FATIGUE AND FRACTURE OF STEELS 221 FATIGUE LIMITS PREDICTION OF SHOT PEENED MATERIALS

Shot peening is an effective method of improving the fatigue strength of and structure. The change in surface layer properties caused by shot evaluated by residual stress and cold work. The X-ray diffraction no method of measuring is used. In order to predict fatigue strength of components, it is necessary to apply a fatigue limit criterion that take consideration compressive residual stress and cold work. The theoretical 1~106liiel~ gives a better approach of shot peening material fatigue behaviour. The mode & takes into account two essential beneficial effects that are: compressive residual stresses and the increase of cold work. It was demonstrated that the effect of cold work on fatigue strength is more important than that of residual stress. The fatigue limit criterion predicts that the crack origin is located into the region under the surface hardened layer. Comparison of predictions of this criterion against experimental fatigue limit data showed good agreement. The methodology followed to build this model could be adequately modified to derive models for other surface treatments