Frequency dependence of electrorheological fluids in an ac electric field

Abstract

The frequency dependence of the shear stress of electrorheological (ER) fluid has been studied. We find that the shear stresses of some water-free ER fluids increase monotonically with the frequency and tend to reach saturated values at high frequency. The measurements on ${\mathrm{KNbO}}_{3}$-silicone-oil ER fluid show that the shear stresses under a ${10}^{3}$ Hz frequency ac field are several times or even an order of magnitude larger than that under a dc field for the same field strength. The polarization current of the particles in an ac field may strengthen the interaction between them. (c) 1995 The American Physical Society