Experimental and numerical investigation of the evolution of residual stresses under cyclic mechanical loading

Abstract

Forming-induced residual stresses highly influence the performance of metallic engineering components. They offer great potential particularly for increasing fatigue life by targeted introduction of compressive residual stresses in failure-critical areas. However, this only holds true if one can understand and predict the change of residual stresses under cyclic mechanical loading and thus ensure their stability. In the present paper, we introduce a combined experimental and numerical approach for the investigation of residual stress evolution under cyclic mechanical loading. Therefore, a suitable experiment is conceptualized and realized using a 4-point bending setup. The initial plastic deformation of each specimen is followed by a certain number of load cycles and experimental residual stress analyses. From this, a course of residual stresses over the fatigue life is constructed. In order to simulate the determined change in residual stresses, a cyclic plasticity model is proposed that takes into account the nonlinear kinematics due to the large deflection of the beam. A parametrization algorithm is presented, which employs a global optimization strategy using uniaxial stress–strain data from various parametrization experiments. The final comparison of experimental and numerical results shows a qualitative agreement. Their stabilization level after a few thousand load cycles can be predicted.