Effect of clamping area and welding speed on the friction stir welding-induced residual stresses

Effects of clamping area and welding speed on the development of residual stress fields in aluminum plates joined by the friction stir welding process were investigated in this paper. Friction stir welding on two aluminum alloy 6061-T6 plates was simulated in a three-dimensional, two-step thermo-mechanical analysis using the finite element program ANSYS. In the simulation, effects of welding tool plunging force, formation of heat-affected zone, and clamping fixture release were considered. The finite element results revealed that the clamping area plays a significant role on the formation and magnitude of friction welding-induced residual stresses. The models with greater clamping areas showed a 40 % lower maximum tensile residual stress in comparison with models with small clamping areas. Furthermore, for models with small clamping area, the effect of speed on the magnitude of residual stress was negligible. For models with large clamping area, the magnitude of maximum tensile residual stress was increased up to about 50 % with an increase of welding speed.