Mechanistic models and experimental analysis for the torque in FSW considering the tool geometry and the process velocities

Friction Stir Welding (FSW) offers great advantages over conventional welding due to the absence of melting and a small energy requirement. Consequently, the quality of the welded join is better. Torque is a fundamental process quantity in FSW because it is related to weld quality, process control, and mechanical properties of the weld. However, models and experimental studies to determine the effect of each tool part on the torque during the plunging and welding phases have received little attention. In this paper, the influence of the pin and shoulder on the torque is separately considered and three models are developed to describe the torque as a function of the tool geometry and the rotational, plunging and welding speeds. The first model considers only the influence of tooĺs pin, the second model considers only tooĺs shoulder and the third model considers the complete tool. The torque was measured during FSW experiments for different combinations of the main welding parameters. The experimental results were used to estimate the model parameters via inverse problem. The results showed a good agreement between the experimental data and the models.