Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.
From application view point simple looking process of Friction Stir Spot Welding (FSSW) works on a complex thermo-mechanical mechanism. The strong inter-dependency of parameters responsible for heat generation and material flow like friction co-efficient, vertical force, rotational speed, tool geometry & dimensions, shear yield strength, conductivity and heat capacity etc. makes it a challenge to investigate the mechanism for FSSW process. At the start of the process, rigid solid behavior of work piece dominates. As the process proceeds, the rise in temperature due to frictional and deformation heat inputs, softens the material and it is assumed that the material transfer under the tool behaves like that of a fluid. In this part of on going research for FSW at IWS, a thermo-fluid coupled, three dimensional and transient model for quasi–steady state condition during FSSW process, is developed. The effects of different process parameters like tool geometries, rotational speed and dwell time on material flow patterns are studied experimentally and modeled, using general purpose FE software package MSC Marc®. The predicted results of the Finite Element study in terms of fluid velocity profile, nugget size and shape are compared with experimental observations carried out at IWS laboratories of TU Graz.