Effects of microstructure on very-high-cycle fatigue crack initiation and life scatter for a high strength steel

摘要

A type of high strength steel was tempered at 150℃,180℃,and 300℃ to form three groups of specimens,and rotating bending fatigue tests were performed to investigate the effects of microstructure on the behavior of very-high-cycle fatigue (VHCF) crack initiation.With the increase of tempering temperature,S-N curves for the three specimen groups show a tendency of increasing life scatter and the threshold value of VHCF crack initiation ΔKFGA decreases.For 150℃ tempered specimens,grain boundary initiation is dominant for fatigue crack initiation while inclusion initiation is dominant for the other two groups.Effects of inclusion and retained austenite on fatigue crack initiation are discussed,and reliability analysis based on Tanaka-Mura model is carried out to characterize VHCF life scatter.