Impact Analysis of Surface Roughnessof the Plate-Plate Measuring System on Resistancetorque in Interaction With MR Fluid

Abstract

Magnetorheological (MR) fluids are complex suspensions of magnetic particles in a non-magnetic carrierfluid. They exhibit ‘smart’ properties that enable them to change their rheological parameters in responseto a change in the external magnetic field applied. This behavior is used in some engineering solutions, e.g.MR clutches or brakes. For such systems to work correctly, the resistance torque achieved by contact withthe MR fluid must be properly determined. This paper demonstrates how surface roughness of a contactsurface between the solid and the MR fluid affects the resistance torque value. Measurements were madeon a dedicated rotational rheometer using a shear mode fluid, most closely replicating the way MR clutchesand brakes work. Plate-plate geometry was used, in standard design, and modified by pasting sandpaper withdifferent grit levels. The tests have shown that the roughness of the mating surface affects the resistance torqueresults.