Correlation among energy based fatigue curves and fatigue design approaches

In this paper, with reference to the strain controlled fatigue characterization of AISI 304L stainless steel, the correlations between plain material fatigue curves based on different definitions of the strain energy densities, namely the elastic, plastic and elastoplastic strain energy densities evaluated under the cyclic stress-strain curve and the hysteretic plastic strain energy density (per cycle and total at fracture) are investigated. On this basis a diagram showing the link among the different energy-based fatigue curves is proposed and is applied to find the correlation between plain material strain energy density fatigue curves and some fatigue strength assessment methods for notched structural components, namely the one based on the experimental evaluation of the energy dissipated per cycle and the one based on the linear elastic FEM evaluation of the mean strain energy density in a structural volume.