Multi response optimization of friction stir welding in air and water by analytic hierarchy process and VIKOR method

Friction stir welding of Titanium sheets is carried out under air and water environment and the tensile properties of the joints made are measured. The tool rotational speed and tool traversing speed which significantly influence the tensile properties of the welded joints are considered as input process parameters. This work deals with the application of Analytic hierarchy process to calculate the weights of the relative importance of the output responses using the pairwise comparison of responses and checked for the consistency and acceptability of the assumed comparison. Also, the VIKOR optimization technique, a multi-response multi criterion method, is used for determining the optimum process parameters. From the VIKOR optimization method, it is observed that the higher tool rotational speed and lower tool traversing speed are the optimum process parameters in both conventional and under water FSW. The results from the experimental measurements and the study of microstructure supports the results obtained from VIKOR optimization method.