Magnetorheological bypass damper exploiting flow through a porous channel

A magnetorheological (MR) damper with a bypass valve containing porous media is developed. Movement of the piston forces MR fluid to flow from one side of the piston to the other, through an externally mounted bypass packed with magnetic spheres. The passageways between the spheres provide narrow, tortuous channels that act as a controllable valve when subjected to a magnetic field. A stationary magnetic coil is wrapped around the so-called porous valve, which is isolated from the MR fluid and external to the primary hydraulic cylinder. While flowing through the tortuous channels in the porous media created by the packed spheres, the MR fluid experiences varied local flow directions, and thus an external field can be applied in any direction to adjust damping levels. Additionally, the use of long channels, which are tightly packed to create narrow passageways, allows a very high damping force to be generated by a relatively compact damper. Furthermore, use of an externally mounted coil allows for maintenance accessibility, and the magnetic flux return path can be either empty (air) or any high permeability material. The damper is tested for steady-state sinusoidal displacements, and equivalent viscous damping and complex stiffness are computed. It is shown that the porous bypass valve MR damper can provide high controllable damping force and a wide force range.