A simple methodology to define conical tool geometry and welding parameters in friction stir welding

The friction stir welding is a solid state welding process which has been successfully applied for industrial parts. The process development has been supported by experimental and theoretical studies related to weld outcome, material flow and tool geometry. In this study, we propose a new methodology to define the geometry of a conical tool as well as welding parameters for the friction stir welding of thin plates of a given material. This is based on a concept that the tool geometry and process parameters must satisfy four heuristics: a thermal condition and rules relevant to volume, surface and material flow. This all should tend to ensure that the matter reaches an appropriate processing temperature and remains confined to the tool zone without any loss to the surroundings. A calculation algorithm that integrates a basic thermal model, tool geometry and process kinematics is proposed. The methodology and details of tool design are further discussed in relation with the definition of a process window. Experimental investigations on Al 2017-T4 alloys by using a shouldered unthreaded conical tool are presented in support of the model. The outcome of the model and experimental studies is further substantiated by using the published results.