Mechanical design of a heterogeneous test for material parameters identification

The main goal of this work is to design virtually a heterogeneous test, with appropriate specimen shape and boundary conditions, which leads to an inhomogeneous strain field promoting the mechanical behavior characterization of thin metallic sheets under several strain paths and strain amplitudes. Finite element simulations were carried out with a virtual material, described by an anisotropic yield criterion (Yld2004-18p) associated to a mixed hardening law. The material parameters were derived from a large experimental database of quasi-homogeneous classical tests. A shape and boundary conditions optimization process was developed based on a quantitative indicator rating the strain field information and used as a cost function for guiding the test design. A heterogeneous test showing a butterfly shape was obtained, with strain states ranging from simple shear to plane strain tension. In addition, the designed heterogeneous test was used to determine the material parameters of the aforementioned constitutive model. The reliability of this identified material parameters set was then assessed and compared with the one coming from the experimental database composed by the quasi-homogeneous classical tests.