AAMA - Architectural Aluminum Manufacturer’s Association.

Abel Flashpoint Apparatus - A petroleum-testing apparatus for determining the flash point.

Abhesive - A substance which prevents two materials sticking together, e.g., teflon on frying pans.

Abiotic environment - The part of an ecosystem that includes the nonliving surroundings.

Ablating Material - A material designed to provide thermal protection to a body in a fluid stream through loss of mass.

Abney Level - Hand-held instrument in which angles of steep sights are measured while simultaneously viewing a spirit-level
bubble.

Above-grade - The portion of a building or other item that is above ground level.

Abraded - Pertaining to a surface that has been worn by surface rubbing.

Abrasion - A process where hard particles are forced against and moved along a solid surface.

Abrasion Hardness - Resistance to abrasive wear.

Abrasive - A very hard, brittle, heat-resistant substance that is used to grind the edges or rough surfaces of an object.

Abrasive Wheel - A grinding wheel composed of an abrasive grit and bonding agent.

Absolute Pressure - Pressure measured from a starting point of 0 in perfect vacuum.

Absolute Zero - A hypothetical temperature at which there is total absence of heat.

Abut - The action of two gear teeth making contact.

Abutment - A part which stops the motion of another part from proceeding any farther.

Abutting Edge - The side or edge of a panel which joins another panel.

A/C Circuit - (Alternating Current) The flow of current through a conductor first in one direction then in reverse. It is used
exclusively in residential and commercial wiring because it provides greater flexibility in voltage selection and simplicity of
equipment design.

AC Induction Motors - These are generally used for constant speed applications where a fixed frequency power source such
as 60 Hz or 400 Hz is available.

Acacia - A durable wood used for palings and posts.

Accelerance - For a point excitation of a mechanical system this is the complex ratio of acceleration to applied force.

Accelerator - Any material added to stucco, plaster or mortar which speeds up the natural set.

Accelerator Pedal - A pedal that when pressed is connected to the engine and demands more torque.

Access - A way of reaching something that is usually hidden or covered.

Accumulator - A device by which energy or power can be stored.

Ackermann Angle - The toe-out or toe-in of a vehicle with Ackermann steering when the wheels are positioned straight
ahead.

Ackermann Steering - A double-pivoting steering system.

Acme Thread - A screw thread having a 29 degree included angle. Used largely for feed and adjusting screws on machine
tools.

Acoustic Emission - A measure of integrity of a material determined by sound emission when a material is stressed.

Acoustic Filter Elements - There are a number of different types of acoustic filter elements that are used in many different
applications.

Acoustic Pack - Name given to all of the soft absorptive parts used to reduce noise in a vehicle.

Acoustic Streaming - Unidirectional flow currents in a fluid that are due to the presence of sound waves.

Acre - 43,500 square feet.

Acrylic - Synthetic resin made from acrylic acid or a derivative thereof; acrylics possess the property of transparency and offer
flame resistance.

Activation energy - The energy that must be overcome in order for a chemical reaction to occur.

Activator - Substance that enhances the ability of a flux to remove oxides and other contaminants from surfaces being joined.

Actuator - The part of a switch that is acted upon to cause the switch to change contact connections.

ADA - Americans with Disabilities Act

Addendum - That portion of a gear tooth that extends from the pitch circle to the outside diameter.

Adhere - To stick or be glued to something.

Adhesion - The state in which two surfaces are held together by interfacial forces which may consist of valence forces or
interlocking action.

Adhesive - A substance capable of holding material together by surface attachment.

Adhesive Tape - A tape with a sticky substance on one side.

Adjustable Spanner - A tool which has a fixed jaw and a movable jaw which is controlled by a spiral gear.

Admittance - The ratio of current to voltage, the reciprocal of impedance.

Adsorption - A surface phenomena in which a solute (soluble material) concentrates or collects at a surface (the adsorbent).

Aerodynamic Drag - Resistance of a vehicle body to motion through the air. A smooth surface has less drag than a rough one.

Aerofoil - An aerofoil is shaped so that air flows faster over the top than under the bottom. There is, therefore, a greater
pressure below the aerofoil than above it. This difference in pressure produces the lift.

AFE - Authority for expenditure

Afterburner - Thrust augmentation feature of a gas turbine engine.

Ageing - A change in the properties of certain metals and alloys that occurs at ambient or moderately elevated temperatures
after hot working, heat treatment, or a cold working operation.

Aggravated Test - A test in which one or more conditions are set at a more stressful level that the test item will encounter in
the field, in order to reduce test time or assure a margin of safety.

Aggregate - Crushed stone, slag or water-worn gravel that comes in a wide range of sizes that is used to surface built-up
roofs.

Air Bearing - A bearing which uses an air cushion to separate its rotating surfaces.

Air Brake - Used to reduce the speed of an aeroplane.

Air changes - The amount of air leakage into or out of a building or room in terms of the number of building volumes or room
volumes exchanged.

Air Hammer - A hammer that is powered by compressed air.

Air Infiltration - The amount of air leaking in and out of a building through cracks in walls, windows and doors.

Air Lock - An intermediate enclosed chamber of a vacuum or pressure system through which an object may be passed
without materially changing the vacuum or pressure of the system.

Air Spring - A simple mass on an air spring.

Airbag - A bag that is inflated when an impact is detected to restrain a vehicle passenger.

Aircraft - Any structure, machine, or contrivance, especially a vehicle, designed to be supported by the air.

Airflow - A flow or stream of air.

Airflow Resistance - The quotient of the air pressure difference across a specimen divided by the volume velocity of airflow
through the specimen. The pressure difference and the volume velocity may be either steady or alternating.

Airfoil - A structure designed to obtain a useful reaction on itself in its motion through the air.

Airframe - The structure of an aircraft, without power plant and systems.

Alder - This wood is very durable in water and not so durable in dry conditions. Historically it was used a lot in pumps, piles
and sluices.

Align - To adjust or set to a line or centre.

Alignment - A condition whereby the axes of machine components are either coincident, parallel or perpendicular, according
to design requirements, during operation.

Alkali - Any substance having basic (as opposed to acidic) properties.

Alkalinity - The capacity of a water to neutralize acids.

Alkylation - A process using sulfuric or hydrofluoric acid as a catalyst to combine olefins and isoparaffins to produce a high-
octane product known as alkylate.

Allowance - The prescribed difference in dimensionsof mating parts to provide a certain class of fit.

Alloy - A metal produced by mixing other metals.

Alloying Elements - Chemical elements added for improving the properties of the finished materials.

Alluvium - Soil deposited by water flows such as floodplains, lakes, rivers and fans at the foot of mountain slopes.

Alpakka - A nickel silver made from 65% copper, 22% zinc, 13% nickel.

Alpha Iron - The body-centered cubic (BCC) form of pure iron, stable below 910°C.

Alpha Stirling Engine - A striling engine that has two separate power pistons, one hot and one cold.

Aluminium - Basis for a number of alloys.

Amalgam - An alloy that contains mercury.

Ambient Environment - The conditions characterizing the air or other medium that surrounds material.

American Wire Gauge - A numbering system for standard wire diameters, often abbreviated as AWG.

Ammeter - Device to measure the current flowing in a circuit.

Amorphous - Non-crystalline, without long-range order.

Amps (Amperes) - The rate at which electricity flows through a conductor.

Anaerobic Adhesive - An adhesive which hardens in the absence of air, such adhesives are often used as a thread locking
medium.

Anaerobic Process - A process which only occurs in the absence of molecular oxygen.

Anchor - A weighty grappling hook used for holding a ship fast.

Anchor Bolts - Bolts which fasten columns, girders, equipment, or other members to concrete or masonry such as bolts used
to anchor sills to masonry foundation.

Ancillaries - Name given to components such as alternator, power steering pump and air conditioning compressor driven by
the engine.

Anelasticity - The property of a solid in which deformation depends on the time rate of change of stress as well as on the
stress itself.

Angle Iron - An iron or steel structural member that has been cast, rolled, or folded so that its cross section is L-shaped.

Angle Plate - A precision holding fixture made of cast iron, steel, or granite.

Anhydrous - Devoid of water.

Aniline Number - Lowest temperature at which equal parts of aniline and a sample of oil are completely miscible.

Anion - Negatively charged ion.

Anisotropic - Unequal physical properties along different axes.

Annealing - Heating to and holding at a suitable temperature and then cooling at a suitable rate, for such purposes as
reducing hardness.

Annealing Twin - A twin formed in a crystal during recrystallization.

Anodize - To coat a metal with a protective film by electrolysis.

ANSI - American National Standards Institute

Anti Lock Brake System - A system that can modulate the brake pressure under hard braking conditions to avoid a brake
locking and resultant skidding.

Antiferromagnetism - A phenomenon observed in some materials in which complete magnetic moment cancellation occurs as
a result of antiparallel coupling of adjacent atoms or ions.

Antinode - Point of maximum displacement.

Anvil - A heavy iron or steel block upon which metal is forged or hammered.

API Gravity - An arbitrary scale adopted by the American Petroleum Institute to designate the specific gravity of mineral oils.

A-Pillar - The first, or most forward, roof support pillar located on either side of the windshield.

Apparent Mass - Force per unit acceleration.

Appold Dynamometer - This is a friction based dynamometer with a water cooled drum and automatically corrects any
variations of load due to changes in the coefficient of friction.

Aquaplaning - When water stands on a road or race track it may not be dispersed effectively from the tyre contact area with
the road.

Aquifer — Saturated permeable geological formation that can transmit significant quantities of water under ordinary hydraulic
gradients.

Arbor - A shaft or spindle for holding cutting tools; most usually on a milling machine.

Arbor Press - A hand-operated machine tool designed for applying high pressure for the purpose of pressing together or
removing parts.

Arc Brazing - A brazing process wherein the heat is obtained from an electric arc formed between the base metal and an
electrode.

Arc Cutting - A group of cutting processes in which the cutting of metals is accomplished by melting with the heat of an arc
between the electrode and the base metal.

Arc Oxygen Cutting - An oxygen-cutting process used to sever metals by a chemical reaction of oxygen with a base metal at
elevated temperatures.

Arc Welding - A group of welding processes in which fusion is obtained by heating with an electric arc or arcs, with or without
the use of filler metal.

Arko Metal - A brass made with 80% copper and 20% zinc.

Aromatics - One of the three principal groups or series of hydrocarbon compounds that occurs naturally in crude oil. New
formulations of gasoline with increased octane levels often contain increased amounts of aromatics.

As Welded - The condition of weld metal, welded joints, and weldments after welding and prior to any subsequent thermal,
mechanical, or chemical treatments.

Asbestos - This description covers a number of fibrous silicate minerals such as calcium magnesium silicate.

Ash - A very tough and elastic timber used for oars, blocks and pulleys, spokes of wheels and milk-pails.

Aspect Ratio - For a graphics device it is the ratio of the screen dimensions, normally defined as vertical screen dimension
divided by horizontal screen dimension.

Asphalt - A black sticky semi-solid material mainly bitumen with minerals, occurs naturally, but made artificially and used in
the construction of roads and buildings.

Aspin Engine - A rotary valve engine developed by Frank Aspin.

ASTM - American Society for Testing and Materials

Asymmetrical Support - A rotor support system that does not provide uniform restraint in all radial directions.

atm - An abbreviation of atmosphere.

Atomize - To break up a liquid into extremely fine particles.

Austempering - Quenching a ferrous alloy from a temperature above the transformation range.

Austenite - Face-centered cubic iron; also iron and steel alloys that have the FCC crystal structure.

Autoclave - An airtight vessel constructed of thick-walled steel alloy for carrying out chemical reactions under pressure and
high temperatures. Auto-claves are used for the industrial processing of composite materials.

Autogyro - An aeroplane that flies by virtue of the lift generated by freewheeling rotating wings set windmill fashion above
the fuselage.

Automatic Gearbox - A gearbox where the ratio between input and output shafts is changed automatically based on load,
throttle application, engine speed and road speed.

Automatic Stop - A device which may be attached to any of several parts of a machine tool to stop the operation of the
machine at any predetermined point.

Automobile - A self-powered vehicle that travels on land typically with three or four wheels and with 2 to 9 seats.

AWG - American wire gauge, a numbering system for standard wire diameters.

Axial - In the same direction as the shaft centreline.

Axial Load - A load applied along or parallel to and concentric with the primary axis.

Axis - The line, real or imaginary, passing through the centre of an object about which it could rotate; a point of reference.

Axis of a Weld - A line through the length of a weld, perpendicular to a cross section at its centre of gravity.

Axle - An axle is a shaft on which a part rotates.
Engineering Glossary, Engineering Dictionary A
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