A graded acoustic metamaterial rod enabling ultra-broadband vibration attenuation and rainbow reflection

Abstract

Broadband vibration suppression poses a significant engineering challenge, and researchers have turned to acoustic metamaterials (AMs) as a promising solution. Traditional periodic AMs, though effective, often have narrow band gaps that limit their practicality. This study focuses on the design of a graded AM rod that achieves ultra-broadband vibration attenuation and rainbow reflection. The graded rod consists of various sections with seamlessly interconnected band gaps. The design is based on the dispersion analysis of an infinite uniform AM rod, complemented by the transmission calculation of a finite graded AM rod. The study emphasizes the importance of incorporating a specific number of identical unit cells in each section and introducing a small amount of damping in each resonator for effective ultra-broadband vibration suppression. The designed AM rod effectively blocks the propagation of longitudinal waves, regardless of their incident direction. Furthermore, the research demonstrates the orderly filtration of frequency components along the wave propagation path, showcasing the phenomenon of acoustic rainbow reflection. This phenomenon is illustrated through finite element simulations. This work not only addresses the pressing engineering challenge of broadband vibration attenuation but also paves the way for the separation, collection and energy harvesting of elastic waves.