The effect of holes quality on fatigue life of open hole

In this paper, a series of study were conducted on the effect of hole quality on the fatigue life of open holes in 2A12-T4 aircraft quality aluminum alloy. Four metrics that can define holes quality are analyzed. They are roughness, verticality, cylindricity and roundness. Firstly, open holes with different roughness were fatigue tested under constant amplitude remote tensile load and post-failure investigations were performed by scanning electron microscope. Further, the effects of another three metrics on the stress distributions around the holes have been studied by the finite element method (FEM). The fatigue lives are determined based on the stress distributions by the method of nominal stress approach. The results show that the fatigue lives of open holes are dependent on the holes quality. For these four metrics, the fatigue lives decrease with the increasing of the values of the tolerance of these metrics. At last, empirical equations that relate these four metrics to fatigue lives were established by linear regression method.