CFD modelling of ultra-high rotational speed micro friction stir welding

Abstract

Ultra-high rotational speed micro friction stir welding is the combination of micro friction stir welding (μFSW) and ultra-high rotational speed FSW to overcome the practical difficulties such as increased heat loss from the workpiece, forging force requirement and fixturing issues associated with μFSW by using ultra-high rotational speeds. This work deals with the CFD modelling of ultra-high rotational speed micro friction stir welding of AA1100 to investigate the heat generation, temperature distribution and material flow in the weld zone at ultra-high tool rotational speeds. The temperature-dependent material properties and coefficient of friction are used in this study. A partial sliding-sticking contact condition is assumed between the tool and workpiece, and the possibility of partial melting occurring at high rotational speed is incorporated using boundary conditions. The predicted temperature field agrees well with the experimentally measured temperature results. The thermo-mechanically affected zone (TMAZ) predicted in the numerical simulation is also comparable with the micrographic studies. It is observed that the contribution of plastic heat generation is more than that of frictional heat generation at high rotational speeds, and partial melting does not occur. Welding speed does not have a significant influence on the peak temperature at high rotational speeds. Micro friction stir welding can be successfully performed at ultra-high rotational speeds to overcome the disadvantages and practical difficulties associated with low rotational speeds.