A time dependent equivalent stress function for proportional and non-proportional transient loaded and notched metallic components

The novel “Modified Mohr Mises” (MMM) Hypothesis allows the assessment of non-proportional stresses within a fully automated process, due to its invariant equivalent stress notation. Those non-proportional stresses are most common in complex structures of aircrafts, spacecrafts and vehicles for instance. The new MMM Hypothesis provides a physically reasonable sign determination derived directly from the effective stress components. Supporting effects through material and adjacent material areas and local geometries are considered in the theory as well. The use of a suitable tension shear strength ratio allows a consideration of anisotropic material behavior in the surface as well. The MMM Hypothesis and its predecessors were formulated to support the development of the fatigue strength assessment of the German FKM Guideline, in order to be able to utilize, among others, the Guideline material-related knowledge for non-proportional components with load-free and fluid-loaded, smooth and notched component surfaces.