RELATIONSHIP BETWEEN CHAIN STRUCTURES AND VISCOSITY IN THE MAGNETO-RHEOLOGICAL SUSPENSIONS STABLE DISPERSING DIFFERENT CONCENTRATION OF IRON PARTICLES WITH SMECTITE

Abstract

Different concentration of spherical iron particles (7 to 8 μm) are dispersed in silicone oil to increase the stability with smectite. The concentration of iron particles is maintained between 2 and 40 volume %. The solenoid coil surrounding the cylinders applies the magnetic field in the longitudinal direction of cylinder, when the cylindrical viscometer is employed. As the magnetic field increases, the diameter of chain structure also increases. The shear stress versus shear rate is proportional relation since the viscosity enlarges as the magnetic field increases at small concentration of iron in MR fluid. Additionally, the more increase of the magnetic field strength caused the decrease of the shear stresses at large concentration of iron in MR fluid, while the share rate is increased for the open system of the cylinders. It is assumed that wider clusters or wider chain structures are partly produced in the cylinder under the certain magnetic field. Therefore, the shear stress is not uniformly increased. On the other hand, when the cone and plate viscometer is used, the magnetic field direction is perpendicular to the flow direction. The shear stress versus share rate behaves like a Bingham fluid type under the effect of the magnetic field. As increasing the iron particles volume %, the chain structures cannot increase and make other ring type structures. When the magnetic field is measured by hall probe, the magnetic field decreased at some amount of volume percentage of iron suspension because of shield effect.