Vibration reduction of cables with pendulum-type elastic metamaterials

Abstract

Elastic metamaterials (EMMs) have been used to reduce the vibration of various mechanical structures. Recent studies have proposed methods to reduce the vibration of cables and space tethers by introducing pendulum-type EMMs. However, the vibration absorption characteristics in the bandgaps of pendulum-type EMMs need to be investigated in relation to the local resonances of the unit cell structure because only beams among the unit cell structure were considered. Furthermore, it is necessary to improve the vibration reduction performance of the pendulum-type EMMs by allocating as many bandgaps as possible in the frequency range of interest. In this study, the effect of the dynamic characteristics of the coupled structure with the same configuration as the unit cell structure including the ring or annular plate as well as the beam were investigated in depth. Further, based on these results, an improved pendulum-type EMM with multiple bandgaps in the frequency range of interest was developed, which is well suited for most practical applications in mechanical systems where the influence of low vibration modes is dominant. The vibration reduction performance and the effect of the bandgaps of the pendulum-type EMM with an annular plate were verified through comparison between the experimental and simulation results. The frequency response experiments and simulation results were consistent in terms of the resonant peak frequencies outside the bandgaps and the low response amplitude within the bandgaps. Moreover, the experimentally visualized and simulated operational deflection shapes showed that the cable hardly vibrates at the frequency within the bandgap; at this frequency, the operational deflection shape of the annular plate is very similar to the mode shape of the vibration mode of the coupled structure.