Fatigue Life under Combined Bending and Torsion with the Mean Stress Value

摘要

The paper contains a comparison of fatigue lives of smooth and notched specimens subjected to combined cyclic bending and torsion for different values of mean stress, calculated and obtained from experiments. The calculated fatigue life was obtained with use of transformation of amplitudes of cycles with non-zero mean values for the equivalent cycles with a higher amplitude and the zero mean value. The authors applied the well known and widely used transformation relationships formulated by Goodman, Gerber, Marin, Morrow and Kliman. 10HNAP steel was tested. It has been shown that for a history with a mean stress value we obtain good agreement of the calculated fatigue life for smooth specimens when Morrow relationship is applied. The relationship formulated by Marin gives good results for notched specimens.