4.4 Hyperelasticity

This section details the syntax of hyperelastic material data input for rubber elements [Vol. Element Library]. An isotropic nonlinear elastic model, accounting for large strains and large displacements, is available. See §16.3 for background theory.

The material data to be specified define a strain-energy function W , strictly separated in a deviatoric part W_d [§4.4.1] and a hydrostatic part W_h [§4.4.2]. Young's modulus and Poisson's ratio are not necessary for rubber elements. Alternatively to the regular models for deviatoric and hydrostatic strain energy you can define the complete hyperelasticity model via a user-supplied subroutine [§4.4.3].