Residual stress effects on crack growth in nugget of Al-Li alloy 2195-T8 friction stir welded joints

In this work, Compact-Tension (C(T)) specimens with transverse welds in the sample centre were designed. The residual stress distributions were measured parallel and perpendicular to the weld nugget. Fatigue crack growth (FCG) rates were measured in the lab air. It is shown that compressive residual stresses around notch have significant effect on FCG rates and the effect deceases with crack growing. FCG rate is lower in the nugget than in parent material. Effects of residual stress were studied with crack growing. The lower crack growth rate in nugget is believed to be linked in part to compressive residual stress, but also in part to a microstructure effect present when crack grows in the recrystallized nugget.