Development of Trivex friction stir welding tool Part 1 – two-dimensional flow modelling and experimental validation

This paper describes the application of the computational fluid dynamics (CFD) code, FLUENT, to modelling the metal flow in friction stir welding (FSW). Through the use of a novel slip model, a two-dimensional pin profile was optimised to minimise the traversing force. Two versions of a tool based on the optimised profile were developed: the plain ‘Trivex’ and the threaded ‘MX-Trivex’. These were tested against one version of the ‘MX-Triflute’ tool that had comparable pin and shoulder diameters. Experiments showed that the traversing force was reduced by between 18 and 25% and the down force was reduced by approximately 12% when compared with the MX-Triflute tool. The different pin designs had little effect on the heat input and the tensile strengths of the welds were comparable. The development and validation of the full three-dimensional model for both the Trivex and Triflute tools is described in Part 2.