A novel method of reducing the acoustic emission wave reflected by boundary based on acoustic black hole

Due to the difference between the characteristic impedance of air and plate structure, the acoustic emission (AE) wave propagating in a plate structure is reflected when reaching the boundary. It leads to the fact that the obtained signal contains not only direct AE components but also reflected components. The existence of the reflected AE wave brings error and difficulty to accurate AE source analysis. This paper attempts to introduce the acoustic black hole (ABH) into an experimental plate structure (a disc structure in this paper) to attenuate the reflected AE wave from the structure boundary and obtain the high Signal-Noise Ratio (SNR) direct AE wave. Firstly, the finite element model of a disc with an ABH is established to verify the attenuation of the reflected AE wave. Then, the orthogonal test is conducted to reveal the influence of geometric parameters of the ABH on reflection attenuation. And a method based on the optimal parameter combination of the ABH is proposed to attenuate boundary reflection. Finally, the broken-lead and friction experiments are performed on the processed disc with the ABH to verify the ability of the ABH to attenuate the boundary reflection of AE wave. Both analytical and experimental results show that the ABH is a candidate tool to reduce the reflected AE wave on the boundary.