Fatigue surface crack growth behavior in flat plate and out-of-plane gusset-welded joints under biaxial cyclic loads with different phases

Although many in-service welded built-up structures, which contain many welded joints as fatigue crack initiation sites, are subjected to many types of loading, their structural integrities are evaluated according to design codes based on theoretical and experimental investigations under uniaxial loading conditions. Additionally, most of these codes implement the S–N curves approach. This study highlights the biaxial cyclic loading with different phases. The fracture mechanics approach toward fatigue life evaluation can obtain the fatigue crack growth history. This paper confirms the applicability of the previously proposed numerical simulation method for obtaining the fatigue crack propagation histories of a cracked plate subjected to biaxial loads with a phase difference for each loading component. A fracture mechanic approach was used to establish the proposed method. The fatigue surface crack growth behavior of a flat plate and an out-of-plane gusset-welded joint under biaxial cyclic loadings with different phases was investigated by extending the applicability of the proposed method to a through-thickness crack. Comparisons between the measured crack evolution and the numerical simulation results were carried out to validate our fatigue crack growth simulation for flat plane and welded joints.