Fatigue strength prediction methodology of shot-peened materials

Abstract

Shot peening is used to enhance fatigue strength, but it is usually neglected by manufacturing design. The main purpose of the present work is to suggest strategies capable of making connection between the process conditions and the fatigue strength. In the present paper, fatigue lives of shot-peened parts were predicted. A new multiaxial HCF model, based on the Crossland criterion, was proposed; it integrates the favourable effects of shot peening that are the combined effect of compressive residual stresses and strain hardening. The plastic strain field accounts for the strain hardening. In order to compute residual stress and equivalent plastic strain profiles due to the repeated impacts, we have modelled and simulated, through a finite element method, the impact of the shot dynamics resulting from the process. The relaxation of induced compressive residual stresses, over the fatigue life, has been considered. For the purpose of spotlighting the capability of the present methodology, the predictions were compared with existing experimental data. This study demonstrates that the single effect of stabilized residual stress is not sufficient to explain the full enhancement of fatigue resistance. The proposed fatigue criterion provides a conservative prediction in terms of endurance limit.