In this study, the friction stir welding process is optimised to improve the fatigue strength of the joints of A6005-T5 alloy sheets. The welding speed, rotational speed and tilting angle of the tool tip are chosen as design variables. Fifteen friction stir welding experiments are performed according to the central composite design table. The regression model function is estimated using the response surface analysis method. Using the model function, sensitivity analysis is carried out and the effect of each design variable on the fatigue strength of the joint is discussed. The optimum values of design variables are determined using the sequential quadratic programming algorithm.
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