Characterization of Fatigue Crack Propagation Under Complex Biaxial Loading

Metallic aerospace components are subject to a variety of uniaxial and multiaxial loading conditions and therefore, characterizing and predicting the fatigue crack growth is of paramount importance to the aerospace industry. The fatigue behavior of metallic materials has been researched over the years and well understood under uniaxial loading conditions. However, aerospace structures are often subject to multiaxial loading and there are a very few studies reported on this topic. In this paper, extensive in-plane biaxial tension-tension fatigue tests were performed on an Al7075-T651 cruciform specimen under varying load conditions such as in-phase, out-of-phase and miniTWIST loading. The fatigue life and crack growth rate were evaluated and fractography was performed to understand the microscale crack initiation and growth under these complex loading conditions.