Experiments and simulation have been carried out to study the effect of variation in welding conditions on process temperature during Friction Stir Spot Welding (FSSW).  Spot Welds were made on automotive grade aluminum alloy (A5083), 1.2mm thick.  The FSSW tool had a concave shoulder with 10mm diameter and a cylindrical pin (threaded) of 4mm diameter. Spot welds were made for a combination of 3 different tool rotation speed - 1500, 2250 & 3000 RPM and 2 different pin lengths - 1.26mm & 1.84mm.  A dwell time of 2 seconds was used for all welds. An Infrared camera was used to capture the surface temperature profile of the workpiece and the tool at several pre-determined locations.  Results show that the peak surface temperature increases by less than 10% from 1500 to 3000 RPM (at constant plunge depth) and insignificanlty when the pin lenght is changed from 1.24mm to 1.64mm (at constant RPM constant). Furthermore, it was also observed that the peak surface temperature was almost constant when the dwell time was increased beyond 5 seconds indicating slip condition between the tool and the material.
A CFD model was concurrently developed to predict the temperature profile on the surface of the workpiece. Experimental data helped to fine tune the model, especially to determine the appropriate boundary conditions. The simulation results can be extrapolated to estimate the temperature in the stir zone. Furthermore, this model can be used to visualize the effect of process conditions on material flow.