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 investig ate the dynamic process of the particle-particle interaction in electr orheological (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 ini tial response time of the glass microsphere is 18 ms and the respectiv e chain and column formation times are measured to be about 125 and 90 0 ms. During particle aggregation, a sensitive shear stress device is applied to test the time dependence of ER effect and the results indic ate that there exist three different stages of increasing effect. In a ddition, it is found that the aggregation of the microspheres becomes faster and the interaction among particles is much stronger under high er field strength. (C) 1998 American Institute of Physics. [S0034-6748 (98)03810-6].