WACE Engineering Studies key terms

Internal force per unit cross-sectional area within a material, measured in pascals or megapascals. It shows how heavily a component is loaded and whether it may fail.

The change in length of a material divided by its original length, a dimensionless ratio. It describes how much a component deforms under load.

The ratio of tensile stress to tensile strain in the elastic region of a stress-strain graph. It measures a material's stiffness and is measured in pascals.

The maximum stress a material can withstand and still return to its original shape when unloaded. Beyond this point permanent deformation begins.

The stress at which a material begins to deform permanently, marked by the end of the straight elastic portion of the stress-strain curve. Designers often keep working stress well below it.

The maximum stress a material can sustain before necking and eventual fracture. It represents the peak of the stress-strain curve in tension.

The ability of a material to be stretched into thin wire or to deform plastically before fracturing. Ductile metals bend and stretch rather than snapping suddenly.

The ability of a material to be shaped by compressive forces, such as hammering or rolling, without cracking. It differs from ductility, which concerns pulling into wire.

The amount of energy a material absorbs before it fractures, represented by the area under a stress-strain curve. Tough materials resist impact and sudden failure.

The tendency of a material to fracture with little plastic deformation when loaded. Brittle materials such as cast iron or glass show almost no warning before breaking.

A material's resistance to scratching, indentation, or abrasion on its surface. It is often tested with methods such as Brinell or Rockwell scales.

Progressive damage and eventual cracking of a material caused by repeated or fluctuating loads well below its static strength. It is a common cause of shaft and aircraft failures.

Slow, permanent deformation of a material under a constant load held over a long time, especially at high temperature. It is important in boilers and turbine components.

Localised increase in stress where a component changes shape abruptly, such as at holes, notches, or sharp corners. It can cause cracks to start and so is reduced by fillets.

The ratio of a material's failure stress to the maximum working stress expected in service. A value above one provides a margin against uncertainty and overload.

The turning effect produced at a section of a beam by forces acting on one side of that section. It causes bending stress and is calculated from free-body diagrams.

The internal force acting parallel to a cross-section of a beam, tending to slide one part past another. Its variation along a beam is plotted on a shear force diagram.

The twisting of a shaft or member caused by a turning moment applied about its longitudinal axis. Torsion produces shear stress that increases with distance from the centre.

A geometric property of a cross-section describing how its area is distributed about an axis, governing resistance to bending. Larger values make a beam stiffer.

A cross-section property describing the distribution of area about the longitudinal axis, governing resistance to twisting. Solid circular shafts have a value of pi times diameter to the fourth power divided by 32.

A framework of straight members joined at pin joints and arranged in triangles so that loads produce mainly axial tension or compression. Trusses are analysed by resolving forces at joints.

A sketch showing a body isolated from its surroundings with all external forces and moments drawn as vectors. It is the starting point for solving statics problems.

The condition in which the net force and net moment acting on a body are both zero, so it remains at rest or moves at constant velocity. It is used to find unknown reactions.

The process of splitting a force or velocity into perpendicular components, usually horizontal and vertical, so that forces can be added and analysed algebraically.

The ratio of load force to effort force in a machine or mechanism. A value greater than one means the machine multiplies the applied effort.

The ratio of the distance moved by the effort to the distance moved by the load in a machine. It depends only on geometry, not on friction.

The ratio of useful output energy or power to total input energy or power, usually expressed as a percentage. Losses arise from friction, heat, and other inefficiencies.

The ratio of the number of teeth on a driven gear to that on a driving gear, which sets the change in speed and torque. It is inversely related to speed change.

The turning effect of a force about an axis, equal to force multiplied by perpendicular distance from the axis. It is measured in newton metres.

The rate at which work is done or energy is transferred, measured in watts. In rotating systems it equals torque multiplied by angular velocity.

The permissible variation between the maximum and minimum limits of a dimension on a manufactured part. It controls how closely parts must be made to fit together.

The relationship between the sizes of two mating parts, such as a hole and shaft, determining whether they assemble with clearance, transition, or interference. It is set by their tolerances.

A reference point, line, or surface from which dimensions and tolerances are measured on an engineering drawing. Consistent datums ensure parts assemble correctly.

A drawing method that shows an object from several directions using separate flat views, such as front, top, and side. It communicates exact shape and dimensions for manufacture.

A drawing view in which part of an object is imagined cut away to reveal internal features, with cut surfaces shown by hatching. It clarifies holes and cavities hidden in normal views.

A three-dimensional pictorial drawing in which the three principal axes are equally inclined and drawn at full scale along them. It gives a realistic overview but is not used for precise dimensioning.

A structured list of all parts, materials, and quantities needed to manufacture an assembly. It supports purchasing, costing, and production planning.

A systematic method of estimating environmental impacts of a product across raw material extraction, manufacture, use, and disposal. It guides sustainable design decisions.

Meeting present needs without compromising the ability of future generations to meet theirs, applied to materials, energy, and design choices. It considers environmental, social, and economic effects.

Designing a product so it can be produced efficiently and economically with available processes, minimising parts and operations. It reduces cost and production time.