Influence of critical plane definition on fatigue lifetime estimation under variable amplitude nonproportional multiaxial loading.

Abstract

In real operation, most of load bearing parts are commonly loaded with multiaxial variable amplitude loading. Fatigue lifetime estimation of such a component consists of multiple tasks. One of the most important problem to solve is how to handle multiaxiality of loading signal. Nowadays, the most commonly used way is use of multiaxial fatigue criterion based on critical plane theory. These criterions are based on assumption that fatigue lifetime of a component is determined by combination of shear and normal stresses (strains) in particular plane (critical plane). The definition of such a plane varies depending on different used criterions. While fatigue lifetime of component loaded with proportional loading signal can be estimated based on damage accumulated in critical plane, during the fatigue lifetime estimation under variable amplitude nonproportional loading the damage in noncritical plane has to be considered as well. This, however, leads to inaccuracy of the final results as multiaxial criterions often incorrectly calculate damage in noncritical plane. The aim of this paper is to discuss the influence of critical plane definition on fatigue lifetime estimation under variable amplitude nonproportional multiaxial loading. The results from fatigue lifetime estimations of component loaded by modeled signal using multiple different multiaxial criterions (with different critical plane definition) are presented and critically discussed.