Master of Science, The Ohio State University, 2018, Mechanical Engineering

The application of hydraulic body mounts between a pickup truck frame and cabin have been shown to reduce freeway hop and smooth road shake; yet, this process is typically performed through iterative prototype evaluations on vehicles. Prior studies developing physics-based reduced-order models have demonstrated the preload and amplitude dependence of these components; however, the nature of the component's geometric nonlinearities has not been examined. Here, physical insight is provided through the development and analysis of three illustrative hydraulic mounts configurations. The chamber compliance and effective pumping areas are shown to be constant, preload dependent, or chamber pressure-differential dependent depending upon the placement and shape of the internal elastomeric springs. This thesis develops methodologies to extract the parameters for the reduced-order model parameters from a detailed dynamic nonlinear finite element hydraulic mount model. The fluid-structure interaction is captured using fluid cavity and exchange definitions within the finite element model. Comparisons are made between the dynamic nonlinear finite element and reduced-order models for purposes of model verification. Finally, the analysis methods are applied to a production hydraulic body mount. It is demonstrated that the middle spring undergoes a snap-through like, geometric nonlinearity that influences the effective pumping area and pressure differential dependence on chamber compliance.

Committee: Scott Noll (Advisor); Shawn Midlam-Mohler (Committee Member) Subjects: Automotive Engineering; Mechanical Engineering

Master of Science, The Ohio State University, 2017, Mechanical Engineering

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 thesis 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. Additional transient testing of the mount is performed, and the model formulation is extended to transient time-domain solutions based on the frequency domain characterization. The models provide insight into which features within the mount assembly drive the dynamic amplitude and preload dependence in both frequency and time domains.

Committee: Jason Dreyer (Advisor); David Talbot (Committee Member) Subjects: Engineering