Destructive testing
- Destructive tests break or damage samples to find material properties.
- Tensile test: a sample is stretched until it breaks. The load–extension graph shows the elastic region, the yield point, the ultimate tensile strength and ductility (from how far it stretches).
- Hardness tests press an indenter into the surface: Brinell uses a hard ball, Vickers uses a diamond pyramid, and Rockwell measures the depth of the dent.
- Impact tests (Charpy and Izod): a swinging pendulum breaks a notched sample. The energy absorbed shows toughness.
- Other tests: bend tests, fatigue tests (repeated loads) and corrosion tests.
Non-destructive testing (NDT)
- NDT checks finished parts without damaging them, such as aircraft parts, welds and pipelines.
- Visual inspection, dye penetrant (shows surface cracks), magnetic particle testing (for ferrous metals), ultrasonic testing (finds internal flaws using sound waves) and X-ray (radiography).
Modelling and investigation
- Engineers use models and prototypes to test designs, virtual testing (such as finite element analysis, which simulates stresses) and test rigs.
- A fair test changes one variable, measures another and keeps the rest the same. Results are recorded, repeated and analysed, often with graphs.
- Quality control checks products against specifications, using tolerances and gauges.
Key terms
- Destructive testing
- Tests that damage or break a sample.
- Non-destructive testing
- Tests that check parts without damaging them.
- Tensile test
- Stretching a sample until it breaks.
- Impact test
- Striking a notched sample to measure toughness.
- Ultrasonic testing
- Using sound waves to find internal flaws.
- Finite element analysis
- Computer simulation of stresses in a design.
- Prototype
- A test version of a product.