| Rubber bushings are commonly used in engine sub-systems, vehicle body, and vehicle suspension to damp their oscillations excited by dynamic loads, thus improving driving safety, ride comfort and handling performances. Compared with conventional rubber bushings, Hydraulically-damped rubber bushings(HDB) can provide a high viscous damping coefficient in certain frequency range. At present, the design ability of HDB in China is at initial stage. Therefore, extensively and systemically studies on the design methods and techniques for HDB are in urgent need. To achieve these goals, the main research works of this dissertation are as follow:(1) Although HEM and HDB’s working mechanism are structurally similar, their performances are significantly different. In this work, efforts have been made to understand the cause of the differences in performance between them. Firstly, analytical models are proposed for HEM and HDB. The continuity equations, momentum equations and the transfer forces for the bushings and mounts are compared. Also, the equivalent mass, the magnification of the damping, and the equations of the pressure and the flow responses are compared to interpret the working mechanism difference of these two hydraulic devices. It is found that the difference in the volumetric compliances of the hydraulic devices is the essential reason. By choosing a proper volumetric compliance, a unified analytical model which is able to describe both HEM and HDB is proposed. The unified analytical model is helpful in the guidance of HEM and HDB design.(2) Characteristics of different structures of hydraulic bushings with multiple fluid tracks used in vehicle suspension and their rubber springs are thoroughly studied by experimental method. The influences of excitation frequency, excitation amplitude and preload on the dynamic stiffness of HDB with multiple fluid tracks and its main rubber spring are investigated. The working mechanisms of different structures of HDBs are compared. Besides, the influences of different temperatures(-30℃, 23℃and 80℃) and preloads on the static and dynamic performances of a typical vehicle subframe hydraulic bushing are investigated. The viscosity-temperature curve is obtained. The conclusions and discussions can be used for analyzing the performances of a hydraulic bushing with different structures before prototype.(3) The model parameter identification methods for HDB with FSI FEA techniques and analytical analysis are discussed and the results are compared. These simulation methods for determining the system parameters make parameters identification techniques independent of experiment. Lumped parameter models for the HDB with multiple inertia tracks and orifices under different frequencys are proposed in order to understand the relations between the HDB’s structure features and their dynamic performances analytically. The LP models are validated via benchmarking the simulated dynamic performance against test data. Based on the LP models, it is found that increasing the number of the inertial track and/or orifice would benefit the HDB’s performance a great deal, since the dynamic stiffness, the amplitude and the corresponding frequency of the loss angle would be significantly improved. These proposed methods of modeling and analysis can be utilized to guide the design of the HDB with multiple inertia tracks and orifices.(4) These experimental procedures for testing hyper-elasticity of rubber material are discussed under different temperature(-30℃, 23℃and 80℃). Uniaxial tension, biaxial tension and planar tension tests for obtaining the characteristics of a rubber specimen under different temperatures are conducted. Compared with high temperature, the stress-strain relation under 23℃ exhibits non-linear behavior. The system parameters identification methods for HDB with FSI FEA techniques and analytical analysis are discussed and the results are compared under different temperatures. The last analytical results suggest that these properties of the rubber spring and fluid are influenced by temperatures greatly. |
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