Lifetime Model for Various Elastoplastic-Material Models

—Three material lifetime models are compared within the framework of the hypothesis of accumulation of residual strains. The models are based on the Ramberg–Osgood law, an alternative empirical law, and a so-called theoretical law constructed from the solutions of various differential equations in linear and nonlinear sections in a stress–strain curve. Postulating a linear section in a stress–strain curve is shown to automatically leads to the fact that the endurance limit is determined by the point of proportionality limit.