ABSTRACT
The electrorheological (ER) effect, sometimes referred to as the Winslow effect after the person who first investigated it (Winslow, 1949), is a phe nomenon in which the resistance to flow or to deformation of certain types of fluid can be changed by the application of an electric field. The fluids used by Winslow were nonaqueous silica suspensions that had been acti vated by a small amount of water. More recently there has been a large amount of work devoted to the development of other fluid types (e.g., Block and Kelly, 1988). All of these fluids are essentially comprised of a dielectric oil (such as a silicone oil) and some dispersed particulate. On application of an electric field, the solid phase forms a series of chainlike bridges in a direction roughly orthogonal to the electrodes (Fig. 1), thus producing a pronounced structural inhomogeneity. Under this condition, the liquid state of the unstressed fluid is replaced by that of a rigid gel, the transition occurring rapidly (typically in a millisecond).
