FREQUENCY-DEPENDENCE OF METAL-PARTICLE INSULATING OIL ELECTRORHEOLOGICAL FLUIDS

The frequency dependence of the shear stress of metal-particle/insulat ing oil electrorheological (ER) fluids under an ac electric field has been studied. The results show that the shear stress of the metal-part icle ER fluid under a fixed electric field increases with increasing f requency and then tends to a saturated value at higher frequency. The shear stress at 10(3) Hz is much larger than that under a de field, Th e transition of the shear stress shifts to higher frequency when the c onductivity of the fluid is larger. The measurements are consistent wi th the theoretical model proposed by Davis [J. Appl. Phys. 73, 680 (19 93)]. (C) 1995 American Institute of Physics.