| In this study, 2-D and 3-D models based on a commercial computational fluid dynamics (CFD) code (FLUENT) and suitable user defined viscosity law are used to capture many of the trends observed in FSW. The fully thermo-mechanically coupled 2 D CFD model can run in a few hours on a PC based system. The low computational cost for 2-D model enables rapid assessment of the effects of various material properties and the criticality of inclusion or exclusion of some property details.; The effects of varying material properties and process parameters, on the trends in x-axis forces and potential weld defect formation (via material flow pattern) are studied and compared with the experimental observations. It was found that the minimum x-force that occurs in the median RPM range is strongly influenced by the cutoff temperature in the viscosity law. The bifurcation of material flow in the weld path also occurs when the maximum temperature ahead of the pin surpasses the cutoff temperature.; Aluminum alloys AA2219, AA5083, AA6061, and AA7050 were welded using constant welding speed and linearly increased RPM. The grain sizes in the welds were measured and the applied torque and x-force during friction stir welding process were recorded. The correlations of the grain size, the applied torque and x-force were studied using simulation and the experimental methods. The 2D and 3D CFD model simulation results compare well with experimental measurements. Based on the 2D model results, the material's simulated thermo-mechanical history was also studied. The model predicts that the material in the weld region experiences a high temperature after the deformation is complete. This thermo-mechanical history indicates that metallurgical transformations may continue after the end of deformation and that the grain size in the weld cannot be adequately described using a Zener-Holloman parameter approach or by invoking the continuous dynamic recrystallization process. |
