Theoretical Modeling and Optimal Design of Compound Periodic Acoustic Black Hole Beams

Acoustic black hole (ABH) structures have been widely studied for the potential in vibration reduction. However, traditional ABH structures are only effective above the cut-on frequency and suffer from structural strength problem, which significantly hinder the practical application. Our previous investigation shows compound periodic ABH beams contribute to solve these limitations. However, the complex double-layer vibration characteristics of the structure lead to the research method being limited to FEM and the absence of performance optimization. In this paper, a theoretical model of compound periodic ABH beams is established by using the Timoshenko beam theory and the wavelet decomposition energy model. In order to obtain broadband band gaps over the whole frequency range, especially at the low frequency region, while keep relatively high structural strength, a multi-objective optimization is carried out based on the fast elite non-dominated sorting genetic algorithm II (NSGA-Ⅱ). The optimization shows a middle reinforcement connecting ABH profiles helps to tremendously widen band gaps with the combination effect of local resonances and Bragg scattering, and meanwhile increase the structural strength.