A Modified Johnson-Cook Model Considering Strain-Temperature Coupling for Welding Simulation of Aluminum Alloy Bumper

The metal inert-gas (MIG) welding technique employed for aluminum alloy automotive bumpers involve a complex thermo-mechanical coupling process at elevated temperatures. Attaining a globally optimal set of model parameters continues to represent a pivotal objective in the pursuit of reliable constitutive models that can facilitate precise simulation of the welding process. In this study, a novel piecewise modified Johnson-Cook (MJ-C) constitutive model that incorporates the strain-temperature coupling has been proposed and developed. A quasi-static uniaxial tensile model of the specimen is constructed based on ABAQUS and its secondary development, with model parameters calibrated via the second-generation non-dominated sorting genetic algorithm (NSGA-II) method. A finite element simulation model for T-joint welding is subsequently established, upon which numerical simulation analyses of both the welding temperature field and post-welding deformation can be conducted. The results indicate that the implementation of the MJ-C constitutive model improves the precision of the simulation by 78.8% and provides an accurate representation of the mechanical behavior of the T-joint of aluminum alloy sheet metal during the welding process. Ultimately, the calibrated heat source model and constitutive model are employed to construct the welding model of the automotive bumper, accurately predicting the deformation and residual stress that arise during the welding process of the bumper while identifying the optimal welding sequence. This optimal sequence achieves a 41.3% reduction in welding deformation of the bumper, benefiting the bumper bolted to the body. Through the simulation and optimization method, lowering costs and expediting the design cycle.