| Magnetorheological(MR)fluid with unique MR effects,can rapidly transform from liquid state to semi-solid state under magnetic field,accompanied by an increase in the shear yield stress that can be effectively controlled through adjusting the exciting currents.Taking MR fluid as transmission medium,MR transmission presents the advantage of quick response,strong anti-interference ability and high controllability,which has broad application prospects.Aiming at the problems existing in the research area of MR fluid and MR transmission,this work is carried out through micro aspects and macro aspects,which applies the combination of theoretical analysis,numerical simulation and scientific experiments based on MR fluid characteristics and MR transmission conditions.The researches in this work are as follows:(1)The mechanical properties of magnetorheological fluid are investigated in the absence of magnetic field and under magentic field,of which the causes are analyzed by microscopic images.The accuracy of Bingham model,Herschel-Bulkley model and Casson model are researched under the working conditions of different magnetic field strengths,particle concentrations and shear rates.Besides,the error causes of above three constitutive model are analyzed,and the appropriate system is established to evaluate the applicable scopes of the three models.(2)The apparent properties and mechanical properties of MR fluid is tested at different temperatures,and the error rules of constitutive models of MR fluid is analyzed at high temperatures.The high-temperature characteristics of three main components of MR fluid are investigated,and the mechanism of the effects of temperature on MR fluid is revealed.A novel temperature-dependent constitutive model of MR fluid is proposed by analyzing the intercomponent forces,of which the accuracy is verified under different conditions of temperature and magnetic field strengths.(3)The magnetic force on particles is calculated by dipole method,magnetic energy method and finite element method,respectively.The double-chain model is established by linking two single chains with particle link and node particle.The yield process of MR fluid is revealed at micro scale,and the effect mechanism of particle size,particle concentration,magnetic field strength and temperature on the shear yield stress of MR fluid are revealed.(4)The evaluation indexes of the shear thinning effect are proposed for MR fluids,and the effects from particles concentration,magentic field strength are obtained.On this basis,the shear thinning effects are revealed under different working conditions.The materials are selected and tested for the MR fluid with high temperature and shear thinning resistance.A novel MR fluid with high temperature and shear thinning resistance is prepared,and experiments are carried out to test its apparent properties and mechanical properties.(5)The MR transmission forms are analyzed and MR transmission model is established.The MR transmission prototype is designed,and its magnetic circuit is calculated and verified.On this basis,the MR transmission system is constructed by using multiple devices and sensors.The no-field,static,dynamic,torque and temperature characteristics of MR transmission system are tested under different working conditions,of which the mechanism is analyzed in relation to the characteristics concluded above.The research results achieved in this work will provide scientific theoretical basis and high-performance medium for MR transmission,which can support the application of MR transmission devices.The dissertation involves 116 figures,19 tables and 122 references. |
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