Rotating bending fatigue tests were carried out on an 18%Ni maraging steel
to investigate the effect of shot peening on fatigue strength. Fatigue stre
ngth was increased markedly by shot peening. The increase in fatigue streng
th due to shot peening depended on shot size and stress level. Fracture mod
e changed from surface fracture in the short-life region to interior fractu
re, i.e., fish-eye fracture, in the long-life region. Tn the middle-life re
gion, however, cracks initiated from both the surface and the inside of the
material individually coalesced and led to the final fracture. These resul
ts were discussed on the basis of the effects of shot size on surface rough
ness, the depth and magnitude of compressive residual stress and work harde
ning.