Enhanced vibration absorption of plates with circular metasurface composed of lossy acoustic black hole subunits

Metasurfaces and acoustic black holes (ABHs), as two kinds of emerging structures exhibiting extraordinary performances in steering and trapping waves, respectively, both have attracted extensive attention of researchers due to their potential applications in vibration control. However, studies combining the merits of them are rarely reported. In this paper, we propose a lossy circular ABH metasurface (LCAM) composed of gradient ABH subunits pasted with damping layers to realize the enhanced omnidirectional vibration absorption of plates in broadband, which is attributed to the introduced multiple reflection effect in the lossy ABH subunits. The phase shifts of the lossy ABH subunits are derived by using the transfer matrix method and integral method, and the effective loss factors are obtained through the effective medium theory. Based on the theoretical analyses, the LCAM is designed, and the results of simulations and experiments show that the designed LCAM realizes enhanced omnidirectional vibration absorption of the plate. The LCAM is applied to plates with different dimensions and boundary conditions to show its strong adaptability. Our design improves the ABH effect by taking advantages of the multiple reflection effect in metasurfaces, which provides an effective method for passive structural vibration control.