EXPERIMENTAL INVESTIGATION OF DIPOLE-DIPOLE INTERACTION IN A WATER-FREE GLASS PARTICLE OIL ELECTRORHEOLOGICAL FLUID/

An experimental investigation of the dipole interaction in a water-fre e glass/oil electrorheological fluid under an alternating electric fie ld is presented in this letter. The values of the dielectric constant epsilon and conductivity sigma of glass and oil with respect to the fr equency of the external electric field are measured, respectively. Cor responding to the changes in epsilon and sigma, the square of the abso lute dielectric mismatch parameter \beta\ {beta=(<<(epsilon)over tilde >(p)(omega)-<(epsilon)over tilde>(f)(omega)]/[<(epsilon)over tilde>(p) (omega)+2<(epsilon)over tilde>(f)(omega)], where <(epsilon)over tilde> =epsilon +sigma/i epsilon(0) omega, and subscripts p and f indicate th e glass and oil} decreases as the frequency is increased. After compar ing the variation tendency of the \beta\(2) with the yield stress of t he electrorheological (ER) fluid in a measured frequency range we foun d that they coincide very well. This result confirms that the polariza tion theory can explain the mechanism of the ER effect not only in a d e electric field but also in that with a wide frequency range. However , the interaction within the multipoles should be considered in an exa ct calculation. (C) 1991 American Institute of Physics.