Why do materials (such as steel, polymer and plastic) undergo fatigue? When steel experience fatigue, what...

Question

Question

Why do materials (such as steel, polymer and plastic) undergo fatigue? When steel experience fatigue, what happens to it?

Answer 1

Answer #1

Fatigue :- failure of a material below it's yield strength because of the cyclic loading.

Every material fails at different number of cycles based on its environment ,structure, applied load and temperature also.

Fatigue generally starts from surface. If any damage happens to surface in anyway materials fail catastrophically.

Fatigue done in three stages

1. Crack initiation ( 45 degrees to applied load from surface)

2. Crack propagation ( intrusion and extrusion) only in tension crack can propagate.

3. Catastrophic failure below it's yield strength.

Fatigue based on its number of cycles

N < 10^ 4 cycles ----------> low cycle fatigue

N > 10^4 cycles -----------> high cycle fatigue.

steel has endurance limit

above it only steel fails by fatigue other it can bare infinite number of cycles.

Answer 2

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