Thermal-Mechanical Coupled Finite Element Analysis of T-type Friction Stir Welding

In this paper, the whole process of T-type friction stir welding of aluminum alloy is analyzed by full thermal-mechanical coupling finite element method. The three steps of T-type friction stir welding process are analyzed and simulated: pressing, preheating and welding. In order to solve the problem of element distortion in the calculation process, the arbitrary Lagrange-Euler method (ALE) will be used; in order to accurately describe the strain hardening, work hardening effect and thermal softening effect of metal materials during friction stir welding, the Johnson-Cook material constitutive equation was adopted. In order to verify the finite element simulation results, a T-shaped friction stir welding experimental device was established for welding verification. The results show that during the T-type friction stir welding process, the maximum temperature on the workpiece is 500 ℃ when the welding is stable, reaching 86% of the melting point of the base metal 582 ℃; the friction between the workpiece and the tool shoulder is the main source of heat in the friction stir welding process. The change of equivalent plastic strain value in the welding area is gradient, and the welding area is fish scale distribution. The stress on the workpiece during the whole welding process is symmetrical about the welding direction; the stirring head will be subjected to a very large reaction force in the pressing stage.