Engineering Materials
Core concepts
Know the properties of ferrous and non-ferrous metals: plain carbon steel, alloy steel, stainless steel, cast iron, aluminium alloys, copper alloys, and titanium. Understand crystal structure, grain size, and the effects of alloying elements. Study heat treatment processes: annealing, normalising, hardening, tempering, and case hardening. Understand mechanical properties: tensile strength, yield strength, ductility, hardness, toughness, fatigue, and creep. Learn non-destructive testing methods and corrosion types, including galvanic, pitting, crevice, stress, and erosion-corrosion, and their prevention.
Common traps
Questions often confuse hardness with toughness, or annealing with normalising. Watch for the difference between strength and stiffness. Galvanic corrosion requires two dissimilar metals and an electrolyte; the more active metal becomes the anode. Stainless steel is not immune to corrosion, especially in chloride environments.
Worked example
A tensile specimen with an original length of 50 mm extends to 60 mm before fracture. Percentage elongation = (60 − 50)/50 × 100 = 20%. Rule of thumb: elongation above about 5% indicates ductile behaviour; below that, the material is considered brittle.
Study approach
Link material selection to marine components such as shafts, propellers, and piping. Practise interpreting stress-strain curves and heat treatment outcomes.