Safe Service Life Design of 20CrMnTi Linkage Steel Based on Fatigue S-N Curve

Samples were cutting from a 20CrMnTi steel linkage which fractured early in fatigue form,and then rotating bar bending fatigue test was done to them using up-and-down method and group method to get the S-N curve with 0.1% failure probability and 95% confidence,and upon which the safe service stresses could be designed reasonably.The results show that according to the S-N curve with 0.1% failure probability and 95% confidence,this type of linkage should be service with alternating load not higher than 229 MPa in order to reach the life cycles of 2×106.