An original simplified method based on the use of an adjustable localization operator for low-cycle fatigue life predictions in the case of confined plasticity

This study aims to propose a methodology to rapidly obtain low-cycle fatigue life predictions. The main idea is to use a recently developed simplified method to estimate the stabilized stress-strain curve in confined plasticity in order to apply a fatigue criterion. This original simplified method is based on the use of an adjustable scale transition rule which has been demonstrated to be more robust to multiaxial loadings than classic plasticity correction rules. Different procedures are used to calibrate the localization operator and are compared to each other. The whole method is validated on a double notched specimen subjected either to compressive or tensile repeated loading. Kinematics and isotropic hardenings with threshold are used to model the partial mean stress relaxation that is observed experimentally. A modification of the Morrow fatigue criterion is proposed to enhance the prediction of the influence of the load ratio, represented by the local stabilized mean stress. The full design chain validation on notched specimens has shown a constant conservatism on the fatigue life predictions whatever the nominal load ratio and level. The results obtained with the simplified method are very similar to those obtained with finite elements.