Numerical Simulation on the Effect of Friction Stir Welding Parameters on the Peak Temperature, Von Mises Stress, and Residual Stresses of 6061-T6 Aluminum Alloy

Abstract

The friction stir welding (FSW) has become an important welding technique to join materials that are difficult to weld by traditional fusion welding technology. The model used in this study is a simplified version of the thermo-mechanical model developed by Zhu and Chao for FSW with aluminum alloy A6061-T6. Zhu and Chao presented nonlinear thermal and thermo-mechanical simulations using the finite element analysis code ANSYS APDL 16.2. They initially formulated a heat transfer problem using a moving heat source and later used the transient temperature outputs from the thermal analysis to determine residual stresses in the welded plates via a 3-D elastoplastic thermo-mechanical simulation. Two welding cases with two different parameters the feed rate and the rotation speed are analyzed. In the first part, we fixed the speed of advance and varied the speed of rotation (140 mm/min, 600, 1000, 1400 rpm) and in the second part fixed the speed of rotation and varied the speed of advance (600 rpm, 80, 100, 140 mm/min). The objective of this paper is to study the variation of transient temperature and distribution of Von Mises stress and evaluate the residual stress in a friction stir welded plate of AA 6061-T6. We have used the thermo-mechanical model developed by Zhu and Chao and implemented our program under the code ANSYS APDL. We see that the peak temperature obtained from simulation is approximately near the measured one. However, the peak temperature at the welded joints increased by increasing the rotation speed with the same tool profile and constant value of welding speed. The residual stresses are affected by the FSW processes, otherwise, by the welding temperature and mixing which have a relationship with the welding parameters. An increase in the welding speed apparently lead to an increase in the residual stress. The residual stresses found by this FE model have never exceeded the value of 54% of the elastic limit. We concluded that the model gives a good result in terms of stress. The results of the simulation are in good agreement with that of experimental results.