Application of Reduced Clamping in Self-Reacting FSW of Al
Scott Rose, Brian Martinek, John Baumann, Sean Thuston
Prior efforts to understand the separation forces of self-reacting friction stir welds revealed that separation could be controlled through compensation of the path normal loads experienced during test trials. A fixture for a demonstration article using self-reacting FSW was produced with this compensation requirement in mind. This minimal fixture frame included fixed location points and clamps that were rated to a modest level above the recorded side load during development welds. Thermally complaint springs were attached to these clamps. After welding x-rays were taking of each weld to evaluate weld consolidation.
As is often the case with the scale up from initial experiments to larger scale productions, the application of these reduced clamping methods in practice highlighted the need to consider other aspects to the loaded beyond just the path normal forces. These included a review of the frame stiffness as the fixture size is increased for larger articles as well as the degree of allowed thermal compensation. Subsequent fixture modifications resulted in reduced weld separation and produced an improved joint quality, as verified by separation measurements and non-destructive evaluation.
A review of the effects of rotation and travel direction was also performed on the prior research fixture to verify the effects seen on the larger article.