Mechanical filtering characteristics of passive periodic engine mount

The transmission of automotive engine vibrations to the chassis is isolated using a new class of mounts which rely in their operation on optimally designed and periodically distributed viscoelastic inserts. The proposed mount acts as a mechanical filter for impeding the propagation of vibration within specific frequency bands called the “stop bands”. The spectral width of these bands is enhanced by making the viscoelastic inserts operate in a shear mode rather than compression mode. The theory governing the operation of this class of periodic mounts is presented using the theory of finite elements combined with the transfer matrix approach. The predictions of the performance of the mount are validated against the predictions of the commercial finite element code ANSYS and against experimental results obtained from prototypes of plain and periodic mounts. The obtained results demonstrate the feasibility of the shear mode periodic mount as another means for blocking the transmission of vibration over a broad frequency band. Extending the effective width of the operating frequency bands of this class of mount through active control means is the ultimate goal of this study.