Fatigue life estimation of an engine rubber mount

Fatigue life of an engine mount made of natural rubber was estimated, considering the effects of mean load. In order to develop an appropriate fatigue damage parameter of the rubber material, load-controlled fatigue tests were conducted using three-dimensional dumbbell specimens at different levels of mean load. It was shown that the maximum Green–Lagrange strain and the maximum strain energy density were proper damage parameters, taking the mean load effects into account. Nonlinear finite element analyses of the 3D dumbbell specimen and engine mount were performed using Ogden hyperelastic material model determined from the tensile, shear and biaxial tension tests of the natural rubber, and resulted in relationships between load and maximum Green–Lagrange strain for both the dumbbell specimen and engine mount. A fatigue life curve of the natural rubber represented by the maximum Green–Lagrange strain was determined from the finite element analysis and load-controlled fatigue test of the dumbbell specimen. Fatigue life estimation of the rubber engine mount was finally made by using the maximum Green–Lagrange strain of the engine mount and the fatigue life curve equation of the natural rubber material. Predicted fatigue lives of the rubber engine mounts agreed fairly well with the experimental fatigue lives within a factor of four.