Numerical Modeling of Multiphysics Field in Conventional and Stationary Shoulder Friction Stir Welding of Al-Cu Alloy

In robotic friction stir welding, high rotational speed is constantly employed to reduce both robot torque and the welding load. In this paper, a three-dimensional coupled thermo-mechanical model is developed. This model analyzes the multiphysics field in both friction stir welding and stationary shoulder friction stir welding at relatively high rotational speeds. Both experimental and numerical results indicate that the stationary shoulder friction stir welding joint has homogenous microstructure and temperature gradient distribution. Further research finds the peak temperature in the nugget zone of stationary shoulder friction stir welding and friction stir welding is 490° and 530°, respectively. Meanwhile, the effective strain of the stationary shoulder friction stir welding joint is lower when compared to the friction stir welding. However, the strain rate is higher. While being reduced along the thickness direction, the strongest material flow velocity is observed in the top surface of the workpiece. Stationary shoulder friction stir welding is shown as a favorable process for obtaining the homogeneity of the microstructure and reducing joint softening.