Vibration damping and isolation using negative stiffness structures

This work presents a novel class of engineered structures with significant promise to improve vibration damping treatments and isolation systems: negative stiffness (NS) elements. A mechanical system displaying negative stiffness is characterized by a loading state that requires a decreasing force level to increase the deformation of the system. Systems displaying NS will possess regions of negative curvature in their strain energy response as a function of deformation; hence, they are unstable when unconstrained. Analytical and experimental results will be presented demonstrating that NS systems comprised of buckled beams in parallel with positive stiffness springs can be used to construct quasi-zero stiffness vibration isolation systems, which provide high static but low dynamic stiffness for compact base isolation design. Transmissibility measurements of these same systems show that the nonlinearity of NS systems constructed from buckled beam structures enable tunable vibration isolation behavior and isolation from impact. Finally, modeling results will be presented demonstrating that sub-wavelength NS elements embedded in a viscoelastic material can be used to design vibration damping treatments with increased loss factor and minimally reduced stiffness to reduce the ringdown time for an impulsively loaded multi-layered beam. [Work supported by DARPA, ARO, and NSF.]