The structural design and experimental investigation of focusing lens of A0 mode Lamb waves

The previous flexural wave lenses designed via refractive index are usually perforated on the plate, which destroys the structural integrity and reduces the stiffness and stability. In order to overcome this problem, an A0-wave-based focusing lens is designed based on the interference principle, in which different prisms are distributed on the plate surfaces. Firstly, the prism influence on band gaps is systemically investigated, the quantitative relation between prism height and phase velocity is obtained, and the lens is finalized. After that, the working performance is examined via FEM software, including focusing position, energy distribution near the focusing point, focusing size, frequency region and so forth. Finally, the lens is fabricated and experimental measured, which validates the structural design. Both numerical and experimental results demonstrate that the lens in this paper can efficiently focus the incident flexural wave on a fixed position, and also can work well in a frequency region centered the target frequency. The present design scheme has the advantages of superior focusing performance, high rigidity and easy processing, which provides guidance for the practical applications of acoustic focusing lenses in the fields of nondestructive testing and energy harvesting.