fatigue

Fatigue is a progressive structural damage process that occurs when a material is subjected to cyclic loading. This phenomenon leads to failure at stress levels significantly lower than the material's ultimate tensile strength or yield strength. The fatigue process typically proceeds through three distinct stages: crack initiation, where microstructural defects or surface irregularities develop into cracks; crack propagation, where the crack grows incrementally with each cycle; and final fracture, where the remaining cross-sectional area can no longer support the applied load, leading to sudden failure.