Dependence of fatigue strength on inclusion size for high-strength steels in very high cycle fatigue regime

The fatigue strengths of eighteen kinds of high-strength steel specimens with different inclusion sizes, ultimate tensile strength ranging from 1680 MPa to 2180 MPa, were investigated by using 20 kHz ultrasonic fatigue testing machine. The relation between fatigue strength and inclusion size was examined according to the experimental results. Based on the effect of hydrogen during formation of granular-bright-facet (GBF), a model to predict the fatigue strength of high-strength steels in very high cycle fatigue (VHCF) regime was developed. The predictions are in good agreement with the experimental results.