Enhance the energy dissipation ability of sleeve-type negative stiffness structures via a phase-difference mechanism

Sleeve-type negative stiffness structures (ST-NSSs) can dissipate harmful mechanical energy in a reusable and controllable approach, and they are lightweight and with high mechanical performance, thus have a wide range of application prospects in many engineering fields. However, the load-displacement curve of existing ST-NSSs exhibits a waved shape, which has limited their energy dissipation ability (The ideal energy dissipation structure is required to have a stable and controllable load response). In this work, a new strategy is proposed by combing multiple ST-NSS cells in parallel with a phase-differences mechanism to improve the energy dissipation ability. A theoretical model is created to predict the load-displacement relationship of the parallel structure; a program is developed to obtain the numerical solution of the problem, and these two approaches are verified by quasi-static loading-unloading experiments. The results show that the proposed strategy can significantly improve the energy dissipation ability of parallel structures using a small number of negative stiffness cells. Additionally, it is found that by limiting the displacement range, the energy dissipation ability of the parallel structure can be further improved. This study brings a new way to design reusable, programable, highperformance, and highly adaptable negative stiffness structures for dissipating harmful mechanical energy in impacting and vibration.