Attenuation of magneto-induced yield stress by magnetic carrier liquid in magnetorheological fluids

Abstract

Magnetorheological fluids (MRFs) are composed of magnetic particles and carrier liquid that yield stress responses to the external magnetic field, a phenomenon called the magnetorheological effect. In this work, the attenuation of magneto-induced yield stress in an MRF caused by magnetic carrier liquid was observed. Compared with that of MRFs with nonmagnetic carrier liquid, the average critical strain was correspondingly increased by 53.17%, and the maximum dynamic and static yield stress were reduced by 12.98% and 13.58%, respectively. The attenuation was attributed to the magnetic carrier liquid shunting more magnetic flux density than the nonmagnetic fluid, thus decreasing the magnetization of the magnetic particles. The weakened electromagnetic interaction between particles reduced the strength of the particle chains under the magnetic field, thereby reducing the magneto-induced yield stress. A theoretical model based on the magnetism characterization in the relative permeability of carrier liquid was proposed to explain the attenuation of the electromagnetic force for particles. A physics model of magneto-mechanical coupling was simulated in COMSOL to reveal the attenuation phenomenon. Compared with that when the nonmagnetic carrier liquid with relative permeability of 1 was used, the electromagnetic force in the calculation curves was increased by 26.94 times and decreased by 99.95% when the relative permeability was 0.1 and 10 000, respectively. This work provides a methodology for the intensive mechanism study of magneto-induced yield stress.