Performance of magnetorheological fluids in a novel damper with excellent fail-safe behavior

A novel magnetorheological damper, whose magnetic circuit contains beside an electromagnet also two permanent magnets, is described and tested. Without any consumption of electric energy, a medium damping force is achieved, which ensures an excellent fail-safe behaviour in case of an electric power loss. This medium damping force can be increased or decreased, depending on the polarity of the current in the coil. Furthermore, the performance of the damper with different MR fluids was investigated. By this way, the influence of the composition of the MR fluid in terms of the concentration of iron particles between 20 and 50 vol.% on the damping force could be evaluated. Finally, the damping force after various storage times of the damper was studied and indicated a good redispersibility of the MR fluid.