On the Influence of Mean Shear Stress on Multiaxial High Cycle Fatigue of Metallic Materials

Abstract

A study has been made of the influence of a superimposed mean shear stress on the capability of some multiaxial high cycle fatigue criteria to predicting fatigue behavior of 42CrMo4 and 34Cr4 alloy steels. Five selected critical plane-based criteria, namely Matake (M), Susmel & Lazzarin (S&L), Findley (F), Carpinteri & Spagnoli (C&S) and Liu & Mahadevan (L&M), were applied to a number of published experimental fatigue resistance limit tests, involving synchronous sinusoidal in-phase and out-of-phase bending and torsion. Applying to the same loading conditions a mesoscopic scale-based criterion proposed by Papadopoulos (P), one could verify that predictive capability of such an approach is almost invariably superior to those associated with the M, S&L, F, C&S and L&M models. As the Papadopoulos criterion is independent of mean shear stress, it seems appropriate to conclude that the inclusion of such a stress as loading parameter in the critical plane-based models does, in fact, exert a negative influence on their predictive capability. Finally, it is worth mentioning that, except for the Matake, S&L and L&M criteria, the other critical plane-based criteria exhibit a dependence of the fatigue resistance in pure torsion with respect to a superimposed mean shear stress, in disagreement with well-established experimental observations.

Elliptical Curve Method for Fatigue Life Prediction of Structural Steels Under Multiaxial Loadings

“…18, where the admissible stress amplitude 𝜎 𝑎 (for a given fatigue-life) linearly decreases with the increase of the mean stress 𝜎 𝑚 . It is important to point out that such behaviour is only valid for the case of alternating axial or bending with static normal stress, as well as for the case of alternating torsion with static tension [20], [23]. It is well-established that a superimposed static torsion does not influence the fatigue resistance limit provided that the elastic regime is not exceeded.…”