The target when using polymers for mechanically loaded components is to reach a weight reduction while the reliability and the product life are constant or improved. A safe estimate of the component behaviour under elevated strain levels will be reached by using an adapted potential-body. This description of the material behaviour incorporates the viscoelastic effects and the non-linear stress-strain dependence, i.e. the deformation law includes the time dependence. Because of their molecular structure polymers are compressible. Therefore the mechanical properties depend on the hydrostatic components of the stress tensor. From the lower stiffness of polymers compared to metals follows that small loads may lead to large strains. Starting on a fundamental concept the target of the presented work is to develop simple calculation methods that use the material data of the CAMPUS database.