INFLUENCE OF NON-METALLIC INCLUSIONS ON THE THRESHOLD BEHAVIOR IN FATIGUE

The effect of inclusion content on (a) the endurance limit Se for crack initiation in a smooth specimen and (b) the threshold value ΔKth of the stress intensity factor for crack propagation has been examined in 0.8 wt.% carbon fully pearlitic steels. The data show that the inclusion content, morphology and orientation with respect to the specimen surface will influence the value of Se. This effect is attributed to the stress concentration produced by non-metallic inclusions and its contribution to fatigue crack initiation. ΔKth was found to be independent of the non-metallic inclusion content in pearlitic steels within the range of inclusion content from 0.097 to 0.318 area %. The results presented in this paper show the independent nature of Se and ΔKth. © 1979.