MAGNETORHEOLOGICAL FLUIDS - MATERIALS, CHARACTERIZATION, AND DEVICES

Magnetorheological (MR) fluids consist of stable suspensions of magnet ic particles in a carrying fluid. Magnetorheological effect is one of the direct influences on the mechanical properties of a fluid. It repr esents a reversible increase, due to an external magnetic field of eff ective viscosity. MR fluids and devices have the potential to revoluti onize the design of hydraulic systems, actuators, valves, active shock and vibration dampers, and other components used in mechanical system s. At present, there is a compelling need to develop new and improved MR fluids, to lower their production cost through improved manufacturi ng processes, and to develop MR fluid-based application devices that w ill demonstrate the engineering feasibility of the MR fluids concept a nd will highlight the implementation challenges. To this end, the pres ent study is undertaken. A unique high-speed bead mill machine, especi ally designed to the manufacture of MR fluids, is used to fabricate MR fluids in a laboratory-scale MR fluid fabrication facility at the Cen ter for Intelligent Material Systems and Structures (CIMSS) at VA Tech . Characterization studies are conducted to optimize the quality and t he properties of MR fluids, and different ingredients and formulations are tested to produce MR fluids that meet most appropriately the desi gn specifications. A modified HAAKE cone-plate viscometer is used to m easure the basic properties of the manufactured MR fluids. As a demons tration of MR fluid-based devices, a cross-stepper exercise machine is modified to incorporate an MR throttle valve, which is the most impor tant element of any MR fluid system.