Non-linear models for assessing the fatigue crack behaviour under cyclic biaxial loading in a cruciform specimen

This work addresses FEM-based numerical simulations of fatigue crack propagation in a cruciform specimen under biaxial loading and small scale yielding (SSY) conditions. Three non-linear models are used as fatigue crack propagation laws. The cruciform specimens are made of aluminium alloy D16T and modelled with non-linear material properties. In the experimental tests, starting from a surface flow mechanically created in the centre of the cruciform specimen, biaxial loading conditions are applied to create various pre-cracked configurations that correspond to different values of initial crack aspect ratios. In the numerical simulations, the material behaviour is modelled with a low hardening bilinear law. Each simulation is carried out with one of the established non-linear laws. At the end of the fatigue crack propagation simulations, several crack aspect ratios are obtained. Finally, these aspect ratios are compared with the corresponding experimental tests available in the literature.