Finite Element Simulation of Residual Stress Induced by High Energy Beam Welding in Dual Phase Steel

Abstract

In this study, the residual stresses that arise during the high energy beam welding of dual phase steels were investigated using a sequentially coupled 3D finite element model. To accurately predict the sharp temperature gradients across the different weld zones, a moving volumetric heat source model, combining a spherical and a conical thermal flux distribution was developed. The temperature profiles computed with this heat source model were found to be in excellent agreement with the measured temperatures. Additionally, the simulated weld geometry was compared to the optical micrographs of the weld cross section to validate the heat source model parameters. The time-temperature history recorded at each node of the FE mesh served as input for the metallurgical and mechanical analyses, where the kinetics of phase transformations, the volumetric dilatations and thereby, the residual stresses in the weld joint were calculated. A metallurgical framework that includes the effect of volumetric strains occurring due to the phase transformations on the residual stresses was presented. The results show that the solid-solid phase transition occurring during cooling in a weld procedure can have a large influence on the magnitude of the residual stress. Furthermore, a comparison of the predicted welding residual stresses with the experimental drill-hole test results in both the weld seam and the base material was also reported.