Electrorheological Fluid Hysteresis

Electrorheological (ER) fluids are suspensions of polarizable particles dispersed in insulating liquids. They exhibit a rapid and reversible transition from a liquid-like to a solid-like state upon the application of an electric field. The observed shear stress - shear rate hysteresis makes the precise control of the ER mechanical devices very difficult. Hysteresis behavior of TiO2 ER fluids were observed by varying particle concentration, electric field strength, maximum shear rate, and the time of hysteresis loop. In the absence of an electric field, the stress level of the up curve exceeds that of the down curve. The presence of an electric field, reverses this trend. The extent of hysteresis becomes more significant with increasing electric field strength, particle concentration, and maximum shear rate. Hysteresis behavior of TiO2 ER fluids seems to arise mainly due to the change of the particle structure during shearing. To describe the complex rheological behavior of ER fluids, a kinetic theory is presented. Model predictions show qualitative agreement with the experimental hysteresis data.