Strain Dependence of Dynamic Viscoelastic Properties of ER Fluids with Iron(III) Hydroxide Coated Silica Particles
The electro-rheological (ER) effect is thought to be closely related to the aggregation and yield of polarized particles. These polarized particles aggregate parallel to the electric field to form pairs of particles (short clusters). Then, the short clusters are elongated to bridge between electrodes to form long clusters. Flow resistance of the clustered suspension increases as much as the resistance to break the long clusters which corresponds to the yield stress. On the basis of induced dipole-dipole interaction models1,2, it is expected that the yield strain and stress of the clusters are affected by an external electric field, the dielectric constant of particles and that of disperse phase of the suspension, and the intensity of hydrodynamic deformation, which are included in a general dimensionless parameter called Mason’s number3. Experimentally, the yield strain and stress can be obtained by measuring the stress-strain relation directly at a constant strain rate4. In this method, the strain rate immediately after the onset of deformation should be precisely controlled and the high resolution of small strains should be needed. There can be another method to obtain the yield strain and stress. That is, the yield strain and stress can be estimated from the strain dependence of dynamic viscoelastic properties under sinusoidal oscillating shear flow5,8. The periodic measurement of stress response to the strain stimulus is expected to be the high resolution of small strains, and the oscillatory deformation with a sufficiently low frequency can be assumed to the quasi-static shear deformation.
KeywordsStrain Amplitude Electric Field Strength Loss Tangent Critical Strain Stress Amplitude
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- 7.K. Tanaka, T. Yoshida and K. Koyama, Transient response of ER fluids, in: “Electrorheological Fluids — Proc. 3rd Int. Conf. ER Fluids”, R. Tao, ed., World Scientific, Singapore (1992).Google Scholar