On the critical inclusion size of high strength steels under ultra-high cycle fatigue

In this paper, the critical inclusion size (CIS) of high strength steels with given matrix hardness or tensile strength and the surface roughness under ultra-high cycle fatigue is estimated mainly on the basis of Murakami's theory, i.e., the inclusion effective projected area model. The results show that the CIS decreases with increasing Vickers hardness (or tensile strength) and/or decreasing surface roughness of specimen. The estimated CISs are proved to be reasonable compared with the experimental data.