Effect of notch and stress ratio on Very High Cycle Fatigue characteristics of the carburized 17CrNi high-strength steel and life prediction

Abstract

In order to investigate the notch effect on the structural characteristics of the carburized 17CrNi high-strength steel in the very high cycle fatigue (VHCF) loading, the axial tests with the stress ratio (R) of ‒1 were performed and the S-N characteristics were studied. The microscopic observation revealed that surface induced failure was the only failure mode. Further, the effect of the notch was investigated: Based on the small crack theory, the calculation of the fatigue notch factor (Kf) was performed and has shown that Kf is slightly less than the theoretical stress concentration factor (Kt). Then, Kf was used to study both the notch effect and stress ratio effect on fatigue life. Finally, the life prediction model associated with R and Kf was established and the calculation results are valid according to the good agreement with the experimental data.