ELECTROSTATIC PARTICLE-PARTICLE INTERACTIONS IN ELECTRORHEOLOGICAL FLUIDS

A model for the particle-particle interaction in a chain of spherical particles in an electrorheological (ER) fluid is developed based on an expansion of the potential which satisfies the Laplace equation. The electric-field distribution and force-distance relationship between particles are calculated as a function of K(p)/K(f) (the dielectric constant of the sphere relative to that of the medium) and particle-particle spacing using this model. The calculations predict electric-field concentrations of about an order of magnitude near particle contacts. This gives a force between particles that is approximately an order of magnitude higher than predicted by the classical point-dipole approximation, and is in reasonable agreement with that measured experimentally. Subtle effects of the carrier fluid on the interaction force and an explanation for the non-Ohmic behavior of ER fluids are deduced in terms of its dielectric constant and dielectric strength.