Simulation Study And Process Optimization On Double Pulsed MIG Welding Of Aluminum Automotive Components

The application of aluminum alloy in automobile industry becomes more andmore widely for the purpose of automobile lightweight to save energy and reduceemission. The vehicle body acts as a main structure component of vehicle safety, itswelding quality and distribution of stress and deformation have significant influenceon the performance of loading and energy absorption effect during the collision. Crashbumper made of aluminum alloy was used in this paper to analyze the impact ofdifferent welding parameters exacted on the welding residual stress and deformationduring double pulsed MIG welding (DP-MIG). Numerical simulation has been adoptedto obtain the thermal and stress-strain fields during welding process and to effectivelypredict the overall residual stress and deformation distribution after welding.The welding process o thin sheet6061-T6aluminum alloy with the thickness of2mm was firstly investigated. The process of aluminum alloy T-joint welding duringthe DP-MIG was simulated by the finite element analysis software ABAQUS. Whendescribing the heat source of DP-MIG, the heat input was simplified to change betweenthermal strong and thermal weak at the cycle of low pulse. In addition, FORTRANlanguage was compiled to apply moving heat source load and the technique of elementborn and death was employed to simulate the weld filler in T-joint fillet welds. Theevolution of temperature and stress-strain, as well as welding residual stressdistributions and the overall deformation can be obtained after the calculations. Thesimulation results showed that the stress located at fusion zone induced a1.61°angulardistortion. Besides, temperature and stress fields changed with the cycle of low pulse.The weld pool size was larger and temperature was higher during thermal pulse thanthat during thermal base, resulting in the typical ripples appearance on the weld joint.The stress of weld pool during thermal strong was higher than that during thermalweak, which enhances the flow of weld pool and leads more uniform and finermicrostructure. Then, the welding processes, with conditions of different averagecurrent and of the difference current between thermal strong and thermal weak, weresimulated to analyze their effect on the temperature and stress, and to further illustrateits influence exacted on welding appearance、microstructure and porosity. In addition,the finite element calculation results were compared to the experimental data to verifythe accuracy of simulation. On one hand, the temperature cycle curves of several points at T-joint were measured by thermocouple to identify the temperature field. Onthe other hand, the residual stress was tested for points at different distances among theweld fusion by blind hole method to verify the stress field. The comparison betweenthe experiment and simulation results showed a good agreement.The crash bumper welding process was simulated with the T-joint optimizationparameters and the temperature and stress-strain fields can be acquired. At the sametime, four different simulation sequences were carried out to investigate the effect ofwelding sequence on welding residual stress distribution and final deformation. Incontrast, we can achieve the optimal welding sequence under four welding sequences.