An advanced post-necking analysis methodology for elasto-plastic material models identification

The tensile test is widely used for identifying the material plastic flow curve: this is a fundamental step in the design and in material behavior analysis. However, during these tests on ductile metals the necking phenomenon occurs, and the stress and strain states become triaxial and non-uniform. In the scientific literature several characterization methods have been proposed to properly address these aspects. The present work proposes an alternative strategy for identifying the plastic flow curve, focusing on temperature and strain-rate insensitive elasto-plastic materials. This is a hybrid methodology whereby a FE-based inverse method is combined with the 1D description of necking proposed by Audoly and Hutchinson. Indeed, the inverse method employs as target function the specimen profile, but to properly define it a relationship between the original and the deformed configuration of the tensile sample is required, and it is provided by this 1D model. The accuracy and the validity of the proposed strategy was verified on benchmark cases with ad-hoc experimental profiles obtained via numerical simulations. Finally, this method was applied to real case studies and the identified plastic flow curve was compared with the one obtained using a traditional FE-based inverse method having as target the force-stroke curve.