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

A detailed nonlinear analysis of hydraulic mounts with flexible chambers, e mployed in various automotive applications, is performed to investigate the ir 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 wit h commonly used long orifice on the shock and vibration isolation performan ce 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 orif ice under shocks of varying severity and high amplitude vibration excitatio ns. The results show that inclusion of oscillation flow effects yields lowe r dynamic stiffness and loss angle. It is also concluded that addition of a short orifice within the mount offers considerable potential to enhance th e shock and vibration isolation performance.