Fatigue crack growth behavior of friction stir welded A6063 under non-stationary variable amplitude loading

Abstract

Multiple peak overloading fatigue tests and Hi-Lo two-step loading fatigue tests were carried out to investigate the fatigue crack propagation behavior of friction stir welded A6063 aluminum alloy under non-stationary variable amplitude loading. Crack length was measured using the unloading elastic compliance method with the back strain gauge. It was found that in the case of multiple peak overloading fatigue test, the crack growth rate decelerated after overloading and then recovered to the steady state as crack propagated. In addition, it was found that the stir zone (SZ) is more affected by the overloading than the base metal (BM). Also, in the case of Hi-Lo two-step loading fatigue test, the crack growth rate decelerated after load fluctuation. In addition, when the mean stress intensity factor after load fluctuation is high, the smaller the deceleration of crack growth rate is low.