FE analysis of residual stress and welding deformation of a low-alloy UHS quenched steel fillet joint

In this study, both the distribution of residual stress and welding deformation in a double-pass T-joint made of low-alloy ultra-high strength (UHS) quenched steel have been investigated experimentally and numerically. Using Abaqus software, the primary aim of this study is to develop an advanced computational approach incorporating a highly precise material model that accounts for solid-state phase transformation (SSPT) in the heat-affected zone (HAZ) and softening effect (SE) in the subcritical heat-affected zone (SCHAZ) to simulate residual stress and welding deformation in the double-pass T-joint. The predictions of welding thermal cycles, residual stress distribution, and welding deformation made by the finite element model have been validated against corresponding experimental results. When both SSPT and SE were considered in the finite element model, the predictions closely aligned with the experimental measurements. The experimental findings reveal that the maximum degree of softening in a T-joint subjected to double thermal cycles is more pronounced than in a T-joint subjected to a single thermal cycle. The simulation results indicate that SSPT significantly impacts both the magnitude and distribution of residual stress in the HAZ of the T-joint, while SE also can reduce the magnitude of longitudinal residual stress to a certain extent especially in SCHAZ. Furthermore, the simulation results suggest that SSPT moderately affects the distribution of longitudinal plastic strain in the double-pass T-joint, with minimal influence on angular distortion and transverse shrinkage. Additionally, the simulation results indicate that the SE has a limited impact on the welding deformation of the T-joint.