Electro-rheological (ER) fluid is a suspension of particles dispersed in a nonconductive medium, whose apparent viscosity is increased by addition of an electric field. In general, it is believed that the electro-rheological effect is caused by formation of particulate chains due to interaction through dipole moments of polarized particles. The propriety of a model for polarized particles was discussed based on the result of a computer simulation of the electro-rheological fluid. Two- and three-dimensional molecular-dynamics-like simulations were carried out to analyze principal properties of the electro-rheological fluid, such as formation of particulate chains, short response time, and the dependence on shear rate, electric field strength and electric field frequency. The calculated results were compared with the measured ones for the suspension of poly(sodium methacrylate) particles dispersed in silicone oil. This comparison clarified that the polarized-particle-model can qualitatively explain the most aspects of the electro-rheological effect except for the property at a low shear rate, though the calculated shear stress was one-fifth of the measured one. The electro-rheological effect obtained by the three-dimensional simulation was comparable to that of the two-dimensional model.
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