Numerical and Experimental Study on the Thermally Induced Residual Stresses Behavior in the Hybrid Laser/Arc Welding of Lap Joint

In this study, a three-dimensional (3D) finite element model is developed to investigate a thermally induced stress field during the laser welding and hybrid laser-gas tungsten arc welding (GTAW) process. In hybrid laser/arc welding, the focus on of this study is on the GTAW process sharing a common molten pool with a laser beam and playing an augmented role in the hybrid welding system. An experimentally-based thermal analysis is performed to obtain the temperature history, which then is applied to the mechanical (stress) analysis. The goal is to determine the optimal welding parameter set that yields the minimum stress concentration. A modified material model is used to consider the influence of face-to-face contact between the top and bottom metal sheets in the thermo-mechanical analysis. Results show that the normal stress components prevail in the weld, and maximum thermal-stress exceeding the yield point of the material exists at the heat affected zone (HAZ). However, the stress concentration in the weld is obviously reduced with laser welding augmented by a GTAW arc. In addition, a series of experiments are performed to validate the numerical results, and a qualitative agreement is achieved.