Inhomogeneous thermal-mechanical analysis of 316L butt joint in laser welding

Abstract

Inhomogeneous thermal-mechanical distributions in laser welding of austenite stainless steel 316L were analyzed, and the effect of shear behavior caused by residual stress on tensile strength was also discussed. A double cone combined heat source model was used to simulate the transient distribution of temperature field. The simulation results showed a good agreement with the experiment results in weld geometry, and the maximum prediction error was 5.84%. The temperature gradient at front wall of weld pool was apparently higher than that at back wall. Time- and space-dependent mechanical behaviors such as strain, stress and deformation were analyzed. It was indicated that stresses along longitudinal and transverse directions were related with temperature gradient, while the deformation fluctuation was dependent upon the high temperature gradient at the front wall of weld pool. The tensile test samples obtained at start-end and middle positions showed fracture interface lines with curve and rectilinear shapes, respectively. The reason is that a shear behavior, which could reduce the weld tensile strength, is caused by the coupling compressive stress and tensile stress in the joint with inhomogeneous residual stress. The shear behavior could be intensified with the increased inhomogeneity in weld residual stress.