A MATERIAL MODEL FOR RUBBER-LIKE POLYMERS EXHIBITING PLASTIC-DEFORMATION - COMPUTATIONAL ASPECTS AND A COMPARISON WITH EXPERIMENTAL RESULTS

A finite element formulation is derived, which accounts for materials exhibiting plastic flow after large elastic deformation. Such material behaviour can be observed, for example, in certain kinds of rubber us eful in practical situations due to their high tensile strength and re sistance to aging. For these materials, then, both the elastic and pla stic behaviour must be described by a non-linear material model. Becau se of this, the return mapping algorithm used in this work requires th e solution of several non-linear equations in every Gauss point, which is carried out here via Newton iteration. The fitting of the material model to experimental results demonstrates the necessity of incoporat ing finite elasticity into the material model in order to successfully account for the observed material behaviour. The conseqence of using an oversimplified elastic material model is demonstrated by means of e xamples.