High-frequency mechanical impedance of rubber mounts: Experimental characterization and resonance mechanisms

The characterization of the dynamic behavior of rubber anti-vibration mounts in electric motor systems is crucial for optimizing the vibro-acoustic performance of electric vehicle interiors. The transition to electric propulsion has revealed new high-frequency vibration sources (up to 3 kHz), including electromagnetic harmonics from motor commutation. Addressing these vibrations is essential to improve passenger comfort and promote the adoption of electric vehicles. This study presents an in-depth investigation into the dynamic response of cylindrical rubber mounts, employing a custom-designed test rig capable of evaluating performance up to 3 kHz. The experimental setup follows the UNE-EN ISO 10846 standard to ensure accurate measurements of vibro-acoustic transfer properties. To minimize high-frequency transmission through the test bench structure, a seismic mass serves as a decoupling element and stable reference. Force sensors are integrated into the seismic mass, ensuring that measured forces correspond solely to those applied to the rubber specimen, thus isolating the results from structural influences. The experimental findings reveal significant deviations in both the mechanical impedance modulus and the offset angle compared to behaviors observed at lower frequencies, which have been the primary focus of previous studies on vehicles with internal combustion engines. At low frequencies, stiffness-dominated behavior prevails; however, at higher frequencies, inertial effects and wave propagation phenomena become significant, altering the stiffness modulus curve and leading to the appearance of a peak characteristic of a resonance frequency. High-frequency responses are further analyzed through implicit harmonic analysis using advanced finite element modeling techniques. The experimental results are validated through this analysis, as the frequency at which the observed peak occurs coincides with a resonance frequency of the component identified in the harmonic analysis. Furthermore, this research demonstrates that these resonances, along with wave propagation effects, contribute to a complex deformation field, potentially accelerating material degradation and failure, addressing the importance of optimizing the design of these components to enhance their durability and performance.