FREQUENCY-DEPENDENCE OF ELECTRORHEOLOGICAL FLUIDS IN AN AC ELECTRIC-FIELD

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 KNbO3-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 de held for the same field strength. The polarization current of the particles in an ac held may strengthen the interaction between them.