Fatigue crack deflection in cruciform specimens subjected to biaxial loading conditions

Crack deflection is studied for the aluminum alloys AA2024-T351 and AA5028-H116 under biaxial fatigue loading. With cruciform specimens that have a testing area of about 420 × 420 mm2 a fatigue crack was subjected to nominal biaxiality ratios between 1.0 and 3.0. Consequently, the crack is subjected to different magnitudes of T-stress. Finite element simulations of the growing crack revealed that the crack path is not significantly influenced by the T-stress but the T-stress predicts whether the crack path remains stable. If at least two crack paths are basically possible the crack will kink for positive T-stresses and remain stable for negative T-stresses. Furthermore, small spikes with strain concentrations along the crack path are identified with digital image correlation which might cause crack deflection in this case.