Effects of alignment discrepancies on the weld quality in friction stir welding

Abstract

Friction stir welding is a modern welding technology with which the joining partners are welded in the solid state. The technology is often employed in the aerospace industry due to the excellent mechanical properties of the weld. Process disturbances can cause irregularities in the weld quality. It is still a challenge to avoid part fit-up deviations as a result of part misalignments and tolerances. Several publications have investigated the effect of alignment discrepancies on the weld quality, for example, by introducing a gap between parts, a tool offset, or linearly misaligned sheets. Depending on the application, the effects of simultaneously occurring alignment discrepancies on the weld quality could be critical. In this work, three alignment discrepancies were investigated (gap, linearly misaligned sheets, tool offset). The weld quality was determined using tensile tests. Process data such as the process forces and the spindle torque were also measured during the welding experiments. The results showed that each of the alignment discrepancies had a negative impact on the weld quality. The simultaneous occurrence resulted in an even lower weld quality. Some alignment discrepancies can probably be detected in the future using process data (e.g., the lateral force).