A simplified and fast method to predict plain and notch fatigue of shot peened high-strength aluminium alloys under reverse bending

Abstract

A simplified and fast method to predict plain and notch fatigue resistance of shot peened Al-7075-T651 is presented. For this purpose, different shot peening treatments were carried out on plain and notched samples. Reverse bending SN curves were determined for both notched and unnotched conditions. Initial and stabilized residual stresses were measured by X-ray diffraction on plain samples. An evolution to stabilised values of the surface stresses, depending on the applied loads, was observed. Residual stresses measured on plain samples were used for predicting, by means of finite element modelling, respectively the residual stress distributions in the notched samples and the residual stress relaxation in the vicinity of the notch due to the application of different fatigue loads. The results of the numerical analysis were used to validate a simplified analytical approach developed for computing residual stress relaxation and surface residual stress field both in plain and notched samples. The predicted residual stress distribution was finally incorporated into a multiaxial fatigue criterion. Specifically, the critical distances theory was used to predict the fatigue resistance of notched samples in the presence of a compressive residual stress field.