| A-basis |
Mechanical property value above which at least 99% of the population of values is expected to fall, with a confidence of 95%. Also called A-allowable. |
| Abelian group |
Property of a group of elements associated with a binary operation. In an Abelian group, the group elements commute under the binary operation. If a and b are any two group elements and if the (+) sign denotes the binary operation, then, for an Abelian group, |
| Ablation cooling |
The cooling of a surface exposed to very high external gas temperature which causes the surface material to sublime, melt or decompose. The chemical process absorbs heat while the mass flow of material away from the surface blocks the heat flux from the hot gas. |
| Ablative materials |
Materials, especially coating materials, designed to provide thermal protection to a body in a fluid stream through the loss of mass. |
| Abradant |
The differently sized grits of hard materials such as emery employed for grinding, polishing, etc. The abrasive grade is determined by the grit size (grit number) originally related to the hole sizes in wire sieves. |
| Abrasion |
The removal of surface material by the scratching action of hard particles, either deliberately (abrasive papers, abrasive cleaning, abrasive machining) or as a consequence of operation (wear). |
| Abrasive wear |
The removal or displacement of material from a surface when hard particles slide or roll across the surface under pressure. The particles may be loose or may be part of another surface in contact with the surface being worn. Contrast with adhesive wear. |
| Abrasivity |
The extent to which a surface, particle, or collection of particles will tend to cause abrasive wear when forced against a solid surface under relative motion and under prescribed conditions. |
| ABS polymer |
A class of thermoplastic co-polymer consisting of the three monomers acrylonitrile, butadiene and styrene that has improved properties (particularly toughness) over the individual constituents. |
| Absolute expansion |
The true volumetric expansion of a liquid with temperature, after account is taken of any expansion of the container in which it is held. |
| Absolute humidity |
The weight of water vapor in a gadwater vapor mixture per unit volume of space occupied, expressed, for example, in grains or pounds per cubic foot. |
| Absolute manometer |
A manometer that measures absolute pressure, i.e. pressure measured relative to a perfect vacuum. Absolute pressure cannot be negative. |
| Absolute pressure |
1. The pressure measured relative to zero pressure (vacuum). 2. Gage pressure plus barometric pressure in the same units. |
| Absolute rating |
A theoretical size designation which is an estimation of the largest particle, by length, that can pass through a filter with a specific |
| Absolute specific gravity |
The ratio of the weight of any volume of a substance to the weight of an equal volume of a reference substance at the same temperature, often water at 4°C, both measured in a vacuum to avoid any effect of buoyancy. |
| Absolute stability |
Condtion of a linear system in which there exists a limiting value of the open-loop gain such that the system is stable for all lower values of that gain, and unstable for all higher values. |
| Absolute temperature (Unit K) |
A temperature T measured relative to absolute zero, 0 K or −273.15°C, the lowest temperature achievable at which molecular motion vanishes so that a body would have zero heat energy. The kelvin is equal in magnitude to the degree Celsius (°C). The kelvin temperature scale (kelvin absolute temperature scale) is an absolute or thermodynamic temperature scale derived from the Celsius scale: T(K) = T(°C) + 273.15. The Rankine absolute scale is derived from the Fahrenheit scale such that T(R) = T(°F) + 459.67, i.e. a scale relative to 0 R or −459.67°F where R is the Rankine degree symbol and °F is the Fahrenheit symbol. |
| Absolute value error |
The magnitude of the error dlsregarding the algebraic sign, or, for a vectorial error, disregarding its function. |
| Absolute viscosity |
A measure of the internal shear properties of fluids, expressed as the tangential force per unit area at either of two horizontal planes separated by one unit thickness of a given fluid, one of the planes being fixed and the other moving with unit velocity. |
| Absolute zero |
Temperature of -273.16″C or 459.69″F or OK at which molecular motion vanishes and a body has no heat energy. |
| Absorber |
1. An auxiliary vibratory system that favourably modifies the vibration characteristics of a main system. 2. Part of an absorption refrigeration system in which the refrigerant is absorbed by a transport medium. 3. The absorber plate is the receiver of a concentrating solar collector where the radiation is absorbed. |
| Absorptance |
(absorptivity, absorption coefficient, α) The fraction of radiant flux incident on a surface that is absorbed by the surface. The term also applies to absorption of radiation by a volume of fluid. For a semi-transparent surface, α + ρ + τ = 1, where ρ is the reflectance and τ is the transmittance. |
| Absorption |
The process whereby a fluid permeates a porous solid, or a gas is dissolved by a liquid. |
| Absorption dynamometer |
A dynamometer in which input work or power is dissipated by mechanical friction, electrical resistance, hydraulic resistance, etc. |
| Absorption hygrometer |
An instrument that determines the content of water vapour in the atmosphere by it being absorbed into a hygroscopic medium. |
| Accelerated testing |
A type of testing, for rates of wear, fatigue, corrosion etc., in which failure times are reduced by employing greater loads, more frequent power cycling, higher vibration levels, higher humidity, higher temperatures, greater potential differences etc. than would be encountered in normal operation. |
| Acceleration due to gravity |
(acceleration of free fall, gravitational acceleration, g) (Unit m/s2) The acceleration of a freely-falling body in a vacuum, with a mean value at sea level of approximately 9.81 m/s2. |
| Acceleration-error constant |
When the reference (demand) input to a control system is parabolic, the output signal will also be parabolic in steady state. The signal that is constant in this situation is the acceleration and thus for a parabolic input the steady-state error, referred to as the acceleration-error constant, is the error in the acceleration. |
| Accommodation |
The ability of a robot to respond to changes in the environment. |
| Achme thread |
A screw thread having an included angle of 29° and largely used for feed screws on machine tools. |
| Acicular ferrite |
A highly substructured non-equiaxed ferrite that forms upon continuous cooling by a mixed diffusion and shear mode of transformation that begins at a temperature slightly higher than the temperature transformation range for upper bainite. It is distinguished from bainite in that it has a limited amount of carbon available; thus, there is only a small amount of carbide present. |
| Acicular ferrite |
Ferrite crystallite growing, apparently, as in the course of bainitic transformation. It has a lath-like shape and an increased dislocation |
| Acid rain |
Any form of precipitation, including rain, snow, sleet, fog, dew, and particulates, which contains higher than normal levels of sulfuric and nitric acids. These acids result from natural and man-made emissions of sulfur dioxide and oxides of nitrogen, respectively. Acid soot consists of unburned carbon particles, typically larger than 10 μm, in the atmosphere contaminated with sulfuric acid. The particles result from poor combustion of fossil fuels. |
| Ackerman linkage |
A steering linkage on a motor vehicle that approximately gives rolling without slipping of both wheels about the turning point. This is achieved by having the inner stub axle (on the inside of the turning curve) move through a greater angle than the outer stub axle. |
| Acoustic droplet ejection |
The ejection of small droplets from the surface of a liquid that results from focusing high-intensity ultrasound near the surface. |
| Acoustic emission |
(stress-wave emission) Sound emitted by some materials when deformed under load. It arises from stress waves emitted by sudden dislocation motion in crystals, slip, crack growth, etc. |
| Acoustic power |
(sound power) (Unit W) The rate of flow of acoustic energy across a specified surface. |
| Acoustic pyrometer |
A non-intrusive pyrometer based on the principle that the sound speed in a gas is proportional to the square root of its absolute temperature. |
| Acoustic separation |
(Unit m) The separation of particles in a fluid using standing acoustic waves, typically ultrasound, to drive them to nodal points (acoustic particle concentration). |
| Acoustics |
The science and engineering of sound; its production, propagation, control, interaction with materials, etc. |
| Activation energy |
(Ea, U) (Unit kJ/mol) The minimum energy for a chemical reaction to occur or for processes such as diffusion to take place in crystals. |
| Active accommodation |
The use of information from sensors, for example, in a vision system, that allows a robot to show accommodation to the environment. |
| Active vibration suppression |
The reduction of undesirable vibration in components by feedback control. |
| Actual cubic feet per minute |
(acfm) An obsolete (i.e. non-SI) measure of volumetric flow rate; the volume of a gas flowing per minute at actual operating pressure and temperature, as opposed to the corresponding volume flow rate at STP. |
| Actual power |
(actual horsepower) (Unit W or hp) The power delivered at the output shaft of an engine, before subsequent transmission through a gearbox etc. |
| Actual value |
The output of a plant that is being controlled, i.e. the controlled variable. Not directly accessible by the control system, as it can only be measured by a sensor which may distort the measurement. |
| Actuating system |
A system in which an electrical, pneumatic or hydraulic input supplied to an actuator produces force, torque, or displacement, usually in a controlled way. |
| Adhesive joint |
The point or area in which two structures are held together by an adhesive. |
| Adhesive strength |
The strength of an adhesively bonded joint, usually measured in tension (perpendicular to the plane of the bonded joint) or in shear |
| Adhesive wear |
The removal or displacement of material from a surface by the welding together and subsequent shearing of minute areas of two surfaces that slide across each other under pressure. In advanced stages, may lead to galling. Contrast with abrasive wear. |
| Adhesive wear |
Wear that develops when two surfaces slide across one another under pressure. |
| Aerated bath nitriding |
A type of liquid nitriding in which air is pumped through the molten bath creating agitation and increased chemical activity. |
| Age hardening |
Hardening by aging, usually after rapid cooling or cold working. |
| age hardening |
Raising the strength and hardness of an alloy by heating a supersaturated solid solution at a relatively low temperature to induce precipitation of a finely dispersed second phase. Also known as aging or precipitation hardening. |
| Age softening |
Spontaneous decrease of strength and hardness that takes place at room temperature in certain strain hardened alloys, especially those of aluminum. |
| Aging treatment |
Heat treatment aimed at age hardening; it comprises solution and precipitation treatments. |
| AISC |
The American Institute of Steel Construction. |
| Air classifier |
(air elutriator) A device in which an airstream, which may be swirling, sorts particles by a combination of size, shape, and mass. |
| Air cleaner |
A device, such as a filter, hydrocyclone, or electrostatic precipitator, that removes particles and aerosols from a flow of air. |
| Air composition |
The sea-level composition (in per cent by volume) of air at a temperature of 15°C and a pressure of 1 atm is mainly 78.084% nitrogen, 20.947% oxygen and 0.934% argon. The remaining 0.035% consists of carbon dioxide, neon, helium, methane, krypton, hydrogen, oxides of nitrogen, xenon, ozone, iodine, carbon monoxide, and ammonia. Different sources give slightly different figures for the composition. Not included are water vapour (typically 0.4%) and pollutants such as sulfur dioxide. |
| Air compressor |
A turbomachine that draws in air and delivers it at higher pressure, temperature, and density. It can be of axial, fan, reciprocating, or rotary design. |
| Air conditioning |
The process of controlling the temperature and humidity in rooms, buildings, aircraft, passenger vehicles, etc. More generally it includes control of dust, levels of radiant heat, etc. |
| Air pump |
A machine for providing a flow of air or for increasing or decreasing the mass and pressure of air in a closed container. The term pump is more usual when the working fluid is a liquid, while compressor is more usual for gases. |
| Air-cooled condenser |
A heat exchanger, in which the cooling medium is air, used to condense the exhaust steam from a steam turbine, the condensate being returned to the boiler. |
| Air-cooled engine |
An internal-combustion engine directly cooled by airflow, rather than by water flowing through the engine block being cooled by a radiator. |
| Air-hardening steel |
A steel containing sufficient carbon and other alloying elements to harden fully during cooling in air or other gaseous mediums from a temperature above its transformation range. The terms should be restricted to steels that are capable of being hardened by cooling in air in fairly large sections, about 2 in. (50 mm) or more in diameter. Same as self-hardening steel. |
| Allotropy |
A near synonym for polymorphism. Allotropy is generally restricted to describing polymorphic behavior in elements, terminal phases, and alloys whose behavior closely parallels that of the predominant constituent element. |
| Allowable stress |
The maximum stress a designer can assume that the parts will stand. It is always less than the minimum strength of the material. For example, the ASME Boiler and Pressure Vessel Code typically specifies an allowable stress that is one-quarter of the service temperature yield strength of the material. This introduces a four-to-one safety factor into the design process and is intended to compensate for uncertainties in estimates of strength, service loads, etc. |
| Allowable stress design |
A design procedure developed for the AISC by the Research Council on Structural Connections. Purposely underestimates the strengths of bolts and joint materials to introduce safety factors into the design of structural steel joints. It is an alternative to the more recently defined load and resistance factor design procedure. |
| Alloy |
1. A metallic material composed of two or more elements, one of which is usually a metal to which the other elements are added, e.g. iron-carbon or aluminium-copper (binary alloy); nickel-chromium-iron (ternary alloy). 2. A plastic produced as a blend of two or more immiscible polymers. This results in material that cannot be achieved by polymerization. |
| Alloy steels |
Steels that contain alloying elements such as chromium, nickel, molybdenum, manganese, silicon, tungsten, and vanadium. These are added to improve properties such as the hardenability, toughness, strength, wear resistance, and corrosion resistance compared with those of plain-carbon steel. Low-alloy steels have a total alloy content (including carbon) of less than about 8%. They are hardenable and have strength up to 30% higher than plain-carbon steels. High-alloy steels contain considerably more alloy content and are developed for specific properties such as superior corrosion and chemical resistance. |
| Alloying element |
Component added deliberately with the aim of improving the properties of an alloy. Alloying elements can affect the existence range of equilibrium phases present in an unalloyed material, or lead to the occurrence of new phases, or both. In addition, alloying elements strongly affect the kinetics of phase transformations and thus the microstructure formation in alloyed materials. |
| Alpha iron |
The body-centered cubic form of pure iron, stable below 910 °C (1670 °F). |
| Alternating stress |
(Unit Pa) Originally, stresses of changing sign (tension-tocompression-to-tension, etc.) in a component produced by alternating forces acting in opposite directions, but now generally used to describe stresses that vary but may keep the same sign, as produced by periodic, out-of–balance, or vibrational loads. |
| Alternative energy |
(alternate energy) Energy sources that are renewable and do not have the undesired consequences of fossil fuels and nuclear energy. |
| Altitude |
(Unit m) Vertical height measured relative to a specified datum such as sea level. |
| Altitude chamber |
(hypobaric chamber) A chamber in which conditions at different altitudes are simulated by a combination of appropriate pressures, temperatures and relative humidity. |
| Amontons friction |
(Coulomb friction) Friction between surfaces where the ratio of the frictional force F to the normal force N is constant and independent of the area in contact. |
| Amplifier |
A device by which the output of a hydraulic, pneumatic, or electrical source is increased. |
| Anelastic |
Literally ‘not elastic’, but in practice used for materials that display timedependent recovery on unloading. |
| Angle of attack (α) |
(Unit °) The angle between a reference line on a lifting body and the vector direction of the relative velocity between the body and the fluid through which it is moving. In the case of an aerofoil, turbine, or compressor blade, the usual reference line is the chord line. |
| Angle of contact |
(Unit °) The angle subtended at the centre of a pulley or sprocket wheel by the circumferential contact of a belt or chain. |
| Angle of friction |
(friction angle, β) (Unit °) For a body in contact with a plane surface, the angle between the normal to the surface and the resultant force between the body and the surface. If the friction force is F and normal force is N, β is given by F/N = μ = tan β where μ is the coefficient of friction. |
| Angle of thread |
The included angle between the sides forming the groove of the screw thread. |
| Angle of torsion |
(angle of twist) (Unit ° or rad) The angle relative to a chosen section, normal to the axis of twist, through which another part of a component rotates when subjected to a torque. |
| Ångström (Å) |
An obsolete (non-SI) unit of length, sometimes still employed for atomic and crystallographic measurements. The conversion to SI is 1 Å = 10−10 m. |
| Angularity |
The underfaces of the nut and the bolt head should be exactly perpendicular to the thread or shank axes. If the angle between the face and the axis is, for example, 868 or 948, the fastener is said to have an angularity of 48 (sometimes called Perpendicularity). |
| Anisotropy |
The characteristic of exhibiting different values of a property in different directions with respect to a fixed reference system in the material. |
| Anneal to temper |
A final partial anneal that softens a cold worked nonferrous alloy to a specified level of hardness or tensile strength. |
| Annealing |
A generic term denoting a treatment, consisting of heating to and holding at a suitable temperature followed by cooling at a suitable rate, used primarily to soften metallic materials, but also to simultaneously produce desired changes in other properties or in microstructure. |
| Annealing carbon |
Fine, apparently amorphous carbon particles formed in white cast iron and certain steels during prolonged annealing. Also called temper carbon. |
| Annealing twin |
A twin form in a crystal during recrystallization. |
| Anode |
That electrode in a battery or corrosion cell which produces electrons. It is the electrode which is destroyed (corrodes). |
| ANSI |
The acronym for American National Standards Institute. |
| Anti-freeze |
A substance such as ethylene glycol added to the cooling system of a watercooled engine to lower the freezing point of the cooling water and also inhibit the formation of rust and other deposits. |
| Apparent area of contact |
In tribology, the area of contact between two solid surfaces defined by the boundaries of their macroscopic interface. |
| Applied thermodynamics |
(engineering thermodynamics, thermodynamics) The science of the relationship between heat, work and the properties of systems and the ways in which heat energy from fuels can be converted into mechanical work. It involves the study of all aspects of energy use and energy transformation, including power generation, refrigeration, the relevant properties of the substances involved and the relationships between them. The principle of conservation of energy is a fundamental law of nature. |
| Arbitration bar |
A test bar, cast with a heat of material, used to determine chemical composition, hardness, tensile strength, and deflection and strength under transverse loading in order to establish the state of acceptability of the casting. |
| Archimedes screw |
A machine which comprises a rotating helical blade inside a closefitting tube, which may be used to pump liquids, slurries (such as sewage), granular materials, etc. If water flows into the top of an inclined or vertical Archimedes screw, the screw will rotate and can be used to drive an electrical generator. |
| Archimedes Wave Swing |
A machine for tidal-power energy generation consisting of two concentric, air-filled submerged cylinders. The inner lower cylinder is tethered to the ocean floor while the upper floater unit, which is closed at the top, moves up and down due to the variations in hydrostatic pressure caused by the wave motion. The relative movement of the two cylinders is used to generate electricity in which linear motion replaces the more common rotary motion of an electromagnetic generator. |
| Artificial aging |
Aging above room temperature. |
| ASME |
The American Society of Mechanical Engineers. |
| Aspect ratio |
The ratio of the longest to the shortest dimension of a shape or object e.g. the chord-to-thickness ratio of an aerofoil or the span-to-chord ratio of a wing. |
| Assembly drawing |
An engineering drawing that shows how parts are assembled to produce a component or a complete machine. It may include sections to show internal features, dimensions that are critical for assembly, manufacturing information, and part numbers. |
| Assembly line |
A system of mass production in which work is moved progressively from one operation to another, ultimately to give the final complete product. |
| Athermal transformation |
A reaction that proceeds without benefit of thermal fluctuations; that is, thermal activation is not required. In contrast, a reaction that occurs at constant temperature is an isothermal transformation; thermal activation is necessary in this case and the reaction proceeds as a function of time. |
| Atmometer |
(atmidometer, evaporimeter) An instrument that measures the rate of evaporation of water from a surface into the atmosphere. |
| Atmosphere |
1. (atm) An obsolete (non-SI) unit of pressure equal to 101 325 Pa or 1.013 25 bar and approximately equal to the atmospheric pressure (barometric pressure) measured at mean sea level. |
| Atmospheric pressure |
The downward force exerted by the atmosphere because of its weight, (gravitational attraction to the Earth), measured by barometers, and usually expressed in units of millibars. Standard atmospheric pressure at sea level is 1013.25 mb.expressed in units of millibars. Standard atmospheric pressure at sea level is 1013.25 mb. |
| Atom |
The smallest unit of matter that has the properties of a chemical element. The simplest description of an atom (Bohr model) is of a compact nucleus surrounded by one or more orbiting electrons. |
| Atomic volume |
Volume of unit cell per atom. |
| Atomization |
The production of a spray of fine droplets from a liquid, such as diesel oil or petrol, by injection through a nozzle (an atomizer). |
| Atomizing humidifier |
A humidifier that functions by spraying fine droplets of water into an airstream. |
| Ausforming |
Thermomechanical treatment of steel in the metastable austenitic condition below the recrystallization temperature followed by quenching to obtain martensite and/or bainite. |
| Austempered steels |
Medium to high carbon steels with improved mechanical properties as a result of austempering. After heating to between 800° and 900°C to form the austenite phase, they are quenched to, and held at, just above the martensite transformation range (between 260° and 370°C) to form bainite, before cooling further. Austempering of ductile cast irons results in a microstructure of bainite and spheroidal graphite. Austempered ductile irons have excellent toughness and wear properties. |
| Austempering |
A heat treatment for ferrous alloys in which a part is quenched from the austenitizing temperature at a rate fast enough to avoid formation of ferrite or pearlite and then held at a temperature just above Ms until transformation to bainite is complete. Although designated as bainite in both austempered steel and austempered ductile iron (ADI), austempered steel consists of two phase mixtures containing ferrite and carbide, while austempered ductile iron consists of two phase mixtures containing ferrite and austenite. |
| Austempering |
Heat treatment comprising austenitization of a steel article, cooling it to a bainitic range at a rate higher than the critical cooling rate and holding at a fixed temperature until the completion of bainitic transformation. |
| Austenite |
A solid solution of one or more elements in face-centered cubic iron. Unless otherwise designated (such as nickel austenite), the solute is generally assumed to be carbon. |
| Austenite |
Solid solution of alloying elements and/or carbon in γ-Fe. It is named after British metallurgist W. C. Roberts-Austen. |
| Austenite finish temperature (Af) |
Temperature at which the transformation of martensite into austenite completes upon heating. The same designation is also applied to nonferrous alloys in which martensite transforms into some parent phase. |
| Austenite stabilization |
Decrease, in comparison to a continuous cooling, in the amount of martensite occurring from austenite when cooling is interrupted at a temperature between Ms and Mf. This can be explained by the relaxation of stresses induced in the austenite by martensite crystals occurring before the interruption. The relaxation, in turn, leads to the dislocation rearrangement and their interaction with martensite/austenite interfaces, which makes the interfaces immobile. |
| Austenite-stabilizer |
Alloying element expanding the γ-phase field in the corresponding phase diagram, which manifests itself in a decrease of the A3 temperature and an increase of the A4 temperature in binary alloys Fe–M as well as in a decrease of A1 temperature in ternary alloys Fe–C–M (M is an alloying element). The solubility of austenite-stabilizers in ferrite is much lower than in austenite. Under the influence of austenite-stabilizers, austenite can become thermodynamically stable down to room temperature. |
| Austenitic grain size |
The size attained by the grains of steel when heated to the austenitic region; may be revealed by appropriate etching of cross sections after cooling to room temperature. |
| Austenitic stainless steels |
Austenitic stainless steels are non-magnetic. They contain significant additions of chromium (16–30%), but have the austenite (FCC) crystal structure, stabilized by the addition of nickel in the composition range 6–20%. Carbon content ranges from about 0.03 to 0.15%. The ‘18–8’ stainless steels containing approximately 18% chromium and 8% nickel are typical of the class. Austenitic stainless steels have high strength and corrosion resistance even at elevated temperatures, good ductility, good low-temperature properties, and good weldability. Used for aircraft and transport equipment, cutlery, chemical and food-processing equipment, surgical instruments, and cryogenic vessels. |
| Austenitizing |
Forming austenite by heating a ferrous alloy into the transformation range (partial austenitizing) or above the transformation range (complete austenitizing). When used without qualification, the term implies complete austenitizing. |
| Autonomous energy system |
(stand-alone energy system) A sole source of electricity, usually small-scale, for applications remote from a grid, especially with energy storage in the system. Hydroelectric, photovoltaic, wind-power and other renewable systems are well suited to stand-alone applications. |
| Auxetic materials |
Those man-made materials for which Poisson’s ratio is negative, so that the cross section expands when subjected to a longitudinal tensile stress and contracts when subjected to a longitudinal compressive stress. |
| Auxiliary power unit (APU) |
In aircraft–gas–turbine applications, a small gas turbine used to provide start-up power, electrical and hydraulic power, and compressed air for cabin ventilation. In other applications, an APU may be a gas turbine or internal-combustion engine used to provide emergency power. |
| Available draught (Unit Pa) |
The reduced pressure of combustion gases in a furnace or boiler, either forced or due to the buoyancy of hot gases, which is used to draw in combustion air and remove products of combustion. |
| Available head (Unit m) |
In a hydroelectric power system, the difference between the vertical height of the water level in the supply reservoir above the turbine inlet less the head loss due to friction and fittings in the duct leading to the turbine. |
| Available resource |
(total resource) (Unit J) The total annual energy theoretically available from a renewable-energy source, such as ocean waves, the wind, or the total incident solar energy. |
| Avogadro constant |
(Avogadro number, NA) A fundamental physical constant with the fixed numerical value 6.022 140 76 × 1023 mol−1. The mole contains exactly this number of elementary entities. A minor adjustment to the value of the Avogadro constant was made effective on 20 May 2019. |
| Axial load (Unit N) |
In general, a tensile or compressive load directed along the axis of a component. Strictly the load should pass through the centroid of the cross section to avoid inducing bending moments and be perpendicular to the plane of the section. |
