Research On The Wear Characteristics Of Magnetorheological Fluids For Transmission

As a new kind of intelligent material,magnetorheological fluids(MRF)is prepared by magnetic particles,carrier liquid and additives in certain proportion.When there is no external magnetic field,it has the characteristics of Newton fluid.But when the magnetic field is applied,its viscosity can be increased rapidly,becoming solid-like,and this change is continuous and reversible.MRF is used as the working medium in MRF transmission system,using its shear yield stress to realize power transfer.However,in the process of transmission,the wear phenomenon of MRF can lead to the decrease of the transmission accuracy and even the failure of power transmission.Pointing at MRF and the wear problems existing in the transmission application,the following aspects are studied:(1)The MR effect and yield characteristics of MRF are introduced and theoretical models of MRF rheological properties are presented.In order to improve the sedimentation stability of MRF,experimental studies on the optimization of ultrasonic dispersion parameters are carried out.The results show that the optimal process value is in the vicinity of 40 min with ultrasonic power of 260 W.(2)The design requirements of testing device for wear characteristics of MRF for transmission are presented.The mechanical structure and magnetic circuit structure of the testing device are designed.Then the magnetic field of the magnetic circuit is simulated by using Ansoft Maxwell software and the final structure of the testing device is determined.(3)The failure modes of MRF transmission system are presented.The failure of MRF transmission is analyzed in detail from three aspects: the wear of the transmission working surface,the overheating of the excitation coil and the wear failure of MRF.The wear mechanism of MRF is analyzed from the aspects of magnetic particle wear,carrier liquid contamination and damage of additive.The effects of MRF wear on the sedimentary stability,zero field viscosity and shear yield stress are analyzed.(4)The test bed for the wear characteristics of MRF for transmission is set up.The influence of the magnetic particle size,the type of the antiwear agent and the surface morphology of the disks on the wear characteristics of MRF for transmission is studied experimentally.The effects of MRF wear on its shear yield stress,zero field viscosity and settlement stability are analyzed.