The effect of a time-dependent electric field on the dynamic performance of an electrorheological fluid in squeeze

An investigation was carried out into the effect of an ac electric field on the performance of an electrorheological (ER) fluid in oscillatory squeeze flow under various mechanical and electrical conditions. The fluid was sandwiched between two parallel circular electrodes, the upper one fixed and the lower one forced to oscillate sinusoidally normal to its own plane. It is shown how the force transmitted across the fluid is greater with dc and low-frequency ac electric fields. Furthermore, it was seen that the rheological performance of the fluid is highly dependent on the shape of the input electrical waveform, with a square wave producing the optimum working response. The results suggest that under dynamic compressive-tensile loading, the chain structure of the fluid is destroyed and at high electrical frequencies, it does not have time to reform. In addition, the performance of the fluid when energized by a sinusoidal field compares very well with that predicted by a theoretical model which assumes a bi-viscous fluid characteristic. Finally, the implications of the results to vibration control, where the ER fluid is employed in a short-stroke squeeze device, are highlighted.