A Review on Acoustic Black-Holes (ABH) and the Experimental and Numerical Study of ABH-Featured 3D Printed Beams

In the recent decade, there are increasing numbers of reported studies on the use of acoustic black hole (ABH) effects for the damping of flexural vibrations in engineering structures. This effect can be obtained by the use of a high-order power-law profile change in the thickness of the structure to induce a gradual decrease in incident wave velocity, to almost zero, along the propagation distance. ABHs have great potential for mitigating vibrations and noise. This paper covers the review of one-and two-dimensional ABHs and the experimental and numerical study of 3D printed beams with embedded ABH features. Specimens fabricated with the 3D additive manufacturing process were studied due to its expanding applications towards aerospace and automotive industries. However, limitations to the smoothness of the end product may affect the ABH effect, since the printing is typically via bottom-up layering where geometric accuracy is only up to the layer thickness. The vibration response of the 3D printed ABH beams, which has not been reported previously, is analyzed using the mean quadratic velocity and structural intensity parameters.