Fatigue stress concentration sensitivity and stress ratio effect of a 40CrNi2Si2MoVA steel

The axial fatigue tests at room temperature for smooth specimens with theoretical stress concentration factor, K-t=1 and notched specimens K-t=2, 3 and 5 were performed in a high-strength 40CrNi2Si2MoVA steel for different stress ratio, R, that is the ratio of minimum stress to maximum stress, of -1, 0.06 and 0.5, respectively. Fatigue strength/limit for 1x10(7) cycles were determined according to a stair-case method. The stress concentration sensitivity and mean stress sensitivity are characterized by q factor and M factor, respectively. Moreover, a new model for evaluate the mean stress effects of high-strength steels was proposed, which is different from Goodman relation and Gerber parabola.