| The automotive semi-active suspension systems, which consist of passive springs and active dampers with adjustable damping force for different road conditions and automobile running conditions, are the most popular automotive suspension systems due to the active suspension's high cost and passive suspension's limited performances. The controllable dampers are designed according to two basic principles which change damping force by changing the flow area of valves in damper and changing flow behaviors of damping oil. Active dampers designed according to the second principle are divided into Magnetorheological (MR) damper and Electrorheological (ER) damper. MR fluids, characterized by a dynamic yield stress in the presence of a magnetic field, have been viewed as a kind of important actuating material in intelligent structures. Due to their virtues of fast response, low energy dissipation, outstanding rheological effect, less sensitive to contaminants and stability in temperature, MR fluids have been proposed for wide variety of automotive dampers for active damping. In view of the progress of MR techniques and automotive suspension techniques, some MR damping techniques for automotive suspension systems, including system theory, experimental investigation, design method, manufacture technique, and models of the dampers, etc. have been presented in this dissertation in order to progress the MR fluids and automotive suspension techniques based on MR damper. This dissertation are divided into six chapters:1.The purpose and significance of this study are expounded in the first chapter. The application prospect and development tendency of MR fluids and MR devices in the domain of automotive suspension vibration control have been pointed out, on the basis of systematically summarizing of state of automotive suspension technology and MR technique. In view of development tendency of automotive suspension techniques and existing state of MR techniques, the goals and contents of this dissertation have been put forward briefly.2. On the basis of analyzing mechanism of magneto-rheology, some models used to characterize MR effect have been summed up in the second chapter. The reasons, which influence MR effect and sedimentary stability of MR fluids, etc. are analyzed according to models above-mentioned. The MR fluids used to develop automotive MR dampers in this dissertation have been comprehensively tested for the damper design purpose by means of the magnetorheology-meter offered by Department of Engineering Mechanics of Chongqing University.3. According to the working modes of MR devices, combining the ohm's law of magnetic circuit and the design theory of non-steady magnetic circuit, magnetic structures of the automotive damper have been worked out. To emulate the performance of conventional shock absorber, two automotive MR dampers were designed and fabricated at Chongqing University. An applied magnetic field increase the yield stress of MR fluids in flow annular passages, which alters the velocity profile of MR fluid in the passages and raise the pressure gradient between low cavity and high one at some given flow rates. The rheological equations, derived from N-S equation in hydromechanics employing the Newton fluid model and the Bingham plastic model, demonstrate that damping force can be controlled by changing the magnetic field in the gaps.4. In the forth chapter, the performances of MR dampers designed and fabricated at Chongqing University have been tested in National Center for Test and Supervision of Coach Quality, including schematics of damping force vs. displacement of piston head, damping force vs. velocity of piston head, etc. for some given electric currents of the coil. The experimental results demonstrate that damping force offered by MR damper consists of background damping generated by resistance of MR fluid and damping caused by magnetic field.5. In the light of theoretical analysis and experimental results mentioned above, both nonlinear visco-elastic plastic model and neural netw...
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