Temperature effects and temperature-dependent constitutive model of magnetorheological fluids

The knowledge of the temperature effect on magnetorheological fluid is critical for accurate control of magnetorheological devices, since the temperature rise during operation is unavoidable due to coil energization, wall slip, and inter-particle friction. Based on a typical commercial magnetorheological fluid, this work investigates the effect of temperature on magnetorheological properties and its mechanisms. It is found that temperature has a significant effect on the zero-field viscosity and shear stress of magnetorheological fluid. The Herschel-Bulkley model that has high accuracy at room temperature does not describe accurately the shear stress of magnetorheological fluids at high temperatures, as its relative error is even up to 21% at 70 degrees C. By analyzing the sources of shear stress in magnetorheological fluids, a novel constitutive model with temperature prediction is proposed by combining the Navier-Stokes equation and viscosity-temperature equation. The experimental results show that the error of the novel constitutive model decreases by 90% at different temperatures and magnetic field strengths, exhibiting an excellent accuracy. This temperature-dependent constitutive model allows the properties of an MR fluid to be widely characterized only in a few experiments.