ELECTRORHEOLOGICAL FLUIDS - ROLE OF THE D IFFERENT CONSTITUENT CONDUCTIVITIES

The influence of an electric field on the theological properties of su spensions of small particles in an insulating liquid is first recalled . Then general arguments are given which show that, under DC fields, t he particle/particle interaction is controlled by the conduction prope rties of both constituents. The electrorheological effect occurs only for solid that present a higher conductivity than the liquid (in the r everse case, a ''negative'' effect is obtained). Then a model is propo sed which gives estimates of the attraction force between particles of an ER fluid. This model is qualitatively confirmed by results on a la rge scale experiment (spheres of radius R = 0.7 cm) as well as on a re al fluid. The case of AC fields is also examined.