Identification of the material parameters of a viscous hyperelastic constitutive law from spherical indentation tests of rubber and validation by tensile tests

In this article, the material parameters of different rubber compounds are determined by an inverse method based on gradient-based numerical optimization, using experimental data from depth-sensing spherical indentation testing. The deformation behaviour of rubber is described by the Zener model. The indentation test is modeled by a finite strain finite element model, and the gradients necessary for the inverse method are determined by direct differentiation. Four different rubber compounds are analyzed, and the material parameters obtained from spherical indentation testing are used to model a uniaxial tensile test, for comparison with experimental data.