A Simulation And Test Investigation To Dynamic Characteristics Of Hydraulic Mount

Powertrain Mount System (PMS) serves as the most important set of vibration-isolation and noise-reduction for powertrain and the vehicle body. Undesirable vibrations for powertrain mounts are generally from two possible excitation sources. The first one, from engine oscillation, typically contains high frequencies small amplitudes. The second one originates from road inputs and engine torque during harsh accelerations, with low frequencies and large amplitudes. Accordingly, PMS serves two main functions: power train support and bi-directional vibrations isolation in all complex operation modes. The ideal PMS can effectively reduce the vibration generated by the road random spectrum and engine periodic operation. Hydraulic Mount (HM) is widely used in automotive industry in view of good dynamic response and low cost. Great deal of research has been aimed at structure investigation, parameters identification and performance optimization. Problems of HM, including modeling, performance estimation and system identification, have drawn more and more researchers'attention. Increasingly demands on passengers'amenity and the wildly used for 4-cylidner power-intensive engine have raised interests in research of new types of HM. Different configurations of HMs result in diversity in dynamic responses, and in general, the more complex the HM structure is, the better the HM dynamic behavior is.The ability of R&D, design and application for HM in the domestic-made automobiles are in the initial stages. It is urgent that the design methods and techniques for HM be studied extensively and systemically. The thesis is based on the"863"High Technology Development Program Dvelopment of Shanghai Maglev Tracks Inspection Vehicle (No.2001AA505000-114) and the Natural Science Foundation of China (No. 50575073). The paper focused on modeling method on new HM layout, parameters identification, performance analysis, test verification and try to disclose the isolation mechanism, analyze affecting factors of dynamic response on structure parameters and parts, and reduce the time of development and design.The dynamic stiffness and loss angle is chosen as dynamic behavior index. Linear and non-linear Lumped Parameters (LP) models for direct-throttle HM are surveyed with method of Bond Graph (BG), which is considered as the an effective modeling method for the multi-mechanics system. Meanwhile, an universal method based on BG is presented for most of typical layout HM used in the cars presently, including damped orifice HM, inertia track HM, decoupler HM and throttle HM. The simple and effective method is brought forth as the modeling method for hydraulic mount, a typical multiple domain systems.The parameters are identified by experimental approach and the Finite Element Analysis (FEA) method. Most of the model parameters, including volume compliance of the throttle chamber, effective piston area, fluid inertia and resistance of inertia track and throttle are identified by an experimental approach. Numerical predictions are obtained through a finite element method for dynamic stiffness of the rubber spring.In order to deeply investigate dynamic characteristics of HM and disclose the functions of throttle, detailed experiments are carried out for the direct-throttle HM. The HM with throttle is used to verify the influences of preload; excitation amplitude and frequency on the dynamic response are studied in this thesis. The static and dynamic performance of different structure and operation mode is measured by suitable test method. The study affords the approach of structure improvement and performance optimization.Using the LP model and identified parameters, the simulated results and experimental data for the mount dynamic behavior are compared over both the low and high frequency ranges. Comparison of numerical results with experimental observations has shown that the present HM achieves good performance for vibration isolation. The predicted dynamic stiffness and loss angle of the mount for the HM with/without throttle shows that the throttle reduces the dynamic stiffness in high frequency domain. The dynamic performances are compared among HM with inertia track, with throttle and inertia track, with throttle, inertia track and decoupler. Mechanism of vibration-isolation is presented through numerical comparison of above layout HMs. Frequency response of LP parameters, internal pressure and movement of liquid column for example, are studied to reveal the influence for various frequencies domain.FSI models are build in ADINA environment for damped orifice HM and throttle-orifice HM and then comparison are analyzed with finite element method. The dynamic characteristic and pressure field for the two FSI model show that the throttle is the core component to improve dynamic property in high frequency. FSI simulation results show obvious distribution of liquid pressure and velocity due to the intuitionistic results by contrast with LP model. In order to reveal the function of throttle introduced in the HM, comparisons of the numerical predictions with and without throttle for the dynamic responses of the mount are carried out.The work conducted in the thesis present that BG is a simple and effective method for HM modeling. By comparison between numerical and experimental curves, it is demonstrated that a good agreement has been achieved and the LP model behave an excellent accuracy to simulate HM dynamic characteristic. The study presented here can serve as good reference for HM modeling, dynamic analysis, FSI simulation and property optimization.