ABSTRACT
Efficiency requirements concerning rubber material modelling and characterisation methods are evolving because of high calculation efforts due to the complex behaviour of industrial rubber materials, large elastic as well as inelastic strains and increasing precision requirements for industrial components.
Two main contributions to the improvement of efficiency are presented in this paper: A new specimen setup for combined high precision tension-compression measurements with an extended strain range from a compression strain of −45% up to a tension strain of 400% and an approach for a new rheological element with time-rescaling invariance. This means a stress response invariance under uniform time-rescaling of the strain history. The element consists of two coupled differential equations. It is qualitatively compared to a generalized Maxwell model with constant loss modulus.
Moreover, a new, interesting and efficient approach for modelling complex inelastic material behaviour at large strains based on rheological models is presented. The basic kinematic assumption is the additive decomposition of the deformation rate. The framework is implemented in Abaqus via the user interface UMAT using an objective time stepping scheme. The approach is not at all limited to polymers.
