Fatigue analysis of 7075-T6 aluminum alloy under high compressive residual stresses by considering the non-propagating crack region

Abstract

This article is a numerical investigation to determine the fatigue life of cold expanded fastener holes in 7075-T6 aluminum alloy. To estimate the numerical fatigue life, a combination of initiation and propagation lives was used. Three multiaxial fatigue criteria were employed to estimate the initiation life, while the AFGROW software was employed to predict the propagation life. The current research encountered the difficulty of high compressive residual stress at the edge of the cold expanded hole which hinders the crack growth. This overload zone near the hole edge is called the non-propagating crack region. Three models were considered to simulate the effect of the non-propagating crack region. Each model tried to provide the ability of the crack growth in this area by modifying factors such as residual stress and stress intensity factors. The S–N diagrams show longer lives for the cold expanded specimens. Moreover, to ensure the accuracy of the numerical results, they were compared with the experimental data in which the numerical results were in good agreement with the experimental data.