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Material Flow around a Bobbin Tool for Friction Stir Welding

J. Hilgert, L. Hütsch, J. Dos Santos, and N. Huber
GKSS Forschungszentrum GmbH, Geesthacht, Schleswig-Holstein, Germany

This study presents an approach to model the material flow around a bobbin tool for Friction Stir Welding (FSW). In this CFD model the aluminum is treated as a highly viscous non Newtonian shear thinning liquid. The model is formulated in a 3D Eulerian frame. The temperature field and the desired torque acting on the tool are taken from a 3D thermal pseudo mechanical model implemented in COMSOL and Matlab that was presented at last years COMSOL Conference in Milano. The results of the CFD model provide the material flow field, the amount of sticking and slipping at the interface between tool and plates as well as the forces acting on the tool. Experiments on the FlexiStir experimental welding unit have been carried out to successfully validate the torque assumptions and the shear layer shape for welds of aluminum alloy AA2024-T3 4mm sheets.