Design Theory For Magnetorheological Fluid Damper Based On Multi-Radial Flow Mode And Experimental Tests

Fierce hunting influencing the stability of railway vehicles has become oneobstacle of high-speed vehicles. The utilization of anti-yaw damper can effectivelyinhibit the hunting of the truck and improve the hunting stability. At present most of theanti-yaw dampers used in the railway vehicles are cylinder hydraulic dampers.Traditional passive hydraulic damper can be worked well only under certain conditionsdue to unadjustable damping coefficients. Based on the improved semi-active hydraulicdamper controlled by electromagnetic or electrohydraulic valve, the dampingcoefficients can be adjusted in a way, but the structure is complex and expensive.Magnetorheological(MR) technology with wide application prospects is still in theinitial stage of exploration. The problems of low magnetic field utilization and highenergy consumption exist in traditional MR damper based on mixed mode or flowmode.Due to these problems, a novel by-pass MR fluid damper is put forward accordingto technical requirements of railway vehicle anti-yaw damper. The mode of multi-stageradial flow in MR valve can improve the active length of the damping channel and solvethe problem of low magnetic field utilization. More details are as follows:(1) The necessity of installing anti-yaw damper is described, and the developmentof anti-yaw damper at home and abroad is reviewed. Due to the facts of the anti-yawdamper, the purpose and content of this paper are proposed.(2) The mode of multi-stage radial flow is employed in by-pass MR fluid damperof the paper according to the technical requirements of railway vehicle anti-yaw damper.The working principle of the MR fluid damper is introduced. Meanwhile, the design ofworking cylinder and MR valve is finished.(3) Based on the magnetic theory, the equivalent magnetic circuit model is derived,along with the expression of the relationship between the magnetic induction of theworking gap and the exciting current of the field coil. The simulation is given by finiteelement method for the magnetic path in the MR valve. The magnetic induction at theworking gap which compared with theoretical values is tested by experimentalinstrument.(4) Constitutive models for MR fluids are introduced in the paper and the modelparameters have been identified via experiment data. Fluid mechanics are analyzed in the working cylinder, high-pressure oil pipeline and MR valve. The rheologicalequation of MR fluid quasi-static radial flow under a general constitutive model isdevised based on hydrodynamics, and Bi-viscous constitutive model is utilized for thespecial case. The inertia effect is analyzed by the method of averaging inertia effect andperturbation. The theoretical computing method of damping force for MR damper isobtained and the factors of influence are analyzed.(5) In order to analyze the performance of the MR fluid damper designed in thepaper and verify the rationality of theory, the work said the characteristics and speedcharacteristics of the damper are tested by experiments. Experimental damping forcesare compared with theoretical value in different conditions and the main reasons of theerrors are analyzed.(6) The main research work and aspects in the paper are summarized and theproblems need further research are outlined.