Fatigue Crack Growth of Peened Friction Stir-Welded 7075 Aluminum Alloy under Different Load Ratios

The effect of peening on the fatigue crack growth performance of friction stir-welded 7075 aluminum alloy was investigated. The fatigue crack growth rates were assessed for laser- and shot-peening conditions at stress ratios (R) of 0.1 and 0.7. The surface and through thickness residual stress distributions were characterized for the different regions in the weld. The results indicate a significant reduction in fatigue crack growth rates using laser peening compared to shot peening and the as-welded condition. The effect of the compressive stresses obtained through laser peening was deemed responsible for increasing the resistance to fatigue crack growth of the welds.