Influences of thermal effects on residual stress fields of an aluminium-lithium alloy induced by shot peening

Abstract

In this paper, the thermal effects and the corresponding influences on the residual stress fields of a 2060-T8 aluminium-lithium alloy induced by shot peening are investigated both theoretically and numerically. Based on the Hertz contact theory, a theoretical analysis is conducted by considering energy transformation during the shot peening process. Moreover, in the numerical simulation, explicit methods for the coupled thermomechanical problem and the purely mechanical case are employed to compute the dynamic process. The static method is adopted for the spring-back process to acquire the residual stress fields. Then, the numerical model is verified by comparing the predicted temperature with the theoretical results and comparing the residual stress fields with the experimental results. The results indicate that shots with a higher velocity or a larger radius possess greater kinetic energy so that more frictional heat can be obtained from the energy transformation, and the temperature on the contact surface is definitely higher. The compressive residual stresses in the surface layers will decrease after considering the thermal effects. This can be ascribed to the comprehensive influences of thermal relaxation and the decrease in yield strength at high temperatures. As a result, a modified empirical equation is established to describe the distributions of residual stresses considering and neglecting the thermal effects. The proposed models considering the thermal effects can help predict the residual stress distributions under different processing parameters and provide a better understanding of the shot peening process.