Chapter 11 - Magnetorheological Devices

Abstract

The mechanical properties of magnetorheological materials can be changed and controlled by an applied magnetic field. This makes the group of materials interesting for damping applications and vibration control. Most of the work done so far has been performed on magnetorheological fluids, which are suspensions of magnetically polarizable particles in a carrier liquid. For some applications it would be preferable to use a rubber or a gel instead of the liquid. Such magnetorheological solids would not have any problems of sedimentation of particles, the devices could be made smaller and cheaper since there would be no need of a container for the fluid, and the changes in the mechanical properties could be expected to be faster than in a liquid. However, magnetorheological solids work only in the pre-yield region while the fluids typically work in the post-yield region, so the two groups of materials are therefore more complementary than competitive. Examples of rubbers that are interesting for magnetorheological applications are silicone, natural rubber and nitrile rubber. The addition of iron particles to the rubber will influence the service life of these rubber devices. For optimal function of the devices, prediction of service life is necessary. Such predictions are also necessary for magnetorheological devices to become commercially successful.