Pressure responses of electrorheological suspension in a model er damper

The pressure responses of an electrorheological (ER) fluid, containing ion exchange resin particles in silicone oil, in a piston cylinder-ER valve system which is modeled after an ER damper have been measured to investigate the steady ER effects and the transient pressure responses of the ER fluid against the application of electric field to the ER valve. The ER valve has a channel of 0.6 mm height between two fixed parallel electrodes, where the flow establishes the Poiseuille-flow geometry. During testing, the piston is moved at a given constant speed to maintain the mean flow rate through the ER valve constant. The pressure drop across the ER valve, caused by ER effects, increases in proportion to the square of electric field strength E², but decreases exponentially with increasing flow velocity U and then converges to a certain value of the pressure drop at sufficiently high flow velocity, and is characterized by an approximate function of E and U. These characteristics of ER effects are compared with the theoretical results based on the Bingham plastic model. The measured step response of the pressure can be approximated by a first-order response. The rising time constants are much higer than the usual response time constants of ER fluid. The above observations are discussed from the viewpoint of the damping performance and the system characteristics.