Multiaxial high-cycle fatigue failure of 30CrMnSiA steel with mean tension stress and mean shear stress

Experiments had been performed to investigate the effect of the mean tension stress and mean shear stress on the multiaxial fatigue failure of 30CrMnSiA steel. The crack growth path was observed under a metallographic microscope. The stage I cracks were always initiated on the MSSA planes and propagated approximately 20–100 μm for the different load conditions. The stage II crack propagated approximately 400–1000 μm along the MN plane for in-phase loading. The stage II crack initially propagated along the MN plane and quickly deviated from it for 90° out-of-phase loading. Crack initiation and early propagation (<500 μm) occupied more than 70% of the fatigue failure life. Both mean shear stress and mean tension stress reduced the fatigue life. In addition, deficiencies of the critical plane criteria based on the MSSA plane were discussed and more attention should be paid to the effect of mean shear stress.