Competitive advantages of a bistable vibration isolator: Cut-off frequency and operational safety near harmful resonance

Abstract

This study reveals the competitive advantages of a bistable vibration isolator over conven-tional linear and monostable ones. Generally, reducing stiffness improves vibration isolation performance with a lower cut-off frequency but for the linear vibration isolators involves a large-amplitude oscillation. Nonlinear monostable and bistable vibration isolators have been developed to resolve the contradictory issue of the linear case, reducing both the cut -off frequency and the range of oscillation. However, it has not yet been determined what advantages make a bistable vibration isolator more promising than a monostable one. In this study, equivalent linear, monostable, and bistable vibration isolators were found, and their numerical and theoretical dynamic responses compared directly. First, the cut-off frequency tended to be lower in the order of the bistable, equivalent linear, and monostable vibration isolators. In other words, the bistable system provides a wider vibration isolation bandwidth than the equivalent linear one, whereas the monostable one makes it narrower. Second, the bistable vibration isolator enhanced operational safety in the amplification region thanks to its small force transmissibility, while the monostable one exacerbated the risk. Bifurcation analyses of the nonlinear steady-state oscillations of the bistable and monostable vibration isolators were also performed to identify and investigate the dangerous and safe amplification regions. The results of the analyses clearly demonstrated the superior operational safety of the bistable vibration isolator, particularly in terms of a larger safety margin in the amplification region.