Abstract: A tunable and reusable impact energy absorbing system and process includes a control structure comprising a sleeve having an outer surface fixedly attached to a chassis, a seal at each end of the sleeve, a magnetorheological fluid disposed between the seals, and a coil in proximity to the magnetorheological fluid, wherein the seal and the magnetorheological fluid are in sliding engagement with a support member, wherein the impact surface is fixedly attached to a support member. Varying the current to the coil alters the magnetic field upon the magnetorheological fluid, which can be used to tune the yield stress of the sliding engagement.

Abstract: A magnetorheological fluid containing magnetorheological particles which are resistant to oxidation having regions rich in diffused nitrogen located therein and a method for producing such magnetorheological fluid.