Modal Analysis of Passive Engine Mount Assembly using Finite Element Analysis

Abstract

Engine mounts play a vital role in reduction of noise and vibration. For an internal combustion engine, there exist two basic dynamic disturbances: a) the firing pulse due to the combustion of fuel in the cylinder and b) the inertia force and torque caused by the rotating and reciprocating parts. The firing pulses will cause a torque to act on the engine block about an axis parallel to the crank. The inertial forces are both parallel to the piston axis and perpendicular to the crank and piston axes. This dissertation describes the finite element approach for modal and static structural analysis of the engine mount used on an inline four-cylinder petrol engine.  A 3D model of the mount was created with the help of Solid-Edge V19 software and the same was analysed for natural frequencies and total deformation using Ansys Workbench software. Further, torsional stiffness of the mount was obtained using finite element analysis and validated using experimental testing. Viscoelastic behaviour of rubber has also been discussed with the help of a Generalized Maxwell model (GMM). GMM was chosen after reviewing all the commonly used models. Later, an in-depth analysis of transmissibility was carried out using finite element analysis approach and a 6-DOF Mathematical model approach. Random vibration analysis was carried out and the resulting RMS accelerations were compared with the ISO-2631 standard.