Identification of plastic constitutive parameters at large deformations from three dimensional displacement elds

Abstract

The aim of this paper is to provide a general procedure to extract the constitutive parameters of a plasticity model starting from displacement measurements and using the Virtual Fields Method. This is a classical inverse problem which has been already investigated in the literature, however several new features are developed here. First of all the procedure applies to a general three-dimensional displacement eld which leads to large plastic deformations, no assumptions are made such as plane stress or plane strain although only pressure-independent plasticity is considered. Moreover the equilibrium equation is written in terms of the deviatoric stress tensor that can be directly computed from the strain eld without iterations. Thanks to this, the identi cation routine is much faster compared to other inverse methods such as nite element updating. The proposed method can be a valid tool to study complex phenomena which involve severe plastic deformation and where the state of stress is completely triaxial, e.g. strain localization or necking occurrence. The procedure has been validated using a three dimensional displacement eld obtained from a simulated experiment. The main potentialities as well as a rst sensitivity study on the inuence of measurement errors are illustrated.