Abstract
The methodology proposed in this work uses the local measured strain rate history as the applied “load” to the finite element (FE) “material point”. Next, with this strain rate history, two objective functions related to the true stress-strain and volumetric strain response could be minimized to identify some of the material parameters of the constitutive model. The whole identification process, of the 9 material parameters required, is described in detail. In addition, a short description of the hyperelastic-viscoplastic constitutive model used is given with an experimental program including mainly uniaxial tensile tests at different strain rates. The thermoplastic material investigated here is a mineral and rubber modified polypropylene (PP) compound. The main experimental data uses 3D digital image correlation (DIC) to determine full-field displacements and deduce true stress-strain, volume dilatation and local strain rates curves during deformation.