ABSTRACT
Fatigue damage occurs because of the irreversibility of plastic flow during cyclic deformation. Such irreversibility contributes to the cumulative cyclic strain (Laird, 1979; Mughrabi et al., 1983), which ultimately leads to fatigue hardening and softening, formation of persistent slip bands, fatigue crack nucleation, and finally fatigue crack growth and fracture. Although plastic strain irreversibility is the primary factor, an understanding of the fatigue damage is complicated because of the interactive effects of chemistry and metallurgical microstructure, which influence the homogeneity of deformation as well as the degree of slip reversibility. Further complications are due to the interactive effects of stress singularities arising from specimen surface roughness and the effects of temperature and external environments.
