VARIATION WITH DISTANCE OF THE ATTRACTION FORCE BETWEEN SPHERES AND ESTIMATION OF STATIC YIELD STRESS OF ER FLUIDS

In order to estimate the static yield stress of a suspension of monodi spersed spheres subjected to a DC applied field, the knowledge of the interaction force between spherical particles is required. This questi on of variation of the attraction force between spheres as a function of their distance is investigated on the basis of the conduction model in the particular case of saturation regime of bulk electrical condit ion of the liquid. The prediction is tested using a scaled-up two-sphe re experimental model for the particles interaction. Then a rough esti mate of the static yield stress is derived using a linear approximatio n of the force dependence of the spacing s between spheres.