MR FLUID BEHAVIOR UNDER CONSTANT SHEAR RATES AND HIGH MAGNETIC FIELDS OVER LONG TIME PERIODS

摘要

MR fluids are smart materials that reversibly change their Theological properties in the presence of a magnetic field. Their capability to support a high range of shear stresses makes them an ideal component of many mechanical devices. However, to be suitable for applications requiring a large number of cycles, e.g. a clutch, the long term behavior of these fluids needs to be thoroughly investigated and well understood. The paper presents a new MR cell design along with a study of the shear rate, shear strain, magnetic field and time influences on the properties and behavior of a MR fluid tested for long periods of time. The MR cell is cquired to adapt a commercially available rheometer to measure the rheological properties of the fluid. Overall characteristics of the designed MR cell output capability are provided. Constant shear rate tests, two hours in duration, have been performed at shear rates between 0.1 and 200 1/s under magnetic field intensities up to 0.4 T. The rheological measurements indicated that the time, the shear strain and the shear rate influence the fluid's shear stress magnitude.