WACE Engineering Studies flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

Stress

Internal force per unit cross-sectional area, calculated as σ = F/A and measured in pascals (N/m²). It describes how intensely a load is distributed within a material.

Strain

The ratio of change in length to original length, ε = ΔL/L₀, and it has no units. It quantifies how much a component stretches or compresses under load.

Young's modulus

The ratio of stress to strain within the linear-elastic region of a stress–strain curve, E = σ/ε. A higher value means the material is stiffer and deflects less under the same load.

Yield strength

The stress at which a material begins to deform permanently, marking the end of elastic behaviour. Designs usually keep working stress well below this value.

Ultimate tensile strength

The maximum stress a material sustains before necking and fracture on a tensile test. It is the peak of the stress–strain curve, not the stress at breaking.

Factor of safety

The ratio of a material's failure or yield stress to the allowable working stress. Values above one account for uncertainty in loads, material properties and analysis.

Ductility

A material's ability to undergo significant plastic deformation before fracturing, often reported as percentage elongation. Ductile metals such as mild steel give warning before failure.

Brittleness

The tendency of a material to fracture with little or no plastic deformation. Brittle materials such as cast iron and glass fail suddenly, especially under tensile loading.

Free-body diagram

A sketch isolating one body and showing all applied forces and support reactions acting on it. It is the starting point for applying equilibrium equations.

Static equilibrium

The condition where the sum of forces and the sum of moments about any point are both zero. A structure at rest must satisfy these two conditions.

Two-force member

A component loaded only at two points with no applied moment, so the forces at those points are equal, opposite and collinear. Truss members are analysed this way.

Mechanical advantage

The ratio of load force to effort force for a machine, or effort arm to load arm for a lever. It indicates how much a mechanism multiplies an applied force.

Velocity ratio

The ratio of the distance moved by the effort to the distance moved by the load. Unlike mechanical advantage, it depends only on geometry, not on friction.

Efficiency of a machine

Useful work output divided by work input, expressed as a percentage. It is always below 100 percent because friction converts some input energy into heat.

Torque

The turning effect of a force, calculated as force multiplied by the perpendicular distance from the pivot. Measured in newton metres.

Bending moment

The internal moment at a section of a beam that resists applied loads. Maximum bending moment often determines the required beam size and section shape.

Shear force

The internal force acting parallel to a cross-section of a beam or fastener. It tends to slide one part of the material past another.

Second moment of area

A geometric property describing how area is distributed about an axis, governing resistance to bending. Deeper sections have much larger values, so beams are often tall.

Thermal expansion

The increase in length of a material when heated, given by ΔL = αL₀ΔT. Different expansion rates in joined materials can induce internal stress.

Stress concentration

Localised high stress caused by abrupt changes in cross-section, holes or sharp corners. Rounded fillets reduce it and improve fatigue life.

Fatigue failure

Fracture caused by repeated or fluctuating loads well below the static strength. Cracks initiate at stress raisers and grow progressively with each load cycle.

Corrosion

The chemical or electrochemical degradation of a metal, commonly oxidation of iron to rust. Coatings, alloying and sacrificial anodes are common prevention methods.

Alloy

A mixture of a metal with other elements to improve properties such as strength, hardness or corrosion resistance. Steel is iron alloyed mainly with carbon.

Heat treatment

Controlled heating and cooling of a metal to change its microstructure and properties. Processes include annealing, normalising, quenching and tempering.

Annealing

A heat treatment that heats metal then cools it slowly to soften it, relieve internal stress and improve machinability. It typically increases ductility while reducing hardness.

Quenching

Rapid cooling of a heated metal, usually in water or oil, to harden it by trapping a martensitic structure. Quenched parts are hard but often brittle and need tempering.

Tempering

Reheating a quenched metal to a moderate temperature then cooling, reducing brittleness while retaining useful hardness. It relieves internal stresses created during quenching.

Tensile test

A test pulling a specimen until it fractures while recording load and extension. The resulting stress–strain curve reveals stiffness, yield strength, strength and ductility.

Hardness test

A test measuring a material's resistance to indentation by a hardened indenter under a known load. Common scales include Brinell, Vickers and Rockwell.

Design brief

A concise statement of the problem, the intended user and the key constraints and criteria the solution must satisfy. It guides concept generation and evaluation.

Design criteria

The measurable requirements a design must meet, such as strength, cost, mass or safety limits. They are used to compare and select between competing concepts.

Prototype

A physical or virtual model built to test a design concept before full production. It reveals performance, manufacturing and usability issues early and cheaply.

Concurrent engineering

An approach where design, manufacturing, materials and cost specialists work together from the start. It reduces redesign, shortens time to market and lowers production cost.