Fatigue Behaviors of High-Strength Carburized Steel under Different Stress Ratios: Evaluation of Competitive Failure and Prediction of Very Long Life

Abstract

As a metal material with superior mechanical properties, high-strength carburized steel is of great value for the production and manufacture of components in various fields. In this work, based on axial loading tests at stress ratios of −1, 0, and 0.3, the fatigue behaviors of high-strength carburized steels from high cycle to very high cycle are systematically investigated. For defect-fine granular area (FGA)-fisheye induced failure exhibiting long fatigue life, it is verified that the transition sizes between small and long cracks can be approximately equivalent to FGA size. Combined with extreme value estimation, a new mathematical model based on Weibull distribution was proposed to describe the competition among different failure modes. The results show that the probability of interior failure will decrease significantly with the increase of the maximum surface defect size under the condition that the maximum stress exceeds about 900 MPa. Additionally, larger surface defects are more beneficial to the occurrence of surface failure. Finally, combined with the stress correction factor proposed for optimizing the data with large dispersion, the fatigue life is predicted based on the crack initiation and propagation behavior, and the prediction results are in good agreement with the experimental results.