Effect of Stress Ratio and Evaluation of Crack Sizes on Very-High-Cycle-Fatigue Crack Propagation Life Prediction of Carburized Cr-Ni Steel

Carburized Cr-Ni steel is widely used in the manufacture of components many fields due to excellent performance, which service life has been a concern. In order investigate high-cycle-fatigue and very-high-cycle-fatigue properties carburized gear steel, axial loading fatigue tests were performed by QBG-100 with stress ratios −1, 0 0.3. The Generalized Pareto distribution was evaluate inclusion size steel. Based on ratio evaluated crack size, new prediction model for steels constructed. results show that S–N characteristics represent continuously descending tendency. long propagation threshold instability sizes FGA, fisheye surface smooth area (SSA) can be evaluated, respectively. addition, maximum interior are 17.50 μm 6.46 cumulative probability 99.9%. By validating established model, result acceptable according good consistency between predicted experimental life.