Development of evaluation methodology for design of a passive type MR damper

An evaluation method for the damping force characteristics of a passive type MR damper is developed. Although the MR damper is a fully passive device without any active components such as sensors, power supplies and power controllers, it exhibits functionally variable damping characteristic similar to an existing semi-active damper which controls the damping force based on sky-hook theory. The developed evaluation method is based on static magnetic field analysis and simplified fluid flow model which is represented by a quadratic equation for the piston speed of the damper. The developed method was applied to the characteristic evaluation for the prototype of the passive type MR damper. The obtained analytical results agree well with the measured damping force and the response characteristics in a shaking table test with a single-degree-of-freedom system. Moreover, the analytical results clarified some requirement for the performance improvement, for instance, the relative magnetic permeability of the magnetic components such as the cylinder and the piston of the damper should excess 2000 in order to utilize the variability of the damping force effectively. (author)