High-flux Magnetorheology at Elevated Temperatures

Commercial applications of magnetorheological (MR) fluids often require operation at elevated temperatures as a result of surrounding environmental conditions or intense localized viscous heating. Previous experimental investigations of thermal effects on MR fluids have reported significant reductions in the magnetorheological stress with increasing temperature, exceeding the predictions made by considering the thermal variations in the individual physical properties of the fluid and solid constituents of a typical MR fluid. In the low-flux regime, designers of MR fluid actuators can alleviate this thermal reduction in stress by increasing the applied magnetic field strength. However, because the fluid response to the applied field is limited in the high-flux regime by magnetic saturation, the ability to correct thermorheological changes are limited and it becomes necessary to explore and understand the intrinsic limitations of the fluid at elevated temperature. We describe a new magnetorheological fixture that is designed as a removable accessory to a commercial torsional shear rheometer. Careful consideration of the mechanical, thermal and electromagnetic design constraints enabled us to extend the operating range of the device. The assembled fixture is capable of applying magnetic flux densities up to 1T and controlling