ABSRACT Transparent electrode with a conducting film on a glass surface provides us a useful tool to observe the fired-induced structure formation in ER fluids directly under both quiescent and dynamic conditions. In this paper the flow and field-induced structure evolution in ER fluids will be studied in three flow conditions, i.e., (a) ER fluids flowing through a slit channel between two fixed parallel transparent electrodes, which construct a model ER valve, (b) ER fluids being sheared between two concentric transparent electrode tubes, which correspond to a conventional rotary rheometer and (c) ER fluids being sheared between two parallel plate disks, which correspond to an ER clutch. Shear-induced layer structure was observed even when the shear rate reaches 600 s" 1 . A tentative phase transition diagram between the layer structure and the homogeneous flow state will be given.
Experiments on a cone-shaped squeeze-film mode ER damper are reported. An analytical model is developed to calculate the damping force as a function of the vibration amplitude, frequency, the yield stress of the ER fluid. Our calculations agree with the experiments very well at small amplitudes. The cone-shaped electrodes make the damper benefit from both shear mode damper and squeeze-film mode damper. The azimuth angle 0 of the cone electrodes plays an important role in magnifying the damping coefficient of this new type of ER damper.
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