Effect of Tensile Mean Strain on Fatigue Behavior of Al-Li Alloy 2099

Abstract

In this study, the effect of tensile mean strain on the fatigue behavior of aluminum alloy 2099-T83 was experimentally examined for the first time. In order to elucidate the effect of tensile mean strain on fatigue lives, strain-control fatigue testing was conducted at three strain ratios (R = − 1, 0.1, 0.7). Experimental results show that the application of greater mean strains during cyclic deformation resulted in shorter fatigue lives, particularly at lower strain amplitudes. At these lower strain amplitudes, the mean stress response to deformation did not fully relax as it did when subjected to larger strain amplitudes, where the effect of mean strains on fatigue performance was negligible. The Morrow and Smith–Watson–Topper mean strain correction models were implemented using monotonic and fully reversed fatigue properties in order to account for the damage associated with the relaxed mean stresses. A new model is presented that incorporates a mean stress sensitivity material property to capture, within a scatter band of three, the effects of tensile mean strains on the fatigue behavior of AA2099.