WACE Engineering Studies cheat sheet

Engineering Studies - Core Principles and Practice

• Stress σ = F/A (N/m² or Pa); strain ε = ΔL/L₀ (dimensionless); Young's modulus E = σ/ε applies only in the linear-elastic region below the proportional limit.

• Factor of safety = failure (or yield) stress ÷ allowable working stress; a factor of 2 means the design load is half the predicted failure load.

• Static equilibrium requires ΣF = 0 and ΣM = 0 about any point; a two-force member carries load only along the line joining its pins.

• Free-body diagrams isolate one body, replace supports with reaction forces, and show every applied load; omitted reactions are the most common source of error.

• Mechanical advantage of a lever = effort arm ÷ load arm; for pulleys MA equals the number of rope segments supporting the moving block, ignoring friction.

• Efficiency = useful output energy ÷ input energy × 100%; it is always below 100% because friction and deformation dissipate energy as heat.

• A material's properties are tested by tensile test (stress–strain curve gives yield strength, UTS, ductility) and hardness test (resistance to indentation).

• Ductile materials (mild steel) yield and deform before fracture; brittle materials (cast iron, glass) fracture with little plastic deformation and fail in tension.

• Engineering design process order: identify need → define constraints and criteria → generate concepts → analyse and select → prototype and test → evaluate and iterate.