Methods for Estimating Dynamic Stiffness at High-Frequency Ranges of Rubber Mounts with Second-Stage Isolators

Mount is a component used to connect the powertrain and the body, which plays an important role in isolating vibration from motor of electrical vehicles. As for traditional rubber mounts, the dynamic stiffness increases significantly with the increase of excitation frequency and will have a peak value, which is called "internal resonance" phenomenon. Compared with the traditional rubber mount, the rubber mount with second-stage isolators has a smaller dynamic stiffness at high-frequency ranges and is usually used to enhance NVH (Noise, Vibration and Harshness) performance of electric vehicles at high-frequency ranges. This paper investigates a rubber mount with second-stage isolators. The second-stage isolators are assembled with bolt holes connecting with mount and car body. The dynamic shear test of rubber pieces at high-frequency (50~1500Hz) is carried out, and the viscoelastic constitutive model parameters of the rubber material are identified using the measured shear test characteristics. Then, the finite element analysis (FEA) model for a rubber mount with second-stage isolators is established, and the dynamic stiffness of the original rubber mount, second-stage isolators and the rubber mount with second-stage isolators are estimated using the developed model. The result indicates that the high-frequency dynamic stiffness of the rubber mount with second-stage isolators is much lower than that of the original rubber mount. The effect of additional mass and damping characteristics on the dynamic stiffness of the rubber mount with second-stage isolators is analyzed, which has instructional significance for the design of rubber mounts with second-stage isolators.