Nonlinear analysis of automotive hydraulic mounts for isolation of vibration and shock

A detailed nonlinear analysis of hydraulic mounts with flexible chambers, employed in various automotive applications, is performed to investigate their shock and vibration isolation characteristics. The analytical model of a mount with long orifice is initially developed incorporating the reported measured compliance properties of the chambers and oscillation flows within a long orifice. The influence of 'oscillation flow effects' associated with commonly used long orifice on the shock and vibration isolation performance is investigated. In view of the performance limitations under shocks and high amplitude vibration, a concept of hydraulic mount with short and long orifice is proposed. The results of the study are discussed to demonstrate the influence of oscillation flow effects and flows through the short orifice under shocks of varying severity and high amplitude vibration excitations. The results show that inclusion of oscillation flow effects yields lower dynamic stiffness and loss angle. It is also concluded that addition of a short orifice within the mount offers considerable potential to enhance the shock and vibration isolation performance.