Aiming to improve the shear yield stress of magnetorheological fluid, magnetorheological fluids with different particle characteristics are prepared, and the influence rules of particle mass fraction, particle size, nanoparticles content and application temperature on shear yield stress are investigated. Experimental results indicate that shear yield stress increases approximate linearly with the enhancement of particle mass fraction. Particle size and the nanoparticles within 10% mass fraction can improve the shear yield stress effectively. When the application temperature is higher than 100 o C, the shear yield stress decreases rapidly because of thermal expansion and thermal magnetization effect.

A novel magnetorheological (MR) fluids transmission device for high-power applications is designed, simulated and experimented. The transmission device is implemented of multi-hollow drive disc with magnetic conductive columns and adopts water cooling method to heat dissipation. In this paper, firstly, a novel hollow transmission disc with magnetic conductive columns is proposed, and the structure of the high-power MR fluid transmission device is determined. And then, the magnetic circuit is designed in detail, and the magnetic field distribution of the transmission device is analyzed by the method of finite element. Finally, a prototype of the transmission device is fabricated and several tests are carried out to evaluate the torque transmission, time response and temperature rise of the prototype. The results show that the proposed MR transmission device can produce a maximum output torque of 1880 N m and possesses a high slip power of up to 70 kW.

We report the preparation of a high-performance magnetorheological fluid by using silane coupling agent and bentonite as additives at appropriate contents determined by a series of experiments. We also adopted a new preparation process that was optimized through an orthogonal experimental design. The effects of process parameters on the sedimentation stability of the MR fluid were determined. Sedimentation ratio, apparent viscosity, and yield stress were measured to evaluate the performance of the MR fluid prepared by the optimized process. Results indicated that the MR fluid exhibited enhanced sedimentation stability when the silane coupling agent and bentonite mass fractions were 2.88% and 3.60%, respectively. Moreover, the effect of the second stirring process on sedimentation stability was found to be more important than the first. The optimal preparation parameters determined for the high-performance MR fluid are as follows: first and second stirring temperature of 20 °C, first stirring time of 5 min, second stirring time of 5 h, and first and second stirring rotation speed of 2000 rpm. Downloaded by [University of Sussex Library] at 22:54 28 June 2016 2

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On the basis of shear working mode of magnetorheological fluid, in this article, a novel temperature controllable yield stress measurement device is designed, and the double magnetic circuit structure and the heating structure are proposed. And then, the magnetic field and temperature field of the measurement device are simulated, respectively, by the finite element method. Furthermore, several experiments are carried out to evaluate the magnetic field, measurement precision, and repeatability of the self-designed device. The results indicate that the proposed measurement device has uniform magnetic field distribution and controllable temperature and also has high yield stress testing accuracy and repeatability.