Fatigue Crack Growth Behavior in Al-7075 Under In-Plane Biaxial Loading with Mixed-Mode Overloads

Abstract

Fatigue crack behavior in cruciform specimens of Al 7075-T6 under in-plane biaxial loading with mix-mode overloads is investigated. Tests were performed to characterize the fatigue behavior at four different levels of mode-mixity, and for each value of mode-mixity, overloads were applied at three different crack lengths as crack propagated under biaxial tensile loading. A significant change in the fatigue life and the crack growth behavior of the specimen was observed with change in mode-mixity of the applied overload. Although there was an increase in fatigue life for all the cases of mix-mode overloads, the maximum increase was observed for the pure shear overload and the minimum increase was observed for tensile dominant overload. When the shear component in the mix-mode overload was comparable but higher than the tensile component, an increase in mode-mixity value did not always show the increase in the fatigue life of the specimen, which indicates that the increase in fatigue life is not only governed by the combined effect of shear and tensile component of loading but also it is impacted differently by shear and tensile loading.