Investigation of fatigue crack growth under in-phase loading as well as phase-shifted loading using cruciform specimens

The present study examines the effect of planar biaxial loadings on fatigue crack growth in an austenitic stainless steel and an aluminum alloy. Furthermore, phase-shifted loading with different phase shifts phi is considered. The tests were carried out on planar cruciform specimens with centered notches parallel to one loading axis or aligned with an angle of alpha = 45 degrees to both loading axes and a measurement area of 125 mm x 125 mm. The specimens were tested with a constant force amplitude and load ratios of R = 0.1 or R = 0.5 on a servo-hydraulic biaxial tension-compression system with two perpendicular loading axes. The change from in-phase to out-ofphase loading led to a mixed-mode situation with changing Mode I and Mode II portions during each cycle at the crack tip. This resulted in kinking or branching of the crack path. In addition, the crack tip coordinates of the individual tests for different load cycles N are attached as supplementary material.