| It is known that the restrictions of the shear yield stress of magnetorheological fluid(MRF)and the transmission torque of the magnetorheological transmission device are caused by the magnetization saturation of MRF,and the high temperature caused by the slip difference causes the degradation of MRF performance.For these problems,this paper designs a disc-type magnetorheological transmission device based on extrusion strengthening technology according to the characteristic that the shear yield stress of MRF significantly increases under the effect of extrusion strengthening.The research on the transmission and slip characteristics of the device is carried out.The main research work of this paper is as follows:(1)Based on the magnetic dipole theory and the typical microstructural model of the chaining of MRF,the existing model of the shear yield stress of MRF is optimized under the conditions of the magnetic field force,the volume repulsion force and the viscosity resistance of the carrier liquid.The typical microstructural model is improved according to the changeability of the microstructure of MRF,and the model slip power of the MRF is established in combination with the Hertzian contact theory.The effect of the main governing factors,such as volume fraction,shear strain and shear strain rate,on the shear yield stress and slip power of MRF is individually investigated.(2)The basic structure and working principle of the cylindrical and disc-type magnetorheological transmission devices are analyzed,and the corresponding expressions of the transmitted torque are derived.Throughout a comparative analysis,this paper adopts the disc type as the basic form of magnetorheological transmission device.The overall structure of the disc-type magnetorheological transmission device based on extrusion strengthening technology,and its main structural parameters,sealing method,magnetic circuit,etc.,are designed and analyzed in detail.(3)The analysis of the transmission performance of the designed magnetorheological transmission device is conducted,and the effect of factors,such as the current,the width of MRF working gap,and the magnetic flux area on the magnetic circuit of the device is investigated.According to the results of the analysis of the magnetic circuit,the magnetic circuit structure is optimized.The basic heat transfer equation of MRF is established based on the heat transfer theory.The thermal structure analysis of the optimized magnetorheological transmission device is performed in terms of elastic modulus,Poisson's ratio,and thermal expansion coefficient of a solid-like MRF.The effect of the factors,such as the current,the slip difference,and heat dissipation on the temperature and structure of the magnetorheological transmission device are discussed.(4)The transmission torque of the disc-type magnetorheological transmission device under the extrusion strengthening effect is analyzed,and the effect of the compression stress and the current on the transmission torque of the magnetorheological transmission device is investigated.The slip power of the disc-type magnetorheological transmission device under the extrusion strengthening effect is analyzed,and the effect of the compression stress and the slip difference on the slip power of the magnetorheological transmission device is investigated.The maximum slip power of MRF under different working hours and suitable working temperatures is studied.The transmission torque of the disc-type magnetorheological transmission device based on the extrusion strengthening technology under the slip effect is analyzed.The results show that,compared with the nonextrusion condition,the designed disc-type magnetorheological transmission device not only ensures stable working performance,but also significantly increased the transmission torque. |
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