Dynamic Analysis of a Hydraulic Body Mount with Amplitude and Preload Dependence

The application of hydraulic body mounts between a pickup truck frame and cab to reduce freeway hop and smooth road shake has been documented in literature and realized in production vehicles. Previous studies have demonstrated the potential benefits of these devices, often through iterative prototype evaluation. Component dynamic characterization has also shown that these devices exhibit significant dependence to preload and dynamic amplitude; however, analysis of these devices has not addressed these dependences. This paper aims to understand the amplitude and preload dependence on the spectrally-varying properties of a production hydraulic body mount. This double-pumping, three-spring mount construction has a shared compliant element between the two fluid-filled chambers. A physics-based reduced-order model of the mount assembly is developed using parameters derived from inspection of the component geometry and bench experiments on the different elastomeric components and the fluid system. The dynamic properties of the mount are characterized using step sine testing, and the model is validated in the frequency domain. The model analysis provides insight into which features within the mount assembly drive the dynamic amplitude and preload dependence.