Magnetorheological Fluids: Materials, Characterization, and Devices

Magnetorheological (MR) fluids consist of stable suspensions of magnetic particles in a carrying fluid. Magnetorheological effect is one of the direct influences on the mechanical properties of a fluid. It represents a reversible increase, due to an external magnetic field of effective viscosity. MR fluids and devices have the potential to revolutionize the design of hydraulic systems, actuators, valves, active shock and vibration dampers, and other components used in mechanical systems. At present, there is a compelling need to develop new and improved MR fluids, to lower their production cost through improved manufacturing processes, and to develop MR fluid-based application devices that will demonstrate the engineering feasibility of the MR fluids concept and will highlight the implementation challenges. To this end, the present study is undertaken. A unique high-speed bead mill machine, especially designed to the manufacture of MR fluids, is used to fabricate MR fluids in a laboratory-scale MR fluid fabrication facility at the Center for Intelligent Material Systems and Structures (CIMSS) at VA Tech. Characterization studies are conducted to optimize the quality and the properties of MR fluids, and different ingredients and formulations are tested to produce MR fluids that meet most appropriately the design specifications. A modified HAAKE cone-plate viscometer is used to measure the basic properties of the manufactured MR fluids. As a demonstration of MR fluid-based devices, a cross-stepper exercise machine is modified to incorporate an MR throttle valve, which is the most important element of any MR fluid system.