Analysis of the effect of out-of-phase biaxial fatigue loads on crack paths in cruciform specimens using XFEM

In the present research work, a numerical crack growth analysis using linear elastic fracture mechanics is carried out paying attention to the crack paths that grow in the central part of cruciform specimens under biaxial fatigue loads. The crack propagation in this type of specimens has been studied using the extended finite element method (XFEM). The objective is to analyse the effect of different phase angles under biaxial fatigue loads and to assess the different orientation criteria for nonproportional loading, benefiting from the advantages of XFEM. The crack path and the stress intensity factor range of a crack either aligned or inclined to the load directions have been investigated using different crack orientation criteria. Symmetrical branching is predicted for an initial crack inclined at 45 degrees with phase angle of loading equal to 90 degrees and 180 degrees. Numerical results are in good agreement with the experimental observations found in the literature, although the study reveals important differences in the crack path predictions depending on the orientation criteria.