Characterization of Step Response Time and Bandwidth of Electrorheological Fluids

The dynamic behavior of the commercially used electrorheological fluid RheOil3.0 is measured under well-defined conditions. Measurements were carried out in shear mode as well as in flow mode using flow channels that provide similar flow conditions to many electrorheological applications. The response times of the change in flow behavior upon a changed electric field are measured. Measurements were carried out in time domain (single step response) as well as in frequency domain (sinusoidal frequency sweep). In most flow conditions, the observed dynamic behavior is characterized by two leading response times of which the fast one is in the millisecond range. Under stable flow or constant shear rate conditions, ionic conductivity is found to be a limiting factor for a quick step response.