Thermal Control of the Friction Stir Welding Process
Tom J. Stockman, J.A. Schneider
Mechanical Engineering Department
Mississippi State University
FSWing is a solid state joining process in which shoulder driven frictional and pin driven deformational heating combine to heat the metal to a plasticized state. The movement of the rotating tool then stirs the plasticized metal together to produce a weld. Thus the metal temperature is not directly controlled resulting in variations which may prove detrimental to the properties, especially in age hardenable alloys. As the process is theorized to be dominated by a high shear strain at instantaneously high shear strain rates, attempts to model the heat generation are not straight forward. By implementing a non-rotating shoulder, the heat of deformation is input as the temperature of the moving heat source. The shear strain rate and travel combine to produce the temperature at the source based on dwell times. Similar to the Rosenthal approach for fusion welding, this temperature is then translated down the weld seam to generate a global temperature. To maintain constant temperature, an induction coil can be used to preheat the material. Thus as the temperature within the panel is affected by constraints such as workpiece geometry and backing anvil, the coil heating contribution can be increased or decreased.