Temperature control in friction stir welding

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Friction stir welding (FSW) is a solid state joining process producing high weld quality, since the temperature of the material remains below its solidus. Due to this characteristic and the good repeatability FSW has quickly spread in industrial application.The temperature in the weld zone cannot be directly influenced, but results from the chosen process parameters, the tool geometry and other boundary conditions. Yet, the relationship between those independent variables and the weld temperature has been insufficiently in-vestigated. Especially in complex weld tasks changing thermal boundary conditions can affect the weld zone temperature with negative impact on the mechanical joint properties. Thus, controlling the heat input is essential to ensure high weld quality. The aims of the requested research project are to explore the theoretical background and to implement and validate a prototypic control system. Concluding, the main issues can be summarized as: development of a method to determine the weld zone temperature approximately in real-time; development of the process principles regarding the temperature profile in the weld zone; determination of relevant process parameters, which mainly affect the weld zone temperature; implementation of a system for temperature control and demonstration of its functionality in characteristic applications.