Design and characteristic analysis of an X-shaped negative stiffness structure

The quasi-zero stiffness (QZS) mechanism is typically implemented by paralleling negative and positive stiffness structures to enhance the vibration isolation effect. As the core component, a novel bistable X-shaped negative stiffness structure (XNSS) is designed. Based on the geometric relationship between angular and displacement coordinates, the single-layer and multilayer mechanical model is derived from the principle of virtual work. After the non-dimensional process, a set of system parameters is summarized. Ensuring that these system parameters satisfy constraints, the comprehensive effects on XNSS are studied in detail. The parallel connection of XNSS and linear stiffness mechanism can constitute a QZS vibration isolator, and the influence of system parameters on loading capacity, stability of equilibriums, and dynamic stiffness are discussed in detail. The amplitude-frequency response and displacement transmissibility of nonlinear QZS vibration isolation model show excellent vibration isolation performance, compared with the corresponding linear system. The results show that the static analysis of the XNSS system parameters can be a good guide to the design of the QZS vibration isolator in order to obtain better dynamic performance.