A0模态Lamb波聚焦透镜的结构设计及实验研究

基于折射率的弯曲波透镜多在板结构上打孔或挖槽,这种设计破坏了原有的结构,降低了板的刚度和稳定性。鉴于此,通过在板表面镶嵌棱柱的方式设计了A0模态Lamb波的聚焦透镜。首先,详细讨论了棱柱的结构参数对Lamb波带隙的影响机理,获取了波速与结构尺寸的定量关系,并实现了透镜的结构设计;其次,有限元仿真了该聚焦透镜的工作性能,包括聚焦位置、焦点处能量分布、聚焦尺寸、工作带宽等;最后,通过实验验证了该透镜设计的正确性。研究结果表明,设计的透镜能够使弯曲波聚焦在预先设定位置,且在不改变结构参数的情况下具有一定的工作频率带宽。该透镜设计方法具有聚焦性能优越、刚度强、易于加工等优点,为声聚焦透镜在无损检测、能量收集等领域的实际应用提供了参考。

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.