Coupled thermo-mechanical modelling of friction stir welding

Paper presented at the 2007 ASME Pressure Vessels and Piping Conference, 22-26 July, San Antonio, Texas USA. The significant development in welding technology for the last decade is the emergence of Friction Stir Welding (FSW). This paper investigates the thermo-mechanical phenomena involved in the FSW welded plates by Finite Element Analysis. The numerical models are fully thermo-mechanically coupled in that heat generated by material plastic deformation and temperature dependent mechanical material properties are taken into account. The whole FSW process is divided into three distinct stages: plunge, dwell and transverse. The transient temperature, stress and velocity of material particles around the tool are reported from the numerical models. It is found that temperature plays an important role in obtaining a sound weld, and only when a proper temperature field is established can the FSW process proceed to next stage. It is also found that it is not possible to fully simulate the FSW process using the ALE formulation without full remeshing during the travel stage of the process due to excessive element distortion