Investigation of Residual Stress and Temperature Distribution in Friction Stir Spot Welding Process

Investigation of Residual Stress and Temperature Distribution in Friction Stir Spot Welding Process

In the present study, residual stress and transient temperature distributions during Friction Stir Spot Welding (FSSW) process of aluminum 7075-T6 alloy lap-shear joints have been studied, experimentally and numerically. The effects of tool rotation speed, indentation traverse speed, and plunge depth parameters on the temperature and residual stress distributions have been taken into consideration. The welds were made by a rotating tool with a diameter of 16 mm shoulder and a diameter of 6 mm probe pin. The values of residual stresses near the spots have been measured by Ultrasonic method using Echograph Model 1090 Digital UT Instrument, and the transient temperature distribution in the nugget edges has been measured by using a thermocouple. Experimental data have been compared with those obtained from the Finite Element (FE) simulation of the friction welding process using ABAQUS software. The strain-hardening behavior of aluminum alloy has been simulated with the Johnson-Cook plasticity model and its mechanical properties have been considered to be varied with temperature. Among the welding process parameters, indentation traverse speed showed the major impact on the residual stress values near the edges of nuggets so that, with reducing the indentation traverse speed, the values of tensile residual stresses decrease. In general, the experimental data show good consistency with the FE results.