Predicting the Fatigue Limit of Surface-Hardened Parts with Stress Concentrators

The possibility of predicting the fatigue limit of surface-hardened steel 20 with semicircular notches is considered: (1) on the basis of the residual stress at the surface of the cut; (2) on the basis of the integral mean residual stress over the thickness of the surface layer in the most hazardous cross section, which is equal to the critical depth for fatigue-crack propagation. The second approach proves more accurate. Experiments confirm that the critical depth for fatigue-crack propagation depends on the size of the most hazardous cross section.