Subsurface fatigue crack initiation and propagation behavior of induction-hardened shafts under the effect of residual and applied bending stresses

The Society of Automotive Engineers Fatigue Design and Evaluation (SAEFDE) Committee has been conducting a long-term program aimed at the development of a predictive capability for fatigue Life of SAE 1045 induction-hardened shafts. As a part of a larger-scale investigation provided by the SAEFDE committee, this research provided an analytical model capable of predicting the total fatigue Life, both crack initiation and crack propagation of an induction-hardened shaft under applied bending stress. The analysis procedure incorporated the effects of residual stresses. Total stress intensity factors were calculated and superimposed using applied bending stress intensity factors and residual stress intensity factors along the subsurface elliptical crack front. Fatigue tests were conducted using SAE 1045 induction-hardened shafts to verify the analytical models of subsurface fatigue crack growth. The rural fatigue life calculations of subsurface failure showed a factor from 0.6 to 0.8 compared with the experimental results. The analytical model and experimental data confirmed that the majority of the total fatigue life is spent in the crack propagation phase.