RESUMEN
Magnetorheological fluids, especially those in high-power magnetorheological devices, inevitably work at high temperatures because of the wall slip, energized coils and frictions between particles. In order to prepare a magnetorheological fluid for high temperatures, this work investigates the properties of three main components (soft magnetic particles, surfactants and base carrier fluids) for a magnetorheological fluid at high temperatures. On this basis, a novel magnetorheological fluid for high temperatures is prepared. Its sedimentation stability, viscosity and shear yield stress are investigated at high temperatures. The results show that the novel magnetorheological fluid has acceptable sedimentation, suitable viscosity and stable shear yield stress at high temperatures. The novel magnetorheological fluid for high temperatures can be applied to most magnetorheological devices, especially high-power magnetorheological devices.
RESUMEN
A magnetorheological fluid (MR fluid) is mainly composed of soft magnetic particles, surfactants, and the base carrier fluid. Among these, soft magnetic particles and the base carrier fluid influence the MR fluid significantly in a high-temperature environment. Therefore, a study was carried out to investigate the changes in the properties of soft magnetic particles and base carrier fluids in high-temperature environments. On this basis, a novel magnetorheological fluid with high-temperature resistance was prepared, and the novel magnetorheological fluid had excellent sedimentation stability, of which the sedimentation rate was only 4.42% after heat treatment at 150 °C followed by one-week placement. At 30 °C, the shear yield stress of the novel fluid was 9.47 kPa under the magnetic field of 817 mT: higher than the general magnetorheological fluid with the same mass fraction. Moreover, its shear yield stress was less affected by the high-temperature environment, reducing by only 4.03% from 10 °C to 70 °C. The novel MR fluid can be applied to a high-temperature environment, effectively expanding the application range of MR fluid.
RESUMEN
High-precision tension control is very important for industrial production. Benefit from the unique property of magnetorheological (MR) fluid, a MR clutch is a potential device in a tension control system due to its fast response and large output dynamics. In this paper, based on the detailed analysis of axial magnetic induction intensity generated by the coil along the radial distribution, a shear-mode MR clutch with uniform magnetic field distribution along the radial direction is proposed for the tension control system. A theoretical model of torque transmission and a magnetic circuit were derived, and a magnetostatic simulation was carried out to validate the effectiveness of the proposed circuit design. Experimental evaluation was conducted to investigate the static and dynamic transmission torque property. Finally, a proportional-integral-differential controller was designed to regulate the output torque. Experimental testing demonstrated the effectiveness and practical feasibility of the MR clutch in tension control.
RESUMEN
In order to investigate the shear yield stress of magnetorheological (MR) fluid at different temperatures, shear gaps, and shear rates, a ring measurement system is designed based on the MR characteristics. The magnetic field and temperature field of the system are simulated and analyzed, which proves that the design of the measurement system is reasonable. On this basis, the measurement system is manufactured and experiments are carried out to verify its performance. The results show that the system can provide a uniform and strong enough magnetic field to make MR effects occur. Meanwhile, the temperature of the shear gap can reach 100 °C in 610 s, and it can increase up to 240 °C when heating continues, which can provide stable measurement conditions at different temperatures, especially at high temperatures. All the results of the experiments show that the measurement system meets the requirements of measuring the shear yield stress of MR fluid. To test the accuracy of the measurement system, repeated experiments are carried out as well. The shear yield stress by the system is almost the same as that provided by the manufacturer, showing excellent measuring precision. The repeatability error of the measurement system is less than 4.02%, indicating that the measurement system is of high accuracy.