ELECTRO-MAGNETO-RHEOLOGICAL EFFECTS IN PARALLEL-FIELD AND CROSSED-FIELD SYSTEMS

Rheological measurements of electro-magneto-rheological (EMR) fluids w ere carried out by use of modified parallel-plate rheometers equipped with electrodes and magnetic coils. The electric field and magnetic fi eld either parallel or perpendicular to each other were applied to a s uspension of spherical iron particles under a constant shear flow. The EMR effects, evaluated as the stress increase induced by these fields , were compared. It was found that the parallel field gives a marked E MR effect in the spherical iron suspension and that the crossed field also results in an EMR effect though the increase of stress value unde r the crossed field is not so large. The difference in these EMR effec ts has been interpreted in terms of the different orientations of the dispersed particles toward the field directions. Similar experiments u sing a suspension of needle-like iron particles have also indicated th at particle orientation plays a major role in the EMR effects.