Experimental investigation for the time-dependent effect in electrorheological fluids under time-regulated high pulse electric field

A new time-regulated high-voltage power supply is designed to investigate the dynamic process of the particle-particle interaction in electrorheological (ER) fluids. Its shortest acting time on the particle is less than 200 ns and the field strength can be adjusted linearly from 0 to 15 kV. At a field strength of 1.2 kV/mm, it is found that the initial response time of the glass microsphere is 18 ms and the respective chain and column formation times are measured to be about 125 and 900 ms. During particle aggregation, a sensitive shear stress device is applied to test the time dependence of ER effect and the results indicate that there exist three different stages of increasing effect. In addition, it is found that the aggregation of the microspheres becomes faster and the interaction among particles is much stronger under higher field strength. (C) 1998 American Institute of Physics. [S0034-6748(98)03810-6].