The mechanical behaviour of rubber under hydrostatic compression and the effect on the results of finite element analyses

Using finite element tools for the dimensioning of rubber components is state of the art. When conducting finite element simulations, a split of the strain energy function, which results in stresses, into a deviatoric and a volumetric part is made. The mechanical behaviour of reinforced natural rubber under hydrostatic pressure is determined to prove the validity of this assumption. Furthermore, a nearly incompressible material behaviour is assumed in simulations of rubber, which may cause an insufficient outcome quality especially for rubber components that are exposed to hydrostatic pressure like highly confined bushings. In this paper, a method is presented to determine the compressibility, or its reciprocal the bulk modulus of rubber. The effect of the bulk modulus of a natural rubber on the simulation results of a bearing is pointed out. The obtained results are compared to test data to show the significance of the value of the bulk modulus for achieving a satisfactory outcome quality. Therefore, reliable information about the in-use behaviour of rubber components is obtained to reduce the costs and the effort in the dimensioning process.