A novel waveguide rod with acoustic black hole for acoustic emission signal enhancement and its performance.

As an essential auxiliary tool for acoustic emission (AE) detection, waveguide rods are widely used in testing situations where sensors cannot contact the specimens directly, such as high temperature, cryogenic, corrosion, radiation, etc. However, the AE signal attenuation in waveguide rod makes the risk of missing weak acoustic emission events in damage detection, which limits the application of waveguide rods. Therefore, in this work, a novel waveguide rod was presented based on acoustic black hole (ABH) theory to enhance the AE signal before reaching the sensor through the energy convergence effect of the ABH. Firstly, the geometric configuration of the waveguide rod with ABH was designed. The AE signal enhancement effect of the ABH waveguide rod was verified by comparing the amplitude of the AE signal for the traditional waveguide rod and the ABH waveguide rod by the finite element method. Secondly, the influence on the geometric parameters of the ABH waveguide rod for the AE signal enhancement effect was analyzed. The selection method of geometric parameters and the enhancement method of the AE signal with specific frequency bands were proposed to obtain expected AE signal enhancement results. Finally, the pencil-lead breaking experiments were implemented to verify the effectiveness of finite element method and the AE signal enhancement effect of ABH waveguide rod. The results show that the waveguide rod with ABH given in this paper has a significant AE signal enhancement effect and a good application prospect in structural acoustic emission health monitoring.