Broadband Vibration Attenuation of the pipe structure under the Synergistic Effect of Acoustic Black Hole and Local Resonance

In recent years, acoustic black hole (ABH) has developed rapidly in vibration acoustics as a wave manipulation technology. It is currently being tried to be applied to the vibration control of industrial pipes. Usually, the ABH structure has an obvious vibration suppression ability in the middle and high frequency range, but the vibration suppression is insufficient in the low frequency range; at the same time, the embedded ABH structure leads to structural weakening. Considering the advantages of low-frequency control of local resonance (LR), this paper proposes an acoustic black hole-local resonance coupling structure (ABH-LR), which is used in pipe vibration control, by combining the theory of ABH and local resonance. It consists of a one-dimensional ABH structure, damping layers, and oscillators (several for local resonance) attached to the pipe. The results show that at low frequencies such as 190Hz and 440Hz (<500 Hz), vibration amplitude decreases significantly through the local resonance effect and anti-resonance matching in the periodic structure. In the middle and high frequency range (>500 Hz), the vibration energy in the pipe is captured by the ABH and dissipated through the damping layer attached to the central region of the ABH. ABH-LR realizes broadband vibration attenuation. The study reveals the wave blocking mechanism of the local resonance effect and the energy accumulation effect of the ABH structure, through the influence analysis of the material parameters, boundary conditions, and periodical arrangements of the ABH-LR pipe. With the increase of the damping layer thickness and loss factor, the equivalent modal loss factor of the system shows a nonlinear jump feature, with a maximum increase of 5 times. Compared with the single ABH-LR unit model, three-unit models attached to the pipe have better vibration suppression on the pipe. When the boundary conditions change, ABH-LR can still suppress the vibration of the pipe.