R. Avila, J. C. McClure, UTEP, El Paso, TX; A. C. Nunes, NASA-MSFC, Huntsville, AL

Summary: Plunge Force and Torque are calculated using straightforward models of material flow during the plunge phase of Friction Stir Welding. Torque is modeled by a disk of rotating recrystallized material below the pin tool and plunge force is the force needed to force this disk outward and upward around the pin. The models are compared with experiment with good agreement.