A vibration absorber based on two-dimensional acoustic black holes

As a passive damping technique for vibration and noise mitigation, acoustic black hole (ABH) structures have been drawing an increasing attention because of their easy-to-realize and broadband wave focusing and energy dissipation characteristics. Structures with embedded ABHs, however, inevitably compromise the overall structural stiffness and strength, which hampers their use as critical structural components. As an alternative, this paper proposes a new type of device, i.e. a two-dimensional circular ABH-based dynamic vibration absorber (2D ABH-DVA), as an auxiliary component to be added to an existing structure for vibration suppressions. Using a plate as benchmark structure, finite element (FE) simulation results show a systematic reduction of its resonant peaks over a broad frequency range upon the deployment of the ABH-DVA. Analyses uncover two underlying mechanisms which dominate the physical process: dynamic interaction with the host structure and damping enhancement as a result of ABH-specific energy trapping. This is warranted by an effective dynamic coupling between the primary structure and the add-on ABH-DVA, which can be quantified by a mode-specific and location-dependent coupling coefficient defined in the paper. It is further demonstrated that, despite the rich modal contents of the ABH-DVA, strong coupling with the primary structure only takes place through a few DVA modes. Analyses also lead to a simple linear relationship relating the overall system damping with the properties of the damping material over the ABH-DVA. Finally, the broadband vibration suppression ability of the proposed 2D ABH-DVA is verified through experiments. The study demonstrates the unique coupling features between the DVA and the host structure, which provides design guidelines for unsymmetrical 2D or other ABH-DVA designs in the future.