Dielectric relaxation effect on flow behavior of electrorheological fluids

The dielectric relaxation effect on the flow behavior of electrorheological fluids under dynamic shear was studied. The flow curves of electrorheological fluids in the dynamic state were simulated with shear rates from 0.1 to 1000 s ⁻¹ under different relaxation times. When the magnitude of the relaxation time is smaller than 10 ⁻² s, the break shear rate changes little at different relaxation times. But the break shear rate changes obviously when the magnitude of the relaxation time is larger than 10 ⁻² s. To further understand the influence of the relaxation time, Sr/Ba-doped TiO ₂ electrorheological fluids were prepared and their dielectric properties and flow curves under shear flow were tested. The relaxation time of the electrorheological fluid is influenced by the Sr/Ti mole ratio but not the Ba/Ti mole ratio, and the electrorheological effects of the fluids were highly influenced by varying the Sr/Ti mole ratios. The experimental results agreed well with the above computer simulation. Finally, a possible mechanism was proposed to explain the effect of dielectric relaxation on flow behavior of electrorheological fluids.