The multi-stage nature of fatigue: a review

Abstract

Fatigue is a form of fracture anslng from the repetitive action of to-and-fro highly localized inelastic strains, which cause a small, irreversible surface extension leading to or sustaining a crack with each strain cycle. Factors producing this situation in metallic components can be many and varied. Sources for inelastic strains arise from externally applied cyclic load, induced vibration, random noise, thermal stresses, etc. Localization of strain is dependent on specific dislocation, substructural or microstructural characteristics, and upon geometric details such as inclusions, flaws, notches, and surface features. Factors contributing to surface extension include local environmental reactions, trans granular and intergranular fracturing mechanisms, temperature, and time.