Analysis of loads, temperatures and welds morphology in FSW of polycarbonate

The influence of welding and tool rotation speeds on processing loads and temperature distribution developing is Friction Stir Welding of polycarbonate is investigated, experimentally. The development of critical conditions leading to macroscopic defects were correlated to the features of loads and temperature trends. Two macroscopic defects were identified on FSW welds. Under low welding speeds, the welds were characterized by circular rifts. These developed due to unsteady conditions and low contact pressure. High welding speeds involved heavier loads and temperature within the weld seam. This came with the formation of built-up edge (BUE) under the tool shoulder. The BUE induced a "milling action" on the weld path leading to significant thinning of the weld seam. The acquired signals (loads and temperature measurements) revealed the features of the surface morphology. This suggests the possibility to use such measurements to predict (and possibly to avoid) the onset of the aforementioned defects.