Engineering Materials
Domain focus
Engineering Materials tests ferrous and non-ferrous metals, alloys, heat treatment, properties, and failure modes in vehicle components. The exam links material selection to strength, wear, fatigue, and cost.
Core rules
- Ferrous materials include cast iron and steels; non-ferrous include aluminium, copper, and magnesium alloys.
- Strength resists stress; hardness resists indentation and wear; ductility allows deformation; toughness absorbs impact energy.
- Heat treatment: annealing softens, normalising refines grain, hardening and tempering balance hardness and toughness.
- Fatigue failure starts at stress concentrations and repeated loading, often without visible deformation.
- Gaskets, seals, and composites must suit temperature, pressure, and fluid compatibility.
Worked example
A tie rod of 20 mm diameter carries 30 kN. Area = π/4 × 20² = 314 mm². Stress = 30,000 N ÷ 314 mm² = 95.5 MPa. If the material yield strength is 250 MPa, safety factor = 250 ÷ 95.5 = 2.6. This is adequate for static loading, but fatigue at a thread or notch may still govern, so the stress concentration must be considered.
Traps
Using diameter as area, confusing hardness with tensile strength, and assuming a higher safety factor always means a better design. Heat treatment without controlled temperature and cooling can distort parts or leave brittle surfaces.