THE DEPENDENCE OF PARTICLE PERMITTIVITY ON THE SHEAR-STRESS OF ELECTRORHEOLOGICAL FLUIDS

A ferroelectric TGS particle/silicone oil electrorheological (ER) flui d is introduced to investigate the dielectric dependence of the ER eff ect. The dielectric constant of ferroelectric changes violently with t emperature at the Curie temperature (T-c). By measuring temperature de pendence of shear stress across T,, the effect of dielectric constant on shear stress can be directly obtained. All the results are more rel iable due to the same conditions, such as size, shape, composition of particles, as well as the same chemical nature of particles and interf ace property between particles and liquid. The measurement was carried out under a high-frequency (1000 Hz) ac electric field where ER effec t is dielectric constant dominated. For the first time, the dependence of the ER effect on dielectric mismatch has been quantitatively obtai ned experimentally. There is an obvious deviation of available theoret ical calculations from our measured data. A more rigorous theoretical study should be developed to quantitatively interpret the relation of the shear stress and the permittivity mismatch factor. (C) 1998 Americ an Institute of Physics.