Fatigue assessment of mechanical components under complex multiaxial loading

Abstract

Abstract This paper addresses an integrated FEM based approach for crack initiation life assessment of components under complex multiaxial loading. Generally, there are many sources of error in the computational fatigue damage assessments, including uncertainties in analysing complex service environments, complex geometries, and lack of usable material information, etc. This paper is focused in the methodology for handling the effect of non-proportional multiaxial loading, and in improvements in computational algorithms for reducing the computation time for fatigue assessments. Since the effective shear stress amplitude is an important parameter for crack initiation life prediction, the recent approaches on evaluating the effective shear stress amplitude under comlex loading paths are studied and compared by examples. The MCE approach developed on the basis of the MCC approach is described in detail, and it is shown that this approach can be easily implemented as a post-processing step within a commercial FEM code such as ANSYS. Fatigue assessments of two application examples are shown, using the computational procedure developed in this research. The predicted fatigue damage contours are compared for proportional and non-proportional loading cases, it is concluded that the fatigue critical zone and fatigue damage indicator vary with the combined conditions of multiaxial fatigue loading. Advanced multiaxial fatigue approaches must be applied for fatigue assessments of components/structures under complex multiaxial loading conditions, to avoid unsafe design obtained from the conventional approaches based on the static criteria.