Necessity of MRFluid: Magneto rheological (MR) fluids offer solutions to many engineering challenges. The success of MR fluid is apparent in many disciplines, ranging from the automotive and civil engineering communities to the biomedical engineering community. There have been a countless number of studies which identify the benefits of using MR devices in these and other fields. This well documented success of MR fluids continues to motivate current and future applications of MR fluid.
Much of the success of MR fluid devices is largely due to advancements in fluid technology. Today’s MR fluids are capable of achieving yield stresses in excess of 80 kPa which indicates an impressive range of fluid controllability and dynamic range. The fluids have also exhibited improved stability behavior. Moreover, the durability and life of the fluid have developed such that the fluid can be considered for commercial implementation. The performance of today’s MR fluids is the result of a great number of studies which identify the properties and behavior of MR fluids. The literature is well populated with works related to the behavior of MR fluid or the performance of specific MR fluid devices. In many cases, knowledge of the performance of the MR device precedes a thorough understanding of the behavior of the fluid operating in such a device. This is the case for many MR fluid devices. An MR device intended for one application often finds use in an alternate application in which the operating conditions of the fluid differ greatly from the original application. An example of this “borrowed” technology is the many applications of Lord Corporation’s Motion Master™ damper. This damper, originally intended for seat suspensions in trucks and buses, has also been considered for service in civil engineering applications and in prosthetic limbs. In each of these applications, the operating conditions of the fluid vary considerably. Perhaps a more extreme example would be the use of MR automotive dampers (intended for vehicle primary suspensions) in impact or shock loading applications. Here again, the conditions inside the damper vary considerably.