This paper represents the simulation of vibrational behaviour of engine on nonlinear hydraulic mounts. Inertia track and decoupler are included in the model of hydraulic engine mounts and nonlinear factors such as inertia and decoupler resistances in the turbulent region are considered. In order to investigate the responses of the engine under engine and road excitations, engine is located on the 7 DOF vehicle model through its three hydraulic mounts. Primarily, the nonlinear properties of hydraulic mount are identified and a lumped parameter mathematical model of the mount is developed. After that, a thirteen degree of freedom full vehicle model including six degree of freedom for translations and rotations of engine, three degree of freedom in bounce, pitch and roll for sprung mass and one degree of freedom in vertical displacement for each four unsprung masses are developed. The 6 degree of freedom four cylinders V-shaped engine under inertia, balancing masses and mounting reaction forces and torques is considered. In deriving the governing equations of motion of sprung mass, the force exerted by the suspension system on the sprung mass and also the reaction forces from engine mounts are considered. Simulation results can be used to predict the dynamic responses of the system under engine and road excitations in the time and frequency domains. By solving the time domain nonlinear equations of motion of full vehicle model, translational and rotational motions of sprung mass and engine's body are obtained for different engine speeds and base excitations. Transmitted base forces are also determined for each loading condition. Using FFT, the response of the system in the frequency domain is studied. In addition, in order to investigate the efficiency of hydraulic mounts, the obtained results are compared to the corresponding results of engine on rubber mounts. The results show that considerable improvement in vibration and isolation of the engine and the body can be achieved in low frequency region. However, for high frequency region, behaviour of the engine on the hydraulic mounts is the same as on the rubber mounts.
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