A new low cycle fatigue criterion for isothermal and out-of-phase thermomechanical loading

A new multiaxial low cycle fatigue criterion based on a damage parameter is presented as an attempt to condition energy based approaches for the general common use in isothermal and thermomechanical out-of-phase loading. The damage parameter is based on the dissipated plastic strain energy per cycle, with a stress correction factor to account for mean and maximum stress influences, and a thermal term to account for elevated temperature damages. With such a formulation, the low temperature damaging regime (dislocations glide) can be separated from the high temperature one (diffusion processes). Oxidation and creep damages are accounted for in an implicit manner. The prediction capability of the present criterion is compared with that of other classical lifetime criteria using data from uniaxial isothermal and out-of-phase thermomechanical fatigue (TMF) tests performed on three cast iron families which are relevant for different internal combustion engine components. The result is higher prediction accuracy and a capability to estimate TMF lifetime by calibrating on isothermal fatigue tests only, leading to a great potential cost saving for future test programs given similar materials and loading conditions.