Smart colloidal dampers with on-demand controllable damping capability

Smart dampers with on-demand controllable damping curves are key components for the semi-active vibration control of structures. For current smart dampers either utilizing friction or viscosity to dissipate mechanical energy, potential thermal problems are their major drawbacks. Novel colloidal dampers have recently been developed with low heat generation and high damping efficiency; they are, however, passive, and have no on-demand controllable damping capability. In this paper, we propose a smart colloidal damper by employing water-based ferrofluids in damping media. We observe that the corresponding damping hysteresis loops can be affected by applied magnetic fields significantly and rapidly. We further retrieve the instant stiffness and the damping coefficient of the smart colloidal damper from the measured hysteresis loops. It is shown that negative stiffness and a negative damping coefficient may occur during the operation of the smart colloidal dampers.