Effect of aging on engine mount performance

The purpose of this paper is to show how engine rubber mounts performance is affected by rubber aging. Rubber mounts, if well designed, provide efficient vibration isolation to structures. The choice of engine mount position, orientation and stiffness must be made through an extensive dynamic study of the vehicle in order to achieve acceptable performance. Many design methods are proposed in the literature. Torque roll axis decoupling, frequency avoidance and the focalisation method are some examples. All design methods take into account the dynamic properties of new mounts. However, it is well known that cyclic loading and high temperature lead to modifications of rubber molecular structure. As a result, engine mounts become stiffer with time. The purpose of this paper is to show how engine mounts performance is affected by rubber aging. A six degrees of freedom analytical model of the engine on its mounts is used to show the dynamic behaviour of mounting systems designed using different methods. The properties of aged rubber are evaluated using aged rubber data. The dynamic behaviour of each aged mounting system is compared to the inital designs. A conclusion on the robustness of the designs is made, from which a preferred design method is recommended.