Fatigue (material)

When a material starts to become weakened, because of heavy use, this is known as material fatigue. As an example, a screw may be able to hold an object that weights a metric ton. When it is used for an object that weights only 100 kilograms (220 lb) one hundred times it may start to wear out and show signs of fatigue.

Fracture of an aluminium crank arm. Dark area of striations: slow crack growth. Bright granular area: sudden fracture.