Investigation of thermo-mechanical loading effect on the residual stress relaxation in Al6061 alloy using simulation and experiments

Compressive residual stress induced by ultrasonic needle peening has a significant effect on the mechanical properties improvement in metallic parts. However, the initial induced compressive residual stresses may be relaxed under thermo-mechanical loading. Present research deals with the 3-D finite element model for predicting compressive residual relaxation of Al6061 alloy subjected to thermo-mechanical loading. In order to evaluate the numerical model, the residual stress relaxation is measured by X-ray diffraction method. It is revealed that the experimental measurements are in good agreement with obtained numerical results. Moreover, the results show that the compressive residual stresses are relaxed but not completely released at the selected thermo-mechanical loading. It is also concluded that increasing temperature in thermo-mechanical relaxation causes more relaxation of induced residual stresses on the surface and in-depth. (author)