SENB) samples, are important for safety analysis in construction, where they measure material susceptibility to failure by simulating flaws.
Fracture mechanics studies – These refer to the investigation of the behaviour of materials with cracks, incorporating both strength of materials and stochastic approaches, including the examination of micro and macro fracture mechanics and the influence of stress concentrations and thermal activation on the fracture processes.
Fracture mechanics test – It measures a material’s resistance to crack growth, propagation, and unstable fracture under load, determining critical properties like fracture toughness, J-integral, or crack tip opening displacement (CTOD). It involves applying stress to pre-notched samples to simulate, predict, or evaluate safety-critical flaws in materials.
Fracture mechanism map – It is a graphical tool (a diagram) which shows the dominant mechanism of fracture for a given material under different conditions of stress, temperature, or sometimes time. It acts as a guide to identify whether a material will fail by brittle cleavage, ductile rupture, or creep fracture, making it essential for material selection in engineering applications.
Fracture mechanisms – These are the microscopic processes and physical conditions, such as ductile void coalescence, cleavage, fatigue, or stress corrosion, which lead to crack initiation and propagation, culminating in material failure. They dictate how a material responds to stresses, flaws, or environmental factors, categorized mainly by the quantity of deformation (ductile against brittle).
Fracture morphology – It is the study and description of the observable surface features, shape, and fragmentation patterns of a broken material. It analyzes characteristics like tear ridges, cleavage planes, and void formations to determine how a crack initiated, grew, or failed. It is used to identify material failure mechanisms and structural integrity.
Fracture network – It is a system of interconnected, finite fractures, such as joints, faults, and bedding planes, within a rock mass which acts as a conduit for fluid flow. These networks, frequently modeled as ‘discrete fracture networks’ (DFNs), define the spatial distribution, orientation, aperture, and connectivity of fractures, heavily impacting hydraulic conductivity in aquifers and oil / gas reservoirs.
Fracture opening – It refers to the displacement occurring at a mode-I fracture in an elastic medium, influenced by fluid pressure and in situ stress distribution, and is described mathematically by an integral equation which accounts for the fracture’s shape and properties.
Fracture origin – It is the specific, localized point within a material where a crack initiates, typically at areas of high stress, inclusions, or inherent weaknesses. It is identified through fractography by tracing markings backward to locate the flaw responsible for failure, allowing for the analysis of its causes.
Fracture parameters – These are quantitative measures (e.g., stress intensity factors, J-integral, and fracture energy) used to evaluate material resistance to cracking, crack growth stability, and failure mechanisms. These parameters define the stress state near a crack tip and are important for assessing damage and material strength.
Fracture permeability – It is the measure of a rock mass’s capacity to transmit fluids through its network of inter-connected fissures, joints, and micro-cracks, distinct from the porous rock matrix. It acts as a dominant control on sub-surface fluid transport, particularly in tight or crystalline rock formations.
Fracture plane – It is a two-dimensional surface or plane of weakness within a solid, such as rock, crystal, or metal, along which separation or breakage occurs under stress. It represents the specific, frequently weakest, surface where cracks propagate, resulting in failure, and is normally used in structural geology to describe rock joints or in materials science to determine failure modes.
Fracture porosity – It is a type of secondary porosity produced by tectonic stresses which create cracks, fissures, and breaks in rock. It represents the ratio between the volume of open fractures and the total rock bulk volume, normally constituting a small percentage (0.0001 to 0.001) but considerably increasing permeability.
Fracture pressure – It is the minimum internal pressure (wellbore pressure) needed to exceed the rock’s compressive strength and tensile strength, causing it to crack, fracture, or break down. It defines the upper limit for drilling mud weight to avoid lost circulation, ensuring pressure stays between pore pressure and overburden pressure.
Fracture propagation – It is the process where existing cracks, flaws, or discontinuities in a material grow, extend, and expand because of the applied stress or internal pressure. It is a, key mechanism in material failure, transitioning from initiation (nucleation) to substantial crack growth, frequently studied to prevent structural damage or to create, such as in hydraulic fracturing.
Fracture propagation criterion – It is a set of physical conditions or failure theories used to predict if, when, and in which direction an existing crack or flaw is going to extend under loading. It defines the threshold (e.g., critical stress intensity factor or energy release rate) where material resistance is overcome, causing growth.
Fracture properties – These are material characteristics defining resistance to breaking, cracking, or catastrophic failure under stress. Key properties include fracture toughness, which measures resistance to crack propagation, critical stress intensity factor, and energy absorption. These properties are important for evaluating material safety and preventing structural failure.
Fracture repair – It refers to the controlled processes used to close, bridge, or reverse the effects of cracking, separation, or structural failure in metallic components. While a fracture in metal is the separation of a surface because of the stress (ductile or brittle), ‘repair’ implies techniques aimed at restoring structural integrity, such as welding, specialized heat treatments, or the application of strengthening patches.
Fracture resistance – Fracture resistance of a material is characterized by the critical stress intensity factor which can be sustained without fracture.
Fracture roughness – It refers to the surface texture, topography, and geometric irregularity of a fractured metal surface. It is the measure of the ‘hills and valleys (asperities) created on the mating surfaces when a material separates.
Fracture segment – It typically refers to a distinct, separated portion of a material which has broken off or has been isolated between two or more intersecting crack paths or failure lines. It is a localized part of a larger, fracturing metal component which becomes separated because of the stress, frequently associated with brittle fracture, fatigue, or complex, multi-axial loading scenarios.
Fracture sets – These refer to groups of fractures which have approximately the same orientation and are related to the tectonic history of the area, frequently arising from multiple tectonic events. These sets are typically more homogeneous in characteristics such as size and aperture compared to combined sets.
Fracture site – It refers to the exposed surface of a material which has separated into two or more pieces under the influence of stress. The topography and morphology of this site provide critical information about the material’s failure mechanism, loading conditions, and structural integrity, often analyzed through a method called fractography.
Fracture splitting – It is cracked-rod technology. It is a modern manufacturing process used to separate a metal component, very frequently the ‘big end’ of an engine connecting rod, from its cap by deliberately creating a brittle fracture rather than using traditional cutting or sawing methods. It is a precision-controlled, high-impact process often applied to forged steel or sintered powder forging materials.
Fracture strain – It is also called strain at fracture. It is the total plastic deformation (stretching or elongation) a metallic material sustains just before it breaks under load. It is a key measure of ductility and is calculated as the ratio of the change in length to the original length, frequently expressed as a percentage, representing the final point on a stress-strain curve.
Fracture strength – It is the normal stress at the beginning of fracture. It is calculated from the load at the beginning of fracture during a tension test and the original cross-sectional area of the sample.
Fracture stress – It is the true, normal stress on the minimum cross-sectional area at the beginning of fracture. The term normally applies to tension tests of unnotched samples.
Fracture-stress-based criterion – It is a failure model which predicts crack initiation or component failure when the local stress (typically the maximum normal principal stress) at a point exceeds a critical material fracture strength (Sc or Sf). This criterion assumes that material failure is controlled by the intensity of the stress acting on a microscopic level rather than the overall average load, making it important for analyzing brittle fractures and crack growth, particularly in notched structures.
Fracture surface – It is the irregular surface produced when a piece of metal is broken.
Fracture surface markings – These are fracture surface features which can be used to determine the fracture origin location and the nature of the stress that produced the fracture.
Fracture system – It refers to the comprehensive network of crack paths, cleavage planes, and fracture modes which a metal shows when separating under stress. It is characterized by the morphology of the broken surface, which reveals how the material failed because of the internal defects, micro-structure, and applied loads.
Fracture test – It is the test in which a sample is broken and its fracture surface is examined with the unaided eye or with a low-power microscope to determine such factors as composition, grain size, case depth, or discontinuities.
Fracture testing – It is a procedure used to measure a material’s resistance to crack propagation and brittle fracture under stress, frequently by evaluating its fracture toughness. It determines how much energy a material can absorb in the presence of a flaw before catastrophic failure. Key methods include impact testing (e.g., Charpy) and fracture toughness testing (e.g., J-integral).
Fracture tip – It is also called crack tip. It is the leading edge or boundary of a discontinuity (crack, flaw, or notch) in a material where the highest concentration of stress occurs. It is the specific point where the atomic bonds are being broken as a crack propagates, leading to material separation.
Fracture toughness – It is a generic term for measures of resistance to extension of a crack. The term is sometimes restricted to results of fracture mechanics tests, which are directly applicable in fracture control. However, the term normally includes results from simple tests of notched or pre-cracked samples not based on fracture mechanics analysis. Results from tests of the latter type are frequently useful for fracture control, based on either service experience or empirical correlations with fracture mechanics tests.
Fracture toughness test – It is a mechanical test which measures a material’s resistance to brittle fracture when a crack or flaw is present. It determines the critical stress intensity, J-integral, or crack tip opening displacement (CTOD) needed to propagate a pre-existing fatigue crack under load.
Fracture toughness testing – It is a destructive testing method which quantifies a material’s resistance to brittle fracture when a crack or notch is present. It involves applying a progressively increasing load to a pre-cracked sample to determine the stress intensity or energy needed to propagate the crack.
Fracture toughening mechanisms – These are microstructural or macrostructural processes which improve a material’s resistance to crack propagation, allowing it to absorb more energy and withstand higher loads in the presence of a crack or flaw before failing catastrophically. These mechanisms work by either resisting the initiation of a crack (intrinsic) or by reducing the stress intensity at the crack tip (extrinsic).
Fracture volume – It normally refers to the three-dimensional space occupied by a crack, void, or system of interconnected fissures created within a material when it breaks or tears under stress. While sometimes used synonymously with the surface area of a crack, ‘fracture volume’ specifically implies the volume of material removed, damaged, or opened up (such as the volume of a crack tip’s plastic zone).
Fracture wall – It refers to the opposing, newly created surfaces of a material which has separated into two or more pieces because of the applied stress, failure, or crack propagation. These surfaces (sometimes referred to as fracture faces) are studied in fractography to determine the mechanism of failure, such as whether it was ductile or brittle.
Fracture width – It is frequently referred to as the fracture aperture or opening; It refers to the distance between the two matching surfaces (walls) of a crack or separation within a material. This measurement is crucial for characterizing the extent of damage, the type of fracture (brittle vs. ductile), and the residual strength of the material.
Fracturing method – It is the process, mode, or physical mechanism by which a solid metal, under stress, separates into two or more parts. It is the analysis of how cracks initiate and propagate through a crystalline structure, frequently studied through fractography to determine the main causes of failure.
Fracturing process – It is a method used in well completion where high-pressure fluids are pumped into a reservoir section, typically consisting of tight shale rock, to create fractures which improve fluid flow from the reservoir. This process frequently involves multiple stages, starting from the toe of the well, and includes the use of proppants to maintain the fractures.
Fracturing test – It is a destructive experimental procedure used to evaluate a material’s resistance to crack propagation and its overall fracture toughness. It involves applying a progressively increasing load to a pre-cracked, notched, or specifically prepared sample until it fails, allowing for the quantification of energy needed for the crack to grow.
Fragility curves – These are statistical tools which represent the probability of a component or structure exceeding a specific damage state (or performance limit) as a function of an engineering demand parameter, such as seismic intensity, stress, or temperature. These curves provide a continuous probabilistic relationship between the severity of an external action (loading) and the likelihood of failure, rather than a simple binary ‘safe / fail’ assessment.
Fragmentation – It is the process of breaking a solid into finely divided pieces. It is the sub-division of a grain into small, discrete crystallite outlined by a heavily deformed network of intersecting slip bands as a result of cold working. These small crystals or fragments differ in orientation and tend to rotate to a stable orientation determined by the slip systems.
Fragmented material – It refers to a metal or alloy which has been broken into multiple smaller pieces, particles, or shards, frequently due to high-rate deformation, explosive loading, or thermal processes. This deliberate or accidental process results in a high surface-area-to-volume ratio and is used to study material fracture resistance, dynamic deformation, or to enhance processing, such as melting.
Fragmented powder – It is a powder obtained by fragmentation and mechanical comminution into fine particles.
Fragment simulating projectiles – These are the projectiles designed to replicate the characteristics of explosive fragments, including their shape, size, geometry, and cutting and penetrating properties. They are typically made from specific types of steel and are used to simulate the effects of fragments generated during military conflicts.
Frame – It is the main structure of a press. It is also a list, compiled for sampling purposes, which designates the items(units) of a population or universe to be considered in a study. In valves, a frame is the centre enclosure of the actuator housing the yoke mechanism.
Frame alignment – It consists of the adjustment of conveyor frame components to maintain straight and parallel alignment, necessitating routine checks to prevent misalignment issues.
Frame analysis – It is the process of determining the internal forces, bending moments, shear forces, and displacements in structural frameworks, typically composed of beams and columns, under applied loads. It uses methods like finite element analysis (FEA) to ensure structural stability and efficiency.
Frame bounds – These refer to the minimum and maximum values, denoted as A and B, which satisfy the inequalities relating to a frame in a vectorial space, ensuring that the frame provides a stable representation for all vectors in the space.
Frame condition – It refers to the design requirements ensuring a structure (made of beams and columns) remains stable, rigid, and able to support loads through inter-connected members. It involves analyzing forces, moments, and connections (e.g., rigid joints) to ensure the frame does not fail under lateral or vertical loads.
Framed structure – It is a building system consisting of a rigid, interconnected skeleton of columns, beams, and slabs designed to support gravity and lateral loads, transferring them safely to the foundation. Unlike load-bearing masonry, this framework stands alone, allowing walls to serve as non-load-bearing partitions or enclosures.
Framed tube – It is a high-rise structural system where closely spaced perimeter columns (2meters to 4 meters apart) are connected by deep spandrel beams to form a rigid, hollow cylinder. It acts as a vertical cantilever to resist lateral loads (wind / seismic) and gravity, allowing for, but not requiring, fewer interior columns.
Frame foundation – In frame foundation, equipment is supported on the deck slab. This deck slab in turn is supported on base raft through columns, and base raft rests directly over soil or on group of piles. Size of deck slab, number of columns, height of columns above base raft etc. are primarily dependent on equipment layout. In this case, equipment is treated as non-elastic inertia body whereas deck slab, and columns are considered as elastic inertia bodies and soil is considered as elastic media. In certain specific cases, base raft is also considered as elastic inertia body.
Frame generator – It is a computer-aided design (CAD) software design accelerator which automates the creation of structural frames, machine bases, and welded assemblies along sketch paths or skeleton models. It streamlines the selection of standard profiles, placement, and complex end treatments like miters, notches, and trims.
Frame grabber – It is an electronic hardware device or interface card used in machine vision and imaging to capture, digitize, and store individual still frames from a continuous analog or digital video source. It acts as a bridge between an imaging device (such as a camera, microscope, or sensor) and a host computer, enabling high-speed, high-resolution data acquisition, preprocessing, and synchronization.
Frameless solar module – It is a photo-voltaic panel designed without the traditional aluminum frame, normally featuring solar cells encapsulated between two layers of glass (glass-on-glass). These panels offer improved aesthetics, higher durability against corrosion, and reduced soiling since they lack edges for dust accumulation. They are frequently used in rooftop, residential, and commercial projects, needing special clamping systems (e.g., ethylene propylene diene monomer rubber clamps) to hold them securely.
Frame model – It is a structural or computational representation consisting of rigid members (beams / columns) connected at joints to support loads. It simplifies complex structures into 1D beam elements, allowing faster analysis of forces, moments, and deformations compared to 3D solid elements, frequently used for bridges, towers, and building frames.
Frame, picture – It is the picture frame experiment which refers to a testing method that subjects a flat pre-consolidated composite sample to uniform in-plane deformation using a four-bar linkage and a hydraulic testing machine, while operating within an environmental chamber capable of reaching temperatures up to 450 deg C.
Frame rate – It is frequently expressed as frames per second (FPS). It is defined as the frequency (or rate) at which a system, such as a video camera, computer graphics engine, or display, captures, generates, or displays consecutive images (frames). It is a measure of temporal resolution, determining how smoothly motion is portrayed to the viewer.
Frame relay – Ir is a high-performance, packet-switching WAN (wide area network) technology operating at the ‘data link layer’ (open systems inter-connection layer 2) to connect LANs (local-area network) across digital networks. It uses a ‘fast packet’ methodology which boosts efficiency by eliminating error correction, dropping damaged frames and leaving retransmission to endpoints. It utilizes virtual circuits, normally PVCs (permanent virtual circuits), for efficient, bursty data transmission.
Frame size, electric motor – It defines the geometric values of its physical size, i.e., the outer dimensions of the motor flange and bolt circle. It defines its mechanical interface to attached actuators. Motors of the same frame size can have different power, torque etc. but feature the same geometrical properties. The length of the motor housing is not affected by the frame size.
Frame spacer – It consists of cross connections strategically used to ensure appropriate separation between the frame rails in a conveyor system, necessitating routine assessments for stability and alignment.
Frame support structure – It is the framework which provides essential support to the machinery components of a conveyor, demanding regular inspections to uphold structural integrity and alignment.
Frame vector – It refers to a set of vectors defining a coordinate system (frame of reference) used to describe positions and orientations, typically through orthonormal basis vectors (I, j, k). In signal processing, frame vectors refer to a set of vectors which enable a stable representation of a signal by generating coefficients through signal projection, which are then used in a synthesis operation to approximate the original signal.
Framework – It is an organized structure of policies, programmes, and tasks created to achieve a specific outcome. There can be frameworks for broad policies and strategic initiatives at different scales (e.g., operational, financial, marketing, research and development, human resource management and development), programmes and programme delivery, and short-term tasks and projects.
Framing plan drawing – Framing plan drawing is similar to the beam layout. It offers information about the framework, sizes, and positions of the beams. It is helpful since to the site engineers as they can easily understand and layout the plans for the roof, floor, and other such structures which are a necessary part of a building.
Francis-turbine – It is a mixed-flow turbine which that allows water to change direction as it passes through, entering radially and exiting along the turbine’s axis. It is designed to efficiently convert the energy of flowing water into electricity, achieving high energy capture rates, particularly between head heights of 100 meters to 300 meters.
Franck-Condon principle – It states that electronic transitions occur much faster (femto-seconds) than nuclear motion, meaning nuclear positions remain effectively fixed during excitation. As a result, transitions are represented as vertical lines on potential energy diagrams, favoring transitions to vibrational states with maximum overlap (Franck-Condon factors). It is the principle which states that the transition from one energy state to another is so rapid that the nuclei of the atoms involved can be considered stationary during the transition.
Frangible bulb – It is a liquid filled glass device for detecting high temperature. At a pre-determined temperature, the bulb fractures causing the control valve to change state and signal the actuator to close the valve.
Frank dislocation – It is a sessile (immobile) dislocation loop formed in crystal structures (typically face-centered cubic. fcc) by the clustering of vacancies or interstitials on a {111} plane, creating a stacking fault. It is characterized by a Burgers vector ‘b’ perpendicular to the fault plane, normally a/3 <111>, and cannot glide, moving only through climb.
Frank network – It is frequently termed a ‘Frank net’ or Frank dislocation network. It refers to a continuous, three-dimensional network of dislocation lines which exist within a crystalline structure, frequently pinned by microstructural features like precipitates or grain boundaries.
Frank partial dislocations -These are sessile (immobile) defects in fcc (face-centered cubic) crystals formed by vacancy clustering, where a 1/3 <111> {Burger’s vector} sits perpendicular to a {111} stacking fault plane. They act as dislocation barriers, preventing slip and contributing to work hardening, frequently forming during high-temperature quenching or irradiation. A Frank partial dislocation is a perfect dislocation loop in {fcc metals} which surrounds a {stacking fault}. They are formed when a layer of atoms on a {111} plane is either removed ({intrinsic fault}) or inserted ({extrinsic fault}), creating a disc-shaped cavity which collapses.
Frank-Read source – It is a fundamental mechanism for dislocation multiplication in crystalline materials, where a dislocation segment pinned at two points bows out under shear stress, creating new dislocation loops. Operating during plastic deformation, it acts as a main source of increased dislocation density (work hardening) by repeatedly producing dislocation loops and reforming the pinned segment.
Frank–Van der Merwe (FM) growth – It is also called layer-by-layer growth. It is a thin-film deposition mode where atoms bind more strongly to the substrate than to each other (adhesion > cohesion), resulting in 2D, smooth, and complete monolayer formation before the next layer begins. It is important for high-quality epitaxy, minimizing defects in semi=conductor manufacturing.
F-ratio – It is the ratio of two independent unbiased estimates of variance of a normal distribution. It has widespread application in the analysis of variance (ANOVA).
Freckles – These are a metallurgical defect characterized by the formation of small, randomly oriented, equiaxed grains, often appearing in clusters, that disrupt the desired single-crystal structure of castings. They are typically found in superalloys, particularly in turbine blades, and are associated with channel segregation. The formation of freckles is a complex process influenced by thermal, solutal, and fluid flow conditions during solidification.
Freckling – It is a type of segregation revealed as dark spots on a macro-etched sample of a consumable electrode vacuum-arc-remelted alloy.
Fredholm integral equation – It is a mathematical formula where an unknown function appears under an integral sign with constant limits of integration. Fredholm integral equations are used to model complex, linear forward, and inverse problems where physical properties are distributed throughout a material.
Free air conditions – These are specified as those at which pressure is 0.1 mega-pascals absolute (standard atmospheric pressure) and temperature of 15 deg C (standard atmospheric temperature).
Free air conditions are normally used as the reference conditions for the specification of blowers and compressors.
Free Alongside Ship (FAS) – ‘Free Alongside Ship’ means that the seller delivers when the goods are placed alongside the vessel (e.g., on a quay or a barge) nominated by the buyer at the named port of shipment. The risk of loss of or damage to the goods passes when the goods are alongside the ship, and the buyer bears all costs from that moment onwards.
Free ash – It is the ash which is not included in the fixed ash.
Free bend – It is the bend got by applying forces to the ends of a sample without the application of force
at the point of maximum bending. In making a free bend, lateral forces first are applied to produce a small quantity of bending at two points. The two bends, each a suitable distance from the centre, are both in the same direction.
Free-board, ladle – It is the measurement of the area between the top edge of the ladle and the surface of the molten metal inside it. Ladle free-board measurement is important for plant safety and efficiency.
Free-body diagram – It is a drawing which isolates a part of a complete system to determine the forces acting on that rigid body, allowing for the analysis of individual links or subsystems within mechanical systems.
Free carbon – It is the part of the total carbon in steel or cast iron which is present in elemental form as graphite or temper carbon.
Free Carrier (FCA) – ‘Free Carrier’ means that the seller delivers the goods to the carrier or another person nominated by the buyer at the seller’s premises or another named place. The parties are well advised to specify as clearly as possible the point within the named place of delivery, as the risk passes to the buyer at that point.
Free chloride ions – These are negatively charged chlorine atoms (Cl-) dissolved in the pore solution of concrete which are not bound to the cement paste. As the main cause of reinforced concrete corrosion, these mobile ions diffuse toward reinforcing steel, destroying its protective passive film when they reach a critical concentration.
Free chlorine – It is the active, unbound chlorine available for disinfection in water, mainly comprising hypochlorous acid (HOCl) and hypochlorite ion (OCl-). It acts as a rapid disinfectant against micro-organisms before reacting with contaminants to form combined chlorine. Free chlorine (FC) is the very effective sanitizing form.
Free corrosion potential – It is the corrosion potential in the absence of net electrical current flowing to or from the metal surface.
Free cutting steels – These steels are those steels which can be machined rapidly (in terms of productivity) by keeping satisfactory tool life, and by avoiding any machining interruption for chips evacuation. This objective is reached economically by using the cheapest routes, such as increasing the sulphur content of the steel and alloying the steel with lead intended to be machined. These two routes have been used for decades, and their cumulative effects have been the heart of development of the low carbon free-cutting steels. Free-cutting steels are used in a broad variety of applications, mainly in the automobile industry. These steels are used in the production of axles, shafts, connection rods, fitting turn-offs, high-pressure fuel injector parts, screws, bolts, and fittings. This group of steels results from the requirement to automated machining, i.e., they are easier to machine than classical steels resulting in higher cutting speed, lower tool wear, better surface finish, better chip breaking, and lower energy consumption of the machines.
Free cyanide – (i) True: It is the actual concentration of cyanide radical, or equivalent alkali cyanide, not combined in complex ions with metals in solution. (ii) Calculated: It is the concentration of cyanide, or alkali cyanide, present in solution in excess of that calculated as necessary to form a specified complex ion with a metal or metals present in solution. (iii) Analytical: It is the free cyanide content of a solution, as determined by a specified analytical method.
Free edge effects – These refer to the very high interlaminar stresses which can arise at the free edge of a laminate with different ply orientations, potentially leading to premature failure and initiating delamination or compressive failure depending on the laminate configuration and loading conditions.
Free electron – It is a valence electron which has detached from its parent atom and is free to move throughout the metallic lattice. These delocalized electrons form a negatively charged ‘electron sea’ or ‘electron gas’ around positive metal ions, acting as the metallic bond which allows for high electrical / thermal conductivity and ductility. Free electrons originate from the outermost shells (valence shells) of metallic atoms.
Free energy – It refers to the Gibbs free energy (G = H- TS), which is the useful energy available to do work at constant temperature and pressure. It determines the feasibility, spontaneity, and equilibrium of metallurgical processes like reduction, oxidation, and phase changes, where a reduction in free energy (dG is below zero) indicates a spontaneous, possible reaction.
Free energy change – It is the maximum quantity of non-expansion work (e.g., electrical or mechanical work) extractable from a system at constant temperature and pressure. Free energy change defines the spontaneity of a process. Free energy change refers to the change in Gibbs free energy (delta-G) in a system at constant temperature, which determines the direction of a process, such as a chemical reaction. A negative delta-G indicates a spontaneous reaction, while a positive delta-G suggests that the reaction is not going to proceed spontaneously.
Free-energy diagram – It is a graph of the variation with concentration of the Gibbs free energy at constant pressure and temperature.
Free-energy surface – In a ternary or higher order free-energy diagram, it is the locus of points representing the Gibbs free energy as a function of concentration, with pressure and temperature constant.
Free fall – It is defined as the motion of objects under the influence of gravity alone, resulting in a constant acceleration of 9.8 meters per square meters downward when air resistance is negligible. In this context, the gravitational force acting on the object, referred to as weight, is proportional to its mass.
Free-falling particle receiver – It is a type of concentrating solar power (CSP) technology where small solid particles, typically ceramic, fall under gravity in a thin curtain through a cavity receiver, directly absorbing concentrated solar energy. It enables high-temperature operation, frequently exceeding 700 deg C to 1,000 deg C, and serves as both the heat transfer medium and the thermal storage medium, offering superior performance compared to traditional fluids.
Free ferrite – It is the ferrite which is formed directly from the decomposition of hypo-eutectoid austenite during cooling, without the simultaneous formation of cementite. It is also the ferrite which is formed into separate grains and not intimately associated with carbides as in pearlite. It is also called pro-eutectoid ferrite.
Free float – It is the quantity of time by which an activity can be postponed without affecting the early start dates of a successor activity.
Free-flow area – It refers to the minimum net cross-sectional area available for fluid (liquid or gas) to pass through a restricted space, such as a heat exchanger, louvers, or screens. It is defined as the total area of the opening minus the area blocked by obstructions like blades, frames, or tubes. It is also the cross-sectional area through which fluid can flow in a channel, influenced by local flow conditions and geometry, and can be expressed as a function of location in the flow direction.
Free-flowing sand – It refers to sand which readily moves and flows like a liquid, without clumping or sticking together. It is characterized by its ability to be easily poured, transported, and handled using different flow processes. This contrasts with materials which are cohesive or sticky and do not easily flow.
Free formaldehyde – It is defined as the percentage of formaldehyde present in a sample which is not chemically bound to other substances, which can be quantified through a titration method involving sodium sulphite and iodine solution.
Freeform deformation – It refers to the process of modifying objects through smooth deformations such as bending, twisting, stretching, and compressing of surfaces using a space-warping function. Freeform deformation (FFD) consists of advanced metal-forming techniques which create complex, custom, or 3D-curved metal parts, particularly tubes and sheets, without the need for dedicated, high-cost die sets. It frequently involves flexible processes like freeform bending, where a work-piece is shaped through continuous, controlled plastic deformation.
Free-form shapes – These shapes refer to metallic components with intricate, non-analytic geometries which lack axes of rotation or standard geometric definitions (such as planes, cylinders, or spheres). These shapes are frequently characterized by non-constant curvature and complex, flowing contours designed for specific functional, aerodynamic, or aesthetic requirements.
Freeform surface characterization – It is the process of defining, measuring, and analyzing complex, non-rotational, and non-planar surfaces frequently defined by NURBS (non-uniform rational basis spline) or triangulated mesh data, to ensure they meet needed functional, geometrical, and topological specifications. It involves moving from traditional simple 2D height maps to 3D surface representations, allowing for the analysis of intricate geometries such as turbine blades, and moulds, as well as features created through additive manufacturing.
Freeform surface modelling – It is a technique for engineering freeform surfaces with a ‘computer-aided design’ (CAD) or ‘computer-aided industrial design’ (CAID) system. The technology has encompassed two main fields. Either creating aesthetic surfaces (class A surfaces) which also perform a function; for example, car bodies and consumer product outer forms, or technical surfaces for components, e.g., gas turbine blades and other fluid dynamic engineering components. Computer-aided design software packages use two basic methods for the creation of surfaces. The first begins with construction curves (splines) from which the 3D surface is then swept (section along guide rail) or meshed (lofted) through. The second method is direct creation of the surface with manipulation of the surface poles / control points. From these initially created surfaces, other surfaces are constructed using either derived methods such as offset or angled extensions from surfaces; or via bridging and blending between groups of surfaces.
Free formulation – It is also called the ‘free formulation’ method. It is a specialized approach in finite element analysis (FEA). It is an efficient method for creating high-performance finite elements (e.g., shell elements) without relying on strict conformity (conforming shape functions). The free formulation is designed to avoid ‘locking’ behaviours (artificial stiffness) while ensuring convergence in linear and nonlinear analyses. Its core characteristics include weakened constraints, two-part formulation, non-conforming shape functions, and optimal element design.
Free gas saturation (Sg) – It is the fraction of pore volume in a porous medium (rock or sediment) filled with gaseous phase hydrocarbons (non-dissolved gas) rather than oil or water. It represents the fraction, ranging from 0 to 1 (or 0 % to 100 %), and is a critical parameter in reservoir engineering which governs flow, acoustic, and stability properties. It is the volume of free gas divided by the total pore volume (Sg = Vgas/Vpores).
Free graphite – It refers to carbon which exists in a separate, uncombined, elemental form within the microstructure of ferrous alloys, very frequently in cast iron. Unlike combined carbon (which forms iron carbide or cementite), free graphite is physically distinct as crystalline, hexagonal carbon flakes, nodules, or plates. Free graphite is typically found in gray cast iron (flake form), ductile cast iron (spheroidal / nodular form), and compacted / vermicular cast iron. It occurs when carbon precipitates out of solution during the cooling process of molten iron, especially when high carbon equivalent is present or when alloying elements like silicon (a graphitizer) are added.
Free implementation – It refers to a software or hardware realization of a design, algorithm, or specification which grants users the fundamental freedoms to run, study, share, and modify it. In this context, ‘free’ indicates liberty (libre), not necessarily zero cost (gratis), and is frequently synonymous with ‘free and open-source software’ (FOSS).
Free ion – It is a positively (cation) or negatively (anion) charged particle which is not bound to a specific molecule or atom, allowing it to move independently and conduct electricity within a solution, melt, or plasma. Free ions are distinct from ion pairs and are central to electro-chemical reactions, corrosion studies, and plasma physics.
Free layer damping treatment – It is a passive vibration control method where a viscoelastic material (VEM) is bonded directly to a structure. It dissipates vibration energy mainly through alternating extension and compression (hysteresis) of the layer, rather than through shear strain, which is characteristic of constrained layer damping. The layer operates by extending and compressing as the structural substrate bends, converting structural vibration energy into heat.
Free lime – It refers to calcium oxide (CaO) which remains unbound or uncombined with other raw materials (such as silica, alumina, or iron) after the burning, calcination, or sintering process. It is essentially residual, unreacted quick-lime present in a material which is ideally to be fully reacted.
Free machining – It pertains to the machining characteristics of an alloy to which one or more ingredients have been introduced to produce small broken chips, lower power consumption, better surface finish, and longer tool life. Among such additions are sulphur or lead to steel, lead to brass, lead and bismuth to aluminum, and sulphur or selenium to stainless steel.
Free-machining additives – These are specific chemical elements, very frequently sulphur (S), lead (Pb), bismuth (Bi), tellurium (Te), selenium (Se), and phosphorus (P), incorporated into metallic alloys (mainly steel and brass) to improve their machinability. These additives work by modifying the microstructure of the metal to reduce friction, break chips into small pieces, and minimize the formation of built-up edges on cutting tools, thus facilitating high-speed, automated machining.
Free machining alloy – It is an alloy designed to give, when machined, small broken chips, lower power consumption, better surface finish and / or longer tool life. Chemical composition and microstructure both influence this property.
Free milling – It consists of ores of gold or silver from which the precious metals can be recovered by concentrating methods without resorting to pressure leaching or other chemical treatment.
Free moisture content – It is the quantity of easily removable water (unbound water) is known as the free moisture content. It is the unbound water which is associated with a wet solid which exists as a liquid and it exerts its full vapour pressure. It can be removed readily by evaporation.
Free of alloyed steel, scrap – The term free of alloyed steel means that any alloying elements contained in the steel are residual and have not been added for the purpose of making an alloy steel. Ferrous metal scrap is considered free of alloys when the residual alloying elements do not exceed a certain percentage such as nickel – 0.45 %, molybdenum – 0.10 %, chromium – 0.20 %, and manganese – 1.65 %. The combined residuals other than manganese are not to exceed a total of 0.60 %.
Free On Board (FOB) – ‘Free On Board’ means that the seller delivers the goods on board the vessel nominated by the buyer at the named port of shipment or procures the goods already so delivered. The risk of loss of or damage to the goods passes when the goods are on board the vessel, and the buyer bears all costs from that moment onwards.
Free pipe – It refers to the portion of a stuck drill string or piping system that is not anchored or constrained by external forces, allowing it to move, stretch, or bend freely under tensile, compressive, or thermal loads. It is important in drilling for locating stuck points and in piping design for accommodating expansion.
Free-piston compressor – It is a linear, crank-less machine where the piston moves freely, oscillating driven by gas pressure or electro-magnetic force rather than a rotating crank-shaft. It combines a combustion engine or motor directly with a compressor piston, optimizing compression ratios and reducing friction / wear by eliminating linkages.
Free-piston engine – It is a linear, crank-less internal combustion engine where the piston moves freely without a crank-shaft to convert motion. Piston motion is determined by combustion gas forces, a rebound device (gas spring), and a load (e.g., linear alternator or compressor), offering higher efficiency, lower friction, and variable compression ratios.
Free population – It normally refers to entities, such as water molecules, particles, or agents, not restricted by boundaries, structural barriers, or binding forces, allowing them to show isotropic behaviour. This term is used to distinguish free entities from ‘bound’ or constrained ones in systems analysis.
Free probability – It is a non-commutative operator-dependent measure theory which generalizes classical probability to non-commuting random variables (e.g., large random matrices). It replaces classical independence with ‘freeness’, a notion of independence suited for non-commutative algebras. Key tools include free convolution, free central limit theorem, and free entropy.
Free quenching – It refers to the rapid cooling of a heated metal part (normally from austenitic temperatures) by plunging or immersing it directly into a quenching medium, such as water, oil, brine, or polymers, to increase hardness and strength. It is a form of bath quenching or immersion quenching, designed to transform the micro-structure into martensite, resulting in high hardness and wear resistance.
Free radical – It is a molecule or atom which possesses one unpaired electron. In chemical notation, a free radical is symbolized by a single dot (to denote the odd electron) to the right of the chemical symbol. It is also a type of polymerization in which the propagating species is a long-chain free radical initiated by the introduction of free radicals from thermal or photochemical decomposition.
Free radical polymerization – It is a chain-growth mechanism where unsaturated vinyl monomers (e.g., ethylene, styrene) link together to form polymers, initiated by highly reactive radicals. It is an important process involving three main stages, initiation, propagation, and termination, mainly used to produce widely used plastics like poly-ethylene (PE), polyvinyl chloride (PVC), and polystyrene.
Free radical scavenging – It is the process of using anti-oxidant compounds to neutralize highly reactive, unstable atoms or molecules (free radicals) which damage materials, polymers, or fuel cells, frequently by interfering with and terminating degrading oxidation-reduction reactions. It acts as a protective system to improve stability.
Free radical suspension polymerization – It is a heterogeneous liquid-liquid engineering process where monomer droplets (containing an oil-soluble initiator) are suspended in an aqueous phase, stabilized by agitation and dispersing agents. Polymerization occurs within each droplet, creating spherical ‘bead’ or ‘pearl’ polymer particles.
Free rolling – It is the rolling in which no traction is deliberately applied between a rolling element and another surface.
Free rolling tyre – It is a wheel which rolls under a normal load with zero driving or braking torque applied (My = 0), acting as a ‘trailing’ wheel. It is characterized by zero slip ratio and experiences a longitudinal force known as rolling resistance, which acts in the direction opposite to travel because of the hysteresis and material deformation.
Free shear layer – It is also called mixing layer. It is a thin, turbulent region of high velocity gradients which develops between two fluid streams of different velocities, or between a moving fluid and a stagnant fluid, detached from solid boundaries. It represents a ‘free’ flow, meaning it is not directly constrained by or in contact with solid walls.
Free solvated ion – It is an individual metal cation or anion which is surrounded and stabilized by a shell of solvent molecules (such as water, organic solvents, or molten salts) and acts independently within a solution. Unlike ion pairs, these ions are not closely bound to counter-ions, allowing them to move independently to electrodes in refining or plating processes.
Free space – It is defined as a theoretical, perfect vacuum devoid of all matter, particles, and electro-magnetic /gravitational fields. It acts as a reference state for physics and electro-magnetism. In technology, it refers to empty storage capacity on a disk or drive.
Free space optical communications – It is the transfer of information from point to point by a beam of light or infrared energy, instead of a wired connection or radio waves.
Free spectral range – It is the spacing in optical frequency or wavelength between two adjacent transmission peaks or resonant modes of an interferometer, cavity, or diffraction grating. It determines the unambiguous operating range of spectroscopic instruments and sets the mode spacing for lasers.
Free spread – In a bearing, it is the quantity by which the outer circumference of a pair of bearing shells exceeds the inner circumference of the housing.
Free strain – It refers to the deformation a material undergoes, such as thermal expansion, chemical shrinkage, or phase transformation, without the restriction of external forces. These intrinsic strain types are the main cause of residual stresses in composites when mismatch occurs between materials during manufacturing.
Free stream conditions – These conditions define the undisturbed fluid state (velocity, pressure, temperature, and density) far away from a solid body, where viscous shear stresses and boundary layer effects are negligible. It serves as an important reference for computing aerodynamic drag, lift, and thermal transfer.
Free-stream flow – It refers to the velocity and state of molten metal (or gas) which is flowing freely and remains undisturbed by an object, such as a, injection lance, submerged nozzle, or vessel wall.
Free stream Mach number – It refers to the ratio of the local flow velocity to the local speed of sound in the undisturbed flow ahead of an airframe. it serves as a key dimensionless parameter in aerodynamics to characterize flow regimes, compressibility effects, and flight speed without being affected by local flow disturbances.
Free-stream velocity – It is the velocity of a fluid flow (gas or liquid) far from any solid boundaries or objects, where the flow is undisturbed and viscous effects (shear stresses) are negligible. It is the speed of the fluid prior to encountering an object or shockwave. It serves as a reference speed for calculating boundary layer development, convection heat transfer, and aerodynamic drag on submerged objects.
Free-surface – It is the boundary of a fluid (liquid or gas) which is not constrained by a solid surface and is exposed to a gas or another immiscible liquid, typically subjecting it to constant atmospheric pressure. It is characterized by zero parallel shear stress, allowing it to move, deform, and form free surfaces in open-channel flow, sloshing in tanks, and wave dynamics.
Free-surface defects – These are two-dimensional planar imperfections occurring at the external boundary of a crystal or material, where the regular lattice structure terminates. Atoms here have fewer neighbours (lower coordination number), resulting in higher surface energy, atomic bonds being unsatisfied, and susceptibility to chemical reactivity, corrosion, or crack initiation.
Free-surface flow – It is a type of multiphase flow where phases are separated by a distinct interface, allowing the liquid to move independently with respect to a gas, which has a considerably lower density. This flow is characterized by complexities because of the presence of a free boundary, needing specialized numerical methods for analysis.
Free surface fracture prediction – It refers to the theoretical and numerical methods used to forecast the initiation and propagation of cracks on the outer surfaces of metallic materials during manufacturing processes, particularly hot or cold forming. Such fractures occur when free expansion occurs under compression (e.g., upsetting, forging), creating high localized tensile stresses on the surface, which leads to ductile damage.
Free surface profile – It refers to the shape of a liquid’s upper boundary, which is subject to zero parallel shear stress, typically where liquid meets gas (e.g., water / air). It is determined by the balance of centrifugal, gravity, and viscous forces, normally studied in open-channel flow, hydraulic engineering, and fluid mechanics to predict water levels, waves, and turbulence.
Free-swelling index (FSI) – It is a measure of the increase in volume of coal when heated under specified conditions. Free-swelling index method is a small-scale test for getting information regarding the free-swelling properties of a coal. The results can be used as an indication of the caking characteristic of the coal when burned as a fuel. The volume increase can be associated with the plastic properties of coal. Coals which do not show plastic properties when heated do not show free swelling. The quantity of swelling depends on the fluidity of the plastic coal, the thickness of bubble walls formed by the gas, and interfacial tension between the fluid and solid particles in the coal. Higher swelling occurs when the above factors cause more gas to be tapped. Free-swelling index increases when the rank for bituminous coals increases, although, for some individual coals, free swelling indices vary. Results for low-rank coals are lower when compared to bituminous coals.
Free torsion – It is a type of structural deformation where a member of constant cross-section twists under torque without any restriction on its longitudinal fibres or warping. Key characteristics include uniform shear stress distribution (linear across plate thickness, zero at the centre), a constant angle of twist per unit length, and the lack of warping constraints, ensuring pure rotation.
Free variable – It is a placeholder or symbol in an expression which is not constrained by a quantifier, integral limits, or local definition. Unlike bound variables, which have specific values or ranges determined by the context, free variables can take on any value within their domain. In a linear system, free variables are the variables which are not determined by the pivot columns of the coefficient matrix. These variables allow for multiple solutions in the system, contrasting with basic variables which are directly influenced by the pivot columns.
Free vector – It is a vector whose action is defined solely by its magnitude and direction, allowing it to be moved anywhere in space without altering its physical effect. Unlike fixed vectors, free vectors are not tied to a specific point or line of action.
Free vector field – It refers to a set of vectors where each vector’s magnitude and direction are fixed, but it can be shifted to any position in space without changing its meaning. Unlike bound vectors (fixed to a point) or sliding vectors (fixed to a line), free vectors represent properties independent of specific location, such as constant velocity, force couples, or uniform flow.
Free vibration – It is the oscillation of a system, such as a structure or machine, which occurs after an initial disturbance (displacement or velocity) without ongoing external forces. The system vibrates at its inherent natural frequency, determined by its stiffness and mass, and the amplitude decays over time if damping is present.
Free vibration analysis – It is a technique used to determine the natural frequencies and mode shapes of a system oscillating without external forces after an initial disturbance. It calculates the structural response based solely on intrinsic mass and stiffness, identifying frequencies where resonance might occur.
Free volume – It is the portion of a total material volume not occupied by the molecules themselves. It represents the empty space or ‘holes’ between chains which allows for segmental movement, viscous flow, and transport of permeant molecules. It typically increases with temperature. It is the difference between the total specific volume of a substance and the occupied volume of the molecules. It is used to explain polymer behaviour, particularly the glass transition temperature, viscosity, and transport properties (diffusivity).
Free volume model – It defines the unoccupied space within a material (mainly polymers or liquids) between molecules, allowing for molecular mobility and transport, rather than relying solely on thermal activation. Engineering applications use this to predict viscous flow, diffusion, and the glass transition temperature, where high free volume enables faster segment rearrangement.
Free volume theory – It is a concept stating that molecular movement and transport properties (like diffusion or viscosity) in dense systems, mainly polymers and liquids, depend on the unoccupied space (free volume) between molecules. It defines total volume as the sum of occupied and free volume, explaining how increased temperature or pressure affects chain mobility and the glass transition temperature.
Free vortex – It is also called irrotational vortex. It is a fluid flow motion where particles rotate in concentric circles without external torque, meaning angular momentum is conserved. Tangential velocity (v) is inversely proportional to the radius (r), expressed as ‘v x r = constant’, making it faster near the centre.
Free wall – It is the portion of a honeycomb cell wall that is not connected to another cell.
Free warping – It refers to the unconstrained deformation of a beam’s cross-section when subjected to torsion, where the section deforms out of its original plane. Unlike constrained warping, free warping occurs without restriction, preventing the development of normal (warping) stresses, typically found in open thin-walled sections.
Freewheeling diode – It is a diode placed in parallel with an inductive load (like motors, relays, or solenoids) to protect switching components from high-voltage spikes. When the switch opens, the diode provides a path for the stored inductive energy to dissipate safely, preventing damage.
Freeze protection – It refers to methods, systems, and design strategies implemented to prevent fluids (mainly water) within pipes, vessels, and equipment from freezing, solidifying, or causing structural damage (rupturing) because of the expansion in cold weather. It typically involves maintaining system temperatures just above freezing (4.5 deg C to 10 deg C).
Freeze-thaw durability – It is the ability of materials, mainly concrete, to resist deterioration, cracking, and scaling caused by repeated cycles of freezing and thawing while saturated with water. It measures the material’s capacity to withstand internal hydraulic pressure created by ice expansion within pores, ensuring structural longevity in cold climates.
Freezing – It is a phase transition in which a liquid turns into a solid when its temperature is lowered below its freezing point. For most substances, the melting and freezing points are the same temperature. However, certain substances possess differing solid-liquid transition temperatures. For example, agar displays a hysteresis in its melting point and freezing point. It melts at 85 deg C and solidifies from 32 deg C to 40 deg C.
Freezing point – It is the temperature at which a pure metal, compound, or eutectic changes from liquid to solid. It is the temperature at which the liquid and the solid are at equilibrium.
Freezing-point depression – It is a drop in the maximum temperature at which a substance freezes, caused when a smaller quantity of another, non-volatile substance is added. Examples include adding salt into water, alcohol in water, ethylene or propylene glycol in water, adding copper to molten silver (used to make solder that flows at a lower temperature than the silver pieces being joined).
Freezing process – It is an exothermic phase transition where a liquid changes to a solid by removing heat, typically lowering the substance’s temperature below its freezing point. It involves three key stages namely removing sensible heat (pre-cooling), liberating latent heat of fusion (nucleation / growth), and lowering the temperature to storage levels.
Freezing rain – It is a meteorological phenomenon defined as liquid precipitation, rain droplets with a diameter higher than 0.5 millimeters, which becomes super-cooled while passing through a sub-freezing layer of air near the surface, freezing instantly upon contact with structures or the ground which are at or below 0 deg C. This phenomenon is critical because of the glaze ice it creates, which acts as a heavy, transparent, and structurally damaging load on infrastructure.
Freezing range – It is that temperature range between liquidus and solidus temperatures in which molten and solid constituents coexist.
Freezing temperature – It is also called freezing point. It is the specific temperature at which a liquid undergoes a first-order thermodynamic phase transition (solidification / crystallization) to become a solid, typically occurring at standard atmospheric pressure. It is normally characterized as an exothermic process where energy, known as the enthalpy of fusion, is released. It is the temperature where solid crystals begin to form from the liquid phase.
Freight – It is transport of goods in bulk by truck, train, ship, or aircraft.
Freight cars – These are specialized railway rolling stock designed to transport goods, materials, and bulk commodities, excluding passengers. They are engineered for durability and specific cargo types, frequently classified by structure, such as box-cars (enclosed), hoppers (bottom-dumping), tanks (liquids), and flat-cars (oversized machinery, to move items over long distances.
Freight rate – It is the price charged by a carrier to transport goods, calculated per unit of weight, volume, or distance. It represents the total cost of moving cargo (through ship, truck, rail, or air) and includes base fees, fuel surcharges, and terminal handling charges.
Freight ton – It is also called shipping ton, measurement ton or ocean ton. It is a measure of volume used for shipments of freight in large vehicles, trains or ships. Its value varies with country. In United States of America, it is equivalent to 1.1 cubic meter, while in the United Kingdom, it is 1.2 cubic meter.
Freight train – It is also called a goods train or cargo train. It is a railway train which is used to carry cargo.
Freight transport – It is the physical process of transporting commodities and merchandise goods and cargo.
Freight transportation – It is the systematic planning, design, operation, and management of infrastructure and logistics systems to move goods from origin to destination through road, rail, air, or sea. It focuses on optimizing efficiency, capacity, and cost, while addressing environmental impact (sustainability), safety, and the integration of multiple modes.
Freight truck – It is also known as a cargo truck or lorry. It is a heavy-duty motor vehicle designed and used for transporting goods, materials, or merchandise. It is a crucial component of the logistics and transportation industry, facilitating the movement of freight between different locations including warehouses and factories.
Freight vehicle – It is a commercial vehicle specifically designed for transporting goods, materials, or cargo, rather than passengers. These vehicles, including trucks, vans, and rail cars, are built for durability and payload efficiency, frequently optimized for specific cargo types, such as enclosed box trucks for security or specialized trailers for heavy loads.
Freight wagon – It is also called a goods wagon or freight car. It is an unpowered railway vehicle designed to carry cargo, or freight, on a railway network. Freight wagons are a crucial part of rail freight transportation and come in several types to accommodate different kinds of goods.
French curve – It is a template made of metal, wood, or plastic, composed of varied smooth, non-circular, scroll-like curves. It is a manual drafting tool used to draw smooth, precise curves of varying radii, such as parabolas or ellipses, by aligning and tracing segments of the template, frequently called a Burmester set.
French drain – It is a gravel-filled trench containing a perforated pipe which uses gravity to collect and divert surface or groundwater away from structures, preventing water infiltration, foundation damage, and soil saturation. It operates by providing a path of least resistance, allowing water to flow into the gravel, enter the pipe, and be moved to a suitable exit point.
French method – It is a geotechnical technique used to calculate pile bearing capacity based on cone penetration resistance, mainly focusing on unit toe and shaft resistance. It involves analyzing soil types to determine coefficients to predict how pile foundations are going to perform. It differs from the ‘French drain’ (subsurface water management) and French curves (drafting tools).
French stop – it is frequently referred to simply as a ‘stop’ or related to ‘stopping-out’. It is a technique used in metal etching where parts of a metal plate are covered with a resistant substance (ground) to prevent further etching by acid, while other parts remain exposed to be etched further.
Frenkel defect – It is a type of point defect in crystalline solids where a smaller ion (typically a cation) leaves its regular lattice site and occupies an interstitial position, creating a vacancy-interstitial pair. Also known as a dislocation defect, it maintains overall density and electrical neutrality.
Frenkel pair – It is also called Frenkel defect. It is a type of crystal point defect where an atom or ion is displaced from its regular lattice site into a nearby interstitial site, creating a vacancy-interstitial pair. It is important for determining radiation damage in metals (causing hardening / embrittlement) and improving ionic conductivity in solid-state electrolytes for batteries.
Freon – It is a generic descriptor for a number of halocarbon products. They are stable, non-flammable, low toxicity gases or liquids which have been normally used as refrigerants and as aerosol propellants. These include chloro-fluoro-carbons and hydro-fluoro-carbons, both of which cause ozone depletion (although the latter much less so) and contribute to global warming.
Frequency (f) – It is very frequently measured in hertz (Hz). It is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as temporal frequency for clarity and to distinguish it from spatial frequency. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio signals (sound), radio waves, and light.
Frequency accuracy – It defines how closely a generated or measured frequency conforms to its ideal or nominal value, typically expressed as a percentage or in parts per million (ppm). It represents the maximum allowed offset from the desired frequency, determined by factors like reference oscillator stability, aging, temperature, and calibration, resulting in a formula ‘ frequency accuracy = target frequency x accuracy (parts per million per year) x time’.
Frequency agility – It is a technique where a transmitter, typically radar or radio, rapidly changes its operating carrier frequency, frequently pulse-to-pulse or within a pseudo-random sequence. It is mainly used to evade jamming, mitigate interference, reduce tracking error (glint), and operate in crowded electro-magnetic environments.
Frequency analysis – It is a technical process used to determine the spectral components (frequencies), natural modes of vibration, or probability of occurrence of events within a system. It breaks down complex signals, using methods like ‘fast Fourier transform’ (FFT), into individual frequencies to identify vibration sources, analyze structural resonances, or predict environmental extremes like floods.
Frequency, antenna – Antenna frequency defines the number of wave oscillations per second, typically 3 kilo-hertz to 300 giga-hertz, operating as a resonant circuit where optimal size is frequently half the wavelength to efficiently transmit / receive specific signals. Antennas operate in specific bands, with higher frequencies needing smaller physical sizes.
Frequency approximation – It refers to simplified modeling techniques used to calculate, estimate, or analyze systems (electrical, mechanical, or wave-based) by focusing on specific frequency ranges (e.g., low against high frequency) or by simplifying complex, high-order, or non-linear systems into more manageable, lower-order, or linear forms.
Frequency asymptote – It refers to the behaviour of a transfer function at extreme frequency limits, characterized by high-frequency and low-frequency asymptotes which describe how the output magnitude changes in relation to frequency. In particular, for a first-order element, the low-frequency asymptote is a horizontal line at 0 decibels, while the high-frequency asymptote decreases logarithmically with a slope of -20 decibels/decade. It is a straight-line approximation of a system’s frequency response (gain / phase) on a Bode plot, representing its behaviour at very low or very high frequencies.
Frequency atom – It is a waveform highly localized in both time and frequency, used in linear time-frequency transforms to analyze complex signals. It refers to the precise resonant frequency of atomic transitions (e.g., cesium) used in atomic clocks to standardize time, measuring 9,192,631,770 hertz.
Frequency axis – It is the horizontal (x-axis) representation of frequency values, typically in Hertz (Hz) or angular frequency (w), used to display the frequency content of a signal (e.g., Fourier transform output). It normally spans from ‘-fs/2’ to ‘fs/2’, where ‘fs’ is the sampling frequency, mapping the spectral components. Frequency axis refers to the representation of frequency values in a discrete Fourier transform (DFT) output, where the x-axis can display frequencies in Hertz, including both positive and negative frequencies, based on the sampling rate and the number of data points collected.
Frequency bandwidth – It is the range of frequencies, measured in hertz (Hz), over which a signal, component, or system operates, transmits, or processes information effectively. It is defined as the numerical difference between the upper (f2) and lower (f1) frequency limits, normally where signal power drops by no more than 3 decibels (half-power) from the peak.
Frequency behaviour – It refers to how a system, component, or signal responds, oscillates, or distributes energy across different frequencies, typically analyzed through frequency response (amplitude / phase changes) or natural frequency (resonance points). It maps input-output relationships to characterize system performance over frequency, identifying important operating limits and resonance peaks to prevent failure. It refers to the distribution of amplitude across different frequencies in a signal, which can be represented as a frequency spectrum. In the context of process fractals, frequency behaviour frequently follows a power-law relationship, exemplified by different ‘colours’ of noise, such as pink noise, which emphasizes lower frequencies.
Frequency bin – It is a discrete frequency interval representing a specific range of spectral data in ‘digital signal processing’ (DSP), particularly after a ‘fast Fourier transform’ (FFT). Each bin acts as a ‘bucket’ for energy, covering a width of (sampling rate divided by fast Fourier transform size) and provides magnitude / phase information.
Frequency capacitor – It is a passive component that stores charge, whose impedance (Zc) decreases as frequency (f) increases, defined by ‘Zc = 1/(2pi x f x C)’. It is used for filtering, tuning, and coupling by controlling reactance to specific frequencies, frequently behaving as a high-frequency bypass.
Frequency changer – It an electric machine which is used to transfer power between two networks with different frequencies, or, an electronic device (normally called a frequency mixer) which changes the frequency of an input signal to some other frequency.
Frequency characterization – It is the measurement and analysis of a system’s, component’s, or signal’s behaviour across a spectrum of frequencies. It determines how a system responds to different input frequencies (magnitude and phase) or identifies resonant / natural frequencies, necessary for optimizing radio frequency, mechanical, or signal processing performance.
Frequency chirp – It is a signal where the instantaneous frequency increases (up-chirp) or decreases (down-chirp) over time. It is a form of frequency modulation where a pulse’s frequency changes smoothly, used extensively in radar, sonar, and laser systems to improve resolution and increase signal-to-noise ratio.
Frequency coefficient – It frequently refers to a numerical value representing the strength, amplitude, or weighting of a specific sine / cosine component within a signal, calculated through Fourier transform. It acts as a spectral parameter identifying how much a specific frequency contributes to a total signal or system response.
Frequency compensation – It is a technique used in amplifiers (especially with negative feedback) to modify the frequency response to prevent unwanted oscillations and ensure stability. It works by shaping the gain and phase margin, typically by adding capacitors, to prevent high-frequency phase shifts from causing positive feedback.
Frequency components – These are the individual sinusoidal oscillations (sine / cosine waves) which make up a complex time-domain signal, identified by specific frequencies, amplitudes, and phases through analysis methods like the Fourier transform. These components represent how a signal’s power is distributed across different harmonic frequencies.
Frequency condition – It defines the specific operational rate, measured in cycles per unit time (hertz, Hz, needed for a system, component, or signal to function properly, safely, or optimally. It is a constraint on input, output, or vibration which prevents undesirable effects like resonance, signal distortion, or component fatigue.
Frequency content – It refers to the distribution of signal amplitudes, power, or energy across different frequencies. It identifies which frequency components, low, medium, or high, are dominant within a complex, time-varying signal, typically analyzed using Fourier transforms or spectral analysis to understand vibrations, sound, or data. It reveals how the intensity of a signal (like noise or structural vibration) is distributed across a spectrum, rather than just its overall magnitude.
Frequency contribution – It defines how much a specific frequency component, mode, or frequency band contributes to the overall response (e.g., amplitude, vibration, noise) of a system. It identifies dominant frequencies, frequently through modal contribution or spectral density, used to optimize structures, reduce noise, or increase computational efficiency.
Frequency control in power systems – It is the process of maintaining the grid frequency (e.g., 50 hertz or 60 hertz) at its nominal value by balancing generation and load. It acts against power imbalances which cause frequency deviations, using primary (automatic governor action), secondary (automatic generation control), and tertiary (dispatching reserves) levels to maintain stability.
Frequency correlation – It is a measure of similarity or dependency between two signals, systems, or data sets across different frequencies, calculated in the frequency domain. It identifies how spectral components relate to each other,, aiding in system identification, damage detection, and model updating. It is widely used to analyze the coherence of non-stationary signals and in vibration analysis. It is frequently expressed using a frequency domain correlation function, which evaluates how well two signals correspond at different frequency components.
Frequency, cutoff – It is the boundary frequency in a system’s frequency response at which the power of the output signal begins to be reduced (attenuated) rather than passing through. It typically defines the edge of a filter’s passband, commonly set at the -3 dB (decibel) point where power drops to 50 % or voltage / current to around 70.7 % of the maximum.
Frequency decomposition – It is a technique which transforms seismic data into a frequency-tuning volume using ‘short-time Fourier transform’ (STFT), enabling the identification of thin layers and the analysis of complex formations based on their frequency characteristics. This method delineates stratigraphic thicknesses and geological bodies by examining the frequency response of the virtual reflection signal associated with seismic waves. It is a signal processing technique which breaks down complex signals or data sets into their constituent frequency components. By identifying specific frequencies within a signal, this method enables analysis of spectral changes, structural health monitoring, and feature extraction. It is normally used in seismic interpretation to resolve thin layers and in machinery diagnostics.
Frequency difference (df) – It is the quantitative difference between two operating frequencies, normally defined as the slip frequency in motor systems (df = fi -fr). It measures the discrepancy between an incoming (target) source and a running device, important for synchronizing, control systems, and electronics.
Frequency direction – It refers to the orientation, vector, or spectral axis of a signal or wave (spatial or temporal) relative to a reference, frequently used in signal processing, electromagnetics (radio direction finding), or imaging (magnetic resonance imaging). It defines how a signal’s frequency component changes, propagates, or is encoded within a specific spatial direction.
Frequency dispersion – It is the phenomenon where the phase velocity of a wave (electromagnetic, acoustic, or material) depends on its frequency, causing different spectral components to travel at different speeds. This results in pulse broadening or signal distortion as the wave passes through a dispersive medium. It is defined mathematically by a frequency-dependent phase velocity or a non-linear dispersion relation.
Frequency distribution – It is the way in which the frequencies of occurrence of members of a population, or a sample, are distributed according to the values of the variable under consideration.
Frequency distribution curve – It is a smoothed graph representing the distribution of data points (e.g., measurements of material strength, product dimensions) by plotting class intervals on the x-axis and their respective frequencies on the y-axis. It visualizes central tendency, variability, and skewness of data, helping engineers assess process capability. These curves, frequently derived from histograms, identify how data clusters around a mean value, facilitating quality control by spotting if parts fall within needed specifications.
Frequency diversity – it is a technique used to mitigate signal fading and interference by transmitting the same information simultaneously over multiple, widely spaced frequency channels. It relies on the principle that if one frequency experiences deep fading, another frequency is likely to remain unaffected, allowing for reliable communication.
Frequency division duplexing – It is a communication method providing simultaneous bi-directional (full-duplex) transmission by assigning separate, distinct frequency bands for uplink and downlink, separated by a guard band to prevent interference. It offers continuous data flow, low latency, and is standard in cellular networks like LTE (long term evolution).
Frequency division multiple access – It is a channel access method which divides a total available bandwidth into distinct, non-overlapping frequency bands. Each user is assigned a specific frequency channel for the entire duration of their communication, allowing multiple users to transmit simultaneously without interference.
Frequency division multiplexing – It is a technique which transmits multiple signals simultaneously over a single communication channel by assigning each signal a unique, non-overlapping frequency band (sub-carrier) within the total bandwidth. It enables multiple, simultaneous, and distinct transmissions (e.g., radio, voice, data) to share the same physical medium without interference, using guard bands to separate them. Frequency-division multiplexing (FDM) splits available bandwidth into smaller frequency bands (channels), ensuring each signal has its own dedicated spectrum.
Frequency domain – It is a way of representing or analyzing signals by showing how their energy is distributed across a range of frequencies, rather than how they change over time. It decomposes complex, time-varying signals into individual sine / cosine waves of different frequencies, highlighting amplitude and phase. Unlike the time domain, which shows a signal’s change in amplitude over time (e.g., an oscilloscope), the frequency domain shows the signal’s energy relative to frequency (e.g., a spectrum analyzer).
Frequency-domain analysis – It is a signal processing technique which converts time-dependent data (like vibration or acoustic emissions from materials) into a spectrum of frequencies using methods like Fourier transform. It identifies material fatigue, structural integrity, and structural vibrations by analyzing how a material responds to various frequencies, rather than just changes over time. It is mainly used to analyze structural health and fatigue. Complex signals from sensors (e.g., in rotating machinery or metallurgical processing equipment) are broken down to identify specific frequency components.
Frequency-domain criteria – These are design, analysis, and evaluation metrics used in engineering, particularly control systems and signal processing, to describe how a system responds to sinusoidal inputs of varying frequencies, rather than time. Key criteria include gain / phase margins, resonance peaks, and bandwidth, frequently derived from Fourier or Laplace transforms. These metrics evaluate system stability, performance (tracking), and robustness (disturbance rejection) by examining magnitude ratios and phase shifts over a spectrum of frequencies, rather than transient response in the time domain.
Frequency domain processing – It is a technique which analyzes and manipulates signals or data by transforming them from the time or spatial domain into their constituent sinusoidal frequency components. Mainly utilizing tools like the Fourier transform, this method decomposes complex data to enable easier filtering, compression, and analysis of frequency-specific characteristics.
Frequency domain representation – It is a method of analyzing signals or systems by breaking them down into their constituent sinusoidal frequency components, rather than viewing them as a function of time. It maps amplitude / power and phase against frequency, mainly using tools like the Fourier transform, to analyze periodicities, harmonics, and system response, aiding in filter design and communication system analysis.
Frequency domain response – It defines how a system’s output magnitude and phase change relative to a sinusoidal input over a range of frequencies, mainly analyzing steady-state behaviour, not transients. It uses Fourier transforms to map time-series data into frequency components, showing how systems filter or amplify specific frequencies.
Frequency domain solution – It is a method that analyzes signals or system behaviours by decomposing them into constituent frequencies (sinusoids) rather than plotting them over time. It represents signals as magnitudes and phases at specific frequencies, mainly derived using Fourier transforms, such as the ‘fast Fourier transform’ (FFT).
Frequency domain transfer function – It is the relationship between two signals expressed as a function of the complex variable ‘s’, which represents frequency components in the Laplace transform. It characterizes how the output signal responds to the input signal in the frequency domain, such as in the case of an integrator where the transfer function is ‘1/s’.
Frequency drift – It is the slow, unintended, and frequently unpredictable deviation of an oscillator’s output frequency from its nominal (intended) value over time. It occurs because of the environmental changes (temperature, humidity), component aging, or power supply fluctuations. It is a gradual, often non-linear change which can move in either direction.
Frequency, electrical – Frequency refers to the number of times the alternating current (AC) switches between positive and negative in 1 second. This switching does not occur in direct currents (DC). The unit of frequency is hertz (Hz).
Frequency, electrical signal – It is electrical signal frequency which is the number of cycles an alternating current (AC) completes per second, measured in hertz (Hz). It represents the rate of oscillation (directional changes) of voltage or current, typically 50 hertz or 60 hertz for power grids, and varies widely for communications. It applies only to alternating current, not direct current.
Frequency error – It is the discrepancy between a signal’s actual operating frequency and its intended nominal frequency, frequently caused by oscillator drift, modulation, or measurement limitations. It is typically expressed in hertz (Hz) or parts per million (ppm).
Frequency estimates – These estimates refer to the statistical analysis conducted to determine the likelihood of occurrence of hazardous events, based on data collected from actual incidents. These estimates are necessary for assessing the risk associated with different activities or processes.
Frequency estimation – It is the process of determining the specific rate, count, or underlying frequency components of a signal, data stream, or event occurrence, frequently in the presence of noise or uncertainty. It is used to analyze periodic signals (power systems, radar) and compute occurrence counts in data streams.
Frequency floor – It refers to the lower boundary of a floor system’s natural frequency (typically under 10 hertz to 12 hertz), used in structural engineering to categorize structures susceptible to resonant amplification from walking. It separates ‘low-frequency’ (high resonance risk) from ‘high-frequency’ floors (low resonance risk) to ensure occupant comfort and serviceability.
Frequency generation – It is the process of creating a periodic signal, waveform, or new optical frequency, frequently through methods like non-linear optical mixing, summing, or dividing to produce specific wavelengths (e.g., fnew = f1 +f2) or electronic signals. It is necessary for producing wavelengths which lack direct laser sources.
Frequency graph – It is a visual representation of a frequency distribution, showing how frequently each value or range of values occurs in a dataset. Typically, the vertical axis (y-axis) represents the count (frequency) and the horizontal axis (x-axis) shows the variable’s values or categories.
Frequency histogram – It is a graphical representation displaying the frequency distribution of numerical data using contiguous rectangular bars. The horizontal axis (x-axis) represents data intervals (bins / classes), while the vertical axis (y-axis) indicates the count or number of observations within each interval.
Frequency hopping spread spectrum – It is a radio transmission method which rapidly switches a carrier signal among several frequency channels using a pseudo-random sequence known only to the transmitter and receiver. It reduces interference and improves security by spreading signal power over a wide bandwidth, appearing as noise to unauthorized receivers.
Frequency interval – It is a range of frequencies (e.g., 20 hertz to 20 kilo-hertz) within which a signal, wave, or phenomenon occurs, rather than a single discrete frequency. It is used to analyze bandwidths in signal processing or to group numerical data into bins (class intervals) in statistics to identify patterns.
Frequency kernel – It is a function used in ‘time-frequency distributions’ (TFDs) to improve desired signal components (auto-terms) and suppress unwanted interference (cross-terms) by acting as a filter on the ambiguity function, which is a 2D Fourier transform of the signal’s autocorrelation. These kernels are important for analyzing nonstationary signals (signals whose frequency content changes over time).
Frequency limit – It is the threshold (upper or lower bound) of oscillations, cycles, or signal speeds within a system, beyond which performance degrades, wave behaviour changes, or operation stops. Key examples include 3 decibels (dB) cutoff points in circuits and the Nyquist limit.
Frequency localization – It refers to the ability of a signal analysis technique to identify specific frequency components present in a signal while simultaneously determining when they occur, bridging the gap between time-domain (when) and frequency-domain (what) analyses. It is important for processing non-stationary signals where frequency content changes over time.
Frequency method – It refers to a type of time-scale method used in the analysis of non-stationary signals, involving the linear decomposition of a signal by translating, modulating, and scaling a basis function with time and frequency localization.
Frequency modulated continuous wave – It is a type of radar where the transmitter signal is frequency modulated by a linear waveform, allowing for the measurement of target range with high resolution by analyzing the delayed received signal.
Frequency modulated continuous wave radar – It is a sensor which emits a continuous radio signal, constantly changing its frequency (e.g., saw-tooth or triangle wave) to accurately measure both the distance (range) and relative velocity of objects. It works by calculating the frequency difference (beat frequency) between the transmitted signal and the reflected return signal.
Frequency modulation – It is a method of impressing information on a carrier wave by changing its frequency.
Frequency motions – These refer to the oscillations of bonds in molecules, typically occurring at high frequencies, such as bond stretching frequencies around 1000 wave-numbers (per centimeter), which correspond to rapid movements on the order of 10 trillion hertz. These high-frequency motions are frequently less relevant when studying properties like viscosity or phase transitions in molecular dynamics simulations.
Frequency multiplier – It is a non-linear electronic circuit or device which produces an output signal with a frequency which is an integer multiple (e.g., 2x, 3x) of its input signal frequency. It typically uses active components like transistors or non-linear elements like diodes to create harmonics, followed by a filter to select the desired output frequency.
Frequency noise – It refers to random fluctuations associated with the high frequency component of a signal, which increases with bandwidth but can be reduced by limiting the bandwidth. It consists of random, rapid fluctuations in the instantaneous frequency of an oscillating signal (such as an optical or electronic field), often characterized as time-dependent deviations from a pure, linear phase.
Frequency offset – It is the difference between a signal’s actual frequency and its nominal or expected frequency, normally measured in hertz. It occurs mainly due to carrier frequency mismatches between transmitter / receiver oscillators or through the Doppler effect, resulting in signal distortion, inter-symbol interference (ISI), and reduced communication reliability.
Frequency operation – It refers to the selection of irradiation frequency used in physico-chemical transformations, which is determined by the controlling mechanism. It can involve lower frequencies (10 kilo-hertz to 100 kilo-hertz) for intense physical effects and higher frequencies (a few hundred kilo-hertz to mega-hertz) for chemical effects, with the potential for multiple-frequency operations to improve cavitational activity and energy efficiency.
Frequency oscillator – It is an electronic circuit which converts direct current (DC) from a power supply into a continuous, alternating current (AC) signal, such as a sine, square, or triangle wave, at a specific, stable frequency. It acts as a repetitive signal generator, often utilizing resonant circuits (inductor-capacitor, LC), resistors-capacitors (RC), or quartz crystals to maintain a desired frequency for timing or signal generation.
Frequency plane – It refers to a region in the time-frequency plane where uncertainty relations are defined based on concentration / dispersion measures. It is frequently synonymous with the frequency domain or the time-frequency plane. It is a mathematical space used to represent signals based on their frequency components rather than time. It is used to analyze oscillations, filter signals, and detect signal features through techniques like the Fourier transform, which maps time-domain signals to this plane.
Frequency rate – Data on injuries (lost time and / or the total number) is frequently presented in terms of frequencies by relating the absolute numbers to the total number of hours worked. Frequency rate is the number of injuries in the period multiplied by 100,000 total hours worked during the period.
Frequency ratio – It is the relationship between two frequencies, calculated by dividing one frequency by another (f1/f2). It represents the ratio of operating frequency to natural frequency (fo/fn), indicating vibration amplification or damping.
Frequency relationship – It defines how the number of periodic events per unit time (‘f’ in hertz) connects to other wave properties, mainly time period (T), wavelength (lambda), or amplitude (A). Key relationships include ‘f = 1/T’ (reciprocal of time) and ‘v = f x lambda’ (wave speed), important for acoustics, and structural engineering.
Frequency relay – It is a protective device which monitors the frequency of an electrical power system (typically 50 hertz or 60 hertz), initiating actions like circuit breaker tripping or load shedding when the frequency deviates from set thresholds. It prevents generator damage and system instability by detecting under-frequency (f = below f-nominal) or over-frequency (f = above f-nominal) conditions.
Frequency representation – It is a method of characterizing a signal by its frequency components, showing how different frequencies (sinusoids / complex exponentials) contribute to its overall behaviour, rather than focusing on time-based changes. It decomposes signals, identifying energy distribution across frequencies.
Frequency resolution – It is the ability of a spectral analysis system (like fast Fourier transform, FFT) to distinguish between two closely spaced frequencies in a signal, defined as the spacing between consecutive frequency bins. It is inversely proportional to the total recording time, meaning a longer signal duration improves resolution.
Frequency resource – It refers to a specific, limited physical portion of the electromagnetic spectrum used for wireless transmission, such as subcarriers in OFDM (orthogonal frequency division multiplexing) systems. It is a fundamental unit of capacity in communication, where resources are allocated in chunks, such as physical resource blocks (PRBs), across time and frequency to transmit data.
Frequency response – It is the measure of the output of a system in response to an input of varying frequency. It is a measure of a system’s output spectrum (amplitude and phase) in response to a sinusoidal input signal across a range of frequencies. It characterizes how consistently a device, such as an amplifier, speaker, or filter, processes input signals, with a ‘flat’ response indicating no frequency emphasis or attenuation.
Frequency response curve – It is the variation in sound pressure or acoustic power of a loudspeaker as a function of frequency, while maintaining a constant quantity such as voltage or electrical power.
Frequency response function – It is the ratio of the complex output amplitude to the complex input amplitude for a steady-state sinusoidal input. It represents the system’s response to sinusoidal inputs and is the Fourier transform of the unit impulse function.
Frequency response matrix – It is a mathematical representation describing the output of a linear time-invariant (LTI) system to harmonic input signals across a range of frequencies, mapping input forces to response output (displacement, velocity, acceleration). It is a matrix of frequency response functions (FRFs) characterizing magnitude amplification and phase shift for multi-input / multi-output systems, representing the Fourier transform of the system’s impulse response.
Frequency reuse – It is a cellular network technique where the same radio frequencies are used across different cell sites to increase capacity and spectrum efficiency. It involves using the same channels in non-adjacent cells, separating them far enough to minimize interference. Key applications include mobile networks, and satellite communications.
Frequency sample – It is the rate at which a continuous signal is converted into a discrete signal, measured in samples per second (hertz). It defines how frequently data is collected in time, such as 1,000 hertz for capturing high-speed movements.
Frequency sampling method – It is an FIR (finite impulse response) filter design technique which creates a filter by uniformly sampling a desired frequency response at ‘N’ points, denoted as ‘H(k)’, and applying an inverse discrete Fourier transform (IDFT) to determine the impulse response. It is highly effective for designing arbitrary, frequency-selective filters since it allows for direct specification of the frequency response and provides zero approximation errors at the sampling points.
Frequency-selective channel – It is a communication channel which induces unequal attenuation and phase shifts across different frequency components of a transmitted signal, causing selective fading. It occurs when the signal bandwidth exceeds the channel’s coherence bandwidth, frequently caused by multipath propagation. The channel’s frequency response varies considerably across the signal bandwidth, meaning different parts of the signal fade differently.
Frequency selectivity – It is the ability of a system to distinguish, isolate, or respond to specific frequencies while rejecting others. It is characterized by a narrow response range, a high-quality, sharply tuned filter, in signal processing.
Frequency separation – It refers to techniques which divide power demand into low frequency (steady state driving power) and high frequency (dynamic power), utilizing methods such as filtering and wavelet transformation to manage energy distribution among sources like fuel cells and batteries.
Frequency shift – It is defined as the small variation in resonance frequencies experienced by particular atoms in a molecule, caused by the reduction of the magnetic field because of the electron shielding. This shift is typically measured in parts per million (ppm) and reflects the chemical environment of the atoms.
Frequency shift keying – It is a digital modulation technique which transmits data by shifting a constant-amplitude carrier signal between discrete frequencies. In binary frequency shift keying (FSK), a logic ‘1’ (mark) is represented by one frequency, while a logic ‘0’ (space) is represented by another, offering good noise immunity for communication.
Frequency signal – It is a signal whose frequency content is measured by the Fourier transform, whether it is periodic or aperiodic. It is a key concept in signal processing, communication, and control theory.
Frequency slot – It is a designated, narrow segment of the radio spectrum or optical bandwidth assigned for transmitting data, normally used in flexible grid networks and 5G. These slots enable elastic bandwidth allocation (e.g., 6.25 giga-hertz, 12.5 giga-hertz, or 25 giga-hertz widths) rather than using rigid, fixed channels.
Frequency source – It is a device which generates a stable, specific signal, such as a sine or square wave, used to test, calibrate, or drive electronic systems, communication equipment, and measuring instruments. These sources frequently use oscillators or synthesizers to produce precise frequencies ranging from hertz (Hz) to giga-hertz (GHz).
Frequency specifications – These specifications define the magnitude and phase characteristics of signals or systems, dictating how they operate across specific frequency ranges (e.g., passband, stopband). They are important in electronics to describe performance parameters like resonance, bandwidth, and gain.
Frequency spectrum – It is a graphical representation showing the constituent frequencies (how fast waves vibrate) and their respective amplitudes (strength) contained within a signal or wave. It breaks complex, time-based signals into individual frequency components, ranging from slow to fast, allowing analysis of the signal’s composition, frequently calculated using a Fourier transform.
Frequency spectrum analysis – It is the process of breaking down a complex signal into its individual frequency components to analyze their amplitude, frequency, and phase, frequently using Fourier transforms. It transforms time-domain data into the frequency domain to identify periodicities, evaluate vibrations, and filter noise.
Frequency spread – It is a communication technique which spreads a narrow-band signal over a much wider bandwidth, mainly to improve signal security, resist jamming, and reduce interference. It operates by multiplying the information signal by a higher-frequency, pseudo-random code, causing the power of the transmitted signal to drop near or below the noise floor, hence increasing interference immunity.
Frequency squeal – It is a high-pitched, resonant noise (typically 1 kilo-hertz to 20 kilo-hertz) caused by unstable friction-induced vibrations between components, normally found in mechanical systems like automotive disc brakes (4 kilo-hertz to 20 kilo-hertz) or train wheels on tracks (200 hertz to 2,000 hertz).
Frequency stability – It defines an oscillator’s or system’s ability to maintain a constant, nominal frequency over time despite environmental variations like temperature, voltage changes, or load shifts. It measures how small frequency fluctuations are, normally expressed in parts per million (ppm).
Frequency standard – It refers to a precise and stable frequency used as a reference point in measurements, which is important for ensuring the accuracy and consistency of frequency domain analyses in signal processing.
Frequency, statistics – In statistics, the frequency or absolute frequency of an event is the number of times the observation has occurred / recorded in an experiment or study. These frequencies are frequently depicted graphically or in tabular form. In statistical analysis, the frequency is the number of times that particular values are obtained in a variable. For example, with the data: dry, rain, dry, dry, dry, rain, rain, dry, the frequency of ‘rain’ is 3 and the frequency of ‘dry’ is 5. The sum of the frequencies is the number of observations, ‘n’, in the variable. In this example, n = 8. The percentage is (100*frequency/n), = 100*3/8 = 37.5 % for rain, in this example. With as few as 8 values percentages are not normally used, instead state 3 out of the 8 values are rain.
Frequency structure – It defines the intrinsic vibration characteristics, natural frequencies and mode shapes, of a system, determining how it oscillates when disturbed. It refers to a structure’s modal properties (mass and stiffness), while in signal processing, it refers to a signal’s time-frequency properties, such as constant or harmonic relationships.
Frequency support – It refers to mechanisms, such as fast-acting controls or active power reserves, designed to maintain the stability of an electrical grid’s frequency (normally 50 hertz or 60 hertz) by counteracting power imbalances. It acts to stabilize the grid, frequently provided by synchronous generators, battery systems (battery energy storage system, BESS), or renewables during disturbances.
Frequency synthesis – It is the process of generating a wide range of precise, stable output frequencies from a single, stable reference crystal oscillator. It uses techniques like phase-locked loops (PLL), frequency multipliers, dividers, and mixers to create multiple signals, frequently utilized in communication systems, radar, and signal generators.
Frequency tone – It is a sound wave characterized by its regularity of vibration, defining its pitch through the number of cycles per second, measured in hertz (Hz). Simple tones consist of one frequency, while complex tones contain a fundamental frequency and harmonics. It defines the perceived pitch and quality of sound.
Frequency transformer – It is very frequently a high-frequency transformer. It is a specialized electro-magnetic device designed to operate at frequencies considerably higher than the standard 50 hertz or 60 hertz used in conventional power grids. It a power electronic component which transfers alternating current energy while converting voltage, current, or impedance at frequencies typically above 10 kilo-hertz. These transformers achieve substantial miniaturization, weight reduction, and improved efficiency, normally using ferrite cores rather than traditional iron cores.
Frequency transforms – These are mathematical operations which convert signals (like audio, images, or sensor data) from the time or spatial domain into the frequency domain. They decompose complex signals into a sum of simple sinusoidal components (sines and cosines), making it easier to analyze which frequencies are present, their amplitude, and their phase.
Frequency vibration – It is the number of complete oscillation cycles a vibrating object or wave undergoes per second, measured in hertz (Hz). It quantifies how fast a motion repeats, with higher frequencies representing more energy. This is important for analyzing machinery, structural engineering, acoustics, and diagnosing systems through the identification of dominant frequencies.
Frequency window – It is a mathematical function applied to a signal segment to minimize spectral leakage and discontinuity at the edges of a sampled data block, acting as a filter in the frequency domain. By shaping the data (e.g., tapering edges), it selects a specific range of frequencies for analysis, trading off main-lobe width (resolution) for side-lobe suppression.
Frequency, word – It the method which calculates how many times a word appears in a data set, converting the words into a word count matrix to analyze their occurrence and significance.
Frequency, X-ray – It is the number of alternations per second of the electric vector of the x-ray beam. It is equal to the velocity divided by the wave-length.
Frequency zone – It defines specific ranges of frequency deviations in power systems (50 hertz or 60 hertz) which dictate specific operational responses. It normally refers to ranges within electrical systems where frequency variations need action, such as tripping or power adjustment.
Frequently asked questions – It is a structured document, webpage, or section designed to address common inquiries, problems, or topics related to a specific product, service, or organization. Its purpose is to provide quick, accessible information, reduce customer support volume, and improve user experience.
Fresh cement paste – it is a plastic, workable, and viscous mixture of Portland cement and water (sometimes with admixtures) which acts as the binding matrix in concrete before hardening. It acts as a concentrated suspension where cement particles are distributed in the liquid phase, characterized by properties like viscosity, yield stress, and thixotropy.
Fresh layer – It normally refers to a new, recently applied, or added sheet, coating, or stratum of material covering a surface or placed between other layers. It indicates a layer which is currently in a plastic, malleable, or non-hardened state, frequently allowing it to bond with the underlying material.
Fresh properties – These refer to the, in-construction, characteristics of concrete in its unhardened, plastic state, such as workability, consistency, flowability, and cohesion. These properties are important for ensuring proper placement, compaction, and final strength, with key metrics including slump flow (for consistency), cohesion (to prevent separation), and setting time.
Fresh random value – It is a piece of data generated from a random process which is unpredictable, unique, and has not been used previously in the same context. It is critical in fields like cryptography, simulation (Monte Carlo), and communication systems to ensure security and reduce bias.
Fresh solvent – It is a pure, unused liquid (or gas / supercritical fluid) used to dissolve, suspend, or extract materials without containing contaminants or dissolved solids from previous cycles. Mainly used in cleaning, extraction, and chemical processing, it ensures maximum efficiency and purity in several processes.
Fresh water – It is the water with less than 4,000 milligrams per litre of total dissolved solids. It is referred to as non-saline water.
Fresnel concentrator lens – It is a compact, light-weight optical device composed of concentric annular, or linear, prism-shaped grooves which refract light to a common focus. It acts as a thin alternative to conventional lenses, maximizing sunlight collection for high-temperature thermal energy or concentrating solar PV (photo-voltaic) systems.
Fresnel equations – These are also called Fresnel coefficients. These equations describe the reflection and transmission of light (or electro-magnetic radiation in general) when incident on an interface between different optical media. They have been deduced by Augustin-Jean Fresnel who has been the first to understand that light is a transverse wave, when no one realized that the waves have been electric and magnetic fields. For the first time, polarization can be understood quantitatively, since Fresnel’s equations correctly predicted the differing behaviour of waves of the ‘s’ and ‘p’ polarizations incident upon a material interface. When light strikes the interface between a medium with refractive index ‘n1’ and a second medium with refractive index ‘n2, both reflection and refraction of the light may occur. The Fresnel equations give the ratio of the reflected wave’s electric field to the incident wave’s electric field, and the ratio of the transmitted wave’s electric field to the incident wave’s electric field, for each of two components of polarization. (The magnetic fields can also be related using similar coefficients.) These ratios are generally complex, describing not only the relative amplitudes but also the phase shifts at the interface. The equations assume the interface between the media is flat and that the media are homogeneous and isotropic. The incident light is assumed to be a plane wave, which is sufficient to solve any problem since any incident light field can be decomposed into plane waves and polarizations.
Fresnel fringes – It is a class of diffraction fringes which are formed when the source of illumination and the viewing screen are at a finite distance from a diffracting edge. In the electron microscope, these fringes are best seen when the object is slightly out of focus.
Fresnel lens system – It is a compact, lightweight optical assembly which focuses light using concentric, annular prisms rather than a thick, continuous curve. It reduces material volume by dividing the lens into zones, allowing for large apertures and short focal lengths without the bulk of conventional lenses. Common types include lighthouse lenses, solar concentrators, magnifying sheets, and stage spotlights.
Fresnel number (F or Nf) – It is a dimensionless quantity used in optics to define the transition between near-field (Fresnel) and far-field (Fraunhofer) diffraction regimes. Defined as ‘F = a-square/L x lambda’ (where ‘a’ is aperture size, ‘L’ is distance, ‘lambda’ is wave-length), it measures the importance of diffraction, with ‘F’= above or around 1’ indicating near-field and ‘F = much below 1’ indicating far-field.
Fresnel reflection loss – It refers to the reduction in transmitted light energy which occurs when light passes through the boundary between two different materials with different refractive indices. In the context of materials science and metallurgy, this loss occurs at the interface of a metal surface and its surrounding medium (like air, water, or a coating) because the mismatch in refractive indices causes a fraction of the incoming light to be reflected away rather than transmitted into or absorbed by the material.
Fresnel reflections – These refer to the partial reflection of electro-magnetic radiation (such as light or lasers) which occurs when it passes through an interface between two materials with different refractive indices, such as air and a polished metal surface. Named after Augustin-Jean Fresnel, these reflections determine how much light is reflected versus transmitted, based on the material’s properties, polarization, and angle of incidence. These reflections determine how much light is reflected versus transmitted, based on the material’s properties, polarization, and angle of incidence.
Fresnel reflector – It is a solar concentrator technology which uses long, narrow, segmented mirrors to track the sun and focus solar radiation onto a fixed, stationary receiver (tube) to generate heat, normally for producing steam in power plants. These systems are designed to be cost-effective and efficient, utilizing a linear, modular approach for medium- to high-temperature solar applications.
Fresnel zone – It is one of a series of confocal prolate ellipsoidal regions of space between and around a transmitter and a receiver. The size of the calculated Fresnel zone at any particular distance from the transmitter and receiver predicts whether obstructions or discontinuities along the path is going to cause substantial interference.
Fretting – It is a type of wear which occurs between tight-fitting surfaces subjected to cyclic relative motion of extremely small amplitude. Normally, fretting is accompanied by corrosion, especially of the very fine wear debris. It is also referred to as fretting corrosion and false brinelling (in rolling-element bearings).
Fretting corrosion – It is the accelerated deterioration at the interface between contacting surfaces as the result of corrosion and slight oscillatory movement between the two surfaces. It is also a form of fretting in which chemical reaction predominates. Fretting corrosion is frequently characterized by the removal of particles and subsequent formation of oxides, which are frequently abrasive and so increase the wear. Fretting corrosion can involve other chemical reaction products, which may not be abrasive.
Fretting damage – It is a wear and corrosion mechanism occurring between tightly fitted surfaces subjected to slight relative motion or vibration. It causes pits, grooves, and metal oxide debris, Common examples include bolted joints, bearings, splines, and press-fits.
Fretting fatigue – It is the fatigue fracture which initiates at a surface area where fretting has occurred. It is the progressive damage to a solid surface which arises from fretting. If particles of wear debris are produced, then the term fretting wear can be applied.
Fretting fatigue cracks – These are a failure mechanism where small-amplitude oscillatory motion (micro-slip) between contacting surfaces under load triggers premature crack initiation and propagation. This damage typically occurs at the trailing edge of contact zones, considerably reducing a material’s fatigue strength, frequently by one-half to one-third, through combined abrasive wear and cyclic tension
Fretting wear – It is a damage mechanism occurring between two contacting surfaces subjected to small-amplitude oscillatory motion (typically 1 micro-meter to 100 micro-meters) because of the vibration or thermal expansion. It causes localized metal-to-metal contact, producing hard oxide debris (fretting corrosion) that traps in the interface, creating abrasive scars and frequently initiating fretting fatigue cracks.
Freundlich adsorption isotherm– It is an empirical mathematical model which describes the adsorption of a gas or liquid solute onto a solid surface (such as a metal or porous material) at a constant temperature. It is widely used to represent the relationship between the quantity of material adsorbed per unit mass of the adsorbent and the concentration or pressure of the substance in the surrounding medium.
Freundlich behaviour – It refers to an empirical adsorption isotherm model used to describe how a solute (such as metal ions, inhibitors, or gases) adsorbs onto a heterogeneous solid surface (like metallurgical slags, ores, or metal surfaces). Unlike the Langmuir model, which assumes a uniform surface, the Freundlich model assumes that the surface contains sites with varying adsorption energies and that multilayer adsorption can occur.
Freundlich equation – It is also called Freundlich adsorption isotherm. It is an empirical mathematical relationship used to describe the adsorption of solutes (e.g., metal ions) from a liquid phase onto a solid surface (e.g., activated carbon, soils, minerals). It is specifically used to model adsorption behavior on heterogeneous surfaces where adsorption energy varies, rather than being uniform.
Freundlich model – It is an empirical, non-linear adsorption isotherm used to describe the equilibrium relationship between the concentration of a solute (adsorbate) on the surface of an adsorbent (e.g., activated carbon, metal oxide, mineral) and its concentration in the surrounding fluid (liquid or gas) at a constant temperature. Unlike the Langmuir model, the Freundlich model assumes heterogeneous surfaces, meaning the surface has multiple types of adsorption sites with varying affinities, and allows for multilayer adsorption.
Friable – It means easily broken into small fragments, crumbled, or reduced to powder. The term used in the asbestos industry to describe asbestos that can be reduced to dust by hand pressure.
Friable material – It refers to any substance, particularly asbestos or soil, which can be easily crumbled, pulverized, or reduced to powder by hand pressure when dry. It indicates a high risk for releasing airborne particles or fibres.
Friction – It is the resisting force which is tangential to the common boundary between two bodies when, under the action of an external force, one body moves or tends to move relative to the surface of the other. Friction is caused by the interactions at the surfaces of adjoining parts. The frictional forces oppose the relative motion between the moving parts of the machine. Movement of surfaces needs an applied force high enough to overcome microscopic surface interactions. Hence, extra energy is needed to be spent to overcome the friction. The friction between the moving parts of the machine also produces heat which causes damage to the machine. Hence, friction causes wear and tear of the moving parts of the machine in contact and therefore the machine loses its efficiency.
Frictional behaviour – It refers to the resistance encountered between contacting bodies when one moves relative to another, resulting from the interaction of molecular bonds at their surfaces. It includes static friction, which opposes initial motion, and kinetic friction, which opposes ongoing motion, both of which are influenced by the materials in contact and their surface characteristics.
Frictional condition – It refers to the specific state, environment, and physical characteristics at the interface of two contacting bodies which determine the resistance to their relative motion. It encompasses the surface properties, lubrication, load, and speed which dictate whether the interaction involves adhesion, deformation, or wear, and is often characterized by the coefficient of friction (mu).
Frictional contact – It refers to the interaction between two surfaces touching, where tangential forces resist relative motion, defined by normal force (preventing penetration) and frictional resistance (opposing sliding). It is necessary for modeling rolling, and wear, frequently using Coulomb friction laws to determine when surfaces stick or slip.
Frictional dissipation – It is the irreversible conversion of a system’s useful mechanical energy into unrecoverable thermal energy (heat) when two surfaces rub together or when materials deform. It represents the energy lost to friction, calculated as the product of the kinetic friction force and the sliding distance, resulting in heat generation or increased entropy.
Frictional drag – It is frequently termed fluid friction or fluid resistance. It is the force exerted by a fluid (liquid or gas) which opposes the motion of a solid object moving through it. Unlike solid friction, drag acts in the opposite direction of the velocity, increasing with speed and air / water density.
Frictional effect – It is the resistive force generated when two surfaces in contact move or attempt to move against each other, always acting parallel to the interface to oppose motion. It causes energy loss (frequently as heat / sound), slows moving objects, and is caused by surface roughness, or asperities.
Frictional force – When one surface moves over another surface in a machine, resistance to the relative motion of the surfaces takes place. The solid surface appears smooth to the naked eye, but this smooth surface shows irregularities of projections and cavities when seen under high power microscope. At a microscopic level, all surfaces are rough. When one such surface is placed over another, its projections fall into the cavities of the other and get interlocked. Because of this interlocking, there is resistance to the relative motion of the surfaces. This is called the frictional force or frictional resistance. Surface peaks (asperities) can bond to one another or protrude into adjoining surface. In a rolling mill, frictional force is the force between the entrance plane and the neutral point which act in the direction of the rolling to draw the metal into the roll.
Frictional heating – It is the process where mechanical energy is converted into heat at the interface of two surfaces sliding against each other, causing a temperature increase. It is a form of energy dissipation (irreversible process) which can considerably impact material properties and is important for industrial, and geological applications.
Frictional moment – It is also called friction torque. It is the resisting torque generated by friction forces within a mechanical system, such as bearings or rotating joints, opposing motion. It is the sum of moments resulting from rolling, sliding, viscous lubricant-drag, and seal friction (Mtot = Mr + Ms + Mdrag + Mseal). Common in bearing analysis, it determines power loss and starting torque.
Frictional phenomenon – It refers to the resistive force opposing relative motion or intended motion between two solid surfaces, fluid layers, or material elements in contact. It is a surface process involving energy dissipation, frequently caused by microscopic surface irregularities (asperities) interlocking or intermolecular forces. Common types include static, kinetic (sliding), rolling, and fluid friction.
Frictional pressure drop – It is the irreversible reduction in fluid pressure (or energy loss) caused by viscous shear stresses within the fluid and between the fluid and pipe walls, occurring as it flows through pipes, fittings, or equipment. It is a major component of overall pressure loss, heavily influenced by fluid viscosity, pipe roughness, flow velocity (laminar against turbulent), and diameter.
Frictional pressure gradient – It is the rate of pressure loss over a specific distance because of the friction in a fluid flow, frequently expressed as dP/dl. It represents the energy loss per unit length caused by viscosity and flow-pipe surface interaction. This quantity is important to determine pressure drop in pipelines, particularly in turbulent flow.
Frictional pressure loss – It is the reduction in pressure occurring as fluid flows through a pipe or conduit, caused by viscous shear stress between the fluid and the pipe wall. It represents energy lost because of the friction, typically proportional to pipe length, fluid density, and velocity squared, and is calculated using the Darcy-Weisbach equation.
Frictional properties – These are the characteristics of a material which define its resistance to movement when in contact with another material, encompassing how surfaces interact through static or kinetic friction. It determines how materials resist sliding, important for abrasion resistance, stability, and handling.
Frictional resistance – It is the opposition to motion which arises from the imperfections in real systems, resulting in energy dissipation because of the action of electro-magnetic and exchange forces between atoms. This resistance leads to an increase in entropy and is a consequence of the elastic, plastic, and adhesive interactions among surfaces in contact.
Frictional shear stress – It is the force per unit area acting parallel to the surface of two materials in contact, resisting their relative motion. It is calculated as the macroscopic frictional force (Ff) divided by the real contact area (Ar), normally formulated as ‘Fss = Ff/Ar’. Key examples include drag on a sliding surface, metal forming, and fluid flow against a wall.
Frictional sliding – It is also called sliding friction. It is the resistance force generated when two solid surfaces rub against or slide over each other. It is a type of kinetic friction which opposes relative motion, resulting in energy dissipation (heat / wear).
Frictional surface – It is the contact boundary between two materials which generates a force resisting relative motion (sliding or rolling). These surfaces frequently have roughness which creates mechanical locking or molecular attractions which increase resistance, measured by a coefficient of friction.
Frictional torque (Ft) – It is the rotational resistance caused by friction when parts rub, slide, or roll against each other. It acts as a moment of force which opposes the rotation of an object around an axis. It is calculated as the product of the frictional force (Ff) and the radius (r) from the axis of rotation (Ft = Ff x r).
Frictional wear – It is the gradual, progressive removal of material from metallic surfaces caused by mechanical action, such as sliding, rubbing, or rolling contact between two surfaces. It is a surface degradation process driven by adhesion, abrasion, or surface fatigue at asperities, frequently accelerated by heat, debris, or chemical oxidation.
Friction angle – It is the maximum angle at which a body remains stationary on an inclined plane before beginning to slide. It represents the relationship between the inclination angle and the static friction coefficient between the body and the surface.
Friction, bearing – It is the resistance encountered within a bearing because of the rolling and sliding contacts between rolling elements and surfaces, as well as the effects of lubrication and seal friction. It is influenced by factors such as shaft diameter, bearing load, and the properties of the lubricant used.
Friction coefficient – It is the dimensionless ratio of the friction force (F) between two bodies to the normal force (N) pressing these bodies together. (mu or f) = (F/N).
Friction compensation – It is a control technique used in mechanical systems (computer numerical control machines) to counteract resistive forces, specifically static friction (stiction) and Coulomb friction, which cause tracking errors, jerky movement, and steady-state errors. It works by feeding forward calculated torque / current to help motors overcome friction.
Friction condition – It is the state of interaction between two contacting surfaces which determines the magnitude of resistive force opposing motion or potential motion, classified by lubrication level and surface contact. Key types include dry (friction coefficient mu = above 0.3), boundary (mu = 0.1 to 0.3), and mixed lubrication.
Friction constant – It is also called coefficient of friction (mu). It is a dimensionless scalar value representing the ratio of the frictional force resisting motion between two surfaces to the normal force pressing them together. It defines the ‘grip’ or resistance, where a higher value indicates more friction (e.g., rubber on asphalt) and a lower value indicates a smoother, more slippery surface (e.g., ice).
Friction cycle – It refers to the repeated, alternating, or continuous sliding actions between two surfaces in contact, frequently leading to changes in the friction coefficient over time (e.g., polishing or wear). It is frequently used in tribology to analyze how wear and lubrication affect surface interactions over multiple passes, such as in motor wear or material testing.
Friction drag coefficient – It is a dimensionless parameter quantifying the drag force generated by viscous shear stress acting on an object’s surface as fluid flows over it. It represents the ratio of wall shear stress to dynamic pressure, and varies with Reynolds number and surface roughness. It is a parameter which quantifies the drag force because of the friction in a fluid flow, and it is included in the total drag coefficient calculation for different configurations.
Friction drive – In friction drive, the kiln rotation is driven by friction between the rotating support rollers and the kiln tyre. At the same time, a redesigned tyre attachment system allows the kiln shell to expand radially, which means that there is no need for lubrication between the tyre and kiln.
Friction drive press – It is a type of mechanical forging press which uses friction between one or more rotating disks (flywheels) and a transverse shaft (or ‘friction roller’) to move a screw mechanism up and down. It is a traditional, energy-efficient, and versatile machine widely used in metal forming for forging, embossing, stamping, and pressing operations.
Friction drive system – It is a propulsion mechanism reliant on the interaction of the conveyor belt with the drive pulley, demanding frequent inspections for wear and proper tension to ensure optimal functionality.
Friction, dynamic – It is also called kinetic friction. It is the force which opposes the relative motion between two surfaces sliding against each other. As a resistive force, it acts continuously to slow down a moving object. It is normally lower than static friction and remains almost constant for given materials.
Friction effect – It is the resistive force generated when solid surfaces, fluid layers, or material elements slide or interact, converting kinetic energy into heat and causing wear. It opposes relative motion, important for traction (brakes / gears) but causes energy loss and mechanical wear.
Friction element – It is a component or interface designed to resist relative motion between contacting surfaces, dissipating energy as heat. It normal refers to materials (like brake pads) or joints where friction is used to control motion, transmit force, or connect parts. Friction elements frequently convert kinetic energy into thermal energy.
Friction energy – It is the mechanical kinetic energy transformed into heat and wear because of the relative motion (sliding or rolling) between surfaces, frequently involving microscopic surface interactions. It represents energy lost from a system, frequently converted from mechanical work into heat via surface asperities.
Friction extrusion – It is a solid-state, thermo-mechanical metal processing technique which uses frictional heating and severe plastic deformation (SPD) to convert metal feedstock, such as powder, chips, or scrap, directly into rods, wires, or tubes. It eliminates melting and preheating, offering energy-efficient recycling and superior material refinement.
Friction factor – It is a dimensionless parameter which quantifies the resistance to flow (because of the viscosity and pipe roughness) in a pipe or duct, typically used to compute pressure drop. The most common types are the Darcy-Weisbach and fanning factors, with Darcy being four times larger than the fanning factor.
Friction factor model – It is a mathematical representation used to calculate the pressure drop or energy loss caused by fluid friction against pipe walls, mainly based on flow regime (Reynolds number) and relative roughness. It represents the ratio of pressure drop to kinetic energy, important for calculating flow resistance in pipes, conduits, or around objects.
Friction factor ratio – It is the ratio of the friction factor of a duct configuration with inserts to the friction factor of the same configuration without inserts, used to evaluate the head loss or pumping power in heat transfer applications.
Friction force – friction force is the positive force resisting the motion when a rolling body (ball, tyre, or wheel) is on a surface. The force is associated with both elastic and nonelastic deformation behaviour of rolling materials, depending on the applied load.
Friction gearing – It is also called friction drive. It is a method of power transmission using two smooth wheels or disks pressed together to transfer rotational motion through frictional contact rather than interlocking teeth. It is used for smooth, quiet power transfer and to allow for slippage in high-load scenarios to protect machinery.
Friction in pipes – It is also known as pipe friction or frictional loss. It is the resistance to fluid flow caused by viscous shear stresses, turbulence, and roughness at the pipe wall. It is a parameter which causes pressure drop and energy loss, categorized into major losses (straight pipes) and minor losses (fittings / bends).
Friction law – It refers to the established principles which describe the relationship between frictional force and load, specifically stating that the frictional force is directly proportional to the load (first Amontons law) and that the tribological friction coefficient is independent of the contact area and loading force, remaining approximately constant. Friction law defines the resistive force acting tangent to two contacting solid surfaces, opposing relative motion or tendency of motion. It states that the limiting friction is directly proportional to the normal force (F = mu x N) and is independent of the contact area.
Friction limit – It is the maximum static friction force which occurs between two surfaces just before an object begins to slide, acting as the threshold force needed to initiate movement. It is calculated as ‘F = mu x N’, representing the product of the coefficient of static friction (mu) and the normal force (N), and is independent of the contact area.
Friction load – It is the force resisting the relative motion of two solid surfaces in contact, typically defined as ‘F = mu x N’, where ‘F’ is the friction force, ‘mu’ is the coefficient of friction, and ‘N’ is the normal load (perpendicular pressure). It acts to oppose motion, important for stability, braking, and traction.
Friction loss – It is the reduction in pressure or energy (head loss) which occurs as a fluid flows through pipes, hoses, or fittings because of the viscosity of the fluid and its interaction with the container surface. It is basically energy dissipated as heat, normally calculated to determine pressure drops in plumbing, firefighting, and HVAC (heating, ventilation and air conditioning) systems.
Friction material – It is a sintered material showing a high coefficient of friction designed for use where rubbing or friction wear is encountered.
Friction model – It is a mathematical representation, such as Coulomb or viscous, used to simulate resistance forces between contact surfaces in engineering, robotics, and FEA (finite element analysis). These models, ranging from simple static approximations to complex non-linear dynamics, define how surface interactions, including friction coefficients (mu) and normal forces (N), affect motion, stability, and energy loss in systems.
Friction modifiers – These are mild anti-wear additives used to minimize light surface contact, such as sliding and rolling. These can also be referred to as boundary lubrication additives. These additives are used in lubricants to modify the coefficient of friction, hence the name ‘friction modifiers’.
Friction pad – It is a component designed to increase resistance, provide grip, or control motion between two surfaces by creating high friction. Typically made of composite materials, they convert kinetic energy into heat for braking or provide stability. Common examples include brake pads in vehicles, clutch discs, and anti-slip pads.
Friction pair – It refers to two contacting solid surfaces in a mechanical system which experience relative motion (sliding or rolling), where the interaction involves force resistance and wear. Critical for machinery efficiency and lifespan, they are defined by their materials and surface conditions (e.g., piston / cylinder, brake pad / disk).
Friction pair component – It refers to the two contacting, interacting surfaces in a mechanical system, such as piston / cylinder, valve plate / cylinder, or swash-plate / slipper, which experience relative motion, sliding, or rolling friction. These components (also called tribological pairs or friction couples) are critical in determining the service life, energy loss, and wear characteristics of machines.
Friction pile – It is a type of foundation pile that supports structural loads primarily through the shear resistance (friction) between the pile’s surface and the surrounding soil. Unlike end-bearing piles, they do not rely on resting on hard rock. These piles are, also known as floating piles, skin friction piles, or cohesion piles. They are ideal for soft soil conditions where bed-rock is too deep to reach, and they frequently use timber, steel, or concrete, normally used in bridge, building, and road construction.
Friction polymer – It is an amorphous organic deposit which is produced when certain metals are rubbed together in the presence of organic liquids or gases. Friction polymer frequently forms on moving electrical contacts exposed to industrial environments. The varnish like film attenuates or modifies transmitted signals.
Friction process – It is the resistance, heating, and wear generated when two surfaces in contact move or attempt to move against each other. It acts against motion, resulting from inter-molecular attractions and microscopic surface roughness. Common examples include walking, braking, and machinery operation, with key types being static, kinetic, rolling, and fluid friction.
Friction rollers – These are the rollers which provide additional traction to the conveyor belt, necessitating periodic checks for wear, alignment, and smooth operation.
Friction sawing – It is a high-speed machining process used to cut metals by generating intense frictional heat, which softens or melts the material at the cutting point. A toothless or fine-toothed blade rotates at very high speeds, melting through materials, particularly hardened steel and structural shapes, without affecting the overall heat treatment.
Friction scratch – It is a scratch caused by relative motion between two contacting surfaces.
Friction sleeve – It is a component used in geo-technical engineering, specifically in ‘cone penetration testing’ (CPT) to measure the friction along the side of a penetrometer as it is forced into the ground. It quantifies local soil-structure interaction, helping classify soil types based on friction ratio (Rf) and shear strength.
Friction-stir processing – It is a solid-state technique which uses a rotating, non-consumable tool to intensely stir and plastically deform a material, creating fine-grained, recrystallized microstructures without melting. Derived from friction stir welding (FSW), it improves strength, ductility, and surface properties, particularly on cast metals or surface composites. The process mechanism consists of a rotating tool consisting of a shoulder and a pin plunges into the material and moves along the surface, generating frictional heat. This heat, combined with severe plastic deformation, causes localized dynamic recrystallization.
Friction-stir welding – It is a solid-state joining process (non-melting) which uses a rotating tool to generate frictional heat and mechanically stir two metal parts together. It joins materials below their melting point, creating a fine-grained, recrystallized weld zone with high structural integrity, ideal for aluminum, magnesium, and steel alloys. Friction-stir welding (FSW) produces distinct microstructural zones compared to traditional fusion welding, characterized by significant grain refinement,
Friction stress – It is the shear stress acting at the contact interface between a work-piece and a tool (e.g., in forging, rolling, or extrusion) which resists the relative sliding motion during plastic deformation. It is a critical parameter in metal forming, as it directly impacts tool wear, surface quality, required force, and energy consumption.
Friction torque – It is the torque which arises from the sliding of brushes on a commutator and the spinning of a motor shaft in its bearings, influenced by external loads. It includes components of Coulomb friction and viscous friction.
Friction value – It is a dimensionless number representing the resistance to sliding between two surfaces in contact. It is the ratio of frictional force (F) to the normal force (N), calculated as ‘mu = F/N’, where a higher value indicates more grip and a lower value indicates easier sliding.
Friction variable – It normally refers to the coefficient of friction (mu) or the frictional force (F) itself, which represents the resisting force opposing relative motion between two surfaces in contact. It is defined by the formula ‘F = mu x N’, where ‘mu’ is the friction coefficient (dependent on material) and ‘N’ is the normal force.
Friction velocity – It is a theoretical velocity scale used in fluid mechanics to characterize shear stress at a boundary, defined as the square root of wall shear stress divided by fluid density. It is not a real flow speed, but a parameter indicating turbulent characteristics in the boundary layer. It is a characteristic velocity scale used in fluid mechanics to represent boundary shear stress. It is a critical parameter for defining turbulence strength, scaling velocity profiles in turbulent boundary layers, and determining the viscous sublayer thickness.
Friction welding – It is a solid-state welding process which produces coalescence of materials under compressive force contact of work-pieces rotating or moving relative to one another for producing heat and plastically displacing material from the faying surfaces.
Friction work per unit volume – It is frequently referred to as frictional energy dissipation per unit volume, is a measure of the energy lost to friction and converted into heat during the plastic deformation of a metal. It is defined as the total frictional work done (force × distance) divided by the volume of the material deformed.
Friction zone – It is the specific area or range of clutch lever / pedal travel where clutch plates are partially engaged, neither fully locked nor fully disengaged. It allows for gradual power transfer, controlling the transition between standing still and accelerating by managing sliding friction, preventing sudden stalls or wheel spin.
Friedel correlation – It is a widely used, empirical two-phase flow model which predicts the frictional pressure gradient inside tubes. It is mainly used for horizontal and vertical upwards, two-phase flow, calculated as a multiplier to single-phase liquid pressure drop using over 25,000 data points.
Friedel’s network coarsening model – It describes the recovery process in metals where a 3D dislocation network reduces its internal energy during annealing by expanding and reducing its dislocation density (d). This model on dislocation recovery, assumes that the coarsening kinetics depend on the average dislocation link length (l) and that the rate of recovery is initially fast, slowing over time as the network becomes more stable.
Friedel’s theory – It is a foundational framework for understanding the electronic structure of metals, particularly regarding how defects and impurities influence the surrounding metallic lattice. The theory provides a way to describe the perturbed electronic density and charge screening around a foreign atom, defect, or surface in a metal, moving beyond simplistic ‘jellium’ models to include scattering and phase shifts.
Friedman two-way analysis of variance – It is a non-parametric inferential statistic which is used to compare two or more groups by ranks which are not independent.
Fringe effect – It is also called fringing, It refers to the non-uniform bending or spreading of magnetic or electric field lines at the edges of conductors or air gaps. This phenomenon causes fields to extend beyond their intended confined paths, increasing the effective air gap area in magnetic circuits or increasing capacitance in metal plates.
Fringe stop – It is sometimes called a French stop. It is a fixed, positive stop mechanism used to accurately position a metal strip or coil as it progresses through a die.
Frit – In porcelain enamel, it is the small friable particles which are produced by quenching a molten glassy material.
Frobenius norm – It is a matrix norm which measures the ‘size’ or magnitude of a matrix. It is the square root of the sum of the absolute squares of the elements of a matrix, which can also be expressed as the square root of the trace of the product of the matrix and its transpose.
Frontal part – It refers to the projected area of an object which faces the direction of fluid flow (such as air or water). This area is important in calculating drag and aerodynamic resistance, as it represents the silhouette an object presents to the freestream.
Frontal surface – It is the projected area of an object facing the direction of fluid flow (e.g., air or water). It is important for calculating drag resistance and aerodynamic forces. It represents the 2D ‘silhouette’ an object shows to the oncoming flow, determining how much fluid is to be displaced.
Front axle – It is a critical structural assembly in vehicles which supports the front-end weight, facilitates steering, and handles braking / driving torques. It acts as the pivot for steering, using components like kingpins and stub axles, and frequently houses suspension mechanisms. Constructed from drop-forged steel, it connects the front wheels, allowing them to turn and pivot.
Front elevation – It is a flat, 2D orthographic projection showing the exterior facade of a structure as seen from the front, typically facing the street or main entrance. It displays, to scale, the building’s height, width, materials, window / door placement, and roofline, acting as an important, non-perspective guide for construction.
Front-end engineering design – It is a fundamental, early-stage engineering process bridging conceptual design and detailed engineering, focused on defining technical requirements, reducing risks, and estimating costs (+/- 10 % to 15 %) for large projects. It produces a ‘FEED package’, including PFDs (process flow diagrams), 3D models, and layouts, to ensure project viability and secure funding. Front-end engineering design defines project scope, estimate costs, and evaluate potential technical risks before committing to major expenditures. It occurs after conceptual design / feasibility studies and before detailed engineering / construction.
Front face – It refers to the main, forward-oriented surface of a component, vehicle, or structure, frequently used as the main reference for measurement, design, and analysis. It is key for aerodynamics, structural, or orthographic drafting, representing the most characteristic view. In manufacturing, facing is a lathe operation which makes the end of a part square.
Front frame – It is the foremost structural component of a vehicle chassis, designed to support the engine, suspension, and radiator while providing rigid stability. It acts as the main load-bearing assembly ahead of the front axle, frequently made of pressed steel, aluminum, or part of a unitary structure.
Front gauges – These are located in the front of a machine. When gauging from the front of the machine, the operator locates the work metal by means of stops secured in the table or in the front support arms. Power operation of the front support arms allows the blank dimensions to be entered digitally using a computer control. Front gauging is frequently done by means of a squaring arm.
Fronthaul / backhaul – Fronthaul connects remote radio heads (RRHs / radio units) to baseband units (BBUs / distributed units) in centralized RAN (radio access network), needing low-latency, high-speed fibre for digital signal processing. Backhaul connects the baseband units (BBUs / centralized units) to the core network / internet. Fronthaul handles digitized radio data, while backhaul handles processed, aggregated data traffic.
Front panel – It is the main user interface (human machine interface, HMI) for electronic or mechanical equipment, featuring controls (knobs, buttons) and indicators (light emitting diodes, displays) mounted on a sheet metal or plastic substrate. It protects internal components while providing functional, ergonomic interaction. It also defines visual branding and, in software, acts as a virtual instrument interface.
Front panel window – It is the user interface of a virtual instrument, where controls and indicators are placed for user interaction. Controls supply inputs, while indicators display outputs, facilitating data manipulation and visualization during execution.
Front roller – It is a structural component designed to apply pressure, provide guidance, or act as the main contact point at the forward end of a machine. Its function varies considerably depending on the application.
Front shroud – It is a non-structural protective cover, casing, or guiding surface located at the front of a component, designed to manage airflow, protect against heat / fluids, or reduce drag. It frequently acts as an ‘umbrella’ or barrier for components like engines, impellers, or actuators.
Front spar – It is a main structural beam running spanwise near the leading edge of an aircraft wing, functioning as the main forward load-bearing member. It acts as a cantilever beam to carry bending and shear loads, typically positioned around the 25 % chord point, often defining the forward boundary of the fuel tank.
Front suspension – It is a system connecting the front wheels to the chassis, designed to manage vertical wheel movement, steering input, and wheel alignment (camber / toe) to ensure vehicle handling, stability, and passenger comfort. It acts as a structural interface between the road and the frame, absorbing road shocks and maintaining tire contact.
Front wheel steering angle – It is the horizontal angle between the longitudinal centre-line of the vehicle and the plane of the steered front wheel. It is the measured angle by which the front wheels rotate around the kingpin to change direction, typically calculated using Ackermann steering geometry to ensure both front wheels roll without slipping during a turn.
Front-wheel drive – It is a vehicle power-train layout where the engine delivers power exclusively to the front wheels, which are responsible for both steering and propulsion. It normally features a transverse engine, mounted horizontally, and a trans-axle which combines the transmission, differential, and axle drive into one compact unit, maximizing cabin space.
Frost – It is the solid deposition of water vapour from saturated air. It is formed when solid surfaces are cooled to below the dew point of the adjacent air as well as below the freezing point of water.
Frost attack – It refers to the damage which occurs in concrete because of the freezing and thawing of water within the material’s pores, which leads to internal tensile stresses and cracking as ice formation increases volume by around 9 %. This phenomenon is influenced by hydraulic pressures and osmotic forces which arise during the freezing process.
Frosting – It is a form of ball bearing groove damage, appearing as a frosted area, suggestive that surface distress has occurred.
Frost point – It is the temperature at which water vapour in the air condenses into ice crystals (frost) on a surface, rather than liquid dew. It is the temperature at which the air becomes saturated with respect to water vapour over an ice surface. The frost point is always below 0 deg C and is analogous to the dew point, but specifically relates to the formation of frost.
Frost protection – It refers to technical, design-based, and operational methods used to prevent damage caused by freezing temperatures to infrastructure, and equipment. It involves mitigating the effects of ice formation on materials (like concrete) and ensuring systems (such as machinery) operate below freezing by managing heat transfer and moisture.
Frost resistance – It is the ability of a water-saturated porous material (such as concrete, mortar, or brick) to withstand repeated freeze-thaw cycles without substantial loss of mechanical strength, mass, or structural integrity. It is mainly evaluated by measuring a material’s resistance to internal expansion pressure caused by water freezing in its pores.
Froth – It is a stable, three-phase dispersion of gas bubbles within a liquid, frequently carrying hydrophobic solid particles. Specifically in mineral processing, it is the layer formed on top of a flotation cell which separates hydrophobic target minerals from hydrophilic waste (gangue) by attaching particles to air bubbles for removal.
Froth depth – It is the vertical distance between the pulp-froth interface and the overflow lip of the flotation cell. It defines the operating bed thickness where air-entrained particles are separated, directly affecting froth stability, concentrate grade, and recovery.
Froth flotation – It is a process used to concentrate ores, specifically sulphides, by separating valuable minerals from waste gangue based on surface hydrophobicity. Finely ground ore, mixed with water and reagents, forms a slurry; hydrophobic ore particles attach to air bubbles and rise as froth, while hydrophilic gangue sinks.
Froth flotation process – It is a selective physico-chemical separation process, used to concentrate valuable minerals (especially sulphides) from waste gangue by exploiting differences in surface hydrophobicity. Finely ground ore is mixed with water and reagents to make valuable particles water-repellent (hydrophobic), which then attach to air bubbles and float to the surface as froth, while hydrophilic gangue sinks.
Froth flow – It is a highly disturbed, oscillatory two-phase (gas-liquid) flow regime in vertical pipes, characterized by large, chaotic gas bubbles (Taylor bubbles) which break down, creating a thick, unstable liquid film. It is a transitional flow between slug flow and mist flow at high gas velocities.
Froth stability – It is the ability of air bubbles within a foam to resist coalescence (merging) and bursting. It represents a dynamic equilibrium between foam formation and decay, frequently measured by air recovery, bubble lifetime, or foam height, where higher stability normally correlates with increased recovery but lower concentrate grade.
Froth zone – It is the top layer of a flotation cell where air-particle aggregates rise, form a stable foam, and are selectively separated from contaminants (gangue). It acts as an important refining stage, increasing concentration by draining entrained impurities back into the pulp while transporting hydrophobic material to the launders.
Froude modelling – It is a technique used to predict the behaviour of full-scale prototypes (like ships or dams) by testing smaller, geometrically similar models, based on matching the Froude number. It ensures similarity in gravity-dominated flows with free surfaces, such as waves, ship resistance, and open-channel hydraulics.
Froude number (Fr) – It is a dimensionless quantity representing the ratio of inertial forces to gravitational forces, used to model flow behaviour in systems like gas-stirred ladles, where buoyant gas bubbles considerably affect liquid metal motion. It is defined as ‘Fr = V/root (gL)’, where ‘V’ is fluid velocity, ‘g’ is gravity, and ‘L’ is a characteristic length.
Froude similarity – It is a dimensionless engineering principle ensuring dynamic similitude between a model and a prototype where gravity acts as the dominant force, such as in free-surface flows. It needs the Froude number to be identical for both systems, meaning inertial forces scale proportionally to gravitational forces.
Frozen flow – It is a condition in fluid dynamics, particularly in high-speed reacting gas mixtures, where chemical reaction rates are considerably slower than the flow velocity. As a result, the chemical composition and molecular excitation of the gas remain frozen or unchanged, failing to adjust to rapid changes in pressure and temperature during expansion.
FSN analysis – This analysis of the inventory is based on consumption figures of the items. Under this analysis, inventory items are classified into three groups namely ‘F’ (fast moving), ‘S’ (slow moving), and ‘N’ (non-moving).
F-temper – This designation is used for ‘as fabricated’. It indicates that the material has undergone little to no controlled thermal or strain-hardening treatment during or after the fabrication process.
F-test – It is as parametric statistical test of the equality of the means of two or more samples. It compares the means and variances between and within groups over time. It is also called analysis of variance (ANOVA).
FTIR Spectroscopy – It the abbreviation for Fourier transform infrared (FTIR) spectroscopy.
Fuel – It is a substance containing combustible used for generating heat.
Fuel-air mixture – It is a mixture of fuel and air.
Fuel-air ratio – It is the ratio of the weight, or volume, of fuel to air.
Fuel assembly – It is a structured, engineered unit of nuclear fuel rods (or elements) placed into a reactor core, designed to withstand extreme thermal, hydraulic, and radiation conditions. It acts as the functional unit for loading / unloading fuel during refueling, containing several fuel pellets within cladding tubes.
Fuel blend – It is a technical mixture of two or more distinct fuel components, such as gasoline and ethanol or diesel and bio-diesel, to optimize combustion properties, improve performance, reduce emissions, or lower costs. This precise, frequently automated process adjusts the chemical characteristics of the fuel as fired.
Fuel blending – It is the process of combining two or more fuel streams (e.g., gasoline, diesel, bio-fuels) with distinct physical and chemical characteristics to create a final, homogeneous product which meets specific performance, quality, and regulatory standards. It is an important optimization technique used in refineries and depots to optimize costs, boost properties like octane or cetane numbers, and reduce emissions.
Fuel burning rate – It is defined as the speed at which fuel is consumed during combustion, typically measured as mass loss per unit time or per unit area. It represents the velocity of the reaction front (regression rate) in solid propellants or the mass gasification rate in liquid / solid fuel fires.
Fuel cell – It is an electro-chemical device which converts chemical energy from a fuel, typically hydrogen, directly into electricity through a continuous reaction with an oxidant, such as oxygen. Consisting of an anode, cathode, and electrolyte, it operates efficiently without combustion to produce electricity, heat, and water.
Fuel cell applications – These are engineering implementations of electro-chemical devices which directly convert chemical energy (hydrogen, methanol) into electricity, water, and heat. Used in stationary power, transportation, and portable electronics, they provide efficient, clean, and continuous power. Applications include electric vehicles, data centre back-up, and combined heat / power systems.
Fuel cell components – These refer to the important parts of a fuel cell system, mainly including the catalyst, membrane, and gas diffusion layer, which are important for optimizing performance and efficiency in different applications.
Fuel cell design – It is a multi-disciplinary process optimizing electro-chemical, thermal, and fluid-dynamic phenomena to directly convert chemical energy (hydrogen / fuel) into electricity. It involves configuring components, anode, cathode, electrolyte, and catalyst, to maximize power density, durability, and efficiency while meeting application-specific constraints.
Fuel cell efficiency – It is an engineering metric measuring how effectively a fuel cell converts the chemical energy of fuel directly into electrical energy. It is defined as the ratio of useful electric power output (actual voltage current) to the energy input (heating value of fuel), with typical operational efficiencies ranging from 40 % to 60 %.
Fuel cell electric hybrid vehicle – It is a zero-emission vehicle that uses a hydrogen fuel cell as its primary power source, combined with an auxiliary energy storage system (like batteries or ultracapacitors) to provide peak power, handle transient loads, and enable regenerative braking. This hybrid setup improves efficiency, manages power fluctuations, and protects the fuel cell’s lifespan.
Fuel cell electric vehicle – It is a type of zero-emission electric vehicle (EV) which generates electricity on-board using a fuel cell stack, typically fueled by hydrogen gas, rather than relying solely on a large battery. It combines hydrogen with oxygen to generate electricity through an electro-chemical process, producing only water vapour as emissions.
Fuel cell hybrid – It is a configuration combining a fuel cell system (main energy source) with an auxiliary energy storage system (battery or ultra-capacitor) to drive electric vehicles. It optimizes efficiency by allowing the fuel cell to operate steadily while the battery manages transient loads, peak power demands, and regenerative braking.
Fuel cell materials – These are the specialized components, anode, cathode, electrolyte, and catalyst, which form an electro-chemical cell to convert chemical energy (typically hydrogen) directly into electricity and heat. Key materials include platinum catalysts, ion-conducting polymer membranes (proton-exchange membrane), and ceramic oxide electrolytes.
Fuel cell modelling – It is a powerful tool used to explore and characterize fuel cell system performance, involving the selection of appropriate models that balance capabilities, robustness, and accuracy, while ensuring comprehensive validation for predictive power.
Fuel cell performance – It is the electro-chemical efficiency, power output, and durability of a system in converting chemical energy (e.g., hydrogen) directly into electrical energy. It is mainly assessed through metrics like voltage, current density, and power density, influenced by operational stability and degradation rates.
Fuel cell power system – It is an electro-chemical device which converts chemical energy from fuel (like hydrogen) and an oxidant (normally oxygen) directly into electricity, water, and heat without combustion. It consists of an anode, cathode, and electrolyte, frequently organized into stacks to meet power needs, delivering efficient power for transport, stationary, and portable uses.
Fuel cell reaction – It is an electro-chemical process which directly converts chemical energy from fuel (like hydrogen) and an oxidant (normally oxygen) into electricity, with water and heat as by-products. It operates by oxidizing fuel at the anode and reducing the oxidant at the cathode, yielding a net reaction of ‘2H2 + O2 = 2H2O’.
Fuel cells for transportation – These are electro-chemical energy conversion devices which convert chemical energy directly into electrical energy through the reaction of hydrogen and oxygen, powering electric vehicles with water and heat as by-products. These high-efficiency, zero-emission systems are mainly designed for automotive, bus, heavy-duty truck, and rail applications, typically using proton-exchange membrane (PEM) technology.
Fuel cell stack – It is the core component of a hydrogen fuel cell system, consisting of multiple individual cells arranged in series to generate higher voltage and power output. Each cell contains a membrane electrode assembly (MEA) and bi-polar plates, converting hydrogen and oxygen into water, electricity, and heat.
Fuel cell system – It is an electro-chemical device which directly converts chemical energy from fuel (typically hydrogen) and an oxidant (oxygen / air) into electrical power, water, and heat. Unlike batteries, they need a continuous fuel supply and do not need recharging. Systems use stacks for high voltage, frequently involving auxiliaries like pumps, compressors, and cooling loops.
Fuel cell technology – It converts chemical energy from hydrogen (or other fuels) directly into electricity and heat through electro-chemical reactions with oxygen, without combustion. It offers high efficiency (roughly 70 % against 40 % for thermal power) and produces only water and heat, making it a clean, modular energy source for transportation, portable, and stationary applications.
Fuel cell types – The main difference among fuel cell types is the electrolyte, fuel cells are classified by the type of electrolyte. The major types of the fuel cells are alkaline fuel cell (AFC), proton exchange membrane fuel cell, phosphoric acid fuel cell, solid oxide fuel cell, and molten carbonate fuel cell (MCFC).
Fuel cell vehicles – These are the vehicles which use proton exchange membrane fuel cells (PEMFCs) to replace internal-combustion engines, offering higher efficiency and lower greenhouse gas emissions. They are developed for different applications, including passenger cars, utility vehicles, and buses.
Fuel channel – It is an important horizontal pressure boundary component designed to house nuclear fuel bundles, contain high-pressure coolant, and allow heat transfer. It consists of a pressure tube, a calandria tube, and annular spacers, designed to withstand high pressure and thermal stress while allowing for thermal expansion and radiation-induced creep.
Fuel chemistry – Most fuels are hydro-carbons (composed of carbon and hydrogen) or contain organic compounds. These compounds have stored energy. The energy is captured in chemical bonds. Energy is released during oxidation.
Fuel cladding – It is the material which I used to construct reactor components and designed to maintain a separation between their contents and the coolant. An example is the cladding of a fuel pin which separates the fuel pellets from the coolant. Zirconium and zirconium alloys (Zircalloy) are common cladding materials.
Fuel composition – It refers to the specific chemical makeup, mixture components, and molecular structure of a fuel (such as carbon, hydrogen, sulphur, or added additives) which determine its combustion properties, energy content, and environmental impact. It dictates how a fuel burns, affecting engine performance, emissions, and safety, such as in turbines.
Fuel concentration – It is the measurement of the quantity of fuel vapour or liquid present within a specific volume, frequently used to determine the fuel-to-air ratio in combustion systems. It indicates how much energy-producing fuel is mixed with air, normally measured in mass per volume, percentage, or equivalence ratio to optimize engine efficiency.
Fuel cost – It is normally defined as the product of fuel consumption and fuel price (furl cost = fuel consumption x fuel price), frequently analyzed as a cost rate (money value per giga-joule or money value per hour) within total operational costs. It represents the financial expenditure needed for energy production, frequently optimized using incremental cost analysis or by reducing consumption per unit of output.
Fuel cycle – It consists of the sequence of steps involved in supplying, using, and disposing of the fuel used in nuclear reactors. The fuel cycle is ‘closed’ if it includes the reprocessing of spent fuel and recycling of fissile materials resulting from reprocessing. The term ‘open’ or ‘once-through’ cycle means that the fuel is disposed of in a permanent storage site after use in the reactor.
Fuel design – It is the systematic process of creating, optimizing, or selecting fuels, particularly synthetic, alternative, or nuclear fuels, to meet specific performance, environmental, and safety needs. It involves tailoring the physical and chemical properties of fuel mixtures to improve efficiency and reduce emissions, frequently utilizing computational modelling and AI (artificial intelligence) to navigate chemical spaces.
Fuel dilution – It is the contamination of engine lubricating oil by unburned gasoline or diesel fuel which seeps past piston rings into the crankcase. It acts as a contaminant which lowers oil viscosity, reduces lubrication film strength, and increases wear on engine components. Key causes include cold operation, excessive idling, short trips, and malfunctioning fuel injectors.
Fuel direct injection – It is an advanced internal combustion engineering system which delivers fuel directly into the combustion chamber rather than the intake manifold. Operating at high pressure, it allows for precise fuel atomization, improving combustion efficiency, increasing power, and reducing emissions compared to port injection.
Fuel displacement – It refers to the substitution of one type of fuel for another within global energy markets, where the unavailability of a particular fossil fuel source frequently leads to the consumption of a different, potentially higher-cost fuel to meet demand. This concept is important in evaluating the green-house gas emissions associated with fossil fuel projects, as the displacement can influence overall emissions and market dynamics.
Fuel economy – It is the measure of a vehicle’s energy efficiency, defined as the distance travelled per unit of fuel consumed (e.g., kilometers per litre). It is distinct from fuel consumption (fuel used per distance) and represents the thermal efficiency of converting chemical energy into motion.
Fuel economy regulations – These are government-mandated standards designed to improve vehicle energy efficiency, needing manufacturers to meet specific average kilometers per litre or emissions (grams per kilometer) targets for their fleet. These standards mandate technological advancements to reduce fuel consumption and environmental impact, with compliance typically based on harmonized test cycles for city and highway driving.
Fuel economy standards – These are regulated, minimum, or average, performance targets for vehicle energy efficiency, needing manufacturers to reduce fuel consumption (e.g., litres per 100 kilometers) or emissions (e.g., grams per kilometer) across their fleet. Engineered to decrease energy dependence and environmental impact, these standards guide vehicle weight, engine, and transmission design for higher mileage.
Fueled power plant – It is an industrial facility which generates electricity by consuming chemical or nuclear fuel to drive generators, typically through steam turbines or internal combustion. These plants convert the stored chemical energy in fossil fuels (coal, oil, natural gas) or nuclear energy into electricity, frequently utilizing combustion to produce high-pressure steam.
Fuel element debris – It is the material made up of mainly metal components removed from the casing of fuel elements after use.
Fuel energy – It is the chemical energy stored within a material (solid, liquid, or gas) which is released as heat and light during combustion, mainly through the oxidation of carbon and hydrogen. This heat is harnessed and transformed into mechanical, electrical, or thermal energy for industrial or power generation purposes, characterized by high calorific value.
Fuel ethanol – It is a high-octane (around 113 research octane number, RON), volatile, colourless liquid (C2H5OH) produced through bio-mass fermentation and dehydration, concentrated to above 99.5 % purity. It is normally denatured with petroleum products to render it undrinkable, and used as a renewable bio-fuel additive to increase oxygen content, boost octane, and improve combustion efficiency in engines.
Fuel expenditure – It refers to the total amount of fuel consumed by vehicles, machinery, or engines during operation, frequently analyzed to minimize costs and maximize efficiency. It represents the physical quantity or monetary cost of fuel used to produce a specific output, frequently quantified by metrics like ‘specific fuel consumption’ (SFC) or total fuel consumption rates.
Fuel filter – It is an important engine component engineered to remove contaminants, such as dirt, rust, sediment, and water, from fuel before it enters the fuel injection system or carburetor. It ensures clean fuel flow to maximize combustion efficiency, protect high-tolerance injectors / pumps from abrasive wear, and reduce engine damage.
Fuel-fired furnace – It is that furnace which combust fuel with the purpose of releasing chemical energy as heat. Furnace designs vary as to its function, heating duty, type of fuel and method of introducing combustion air. Heat is generated by mixing fuel with air or oxygen. The residual heat exits the furnace as flue gas.
Fuel flow – It is the rate at which fuel is delivered to a combustion system, engine, or burner, normally measured in mass (kilo-grams per hour) or volume per unit time (cubic-meters per hour). This parameter is important for controlling combustion efficiency, maintaining specific temperatures, and achieving the desired stoichiometry (fuel-to-air ratio) for heating or melting metals. Transmitters are used to measure the rate electrically, and indicators display the fuel flow to the operator.
Fuel gases – These are the gases normally used with oxygen for heating such as acetylene, natural gas, hydrogen, propane, stabilized methyl-acetylene propadiene, coke oven gas, blast furnace gas, converter gas and other synthetic fuels and hydro-carbons.
Fuel gasification – It is a thermo-chemical process which converts carbonaceous materials (such as coal, coke, or bio-mass) into a combustible gaseous product, known as syngas (synthesis gas or producer gas), through controlled, incomplete oxidation at high temperatures (above 700 deg C, frequently 900 deg C to 1,600 deg C). Unlike combustion, which aims to burn fuel completely to produce heat, gasification utilizes a restricted quantity of oxygen or air, sub-stoichiometric conditions, to break down molecular bonds and produce valuable gaseous fuel rather than just heat and carbon di-oxide (CO2).
Fuel heating – It refers to the process of generating, transferring, and applying thermal energy derived from the combustion of fuels (solid, liquid, or gaseous) to metals or ore, normally within a furnace environment. This process aims to raise the temperature of the material to a specific level for processing, such as smelting, melting, or heat treatment.
Fuel inflation rate – It is the percentage rate at which the cost of energy sources (such as coal, natural gas, or electricity) increases over a specific time period. It is an important component of cost-push inflation where rising energy prices drive up the cost of production for metals, which can subsequently cause a general rise in prices.
Fuel injection – It is a, normally electronic, system in internal combustion engines which atomizes and sprays fuel directly into the intake manifold or combustion chamber. Using a pump and nozzle, it precisely manages the air-fuel ratio to optimize power, reduce emissions, and increase fuel efficiency compared to carburetors.
Fuel injection system – It is a modern engine component which atomizes and sprays pressurized fuel directly into an engine’s combustion chamber or intake manifold. It replaces older carburetors, using sensors and an electronic control unit (ECU) to precisely regulate fuel delivery, which boosts efficiency, power, and reduces emissions.
Fuel life cycle – It is frequently analyzed through ‘life cycle assessment’ (LCA). It is the comprehensive, ‘cradle-to-grave’ assessment of environmental impacts, energy consumption, and emissions generated throughout a fuel’s entire existence, from extraction to final consumption and disposal. It focuses on minimizing environmental impacts by evaluating multiple stages rather than just tailpipe emissions, helping to avoid shifting problems from one stage to another.
Fuel methanol – It is a colourless, volatile, flammable liquid alcohol (CH3OH) used as an alternative transportation fuel or energy carrier. It is produced mainly from natural gas or coal, though it can be generated from renewable bio-mass (bio-methanol) or captured carbon di-oxide (e-methanol). Methanol is used in industrial processes as a reducing agent or a source of gaseous atmospheres (such as synthesis gas) for heat treating and refining metals
Fuel nozzle – It is a device which directs, controls, and atomizes fuel (liquid or gas) into a combustion chamber (injector nozzle) or dispenses it into a tank (dispensing nozzle). It optimizes spray patterns for efficient combustion or ensures safe, accurate fueling, frequently featuring automatic shut-off.
Fuel oil – It is any of different fractions obtained from the distillation of petroleum. Such oils include distillates and residues. Fuel oils include heavy fuel oil, marine fuel oil, furnace oil, gas oil, heating oils, diesel fuel, and others.
Fuel oil ash – It refers to the non-combustible, inorganic, metallic residue which remains after heavy fuel oil (HFO) or residual fuel oil is burned. It is a major cause of high-temperature corrosion, fouling, and deposit formation on metal components such as boiler tubes, gas turbine blades, and heat exchangers.
Fuel oil ash corrosion – It is a high-temperature damage mechanism where contaminants in fuel oil, mainly vanadium, sulphur, and sodium, form molten salts (slags) which dissolve the protective oxide layer on metal surfaces, resulting in severe accelerated corrosion and metal loss. This type of hot corrosion frequently occurs in boilers, gas turbines, and fired heaters operating at high temperatures, frequently manifesting as deep pitting, ‘alligator hide’ patterns, or surface grooving.
Fuel pellet – It is a compressed, cylindrical, or spherical form of solid energy, normally made from bio-mass (wood / paper) for heating or uranium di-oxide (UO2) for nuclear power. They are designed for high-efficiency combustion or fission, offering uniform size for automatic feeding in stoves or reactors.
Fuel pipe – It is also called fuel line. It is a reinforced hose or rigid tube designed to transport liquid fuel or fuel vapours safely between components in a vehicle or machine, such as from the fuel tank to the engine. Normally made of reinforced rubber, plastic, or steel, they are required to withstand high pressure, heat, and corrosive fuel blends.
Fuel processing – It is the conversion of raw hydro-carbon fuels (such as natural gas, propane, gasoline, or bio-fuels) into hydrogen-rich synthesis gas (hydrogen, carbon mono-oxide, carbon di-oxide) suitable for fuel cells. It involves cleaning, desulphurization, and chemical reforming (steam reforming, partial oxidation) to remove impurities and generate electricity efficiently.
Fuel processing system – It is a system which converts raw hydro-carbon fuels, such as natural gas, liquefied petroleum gas (LPG), or methanol, into hydrogen-rich gas suitable for fuel cell stacks, typically involving reforming, desulphurization, and water-gas shift reactions. These systems allow fuel cells to operate on conventional fuels rather than pure hydrogen.
Fuel processor – It a device or system which converts conventional hydro-carbon fuels, such as natural gas, liquefied petroleum gas (LPG), gasoline, or diesel, into a hydrogen-rich gas stream suitable for use in fuel cells. It acts as a reformer, breaking down fuel through processes like steam reforming or auto-thermal reforming to produce hydrogen (H2), while also cleaning the gas of contaminants like carbon mono-oxide (CO). It operates through chemical processes like reforming, water-gas shift reactions, and purification to remove impurities, enabling cleaner energy production.
Fuel processor system – It is a technology which converts hydro-carbon fuels (such as natural gas, propane, or methanol) into hydrogen-rich gas for use in fuel cells, frequently including purification steps to remove impurities like carbon mono-oxide (CO). It acts as an on-site or on-board hydrogen generator, bridging conventional fuels with electro-chemical power generation.
Fuel production – It is the industrial, chemical, or biological process of creating energy-dense substances, such as gasoline, diesel, hydrogen, or bio-fuels, by extracting, refining, or transforming raw materials (feedstock) like petroleum, coal, or bio-mass. These activities include extraction, purification, and manufacturing to generate power-generating products.
Fuel purification – It is the process of removing contaminants, such as water, sludge, rust, and microbial growth, from fuel (e.g., diesel, heavy fuel oil) to ensure efficient combustion, prevent engine damage, and reduce emissions. It typically uses techniques like centrifugation, filtration, and coalescing to separate water and impurities based on density differences.
Fuel quality – It refers to the physical and chemical properties of a fuel, such as purity, energy content (calorific value), composition, and thermal characteristics which determine its performance, efficiency, and environmental impact during combustion. It dictates suitability of the fuel for high-temperature smelting, refining, and heat treatment processes. High-quality metallurgical fuel (such as coke or high-grade coal) is required to provide maximum heat, consistent chemical reduction properties, and minimal harmful impurities to ensure efficient operation.
Fuel quality standards – These consist of a set of specifications, including chemical composition, physical properties, and impurity limits, which ensure fuel (coal, coke, oil, or gas) enables efficient reduction, melting, and refining of metals while minimizing damage to furnace refractories and equipment. These standards are important since fuel impurities directly affect the final alloy chemistry and process efficiency.
Fuel ratio – It is frequently referred to as air-fuel ratio (AFR). It is defined as the mass ratio of air to fuel present in a combustion process. It indicates the proportion of air mixed with a given quantity of fuel for combustion in furnaces or reactors.
Fuel reactor – It is also called nuclear reactor core. It is the central component of a nuclear power plant where fissile material (such as uranium-235 or plutonium-239) undergoes a controlled nuclear fission chain reaction to generate heat. Fuel reactor is basically a high-temperature, high-radiation pressure vessel containing materials designed to withstand extreme environments.
Fuel reforming – It is the process of converting hydro-carbon fuels (such as methane, natural gas, propane, or diesel) into a hydrogen-rich gas mixture, frequently called syngas (hydrogen and carbon mono-oxide), through catalytic reactions. While also important for high-octane gasoline production (catalytic reforming), in the context of metallurgical reduction, fuel reforming is used to produce reducing gases which transform metal oxides into raw metals.
Fuel reprocessing – It is the method of processing reactor fuel in order to separate the reusable fissionable material from waste material.
Fuel rod – It is a cylindrical, metallic cladding tube, typically made of a zirconium alloy, which encapsulates stacked ceramic uranium dioxide (UO2) fuel pellets. It serves as the main containment barrier against radioactive fission products while enabling heat transfer in a nuclear reactor.
Fuel rod assembly – It is a long, cylindrical rod, frequently 3.66 metres to 4.27 metres in length, made up of fuel pellets containing enriched uranium in cladding. Fuel rods are bundled into fuel assemblies.
Fuel route – This term is used to refer to the set of processes and areas which the fuel passes through to be brought onto a nuclear licensed site, i.e., prepared prior to use, used for fission, stored on site, undergo its initial on-site treatment, and then be removed from site (as spent fuel) for onward processing.
Fuel specifications – These specifications define the precise chemical and physical requirements for fuels (such as coke, coal, natural gas, or oil) used in metal processing, extraction, and refining. These specifications ensure the fuel provides necessary heat, controls furnace emissions, maintains reducing conditions (if needed), and minimizes contamination of the final metal product.
Fuel spray – It is a technique where liquid fuel (such as kerosene) or fuel gas (such as acetylene or propane) is combusted with oxygen to produce a high-temperature, high-velocity gas jet. This jet is used to melt, accelerate, and propel metallic or ceramic powder particles onto a substrate to form a dense, high-performance coating.
Fuel supply – It refers to the system and logistics of providing the necessary thermal energy and reducing agents (such as coal, coke, natural gas, or oil) to high-temperature furnace operations (e.g., blast furnaces, smelting, refining). It encompasses the storage, handling, preparation, and injection of fuels, such as pulverized coal or metallurgical coke, designed to maintain consistent, high-pressure, and precise combustion within furnaces for iron and steel making.
Fuel supply system – It is the integrated arrangement of components designed to safely store, transport, regulate, and deliver fuel (such as natural gas, propane, or oil) from the source to the burner for combustion. Its main purpose is to provide a consistent, metered flow of fuel to ensure efficient, controlled heat generation. This involves selecting specific metals (e.g., steel, aluminum) for tanks, pipes, and pumps, along with surface treatments, to withstand pressure, corrosion, and wear.
Fuel synthesis – It is the artificial creation of liquid or gaseous fuels (such as synthetic diesel, gasoline, or kerosene) from carbon-rich non-petroleum substrates. These processes normally involve converting raw feedstocks, like coal, bio-mass, or natural gas, into a gaseous intermediate known as synthesis gas (syngas, a mixture of carbon mono-oxide and hydrogen), which is then refined into usable liquid fuels.
Fuel system – It is the assembly of components, including pipes, valves, pumps, or regulators, designed to store, transport, and control the flow of fuel (natural gas, oil, or propane) to the burner. It manages the safe delivery of fuel to be combined with air for combustion, ensuring consistent heat release for industrial processes or heating.
Fuel technology – It refers to selecting, processing, and utilizing fuels specifically to generate heat, reduce metallic oxides, or control atmospheres in furnaces for metal extraction, refining, and heat treatment. It focuses on improving energy efficiency, lowering costs, and minimizing environmental impact through the combustion of fossil fuels (coal, coke, oil, gas) or alternative fuels.
Fuel-to-steam efficiency – It is the ratio of heat added to boiler feed-water to produce the output steam to the quantity of energy inputted with fuel.
Fuel utilization – It refers to the efficiency with which energy resources (such as coal, coke, natural gas, or oil) are used in metallurgical furnaces and processes to produce heat or perform chemical reductions. It is an important performance indicator aimed at optimizing energy consumption, reducing operational costs, and maintaining quality control in smelting and melting operations.
Fuel utilization efficiency – It is the ratio of heat energy effectively used for heating, melting, or chemical reduction processes to the total heating value of the fuel consumed. It measures how effectively fuel (e.g., natural gas, coke) is converted into useful metallurgical heat rather than being lost through exhaust gases, radiation, or incomplete combustion.
Fuel utilization ratio – It refers to the efficiency with which nuclear fuel is used in a reactor, indicating the proportion of the fuel which undergoes fission compared to the total fuel loaded, hence improving the overall performance and sustainability of the nuclear fuel cycle.
Fuel vehicle – It is a transport machine powered by a substance which releases energy through chemical or nuclear means, very frequently by burning hydro-carbon-based fossil fuels such as gasoline, diesel, or liquefied petroleum gas (LPG). These vehicles utilize an internal combustion engine (ICE) or a fuel cell system to convert chemical energy into kinetic energy for movement.
Fuel volume – It is the total space occupied by a fuel (liquid or gas) at specific conditions, normally measured in litres, or cubic-meters, or defined as the rate of fuel delivery (flow) per unit of time. It acts as a measure of fuel capacity in tanks or the needed quantity to satisfy an engine’s operational needs (e.g., litres per minute).
Fuel washing – It is a liquid fuel treatment process designed to remove water-soluble impurities, specifically sodium (Na), potassium (K), and some calcium compounds, from heavy fuel oils or crude oils before they are combusted. This pretreatment step is important for preventing high-temperature corrosion and ash deposition on metallic components (like turbine blades or boiler tubes) in gas turbines and diesel engines.
Fugacity – It is the pressure which an ideal gas needs to have the same chemical potential as a real gas at a given temperature. In the context of a real gas mixture, the fugacity of a constituent is the partial pressure which the substance has part of an ideal gas mixture under the same conditions of chemical potential and temperature.
Fugitive binder – It is an organic substance added to a metal powder to improve the bond between the particles during compaction and thereby increase the green strength of the compact, and which decomposes during the early stages of the sintering cycle.
Fugitive emissions – The term refer to the unintentional releases of gases or vapours from industrial equipment, frequently because of the leaks or other irregularities. These emissions are not released through a designated vent or stack and can be difficult to quantify since they are irregular and dispersed. Examples include leaks from pipelines, valves, storage tanks, or other equipment.
Fugitive emission (FE) test – A fugitive emission is defined as a leak from a fluid (e.g., hydro-carbons, chemical or mixture of chemicals). The fugitive emission test is carried out to evaluate the ability to suppress and / or the performance level of on / off valves and control valves with regards to fugitive emission. The specification for testing describes the type of detection method and test medium to be used and specify the acceptance and rejection criteria.
Fukui conical cup test – It is a method used to evaluate the formability of sheet metal by drawing a circular blank into a conical cup shape until fracture occurs. It is a formability test which assesses a material’s ability to undergo plastic deformation without cracking or tearing, particularly during processes like deep drawing.
Full annealing – It is a softening process in which the steel section is heated to a temperature above the austenitic transformation range and after being held for a sufficient time at this temperature, is cooled slowly to a temperature below the transformation range. The steel is generally allowed to cool slowly in the furnace, although it can be removed and cooled in some cooling medium. Since the transformation temperatures are affected by the carbon content of the steel, it is obvious that the high carbon steels can be fully annealed at lower temperatures than the low carbon steels. The microstructure of the hypo-eutectoid steels which result after full annealing consists of ferrite and pearlite. Eutectoid and hyper-eutectoid steels often get spheroidize partially or completely on full annealing.
Full bore – It is also called full opening. It describes a valve whose bore (port) is nominally equal to the bore of the connecting pipe.
Full-bridge inverter – It is a power electronic circuit which converts direct current (DC) voltage into alternating current (AC) voltage using four switching devices (insulated-gate bipolar transistors or metal–oxide semiconductor field-effect transistors) arranged in an H-bridge configuration. It generates AC (alternating current) output by toggling diagonal pairs of switches, normally used in high-power applications like UPS (uninterruptible power supply) systems, solar inverters, and motor drives for efficient, stable power inversion.
Full centre – It is the mild waviness down the centre of a metal sheet or strip.
Full column rank – It refers to a condition of an m × n matrix A where its columns are linearly independent. In process modelling, compositional analysis, or X-ray diffraction, a matrix has full column rank when all of its columns are linearly independent. If a matrix ‘A’ has ‘m’ rows and ‘n’ columns (m x n), and it has full column rank, it means that the number of linearly independent columns equals ‘n’. This situation typically applies to ‘tall’ matrices (m = n and above), where there are more equations (e.g., experimental observations) than unknowns (e.g., concentrations of phases).
Full covariance matrix – It is a square, symmetric matrix that quantifies the statistical relationships between multiple material properties, process parameters, or micro-structure features. Unlike a diagonal matrix (which only shows individual variances), a full covariance matrix includes both the variance on the main diagonal and the non-zero off-diagonal elements, capturing how variables change together (e.g., as temperature increases, grain size changes).
Full constraints model – It is frequently called the Taylor-Bishop-Hill model or classical Taylor model. It is a micro-mechanical model to predict the plastic deformation and texture evolution of poly-crystalline materials. It belongs to a family of models which link the macroscopic deformation of a material to the microscopic slip activity of individual grains. The foundational principle of the full constraints model is that every grain within a polycrystal undergoes the exact same deformation as the macroscopic material.
Full-constraints poly-crystal model – It is frequently known as the Taylor model. It is a homogenization approach in plasticity used to predict the deformation behaviour and texture evolution of poly-crystalline materials. The full-constraints model assumes that the plastic strain (or velocity gradient tensor) is identical for every grain within the polycrystal and equal to the macroscopic deformation of the entire sample.
Full duplex – It is a communication method which enables two devices to send and receive data simultaneously, allowing for real-time, bi-directional communication. Unlike half-duplex (one direction at a time) or simplex (one-way only), full duplex increases efficiency and speed by using separate, dedicated paths for transmitting and receiving.
Full face-piece respirator – It is a reusable, tight-fitting mask which covers the nose, mouth, and eyes to protect the wearer from hazardous airborne particles, gases, vapours, and liquid splashes. It uses inter-changeable filters / cartridges, offers superior sealing, and is used in several industries.
Fuller -It is a forging tool with a convex, rounded nose used to shape, spread, or draw out hot metal. It is the portion of the die used in hammer forging mainly to reduce the cross section and to lengthen a portion of the forging stock.
Fullerene cage – It is a closed-cage, hollow carbon molecular structure (allotrope) comprising 20 or more carbon atoms, frequently arranged in hexagonal and pentagonal rings to form spherical (buckminsterfullerene) or ellipsoidal shapes. These stable carbon ‘buckyballs’ function as nano-scale containers to isolate atoms or strengthen alloys.
Fullerene production – It is the synthesis of closed-cage carbon allotropes (like C60 buckyballs) by vapourizing graphite through electric arc discharge, laser ablation, or combustion. It is a metallurgical process involving high-energy carbon evaporation in inert atmospheres (helium / argon) to form fullerene-rich soot, which is then purified using solvents.
Fullerenes – These are a class of hollow, closed-cage carbon allotropes (Cn, where ‘n’ is 20 and above) consisting of graphene-like sheets curled into hexagons and pentagons. Mainly known as ‘buckyballs’ (C60), they are utilized for creating high-strength metal-matrix composites, super-conducting, and hardened materials because of their exceptional thermal stability, extreme pressure resistance, and unique electron-accepting capabilities.
Fullerene synthesis – It involves high-energy vapourization of graphite (arc discharge / laser ablation) or hydrocarbon combustion, producing soot containing fullerenes. This soot is refined using solvent extraction, while endohedral metallofullerenes are produced by trapping metal atoms within the cage during synthesis.
Fullerides – These are a class of compounds formed by the intercalation of metal atoms (predominantly alkali or alkaline-earth metals) into the crystal lattice of fullerenes, very frequently C60. They are basically salts where the fullerene molecules act as negatively charged ions [fullerene anions, (C60)n-].
Fuller impressions – These impressions refer to the rounded, frequently corrugated, depressions or grooves left in the metal stock after fuller tool has been applied. The fullering impression is frequently used in conjunction with an edger (edging impression).
Full factorial design – It is a systematic design of experiments (DOE) method which investigates the effects and interactions of multiple process factors (input variables) on material properties (output responses) by testing all possible combinations of factor levels. This method is used to optimize processes such as alloying, heat treatment, or casting, where changing one factor (e.g., temperature) can produce different results depending on the level of another factor (e.g., cooling rate).
Full-film lubrication – It is a type of lubrication wherein the solid surfaces are separated completely by an elasto-hydro-dynamic fluid film.
Full frame rate – It refers to the maximum frequency (measured in frames per second, or fps) at which an imaging detector, such as a high-speed camera or an infrared camera, can capture and read out the entire imaging sensor area.
Full hard – It is a temper of non-ferrous alloys and some ferrous alloys corresponding approximately to a cold-worked state beyond which the material can no longer be formed by bending. In specifications, a full hard temper is normally defined in terms of minimum hardness or minimum tensile strength (or, alternatively, a range of hardness or strength) corresponding to a specific percentage of cold reduction following a full anneal. For aluminum, a full hard temper is equivalent to a reduction of 75 % from dead soft. For austenitic stainless steels it is a reduction of around 50 % to 55 %.
Full hard cold rolled steel – It is a hot rolled pickled steel which has been cold reduced to a specified thickness and subject to no further processing (not annealed or temper rolled). The product is very stiff. It is not intended for flat work where deformation is very minimal. Full hard temper consists of full hard cold rolled steel produced to a Rockwell hardness of 84 and higher on the ‘B’ scale.
Full heat treatment – For certain alloys, it is the heat treatment cycle consisting of solution treatment followed by artificial age hardening.
Full insert – It is a die insert. It is a separate block of hardened material (frequently high-strength steel or ceramic) which carries the impression (cavity) of the final part shape. This insert is then secured within a larger die holder or die block. Full inserts are replaceable, specialized working components placed inside a main forging die block, rather than machining the forging cavity directly into the main die block itself. They are designed to improve efficiency, reduce maintenance costs, and increase the flexibility of forging operations, particularly in closed-die or drop-forging processes.
Full journal bearing – It is a type of plain bearing where a cylindrical bearing surface (sleeve) completely surrounds (360-degree) the rotating shaft, supporting radial loads through a pressurized lubricant film. It is a sliding, non-rolling element bearing frequently utilized in high-speed, heavy-load applications, such as in turbines, engines, and generators.
Full-length mandrel – It is a specialized, blunt-ended tool, rod, or bar inserted into a hollow work-piece (such as a tube or ring preform) to provide internal support, maintain its shape, and control the inner diameter during deformation. Unlike partial or short mandrels, a full-length mandrel extends through the entire length of the component, allowing for simultaneous deformation and shaping along the whole work-piece, normally used in mandrel forging or saddle forging to produce weld-less, seamless tubes and rings.
Full life cycle – It refers to the entire, end-to-end series of stages an entity, such as a product, system, or project, undergoes from its initial conception or birth to its final termination, or disposal. It encompasses all phases, including development, growth, maturity, decline, and retirement.
Full load amperage – It is the electrical current drawn by the conveyor motor under peak load conditions, necessitating continuous monitoring, and periodic checks to maintain motor health and operational efficiency.
Full load current – It is the current drawn by a motor or other electrical machine at its full rated power and standard voltage.
Full load hours – These hours represent the theoretical number of hours a power plant or technical system needs to operate at its maximum capacity (100 %) to produce the same total energy output as it actually produces over a period (normally one year) at fluctuating or partial loads. It is a metric for evaluating efficiency, utilization rates, and profitability.
Full load test – It evaluates the performance of a system or component when operating at its maximum capacity, simulating real-world conditions with a high volume of users or transactions. The goal is to identify bottlenecks and determine the system’s maximum operating capacity before performance degrades. This helps ensure the system can handle expected load and peak usage without issues like slow response times, errors, or crashes.
Full mould – It is a trade name for an expendable pattern casting process in which the polystyrene pattern is vapourized by the molten metal as the mould is poured.
Full penetration weld – It describes the type of weld wherein the weld metal extends across the entire wall thickness of the joint.
Full-scale fatigue testing – It is an important validation process, mainly in structural engineering, where a complete, full-sized structure (like a bridge section) is subjected to repeated, simulated operational loads to determine its fatigue life. It identifies critical failure points, validates inspection intervals, and verifies safe-life without causing unexpected, catastrophic failure in service.
Full scale output – It is the electrical signal a sensor or transducer produces when operating at its maximum rated capacity, representing the difference between minimum and maximum output. Full scale output (FSO) is typically measured in millivolts per volt of excitation for load cells, serving as a key calibration benchmark for accuracy, linearity, and signal conditioning.
Full-scale plant – It is a commercial-sized manufacturing facility designed for maximum production, efficiency, and profitability, built after testing technology in pilot plant studies. It represents the final, operational scale, transitioning from experimental units to full-volume output.
Full-scale test – It is the comprehensive evaluation of a complete, operational product, structure, or system under real-world or simulated conditions to verify its integrity, performance, and safety. It uses full-sized, assembled prototypes or final products to generate actionable data for certification, safety, or design refinement.
Full-scale testing – It is the evaluation of a complete, operational structure, system, or prototype under real-world or simulated conditions, rather than using models or components. It verifies performance, durability, and safety, frequently ensuring compliance with certification standards in different industries.
Full-scale trial – It is the final, comprehensive evaluation of a production process, technology, or material, conducted at actual commercial production rates and equipment dimensions. It is the last step before full-scale commercialization, frequently aimed at confirming the feasibility of a new process or product under real-world operational conditions, rather than in a controlled laboratory condition.
Full stroke parallelism control – It refers to a specialized, frequently hydraulic or advanced servo-mechanical, press capability which ensures the upper die (ram) remains strictly parallel to the lower die (bolster) throughout the entire descending stroke, even when dealing with off-centre loads. It prevents the ram from tilting when the forging force is not perfectly centered under the ram, protecting tooling and ensuring consistent pressure across the entire die surface.
Full surface coverage – It refers to the condition where an added substance, such as corrosion inhibitors, adsorbate molecules, or nano-particles, completely covers the metal surface. It indicates that 100 % of the available active sites on the metal surface are occupied.
Full vehicle model – It is a comprehensive, multi-body simulation representation used in automotive engineering to analyze the dynamic behaviour of a vehicle, including ride, handling, and vibrations. It typically encompasses the car body (sprung mass) connected by suspension systems to four wheels (unsprung masses). Modern vehicle modeling incorporates material-specific data for lightweighting and safety, such as advanced high-strength steels (AHSS), multi-phase steels (dual-phase steel, transformation induced plasticity steel, and quenching and partitioning steel, and aluminum alloys to determine crash-worthiness and structural integrity.
Full waveform inversion – It is an imaging method used in geophysical exploration which fits simulated seismic waveforms to seismic records, enabling the extraction of detailed information and the construction of an accurate underground velocity model.
Full-wave rectifier – It is a rectifier circuit which converts both positive and negative parts of the input alternating current wave-form into a unidirectional, direct current.
Full width at half maximum – It is a measure of resolution of a spectrum or chromatogram determined by measuring the peak width of a spectral or chromatographic peak at half its maximum height.
Fully charged battery – It is the state where the active materials on the plates (electrodes) have been converted by electro-chemical action to their maximum potential to deliver electrical energy. This state is reached when all available active material has been converted into high-energy chemical form, resulting in maximum open-circuit voltage and maximum electrolyte density.
Fully cylindrical dies – These dies are used for the forging of long members. They are made most economically by being built up with rings, with a cutaway portion just large enough to feed in the forging stock. Fully cylindrical dies are sometimes more efficient than semi-cylindrical or flat-back dies because of the larger periphery available for the forging action. However, one disadvantage of fully cylindrical dies is that the opening is too small to permit continuous movement of the work-piece to the next impression in a multiple-impression roll die. hence, these dies need control of rolling motion by a clutch and a brake.
Fully dense material – It is a solid component with minimal to zero internal porosity, meaning its actual density is equal to or extremely close to its theoretical crystalline density. It represents a compact, void-free microstructure, frequently achieving nearly 100 % of the material’s potential density. This structure is typically produced through advanced processing techniques like hot isostatic pressing, spark plasma sintering, or specialized powder metallurgy to maximize mechanical and magnetic properties.
Fully developed crack – It is frequently termed a ‘fully propagated crack’ or ‘mature crack’. It refers to a physical discontinuity which has initiated from a microscopic defect and extended into a distinct, measurable, and stable macroscopic size. Unlike an incipient crack (or crack nucleation), which is in its early, frequently non-detectable stage, a fully developed crack has established a clearly defined crack tip and normally extends perpendicular to the main loading axis.
Fully developed flow – It occurs when the fluid’s boundary layers merge and the velocity profile ceases to change along the flow direction, meaning ‘du/dx = 0’. Frictional effects have stabilized across the entire cross-section, resulting in a constant, predictable velocity profile, parabolic for laminar and flatter for turbulent flow.
Fully developed laminar flow – It is defined as a type of viscous fluid flow in a stationary straight duct where the fluid velocity distribution at a cross-section remains constant and invariant, characterized by fluid particles moving along definite paths called streamlines, with no velocity components normal to the duct axis. This flow condition persists up to a Reynolds number of 2300 for a duct length higher than the hydro-dynamic entry length.
Fully developed region – It is the area in a fluid flow where the hydrodynamic or thermal boundary layers have stabilized and travel unaffected through the channel after reaching the same point. This occurs after a specific length known as the hydrodynamic or thermal entrance length. It also refers to a stage in deformation or welding where a specific structural or mechanical change has spread throughout the entire volume of interest (the gauge area) and reached a steady state.
Fully developed velocity profile -It is a state in fluid flow where the velocity distribution remains constant along the length of a pipe, needing a specific length of tube to achieve this condition based on parameters such as diameter and flow characteristics. It describes a stable, unchanging velocity distribution across a channel or mould after the boundary layer has fully grown. At this stage, the velocity profile remains constant in the flow direction, meaning the viscous shear forces are fully established and balanced, and the shear stress at the wall remains constant.
Fully martensitic structure – It is a metastable crystallization phase of steel, achieved by rapid quenching to convert 100 % of austenite into martensite, resulting in a body-centered tetragonal (BCT) crystal structure. It is characterized by high hardness and brittle, needle-like microstructure, produced by a diffusion-less, shear-type transformation.
Fully plastic condition – It occurs when the entire cross-section of a structural component or material sample has yielded, with plastic deformation dominating the behaviour. At this stage, the material is no longer acting elastically, and the stress distribution across the material corresponds to the yield strength, neglecting any further increases from strain hardening.
Fully reversed loading – It is a cyclic fatigue condition where a material is subjected to equal magnitude tensile and compressive stresses, resulting in a mean stress of zero (Sm = 0). The stress alternates symmetrically between a maximum positive tension and a maximum negative compression (Smax = – Smin), normally represented by a stress ratio R = -1.
Fully saturated porous medium – It is a material, frequently a solid skeleton or matrix, where all interconnected voids or pores are completely filled with a fluid (liquid or gas), with saturation at its maximum (s = 1). This implies the coupling of the solid structure and pore fluid dynamics, where pore fluid pressure considerably affects the overall behaviour.
Fully stressed design – It is an optimality criterion method used in structural engineering to proportion structures (like trusses or frames) so that every member, or every point within a component, reaches its maximum allowable stress limit under at least one of the applied design load conditions.
Fully turbulent region – It is the zone within a flowing fluid, such as molten metal, where turbulent eddies dominate momentum and heat transfer. In this region, inertial forces dominate, and the effects of viscosity are negligible compared to the random, chaotic movement of fluid particles.
Fully-welded ball valve – It refers to a ball valve whereby the body and closure joints are fully welded to complete the valve assembly. This type of valve construction cannot be disassembled nor repaired at site.
Fulvic acids – These are low-molecular-weight, water-soluble, yellow-to-amber organic acids derived from humus, formed through microbial decomposition of plant matter. They are highly reactive components of humic substances, characterized by their solubility in both strong acids and bases and their ability to considerably improve nutrient absorption, transport, and chelation in soils.
Fumaroles – These are openings in volcanic areas which emit gases and vapours, frequently utilized for the collection and analysis of volcanic gases, such as hydrogen sulphide (H2S) and sulphur di-oxide (SO2). They can be connected to devices for the separation and measurement of these gases and associated water vapour.
Fume control – It refers to systems, techniques, and equipment designed to capture, extract, and filter hazardous vapours, gases, and particulate matter at their source. It is important for protecting worker health from toxic emissions, maintaining air quality, and complying with environmental regulations in industrial and laboratory settings.
Fume cupboard – It is a partially enclosed work-station designed to protect operators by containing airborne contaminants and limiting their spread through a mechanically induced inward airflow. It typically includes an extraction system for the safe release of contaminated air while aiming to reduce transient emissions to acceptable levels.
Fumed silica – It is also known as pyrogenic silica. It is an ultra-fine, high-purity, white powder produced by burning silicon tetra-chloride in an oxygen-hydrogen flame. It is widely used as a universal thickening agent, reinforcing filler, and anti-caking agent, featuring extremely low bulk density and high surface area.
Fume exhaust blower – It is also known as a fume exhaust fan. It is a device which uses a fan to draw out fumes, vapours, and particulate matter from an enclosed space, like a laboratory or workshop, and expels them outside. This process improves air quality and prevents the buildup of hazardous substances. Fume exhaust blowers are a critical component of fume hoods and other ventilation systems designed to protect workers from harmful fumes. Fume exhaust blowers are specifically designed to remove hazardous fumes and particulate matter generated by various industrial and laboratory processes.
Fume exhaust fan – It is a type of exhaust fan specifically designed to remove contaminated air, including fumes, vapours, and dust, from a specific area, frequently within a fume hood or other enclosure, to improve air quality and protect users and the environment. These fans are crucial in settings where hazardous substances are handled, such as laboratories or industrial work-places. Fume exhaust fans primarily aim to remove harmful airborne contaminants, preventing them from spreading and endangering individuals or contaminating the surrounding environment.
Fume exhaust system – It is a type of air purification system designed to remove harmful or hazardous fumes, vapours, and particulate matter from the air, particularly in industrial and commercial settings. These systems capture pollutants at their source, preventing them from spreading and potentially harming workers, equipment, or the environment.
Fume hood – It is a ventilated enclosure in which gases, vapours and fumes are captured and removed from the work area. An exhaust fan pulls air and airborne contaminants through connected ductwork and exhausts them to the atmosphere. The typical fume hood is equipped with a movable front sash and an interior baffle. Depending on its design, the sash can move vertically, horizontally or a combination of the two and provides some protection to the hood user by acting as a barrier between the worker and the process. The slots and baffles within the hood direct the air and, in several hoods, can be adjusted to allow the most even flow. It is important to prevent the baffles from becoming blocked, by excessive material storage or equipment, since this considerably affects the exhaust path within the hood and as a result, the efficiency of hood capture.
Function – It is a specific task, action, or intended behaviour a system performs, typically transforming input flows (materials, energy, data) into desired output flows. This definition is important for systems design, mapping what a system is required to do (function) to how it achieves it (physical behaviour), frequently aimed at maximizing performance and efficiency.
Functional abstraction – It refers to the process of abstracting the behaviour of a system as per its functional and teleological understanding, aiming to show the functional roles of structural components in achieving the overall function of the system.
Functional analysis – It is a branch of mathematical analysis focused on infinite-dimensional vector spaces and the continuous linear operators acting upon them, often utilizing concepts like Banach and Hilbert spaces. It studies properties such as convergence, continuity, and compactness in spaces of functions, extending linear algebra techniques to higher dimensions.
Functional assembly – It is a combination of components or sub-assemblies designed to work together as a single unit to perform a specific, intended function. They are important in engineering, ranging from rigid structures to movable mechanisms like gears. Functional analysis frequently separates components into main (important for function) and secondary parts (fasteners, connectors) to increase design efficiency.
Functional basis – It is a standardized design language consisting of a set of functions and flows used to describe the overall function of a product or process, broken down into simpler sub-functions. It serves as a common vocabulary for engineering design, enabling the systematic modeling, comparison, and analysis of products.
Functional block diagram – It depicts the functions of the major elements of a circuit, assembly, and system etc. in simplified form. It is prepared to illustrate the functional relationship of major elements of an assembly, and system etc. It includes major circuit functions depicted by single lines, rectangular blocks, and explanatory notes or text.
Functional clothing – It is engineered apparel designed to provide specific performance, protection, or comfort benefits beyond basic aesthetics, such as moisture-wicking, thermal regulation, or hazard protection. These clothing utilize advanced materials, smart textiles, and specialized designs to improve user capability or protect them in extreme environments.
Functional component – It is a fundamental, reusable building block in system design, software engineering, or physical engineering which performs a specific, defined task. It transforms inputs into outputs and is designed based on needed functionality, frequently mapped to a physical part later in the development cycle.
Functional decomposition – It is a hierarchical breakdown of a design or product into the basic functions which are to be achieved. This is done by asking the question how? For example, the basic function of a copier is to make copies. Asking how leads to the next level of functions i.e., feed paper, make marks, and handle documents etc. Each function is stated by a verb and a noun.
Functional diagrams – Functional diagrams are a unique form of technical diagram for describing the abstract functions comprising a control system, e.g. proportional integral derivative (PID) controllers, rate limiters, manual loaders. This form of document finds wide application in several industries to document control strategies. Functional diagrams focus on the flow of information within a control system rather than on the process piping or instrument interconnections (wires, tubes, etc.). The general flow of a functional diagram is top-to -bottom, with the process sensing instrument (transmitter) located at the top and the final control element (valve or variable-speed motor) located at the bottom. No attempt is made to arrange symbols in a functional diagram to correspond with actual equipment layout. These diagrams are all about the algorithms used to make control decisions, and nothing more.
Functional differentiation – It is a process which determines the change in a functional because of the variations in a function across its domain, typically represented as an integral involving the functional derivative. It parallels the rules of conventional calculus, adapting discrete changes in functions to continuous variations in functionals.
Functional engineering – It is a design approach prioritizing the practical utility, efficiency, and operational flow of a system over its aesthetic appeal, aiming for optimal performance with minimal barriers. It connects engineering, production, and service by focusing on functional modules rather than just components, frequently incorporating standards like International Electrotechnical Commission standard IEC 81346 to improve collaboration and efficiency.
Functional entity – It is an active, modular component, such as a person, machine, or software application, which performs specific services, actions, or data transformations within a system. These entities process inputs to generate outputs to achieve specific system objectives and can be combined to form higher-level systems.
Functional exercise – It is an operations-based simulation designed to test and evaluate the organization’s emergency plans, policies, and procedures in a realistic, real-time environment. Unlike a full-scale exercise which moves physical resources, a functional exercise focuses on the coordination, command, and control functions of personnel within an ‘emergency operations centre (EOC) or command post, normally without moving actual field equipment.
Functional fibres – These are textile materials which possess specific functionalities beyond comfort and aesthetics, such as protection, comfort, or intelligent functions, frequently achieved through specialized treatments or inherent properties.
Functional fillers – These are solid additives, typically minerals, metals, or ceramics, incorporated into plastic, rubber, or composite matrices to improve mechanical, thermal, electrical, and optical properties beyond mere bulk addition. Unlike inert fillers, they improve performance like stiffness, durability, or conductivity, while reducing formulation costs.
Functional finish – It is a surface modification, treatment, or coating applied to a component to impart specific performance properties, such as corrosion resistance, reduced friction, increased wear resistance, or improved sealing, beyond just aesthetic appearance. These finishes are important for component reliability and are frequently dictated by surface roughness (Ra) standards on technical drawings.
Functional group – It is a specific group of atoms within a molecule which is responsible for the molecule’s characteristic chemical reactions and properties. These groups dictate how a molecule behaves in chemical reactions, regardless of the overall size or structure of the molecule. Functional group has characteristic properties. Examples are hydroxyl and carboxyl groups.
Functional hazard analysis – It is a top-down, qualitative, early-stage process used to identify potential failure conditions of a system function and assess their consequences. It determines how safe a system is required to be by classifying the severity of hazards (e.g., catastrophic, critical) to define safety requirements. Functional hazard analysis (FHA) evaluates the effects of malfunctioning, failed, or missing functions on the overall system and its operational context.
Functionality – It refers to the capacity of a metal or alloy to fulfill specific engineering, physical, or chemical requirements in a target application, tailored through controlled composition, structure, and processing. It can refer to the bulk material properties or specialized surface properties induced by techniques like plating or diffusion. It represents the ‘useful phase’ or performance characteristics of a component, such as its strength, conductivity, or corrosion resistance. Modern metallurgy allows functional materials (e.g., iron, samarium, cobalt, and nickel) to be designed by changing their microstructure and composition to suit needs like magnetic memory, high-strength components, or electrical conductivity. Functionality is achieved through specific processes like alloying, heat treatment (annealing, quenching, tempering), and mechanical working (forging, rolling). Functionality is also the number of covalent bonds which a monomer can form when reacting with other monomers.
Functionalized graphene sheet – It is a single or few-layer graphene structure modified through chemical or physical approaches to introduce functional groups (like -OH, -COOH) or heteroatoms, improving solubility, reactivity, and stability. Mainly, this process optimizes graphene for applications in electronics, and composites by reducing re-agglomeration and enabling interfacial coupling with other materials.
Functional layer – It refers to a distinct, specialized stratum within a system, whether software, material, or structural, which is designed to perform specific tasks, improve performance, or enforce separation of concerns. It acts as an abstraction level which separates core logic, processing, or functionality from the underlying physical infrastructure or user interface, allowing for modularity and easier maintenance.
Functional layers – These refer to additional layers introduced in membrane structures which improve performance, such as fouling resistance or charge-carrying capabilities, allowing for precise control over membrane chemistry and structure at the nano-scale.
Functionally graded material plate – It is an advanced composite structural component where material properties (such as composition, density, or elasticity) vary smoothly and continuously across its thickness or dimensions, typically from a ceramic surface to a metallic one. Unlike traditional composite laminates with abrupt interfaces, functionally graded material (FGM) plates reduce stress concentrations and provide tailored properties (e.g., high-temperature resistance, corrosion resistance, or high structural toughness).
Functionally graded materials – These are advanced composite materials featuring a gradual, continuous, or step-wise spatial variation of chemical composition, micro-structure, or porosity, designed to achieve superior site-specific properties. They eliminate distinct interfacial boundaries, reducing stress concentrations common in traditional laminates, frequently blending metals and ceramics for high thermal resistance, wear resistance, and high-temperature strength.
Functional membrane – It is a thin, tailored barrier, typically polymeric, ceramic, or metallic, designed to selectively separate species (molecules, ions, particles) from a fluid mixture based on physical or chemical properties. These materials provide specific functionalities, such as permeability, charge, or reactivity, allowing, for example, water purification, gas separation, or energy storage in fuel cells.
Functional monomer – It is a monomer unit containing active side-chain groups (e.g., hydroxyalkyl, carboxyl, glycidyl, or vinyl) which can be polymerized to introduce specific chemical, physical, or mechanical properties into a polymer. They enable customization of solubility, reactivity, or adhesion in the final material.
Functional notation – It is a standardized method, frequently written as ‘y = f(x)’, to explicitly define a dependent variable [y or f(x)] as a function of an independent variable (x or input). It clarifies that for every input ‘x’ in a domain, there is exactly one output ‘y’ which is important for modelling, simulating, and designing systems with precise, deterministic behaviour.
Functional packaging design – It focuses on creating packaging which goes beyond mere containment to offer utility, such as protection, convenience, and interactivity. When combined with casting processes, such as die casting, investment casting, or casting of composites, this approach facilitates the creation of complex, high-performance, and lightweight structures.
Functional performance – It is the measurable capacity of a system, product, or component to execute its intended utility, operating effectively within defined constraints. It verifies that design outputs meet functional requirements, focusing on efficiency, reliability, and objective, data-driven verification of operational goals.
Functional prototype – It is a working model of a product designed to test and validate core functionality, performance, and usability before mass production. Unlike visual models, these prototypes include critical operational components and simulate real-world behaviour, enabling engineers to identify design flaws and reduce production risks.
Functional recovery – In earthquake engineering, functional recovery is a design objective where structures are engineered to maintain or rapidly restore their intended utility within a reasonable, specified timeframe after a disaster, moving beyond merely saving lives (safety) to minimizing downtime and ensuring building usability.
Functional relationship – It defines how one physical quantity (output) directly depends on another (input), where each input produces one unique output, frequently expressed as ‘y = f(x)’. It describes the behaviour of systems, such as energy, material, or information flows, frequently represented by equations, graphs, or tables.
Functional representation – It is a structured method of modeling, documenting, and analyzing the intended purpose, causal behaviour, and structural components of a system. It defines what a system does and how its components interact to achieve that function, frequently using verb-noun pairs, flow models, or formal, computer-interpretable languages to support design, simulation, and diagnostics.
Functional requirements – These are those elements of the design which describe its performance behaviour, including its human interface and the environment in which it is required to function.
Functionals – These are scalar-valued functions defined on a vector space which are linear if they satisfy the property ‘f(a x + b y) = a f(x) + b f(y)’ for all vectors ‘x’, ‘y’ in the space and scalars ‘a’, ‘b’. The set of all continuous linear functionals on a topological vector space forms a vector space known as the dual of the original space.
Functional safety – Functional safety is the property of an engineered system of ensuring safety by virtue of the functions which the system performs and which normally fall into two categories namely (i) control functions to ensure that a piece of equipment remains in a safe state, and (ii) protection functions which put another system into a safe or relative safe state.
Functional safety requirement – It involves deriving specific, actionable safety measures from high-level safety goals to prevent unreasonable risk from malfunctioning electrical / electronic systems, mainly governed by International Organization for Standardization standard ISO 26262 (automotive) and International Electrotechnical Commission standard IEC 61508 (general). Functional safety requirements (FSRs) define safe states, fault handling, and warning concepts, and are allocated to system elements.
Functional specification – It is a formal, detailed document which defines what a system, software, or product is required to do to meet stakeholder needs. It translates requirements into a technical description, including features, inputs, outputs, and user interactions, guiding developers, testers, and stakeholders before design implementation.
Functional split – Within 5G radio access networks (RAN), it refers to the disaggregation of a base station’s protocol stack, separating functions between centralized units (CU), distributed units (DU), and radio units (RU). It defines which processing tasks occur locally at the antenna against centrally, balancing fronthaul throughput, latency, and hardware complexity.
Functional sub-units – These are specialized, distinct components within a larger system which collaborate to perform specific, necessary tasks. Engineering these units involves defining, separating, and manipulating individual parts understand, or purposefully modify, overall system performance.
Functional team – It is a specialized group composed of individuals with the same job type or domain expertise (e.g., mechanical engineers, quality assurance testers) who focus on resolving problems within their specific area. These teams are hierarchically structured, frequently operating as ‘silos’ to build deep technical expertise but needing handoffs to other departments to complete projects.
Functional testing – It is a black-box quality assurance process which verifies software or systems operate as per specified needs, focusing on ‘what’ the system does rather than ‘how’. It involves testing specific features by providing input data and comparing actual outcomes against expected results to ensure a ‘pass / fail’ status.
Functional tests – These are defined as assessments conducted on printed circuit boards (PCBs) to evaluate the functionality of a design, mainly aimed at detecting faults and ensuring the quality of the final product before it enters operation. These tests simulate operating conditions and can be applied to both analog and digital circuitry.
Function analysis – It is a technique which is used in the discipline of value analysis that focuses on the reason-for-being of each element of the product.
Function declaration – It is a statement in JavaScript that specifies a function’s name, optional parameters, and the body containing a series of statements. It establishes the scope of the function from the opening brace to the closing brace, allowing the function to be invoked later using its name followed by parentheses.
Function definition – It is a mathematical expression which describes the relationship between an independent variable and a dependent variable, indicating how changes in the independent variable affect the dependent variable. It can involve one dependent variable and theoretically an unlimited number of independent variables.
Function file – Within MATLAB, it is a separate m-text file containing a user-defined function which begins with a function definition line. It allows for modularity by accepting input arguments and returning output data, with the file name matching the function name to facilitate reuse across different scripts, commands, or other function files.
Function norm – It is a mathematical measure of the size, length, or ‘magnitude’ of a function within a function space, mapped to non-negative real numbers. It generalizes vector length (Euclidean norm) to continuous functions, important for optimizing, error estimation, and system stability.
Function number – It refers to a designation used to identify devices which perform multiple important functions, allowing for the specification of each function, such as in the case of a double function number like 27–59 for an undervoltage and overvoltage relay.
Function of time – It is denoted as f(t). It defines a physical quantity (such as displacement, force, voltage, or velocity) which varies dynamically with respect to time. These functions, frequently analyzed in the time domain, allow engineers to model, measure, and predict how systems respond to dynamic loads or inputs, typically using calculus for analysis.
Function prototype – In software engineering, it is a declaration statement which defines a function’s name, return type, and parameter list (types and order) before its actual implementation. It informs the compiler about the function’s interface, allowing it to check for parameter type and number mismatches. This ensures code reliability by catching bugs at compile-time.
Functions palette – It is a tool used to construct block diagrams through function code and virtual instruments (VIs), and it is accessible only within a block diagram, with subpalettes available based on the types of virtual instruments and their functions.
Function sum – It represents the combined effect of two or more functions, typically defined as ‘S(x) = f(x) + g(x)’, where outputs for a given input (x) are added together. It is fundamental for modelling complex systems, such as combining signals in signal processing, summing loads in structural mechanics, or transforming multi-objective optimization into single objectives.
Fundamental absorption – It is the characteristic absorption of energy by a material’s constituents, occurring when incident photons have energy equal to or higher than a specific threshold (e.g., the bandgap in semiconductors or molecular vibration energy). It causes photons to be absorbed, normally converted to heat, while lower-energy photons pass through.
Fundamental apparent power – It refers to the component of apparent power which is separated from non-fundamental apparent power, particularly in the context of balanced and unbalanced three-phase systems, as defined by IEEE (Institution of Electrical Engineers) standard 1459. It serves as a measure of the effective voltage and current in the presence of harmonic distortion and imbalance.
Fundamental assumption – It is a foundational principle or simplified belief accepted as true to make complex physical systems analyzable and designable, frequently neglecting minor factors for efficiency. These assumptions define the boundary conditions, such as treating materials as homogeneous / isotropic (uniform properties) or assuming structural equilibrium and linearity in stress-strain relationships.
Fundamental band gap – It is the minimum energy difference (measured in electron-volts, eV) between the top of the valence band (filled) and the bottom of the conduction band (empty) in a solid, representing the minimum energy needed to create a free electron-hole pair. It acts as a forbidden ‘gap’ where no electronic states exist.
Fundamental barrier – It is a core limitation, frequently physical, chemical, or technological, which restricts performance or prevents an action. These constraints are intrinsic to the system’s design or physics (e.g., thermal, material, or energy barriers) and cannot be removed without changing the underlying technology.
Fundamental block – It is an important, structural, or functional unit representing a major system component, operation, or process. These blocks form the basis of a block diagram, which outlines the system’s architecture, data flow, or control signals. They enable engineers to model, simulate, and analyze complex systems by breaking them into manageable, interconnected parts.
Fundamental boundary conditions – These are important, predefined constraints applied to the edges, surfaces, or interfaces of a physical system, defining how it interacts with its surroundings. These conditions (e.g., constant temperature, velocity, or displacement) are mathematical requirements placed on differential equations, such as in finite element method (FEM) or computational fluid dynamics (CFD) analysis, allowing for the simulation of real-world scenarios.
Fundamental component – It is an important, core building block, such as beams, plates, or software modules, which constitutes a larger, functional system. A condition is a defined state, constraint, or need (e.g., thermal, mechanical, or electrical) which this component must satisfy to ensure stability, safety, and operational efficiency.
Fundamental connection – It is a designed interface which transfers forces (loads) between structural components while ensuring stability and integrity. These important, frequently permanent, joints manage tension, compression, shear, and bending moments. Key types include rigid joints (no movement) and pinned joints / roller joints (allowing rotation).
Fundamental dimensions – These are also called primary dimensions. These are the basic, independent, physical quantities used to describe nature and derive other measurements, mainly mass (m), length (l), time (t)), temperature (T), electric current (i)), quantity of substance, and luminous intensity. They form the foundation for dimensional analysis, ensuring that equations are physically consistent.
Fundamental formula – It is a mathematical expression which defines a foundational, governing relationship between important variables in a physical system. These formulas serve as the backbone for analyzing, modelling, and predicting system behaviour, frequently representing physical laws which are important for deriving further equations, engineering calculations, and designs.
Fundamental limits – These limits define the ultimate, maximum, or minimum theoretical performance achievable by a system, dictated by physical laws rather than design skill. These thresholds serve as benchmarks, such as in control systems, materials science (limits of plasticity), or quantum detection, outlining the boundaries beyond which improvement is physically impossible. Fundamental limits represent the best possible performance, helping engineers evaluate systems both before and after controller design. These limits are frequently set by physical principles, such as Heisenberg’s uncertainty principle for measurement sensitivity.
Fundamental matrix – It is a matrix which encapsulates the geometric relationship between two views of a scene, characterized by seven independent parameters which map epipolar lines between images. It allows for the specification of epipoles and the mapping of epipolar lines, with its properties being influenced by the relative motion and orientation of the camera.
Fundamental mode – It is the lowest natural frequency and simplest vibration pattern of a system, frequently referred to as the first harmonic (n = 1). It represents the lowest energy state, having the longest wave-length and largest displacement, where the entire structure vibrates as a single unit without intermediate nodes.
Fundamental natural period – It is the longest, slowest time needed for a structure to complete one full cycle of free vibration. It is an important structural property determined by mass and stiffness, normally denoted as the first mode of vibration, where taller and more flexible structures have longer periods.
Fundamental process – It is a foundational, important, or elementary series of actions, operations, or changes which transform inputs into outputs or produce a specific result. These, frequently automatic, actions are important for system function, such as chemical oxidation, cognitive learning, or industrial production.
Fundamental quantities – These are basic, independent physical quantities which cannot be defined or expressed in terms of other physical quantities. They act as the foundation for all other measurements and are independent of each other. There are seven fundamental quantities in the SI (International System of Units) system namely length, mass, time, electric current, temperature, quantity of substance, and luminous intensity.
Fundamentals – These are the core principles used to analyze, design, and improve systems and technologies, acting as the bridge between theoretical science and practical, real-world application. They provide the foundational knowledge needed for problem-solving, material selection, and modelling behaviour for improvement.
Fundamental state – It defines the exact condition of a system at a specific time, characterized by defined properties such as pressure, temperature, and volume, normally in equilibrium. It represents the system’s status (e.g., solid, liquid, gas, plasma) or its operational state (active, idle, error).
Fundamental theorem of algebra – It states which every non-constant single-variable polynomial with complex coefficients has at least one complex root. This implies a polynomial of degree ‘n’ has exactly ‘n’ complex roots (counting multiplicity), important for analyzing system stability, frequency response, and modeling physical oscillations.
Fundamental theorem of calculus – It is the foundational mathematical link which defines differentiation and integration as reciprocal operations. It enables calculating net changes (integration) by evaluating anti-derivatives (differentiation) at boundaries, important for analyzing systems like fluid flow, structural mechanics, and electrical signals.
Funding strategy – It is a written, long-term plan (typically 3 years to 5 years) detailing how an organization is going to secure and manage financial resources to meet its goals. It identifies the optimal mix of capital, aligning financial needs with operational plans to ensure sustainability, liquidity, and cost efficiency.
Fungus resistance – It is the resistance of a material to attack by fungi in conditions promoting their growth.
Funnel mould – It is the mould of the continuous casting of metal with funnel geometry, wherein the mould has a pouring portion with cooled long side walls and short side walls, wherein the pouring portion becomes narrower the shape of a funnel in the casting direction until it reaches the size of the cast strand.
Furan – It is the resin which is formed from reactions involving furfuryl alcohol alone or in combination with other constituents. It is generic term for a family of chemical compounds including furfural and furfuryl alcohol sued as binders for core sands.
Furnace – It is an enclosed space provided for the combustion of fuel. It is an enclosed, refractory-lined industrial structure designed to generate intense heat, through fuel combustion or electricity, to melt, refine, or process metals and ores. Furnaces are necessary in pyro-metallurgy for smelting (reducing ore to metal), alloying, and heat treatment to alter physical properties.
Furnace-anneal – It refers to the thermal process used to improve the crystalline quality of semi-conductor materials by reducing ion implantation damage and activating dopant ions through controlled heating in a furnace environment.
Furnace annealing – It is a heat treatment process where metal is heated in a furnace to a specific temperature (normally above its recrystallization point), held there, and then cooled slowly. It is used to soften the material, improve ductility, relieve internal stresses, and prepare it for further cold-working or manufacturing, such as stamping or machining.
Furnace atmosphere control – The purpose of atmosphere control is to maintain consistent levels of the different constituents which make up the atmosphere and to determine if changes in those levels are needed in order to produce a desired result under a given set of conditions. Controls are needed for different heat-treating operations which use a variety of different atmospheres. All methods of atmosphere control can effectively be divided into two groups: those involving control of the atmosphere once it is inside the furnace and those involving control of the atmosphere supply before it is introduced into the furnace. Such control is achieved through the use of atmosphere control devices. Furnace atmosphere control has become increasingly critical to successful heat treating with more precise metallurgical specifications. The prevention of surface oxidation or scaling when metals are exposed to high temperatures remains an important task of the furnace atmosphere. In a more sophisticated view, the atmosphere within the furnace chamber is a full-fledged partner in achieving the chemical reactions that occur during heat treating.
Furnace brazing – It is a mass-production brazing process in which the filler metal is preplaced on the joint, then the entire assembly is heated to brazing temperature in a furnace.
Furnace classification – Furnaces are classified mainly by shape (vertical, horizontal, circular, barrel), heat source (electric, fuel), operation method (batch, continuous), or process (smelting, melting, heat treatment).
Furnace furniture – It refers to the internal components, structures, and tools made of refractory materials or heat-resistant alloys that are placed inside a furnace to support, hold, or contain the material being heated (the charge). It is designed to withstand extreme thermal stress, protect the furnace lining, and ensure uniform heat distribution.
Furnace gas – It is a low-grade producer gas generated by the partial combustion of coke in a blast furnace, characterized by a higher carbon di-oxide content and lower hydrogen levels compared to typical producer gas, and frequently containing substantial quantities of dust.
Furnace hardening – It is a heat treatment process where metal parts are heated in a furnace to a specific austenitizing temperature, held there to form a uniform structure, and then rapidly cooled (quenched) to increase surface hardness, wear resistance, and strength by transforming the structure into martensite.
Furnace heating – It is an industrial process which uses high-temperature chambers, fueled by electricity, gas, or oil, to heat metal components for shaping, melting, or modifying their physical and mechanical properties (e.g., hardness, ductility). For furnace heating, radiation heat dominates the temperature distribution of the work-piece. Excessive furnace heating can promote undesirable grain growth. On the other hand, insufficient heating can result in cracking. Furnaces used for heating can be fuel-air, fuel-oxygen, or electric. Each heating method has distinct characteristics and advantages. Control of environment and temperature uniformity is important for any of these heating methods.
Furnace, industrial – It is a refractory-lined thermal enclosure designed to treat raw materials at high temperatures, typically to extract, melt, refine, or alter the properties of metals. These furnaces operate through fuel combustion or electric power to achieve melting, sintering, or heat treatment, acting as reactors or thermal processors in heavy industry.
Furnace injection – It refers to the direct, high-velocity introduction of solid particles, gases, or liquids (such as pulverized coal, oil, natural gas, oxygen, or lime) into a furnace, normally a blast furnace, electric arc furnace (EAF), or converter, to improve combustion, speed up reaction times, or improve refining efficiency.
Furnace, metallurgical – It is a specialized industrial enclosure designed to heat, melt, or refine metals and ores to high temperatures, frequently exceeding 400 deg C, for extraction and processing. These insulated refractory chambers enable pyro-metallurgical processes, such as drying, smelting, roasting, or refining, using fuel combustion or electric power to alter the physical properties / chemical properties of metal, often for iron and steelmaking, casting, or heat treatment.
Furnace oil – Furnace oil is a fuel oil which is dark and viscous. It is a residual fuel oil which is obtained by blending residual products from various refining processes with suitable diluent normally middle distillates to get the needed fuel oil grades. It has a flash point above 66 deg C and the calorific value of 44 mega joules per kilograms. The fuel oil grades are similar in nature and are being marketed under different specifications in different countries.
Furnace pad or foundation – It is the civil foundation on which the steel and supporting structure of the blast furnace is erected. This foundation carries the load of the running blast furnace.
Furnace pressure – It is the pressure occurring inside the combustion chamber. It is positive if higher than atmospheric pressure, and negative if lower than atmospheric pressure, and neutral if equal to atmospheric pressure.
Furnace shell – It is the external, heavy-duty metallic (normally steel) casing of a furnace. It acts as the main structural container, supporting internal refractory linings, bearing thermal stresses, and holding molten metal or raw materials during high-temperature operations. It forms part of the furnace body and supports the overall structure while containing the high-temperature processes occurring within. Furnace shell of a blast furnace is made from crack resistant steel and is normally free standing. It is normally designed after comprehensive stress distribution analysis.
Furnace slag – It is a non-metallic byproduct formed during metal smelting or refining (mainly iron and steel) by combining molten impurities (gangue), such as silicon, aluminum, and phosphorus, with added fluxes like limestone and dolomite. It floats on the molten metal, is separated at high temperatures, and consists mainly of silicates and alumino-silicates of calcium.
Furnace soldering – It encompasses a group of reflow soldering techniques in which the parts to be joined and preplaced filler metal are put in a furnace and then heated to the soldering temperature. Five reflow technologies are presently certified for use in surface-mount technology (SMT) applications. These are (i) type ‘A’ vapour phase, (ii) type ‘B’ area conduction, i.e., linear conduction, (iii) type ‘C’ hot bar, (iv) type ‘D’ convection and convection /infra-red, and (v) type ‘E’ laser. Of these five methods, three are considered to be mass reflow techniques (Types A, B, and D), since all of the solderable inter-connections on the surface of a printed wiring board (PWB) assembly are brought through the reflow heating cycle simultaneously.
Furnace sorbent injection – It is a pollution control process involving the direct injection of dry, powdered alkaline sorbents, typically limestone, lime, or dolomite, into the upper furnace or boiler cavity (750 deg C to 1,230 deg C). It captures acid gases like sulphur di-oxide (SO2) and hydrogen chloride (HCl), forming solid sulphates / chlorides for collection, effectively reducing emissions in high-temperature smelting and combustion.
Furnace temperature – It is the controlled thermal level within an insulated chamber (typically above 400 deg C) designed to heat, melt, or chemically transform metal loads through combustion or electrical energy. It is defined by the heat balance between input energy and the target process, such as annealing (600 deg C to 1,050 deg C), forging (1,050 deg C to 1,250 deg C), or melting (above 1,250 deg C).
Furnace top – It is the upper section of the vertical shaft where raw materials are introduced and top gas exits, incorporating components like pressure relief valves to prevent overpressure and systems for managing emissions during operation. It serves as the main charging point for solid materials and manages the exhaust gases produced during the smelting process.
Furnace treatment – It is a controlled heating and cooling process designed to alter the physical and chemical properties of metals (e.g., hardness, strength, ductility). Work-pieces are loaded into a furnace, heated to specific temperatures, held (soaked), and cooled to achieve desired microstructures. Common types include annealing, tempering, and hardening treatments.
Furnace volume – It is the cubic contents of the furnace or combustion chamber.
Fuse – It is an electrical safety device which operates to provide overcurrent protection of an electrical circuit. Its essential component is a metal wire or strip which melts when too much current flows through it, hence stopping or interrupting the current. It is a circuit protective device. Fuse also means to reduce a substance, specifically metal or ore, to a liquid or plastic state through the application of high heat. It also refers to the process of joining two or more pieces of metal together by melting them, often used in welding or casting.
Fused alumina – It is produced in two forms namely white fused alumina and brown fused alumina. White fused alumina is made from calcined Bayer alumina and different grades are available based on differences in alkali contents. It is used extensively in high-temperature refractory bricks and monolithics.
Fused cast refractories – These are those refractories which are manufactured by melting mixtures of raw material of the desired composition in an electric furnace at a temperature exceeding 2,000 deg C, casting the melt into moulds where it solidifies and cooling the molten refractory material to form a solidified refractory.
Fused coating – It is a metallic coating (normally tin or solder alloy) which has been melted and solidified, forming a metallurgical bond to the base metal.
Fused deposition modelling – It is an additive manufacturing process which builds 3D objects by extruding molten thermoplastic filaments layer-by-layer through a heated nozzle. While mainly used for plastics, it applies to ‘bound metal deposition’ or filament-based sintering, where metal-loaded filaments are printed and then debound / sintered to produce metal parts.
Fused filament fabrication – It is an additive manufacturing process (material extrusion) which builds 3D objects by heating and depositing thermoplastic filament layer-by-layer. It is widely used for prototyping and production because of its versatility, affordability, and ability to create durable, functional parts.
Fused grain refractory – It is a refractory made predominantly from grain which has solidified from a fused or molten condition.
Fused image – It is a single, composite image created by merging two or more registered input images, frequently taken from different sensors, times, or focus depths, to create a more informative and accurate representation of a scene than any single source image can provide. The goal is to retain the most desirable characteristics (such as high spatial resolution, accurate colour, or specific temperature data) from each input image.
Fused magnesite – It is also known as electro-fused magnesia. It is a high-purity refractory material mainly composed of magnesium oxide (MgO). It is produced by melting natural magnesium carbonate (MgCO3) in an electric arc furnace at extremely high temperatures. This process results in a dense, highly crystalline structure with exceptional thermal and chemical stability, making it ideal for high-temperature applications.
Fused product – It is a material or item created by joining two or more components together through heat, pressure, or blending to form a single, new entity.
Fused salts – Thet are called molten salts. These are ionic compounds, such as halides, hydro-oxides, or carbonates, heated above their melting points to become conductive liquid electrolytes. They are mainly used in high-temperature electrolysis to extract or refine reactive / refractory metals (e.g., aluminum, magnesium, sodium, and titanium) and as heating media for heat treatment. Unlike solid salts, fused salts allow ions to move freely, making them excellent electrical conductors for electrolysis. These salts are essential for producing metals that cannot be extracted from aqueous solutions. They act as electrolytes for electro-refining / electro-winning, solvents in smelting, and heat transfer media in steel heat treatment (carburizing, quenching).
Fused silica – It is an amorphous (non-crystalline) glass consisting of ultra-pure silicon di-oxide (SiO2), frequently exceeding 99.9 % purity. It is a synthetic material recognized for its exceptional thermal shock resistance, very low thermal expansion, and excellent ultra-violet (UV) transparency. It is widely used in high-temperature industrial, semi-conductor, and optical applications.
Fused silica refractory – It is a product composed predominantly of fused, non-crystalline silica.
Fused spray deposit – It is a self-fluxing spray deposit which is deposited by conventional thermal spraying and subsequently fused using either a heating torch or a furnace.
Fused zone – It is the area of base metal melted as determined on the cross section of a weld.
Fusel oil – It is a mixture of higher alcohols (mainly amyl alcohol), esters, and fatty acids. It is used as a solvent for lacquers, paints, and to produce amyl alcohols.
Fuse operation – it is the automatic, sacrificial process of interrupting an electrical circuit when excessive current (overload or short-circuit) flows through it. It protects against overheating and fire by melting a metal element to break the circuit, acting as a ‘weak link’. It is frequently called ‘automatic disconnection of supply’ (ADS).
Fusible alloys -It is a group consisting of binary, ternary, quaternary, and quinary alloys which contains bismuth, lead, tin, cadmium, and indium. This term refers to any of more than 100 alloys which melt at relatively low temperatures, i.e., below the melting point of tin-lead solder (183 deg C). The melting points of these alloys range as low as 47 deg C.
Fusible metal – It is an alloy, typically composed of bismuth, lead, tin, indium, or cadmium, designed to have a very low melting point, normally below 150 deg C. These materials are mainly used in safety devices (boiler plugs, sprinklers), solders, casting, and holding fragile parts during manufacturing.
Fusible plug – It is a hollowed threaded plug having the hollowed portion filled with a low melting point material.
Fusing – It is the melting of a metallic coating (normally electro-deposited) by means of a heat-transfer medium, followed by solidification.
Fusion – It is the melting together of filler metal and base metal (substrate), or of base metal only, which results in coalescence. In nuclear metallurgy, fusion means thermo-nuclear fusion which is a process in which two or more light nuclei are formed into a heavier nucleus and energy is released.
Fusion bond – It is a joining technique where two or more materials (similar or dissimilar) are heated to their melting point, allowed to mix in a liquid state, and then cooled to form a solid, integral joint. This process creates a ‘nugget’ or a fusion zone where the materials mix, frequently resulting in larger grain growth and high tensile, shear, and peel strength.
Fusion bonded epoxy (FBE) coating – Fusion bonded epoxy coating of steel materials is primer less, one-part, heat curable, thermosetting powdered epoxy coating which is designed to provide maximum corrosion protection to the substrate steel. It is a coating of very fast curing, thermosetting protective powder which utilizes heat to melt and adhere the coating material to the steel substrate. It is based on specially selected epoxy resins and hardeners which are in the form of dry powders at normal atmospheric temperature. The epoxy is formulated in order to meet the specifications related to protection of steel as an anti-corrosion coating. Heat cured fusion bonded epoxy coatings are 100 % solids consisting of thermosetting materials which achieve a high bond to metal surface as a result of a heat generated chemical reaction. The fusion bonded epoxy coatings can be applied by fluidized bed, flocking (air spray), or electrostatic spray. Fusion bonded epoxy forms an adherent continuous chemically cross-linked protective film. Fusion-bonded epoxy coating principally protects against corrosion by serving as an electro-chemical and a physical barrier which isolates the steel from the oxygen, moisture, and chloride ions which cause corrosion. Fusion bonded epoxy coating is widely used for coating of reinforcement bars, steel pipes, pipe fittings, pumps, and valves used for the transmission of oil, gas, slurry, and water.
Fusion bonded epoxy coated reinforcement bars – These are reinforcement bars which have fusion bonded epoxy coatings.
Fusion boundary – It is also called fusion line). It is the interface between the fusion zone (melted metal) and the heat-affected zone (unmelted but structurally altered base metal). It represents the furthest edge of base metal which has melted during the welding process.
Fusion face – It is a surface of the base metal which is to be melted during welding.
Fusion hard-facing – It is a process by which weld materials, with superior properties than the substrate, are applied to the substrate. Frequently two layers total thickness of 3 millimeters to 6 millimeters are applied to reduce the surface hardness dilution of the relatively low-cost steel substrates in the expansive cobalt-based alloys. Hard-facing processes are very useful for improving wear and corrosion resistance to selected areas of mechanical equipment such as cutting edges of earth-moving machinery or sealing areas of valves. Common hard-facing techniques include arc torch and other processes.
Fusion line – It is also called weld boundary. It is the interface between the weld metal (fusion zone) and the heat-affected zone (HAZ) of the base metal. It represents the furthest edge of material melting and is where the liquid weld pool meets the solid, unmelted base metal during solidification, often acting as a sharp boundary.
Fusion parameters – These are the controllable, main process variables, such as laser power, travel speed, hatch spacing, and layer thickness, optimized to achieve the desired micro-structure, metallurgical bonding, and structural integrity in a weld or melted zone. These parameters directly influence the stability of the molten metal pool, the cooling rate, and the final mechanical properties of the solidified joint.
Fusion plasma – It is a state of matter, the ‘fourth state’ consisting of a fully ionized gas of positively charged ions and negatively charged electrons, heated to temperatures exceeding 100 million degrees Celsius (around 10 times hotter than the sun’s core). In this state, light hydrogen isotopes (deuterium and tritium) gain enough energy to overcome their mutual electrical repulsion (Coulomb barrier) and fuse into heavier helium nuclei, releasing massive quantities of energy.
Fusion point – It is the temperature at which melting takes place. Majority of the refractory materials have no definite melting points, but soften gradually over a range of temperatures.
Fusion power – It is the generation of energy by forcing light atomic nuclei (typically hydrogen isotopes) to merge, or fuse, into a heavier nucleus, releasing massive quantities of energy in the process, similar to the reaction which powers the sun. These needs specialized, radiation-hardened materials capable of withstanding extreme temperatures and high neutron damage.
Fusion power plant – It is a facility designed to generate electricity by harnessing energy from controlled nuclear fusion, where light atomic nuclei (typically hydrogen isotopes deuterium and tritium) collide and combine to form helium, releasing massive quantities of energy. Unlike fission, a fusion plant cannot ‘run away’ or melt down, as fusion needs precise, high-temperature conditions to occur and stops instantly if the plasma is disturbed.
Fusion power systems – These are energy generation facilities which utilize nuclear fusion reactions, the joining of light atomic nuclei (typically deuterium and tritium) at extreme temperatures (above 100 million deg C) to form heavier nuclei (helium) and release energy. These systems need advanced metallurgy to manage intense neutron radiation, high heat flux, and electro-magnetic forces, mainly utilizing low-activation, high-temperature materials for structural components, such as ferritic / martensitic steels and tungsten.
Fusion problem – It refers to the challenge of integrating and analyzing multiple heterogeneous datasets so that they can interact and inform each other, frequently to improve understanding of a system or improve classification performance.
Fusion process – It consists of the collision and fusion of hydrogen or hydrogen isotopes’ nuclei to form a heavier nucleus or helium, releasing energy in the process. This reaction needs the nuclei to achieve high speeds, necessitating temperatures exceeding 200 million deg C, resulting in a plasma state. It also refers to the melting of metal surfaces through the application of intense, localized heat, allowing them to merge into a single, cohesive piece upon cooling. It is the foundational mechanism for fusion welding, where base metals are heated to their melting point, typically with a filler material added to create a molten pool.
Fusion product – It is a sub-atomic particle or atomic nucleus created as a direct result of light atomic nuclei combining (fusing) at extremely high temperatures. It also refers to the material created when two or more metallic components are joined by melting the base metals and allowing them to solidify together, typically forming a ‘fusion zone’. It is a key outcome of fusion welding processes, where the resulting structure often includes a mixture of the base metal and, if used, filler metal.
Fusion reaction – It is the process where light atomic nuclei (typically deuterium and tritium) collide at extremely high temperatures and pressures to form a heavier nucleus (helium), releasing massive amounts of energy. It involves creating a hot plasma to overcome electrostatic repulsion, allowing the strong nuclear force to bind them. – It is also a manufacturing process which joins two metal parts by melting the base materials, typically with a filler material, which then solidifies to form a strong, permanent joint. This process relies solely on heat, frequently provided by an electric arc, laser, or gas flame, to create a ‘molten pool’ which blends the parts together without applying external force.
Fusion reactor – It is a device designed to generate electricity by replicating the nuclear fusion process which powers the sun, combining light atomic nuclei (typically deuterium and tritium) at extremely high temperatures to release massive quantities of energy. Unlike fission, this process offers a near-limitless, low-carbon energy source without long-lived radio-active waste.
Fusion rule – It is an algorithmic method or logical formula used to merge data, signals, or information from multiple sources into a single, more accurate, or consolidated representation. Key applications include image processing (combining high-frequency data), AI (artificial intelligence) threat detection (reducing alert fatigue), and mathematics (decomposing tensor products). They are designed to highlight substantial information while reducing noise or irrelevant data. They enable the creation of a ‘global decision’ based on local inputs.
Fusion scheme – It is a fusion scheme is a method or strategy used to combine information from multiple sources, sensors, or images into a single, improved representation. It is designed to maximize relevant information while minimizing noise, redundancy, and computational costs. It is a method used to combine information from multiple images to produce a single improved image, frequently employing techniques such as wavelets to extract detailed information and standard transformations to integrate it. These schemes can achieve improved results compared to traditional image fusion methods but can need higher computational resources.
Fusion spray – In thermal spraying, it is the process in which the coating is completely fused to the base metal, resulting in a metallurgically bonded, essentially void-free coating.
Fusion structure – It is a methodological framework designed to integrate data, features, or components from multiple sources or layers to create a more comprehensive, accurate, and robust result. Common types include hierarchical, overall, and arbitrary structures, frequently applied in computer vision (early fusion / late fusion), sensor integration, and structural engineering (welding).
Fusion task – In the context of data analytics and systems engineering, it is a structured, purposeful operation that combines heterogeneous, data from multiple sources or sensors to create a more accurate, reliable, or complete representation of an entity, situation, or environment. This process involves integrating data at different levels, raw data, features, or decisions, to support improved decision-making.
Fusion technique – It is a method of combining data, images, or materials from multiple sources to create a single, more accurate, and comprehensive output. It improves information quality by reducing uncertainty and combining complementary strengths. Key types include data fusion, sensor fusion, image fusion, and material fusion.
Fusion welding – It is any welding process which uses fusion of the base metal to make the weld. It uses localized heat, typically from an electric arc, gas flame, or laser, to melt the base materials at their interface, creating a molten pool which solidifies to form a strong, continuous joint. It frequently utilizes filler material and does not need external pressure.
Fusion welding processes – These are defined as methods used to join parts and structures by melting the materials together, where heat is supplied to create a molten interface which fuses the components, often with the addition of a filler rod. This process results in joint formation through the cooling and solidification of the molten material.
Fusion welding techniques – These can be defined as methods which involve the melting of base material, sometimes with the aid of filler material, to create a joint through the mixing of the molten materials at the joining interface. These techniques utilize high temperatures to trigger melting while pressure is applied to keep the parts in contact until solidification occurs.
Fusion zone – It is the area of base metal which is melted as determined on the cross section of a weld.
Future applications – These refer to potential new uses or technologies which can emerge. It can involve reusing existing designs or developing completely new technologies.
Future design – It refers to the proactive, sustainable, and technologically driven evolution of metal extraction, processing, and alloy design, aiming for a net-zero impact and unprecedented performance in future. It merges traditional expertise with artificial intelligence, simulation tools, and environmental foresight to create materials which are lighter, stronger, and entirely recyclable.
Future energy – It refers to the transition toward sustainable, low-carbon, and highly efficient energy sources for the extraction, processing, and recycling of metals. It focuses on replacing fossil fuels with renewable energy (solar, wind, hydro) and hydrogen to minimize greenhouse gas emissions, aiming for net-zero emissions.
Future frame – It represents an intelligent, data-driven reasoning framework applied to production. It moves away from manual, linear quality control toward perceptive, AI (artificial intelligence) embedded systems which interpret material variations as actionable data to optimize production.
Future industry trends – These are emerging patterns, technologies, and shifts in customer behaviour expected to reshape the operational landscape over the coming years. These trends represent the direction of industrial evolution, aiding strategic planning for sustainability, competitiveness, and adaptation to technological advancements, such as artificial intelligence and automation.
Future optical networks – These are defined as intelligent, flexible, and highly secure infrastructure which extends beyond mere data transmission to act as an all-optical, programmable network layer (frequently termed as all-optical network or digital optical network in). They provide high-capacity, low-latency connectivity for services like 5G, data centre interconnects (DCI), and AI (artificial intelligence), utilizing elastic spectrum allocation (EONs) and photonic-layer security.
Future power systems – These are interconnected, intelligent networks integrating decentralized renewable energy, storage, and AI (artificial intelligence) driven control to maximize flexibility and reliability. These are decentralized, data-driven, and renewable-rich grids designed for sustainability, flexibility, and high resilience. Key trends driving this shift are electrification and decarbonization.
Future production – it normally refers to the evolving landscape of manufacturing and industrial processes, characterized by high levels of automation, digitalization, and sustainability. It represents a shift towards intelligent, flexible systems which can adapt to demand changes, customize products at scale, and reduce environmental impact.
Future query – It is a technical approach in data management, graph databases, or planning algorithms which pre-computes or saves requests to provide rapid results for potential subsequent searches, frequently reducing system overhead.
Future technology – It refers to nascent, transformative innovations, such as AI (artificial intelligence), quantum computing, and advanced materials, currently in development which are poised to revolutionize industries, improve sustainability, and redefine human capabilities within the next few years to decades. It focuses on exponential growth, convergence of fields, and high-impact, sustainable solutions.
Future trends – These are the emerging technologies, sustainable practices, and strategic shifts redefining the industry, with a focus on automation, connectivity, and environmental stewardship. Key trends presently include AI (artificial intelligence) integration, renewable energy, quantum computing, and industry 4.0 which is the realization of the digital transformation of the field, delivering real-time decision making, improved productivity, flexibility and agility to revolutionize the way organizations manufacture, improve and distribute their products.
Fuzz – It consists of accumulation of short, broken filaments after passing glass strands, yarns, or rovings over a contact point. Frequently, it is weighted and used as an inverse measure of abrasion resistance.
Fuzzification – It is the process of transforming crisp, precise numerical input values (such as those from sensors) into fuzzy values or linguistic variables (e.g., low, medium, and high). It is the first step in a fuzzy logic controller or system, enabling the system to handle uncertainty, vagueness, or imprecise information by mapping crisp inputs into fuzzy sets using membership functions.
Fuzziness – It refers to the lack of well-defined, sharp boundaries for the set of objects or values to which a particular linguistic label (like hot, high, or fast) applies. Unlike classical crisp logic, which forces items into binary categories (true or false, 0 or 1), engineering fuzziness allows for partial membership, where an element belongs to a set to a specific degree between 0 and 1
Fuzz testing – It is an automated software engineering technique which injects invalid, malformed, or unexpected random data into an application’s inputs to reveal security vulnerabilities, crashes, memory leaks, and improper error handling. It acts as a stress test for input validation, identifying bugs like buffer overflows and unhandled exceptions.
Fuzzy case – It is a methodology used in engineering, artificial intelligence, and data science to define, classify, and handle complex or ambiguous problems where traditional ‘crisp’ (yes / no) logic is inadequate. It utilizes fuzzy set theory to represent imprecise information, allowing for ‘partial truth’ where an element can belong to a set with a membership degree between 0 and 1. This approach is particularly valuable in engineering design, condition monitoring, and risk analysis when expert knowledge is subjective or sensor data is noisy.
Fuzzy cognitive maps – These are soft-computing tools which model complex systems by mapping causal relationships between concepts using graph theory, fuzzy logic, and neural network techniques. They represent systems as nodes (concepts) and weighted, directed edges (causal strengths) ranging between (-1, 1), enabling simulation and ‘what-if’ ” analysis. Fuzzy cognitive maps is defined as an emerging technique for knowledge elicitation and data synthesis which captures cause and effect relationships based on expert beliefs about a problem, noted for its simplicity and adaptability to different applications.
Fuzzy control – It is a control system which relies on fuzzy logic instead of binary true / false conditions.
Fuzzy controller – It is also called fuzzy logic controller (FLC). It is an intelligent control system based on fuzzy logic, a mathematical system which analyzes analog input values in terms of logical variables which take on continuous values between 0 and 1, rather than strict binary 0 or 1 values. It mimics human reasoning, allowing for the control of highly complex, nonlinear, or ill-defined systems without needing precise mathematical models.
Fuzzy decision trees – These are robust machine learning models which extend traditional crisp decision trees by utilizing fuzzy logic to handle imprecise, noisy, or uncertain data. Unlike crisp trees which use binary splits (e.g., yes /no), fuzzy decision trees (FDTs) use fuzzy membership functions (e.g., warm or hot) to allow data points to belong to multiple branches simultaneously with varying degrees of membership, improving classification accuracy and robustness.
Fuzzy expert systems – These are rule-based artificial intelligence systems which utilize fuzzy logic to model human decision-making, capable of handling imprecise, vague, or uncertain data. They bridge human-like reasoning and numerical data, transforming fuzzy linguistic inputs (e.g., high temperature) into actionable, precise outputs (e.g., motor speed) using if – then rules.
Fuzzy expression – It is the process of mathematically defining and refining vague, linguistic concepts (like hot, fast, or low) into precise, actionable membership functions (0, 1) range) for use in computational models and control systems. It translates subjective human knowledge into digital rules which handle imprecision and uncertainty, rather than strict binary (0 or 1) logic.
Fuzzy inference – It is the process of formulating the mapping from a given input to an output using fuzzy logic, which provides a basis for decision-making, pattern recognition, or control. It acts as a bridge between human-like, linguistic reasoning (‘if the temperature is warm, then turn the fan low’) and precise, mathematical control. Instead of binary true / false logic (0 or 1), fuzzy inference utilizes degrees of truth, allowing for gradual transitions and handling of uncertainty, imprecision, or noisy data.
Fuzzy inference system – It is a rule-based, non-linear mapping framework which maps crisp, real-valued input data to scalar outputs using fuzzy logic, if-then rules, and membership functions. This process mimics human reasoning to handle uncertainty, imprecision, and complex, non-linear system modelling where traditional mathematical models are difficult to define. A Fuzzy inference system consists of four main functional blocks namely fuzzification, fuzzy rules / knowledge base, inference engine, and defuzzification.
Fuzzy intersection operation – It frequently fuzzy intersection operation, often referred to as the fuzzy and or conjunction, determines the degree to which an element belongs to both fuzzy sets simultaneously. Unlike classical crisp sets, which use a binary intersection, fuzzy intersection operates on membership values between 0 and 1. The most common (or standard) fuzzy intersection is defined as the minimum of the membership values of two sets.
Fuzzy logic – It is the use of fuzzy sets in the representation and manipulation of vague information for the purpose of making decisions or taking actions. Fuzzy logic enables computers to make decisions based on information which is not clearly defined.
Fuzzy logic control – It is a methodology which utilizes fuzzy rules and sets to represent expert knowledge and control systems, allowing for operation based on human reasoning rather than traditional equations.
Fuzzy logic controller – It is a heuristic control technique which mimics human reasoning by using pre-defined linguistic rules, known as membership functions, to manage non-linear systems without needing precise mathematical models. It processes system feedback through fuzzification and defuzzification to effectively handle ambiguous boundary conditions in various applications.
Fuzzy logic system – It is a computing approach based on ‘degrees of truth’ rather than binary (true / false) logic, used to model complex, imprecise, or ambiguous, information. It maps numerical inputs to fuzzy sets, using linguistic variables like ‘warm’ or ‘cold’, to simulate human reasoning and decision-making in systems such as automatic transmissions, washing machines, and climate control.
Fuzzy logic techniques – These techniques refer to methods which use fuzzy set theory to evaluate and classify data by assigning degrees of membership to elements based on membership functions, allowing for qualitative assessments and decision-making in the presence of uncertainty and vagueness.
Fuzzy membership functions – These are mathematical functions which quantify the degree of membership of an element in a fuzzy set, with common types including impulsive, triangular, trapezoidal (both left and right sided), and Gaussian functions. These functions assign values between 0 and 1 to indicate varying levels of membership based on specific input criteria.
Fuzzy model – It is a mathematical framework which uses fuzzy set theory to model systems with uncertain, ambiguous, or imprecise information. It imitates human reasoning by allowing variables to have partial membership in a set (a degree between 0 and 1) rather than strict binary (true / false) membership. These models are normally used for modeling complex non-linear systems and for control purposes.
Fuzzy network – It is also called fuzzy neural network or neuro-fuzzy system. It is a hybrid computational model which integrates the learning abilities of neural networks with the human-like reasoning and uncertainty-handling capabilities of fuzzy logic. It is designed to manage imprecise, ambiguous, or qualitative data (e.g., ‘high temperature’, ‘somewhat fast’) by replacing the strict true / false (0 or 1) boundaries of traditional logic with partial membership degrees ranging from 0 to 1.
Fuzzy object – It is an entity which lacks crisp, well-defined boundaries or possesses ambiguous, non-deterministic characteristics, frequently represented by degrees of membership rather than a binary ‘in or out’ classification. Derived from fuzzy set theory, this concept allows for modelling real-world uncertainty, where an object can partially belong to a set, with membership values ranging from 0 to1.
Fuzzy Q-learning – It is a reinforcement learning technique which combines fuzzy logic inference with traditional Q-learning to handle continuous state-action spaces, rather than relying on discrete matrices. It uses fuzzy rules to represent and update state-action values (Q-values), allowing agents to learn effectively in uncertain or imprecise environments.
Fuzzy relation – it is an extension of an ordinary relation which allows for expressions involving ambiguity between two sets, X and Y, represented as a fuzzy set of ordered pairs with associated membership degrees. When the sets are the same, it is known as a fuzzy relation on X.
Fuzzy rules – These are conditional statements which relate input fuzzy sets to output fuzzy sets, typically structured in an ‘if-then’ format, such as ‘if X is high and Y is medium then Z’is low’, where X,Y, Z represent variables with fuzzy values.
Fuzzy set theory – It is a mathematical framework extending classical set theory to handle imprecise, vague, or uncertain information by allowing elements to have partial membership degrees, ranging from 0 to 1, rather than binary (0 or 1) membership. It uses membership functions to define fuzzy boundaries. Fuzzy theory – It is also called fuzzy set theory. It is a mathematical framework which models uncertainty and vagueness by allowing partial membership in sets, rather than binary (0 or 1) membership. It uses membership functions to assign degrees of truth ranging from 0 to 1, enabling systems to handle imprecise, human-like reasoning.
f-value – The coefficient ‘f’ (also called artificial or fictive friction or resistance coefficient) is resulting from the correlation between the weights and the motional resistances of the belt conveyor. A typical ‘f’ value is 0.016. In optimum installations with low rolling resistance belts, even ‘f’ values of around 0.010 have been found.
F-value – It is also known as the F-statistic. In the context of ANOVA (analysis of variance), it is a test statistic used to determine if there is a statistically significant difference in the means of two or more groups. It is calculated as the ratio of the variance between groups (signal) to the variance within each group (noise). A higher F-value suggests a stronger effect of the independent variable on the dependent variable.
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