Vertically spaced ring-like elastic metamaterials for broadband tunability of low-frequency flexural waves

Abstract

Achieving continuous and stable tunability of local resonators without requiring ongoing external stimuli, while maintaining a broad low-frequency bandgap, remains a significant challenge in elastic metamaterials. This study introduces a novel tunable metamaterial for flexural wave isolation, consisting of a compact elastic ring-like frame integrated with a central mass block formed by bolt–nut–gasket assemblies. Tunability is attained by adjusting the vertical separation between two stacked elastic layers through the rotational angle of threaded nuts, thereby modulating the system’s flexural stiffness. This approach enables continuous, reversible, and passive control of flexural wave propagation. The tuning mechanism is systematically investigated through theoretical modeling, finite element simulations, and experimental validation, encompassing dispersion analysis and frequency response studies of both infinite and finite structures. Results confirm the effectiveness of the proposed design in low-frequency vibration attenuation. Parametric studies further elucidate the role of geometric features on bandgap tunability. Potential applications, including vibration isolation, flexural wave barriers, and external vibration absorption for tubular structures, are demonstrated, and a comparative evaluation highlights the advantages of the proposed design relative to state-of-the-art tunable metamaterials.