Investigation of Mean Stress Effect for Equivalent Stress Methods and Critical Plane Approaches for High Cycle Fatigue Life Estimations

Zafer Engin and Demirkan Coker

Various critical plane methods were proposed and developed since Findley introduced the idea of using critical plane concept for estimation of high cycle fatigue life. However, still basic equivalent stress methods are used for industrial applications. Aim of this paper is to compare several equivalent stress and critical plane criteria regarding their performance in predicting fatigue life under in-phase and out-of-phase bending (or axial)-torsion loadings that are obtained from the literature. In the present study special attention is given to mean stress effect. To that end, we transform the multiaxial stress state into uniaxial fully reversed stress history by inclusion of well-known mean stress corrections such as Soderberg, Goodman etc. On the other hand, for critical plane methods, stress state is transformed into a damage parameter which is calculated for all material planes. Statistical analysis of estimations is made for comparison of methods.

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