Abstract
The flow properties of electrorheological (ER) fluids change with the application of an electric field. Presently, these materials are a novelty with few direct applications, but they have drawn considerable interest. Proposed applications include lubricants, dampers, clutches, brakes, etc.
Existing ER fluids are best described by the Bingham fluid model. The Bingham material is described by two parameters, a yield shear stress and a viscosity. When the shear stress magnitude exceeds the yield shear stress, quasi-Newtonian flow results; otherwise the material is rigid. For many ER fluids, the yield shear stress is proportional to the square of the applied electric field. In the present study, the Bingham model is applied to a rectangular flow channel. A rigid core forms midway across the film, the core thickness being proportional to the yield shear stress. The damper force is predicted as a function of a dimensionless parameter which depends on the yield shear stress, the flow rate, and channel geometry.
Calculations are performed for a simple vibration isolation system. Such a system may represent a smart shock absorber to minimize vibration response to oscillation input from a bumpy road. The ER damper is shown to be effective in isolating vibration within a band of linear behavior.
THE EFFECT OF ELECTRIC FIELD DIRECTION ON THE-SHEAR STRESS OF ER FLUIDS
