GENERALIZED S-N SURFACE EQUATIONS FOR MULTIAXIAL FATIGUE LIFE PREDICTION

摘要

In fatigue reliability-based design, it is much desired to have formulas with the relation of fatigue life, stress amplitude and mean stress of each stress component of the applied stresses. These formulas are called generalized S-N surface equations. This paper derives the generalized S-N surface equations for multiaxial fatigue life prediction from two ways. (1) Based on the von Mises theory to calculate the equivalent normal stress amplitude and the equivalent mean stress, then a generalized S-N surface equation of Goodman's type for uniaxial fatigue is applied. (2) Based on the Crossland multiaxial fatigue criterion with a new MCE (Minimum Circumscribed Ellipse) approach for evaluating the effective shear stress amplitude. The validity of the generalized S-N surface equations is shown by comparisons with experimental results collected from literature. For out-of-phase loading, the formulas of the second method give better results than the first one.