A technique to estimate the local multiaxial elastic–plastic behavior from a purely elastic solution

In most fatigue applications, the nominal structural behavior is dominated by elastic deformation, but the fatigue lifetime is significantly influenced by plasticity around stress concentrations and flaws. Although the elastic–plastic behavior can be modeled with finite element analysis (FEA), the computational expense may be prohibitive, especially for variable amplitude loading with multiaxial stress states. To overcome this complexity, a local elastic–plastic estimate is explored that utilizes the purely elastic solution. The method is conceptually similar to previous work, but is adapted to be consistent for variable amplitude multiaxial cyclic loading histories. This approach combines a magnitude criterion such as Nueber’s rule, the Masing character of the pseudo-material method, and has the generality to adopt any appropriate multiaxial plasticity model. The assumptions of the current approximation are developed in a general manner, with the potential to adjust the constraint (i.e. direction alignment), magnitude, and the plasticity character as necessary.