Mechanisms of electrorheology: the effect of the dielectric property

TLDR

The study examined how the dielectric properties of electrorheological fluids influence electrorheology in DC electric fields using both hydrous and anhydrous fluids. The authors found that a large electrorheological effect occurs when the relaxation frequency is around 100 Hz, that the effect grows with the dielectric constant contrast across this frequency for both hydrous and anhydrous fluids, that in microcrystalline‑cellulose fluids the rheology curve shifts with adsorbed water content in a way consistent with shear‑rate/polarization coupling, and that the ER mechanism also explains the influence of current density.

Abstract

The effect of the dielectric properties of electrorheological fluids on electrorheology was investigated in DC electric fields by using both hydrous and anhydrous electrorheological fluids. The relaxation frequency, which is defined by a local maximum of the dielectric loss factor of an electrorheological fluid, was in the range from 100- whenever the electrorheological fluid had a large electrorheological effect. This effect increased with increasing difference between the dielectric constants below and above the relaxation frequency both for hydrous and anhydrous electrorheological fluids, when the relaxation frequency was in the range 100-. For the electrorheological fluid containing microcrystalline cellulose, the change of the rheology curve, namely the shear rate versus shear stress ( versus ) curve, with increasing adsorbed water content could be interpreted in terms of the relation between the shear rate and the polarization rate. The mechanism of electrorheology could also explain the effect of the current density on the ER effect.