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A metamaterial ultrasound mode convertor for complete transformation of Lamb waves into shear horizontal waves
Ultrasonics ( IF 4.2 ) Pub Date : 2021-10-19 , DOI: 10.1016/j.ultras.2021.106627
Yiran Tian 1 , Yihao Song 1 , Yanfeng Shen 2 , Zhengyue Yu 3
Affiliation  

This article reports a new mechanism involving a non-perforated resonant elastic metamaterial to achieve the complete conversion of Lamb waves (A0 and S0) into the fundamental shear horizontal (SH0) wave. The proposed metamaterial ultrasound mode convertor is studied via the observation of the special resonant shear motion of its unit cells, initiating with a conventional additive stub design. Thereafter, such a stubbed structure is further modified to fully couple the Lamb modes with the shear horizontal stub motion. By investigating the band structure of the metamaterial unit cell through modal analysis and tuning the shear resonant motions, a complete SH0 mode generation band within the simultaneous Lamb modes bandgap can be established in a wide frequency range. Such a special bandgap situation enables the complete mode conversion from Lamb waves into shear horizontal waves. The transformation capability of the proposed ultrasound mode convertor is further substantiated via the harmonic analysis of metamaterial chain model, showcasing the frequency spectrum of the transmitted wave modes. The optimal configuration is determined by conducting a parametric study to identify the most effective mode conversion performance. Finally, a coupled-field transient finite element simulation is carried out to acquire the dynamic response of the structure. The frequency-wavenumber analysis of the transmitted wave field illuminates the successful realization of the mode conversion behavior. Experimental demonstrations are presented to validate the numerical predictions. The proposed complete mode conversion capability may possess great potential for wave control and manipulation.



中文翻译:

用于将兰姆波完全转换为水平剪切波的超材料超声模式转换器

本文报告了一种新机制,该机制涉及非穿孔共振弹性超材料,以实现兰姆波(A 0和 S 0)到基本剪切水平(SH 0)波的完全转换。所提出的超材料超声模式转换器是通过观察其晶胞的特殊共振剪切运动来研究的,从传统的加法短截线设计开始。此后,进一步修改这种短柱结构以将兰姆模式与剪切水平短柱运动完全耦合。通过模态分析研究超材料晶胞的能带结构并调整剪切共振运动,完整的 SH 0可以在很宽的频率范围内建立同步兰姆模式带隙内的模式生成带。这种特殊的带隙情况可以实现从兰姆波到水平剪切波的完整模式转换。通过超材料链模型的谐波分析进一步证实了所提出的超声模式转换器的转换能力,展示了传输波模式的频谱。通过进行参数研究来确定最有效的模式转换性能,从而确定最佳配置。最后,通过耦合场瞬态有限元仿真获得结构的动力响应。透射波场的频率波数分析阐明了模式转换行为的成功实现。实验演示被提出来验证数值预测。所提出的完整模式转换能力可能具有用于波控制和操纵的巨大潜力。

更新日期:2021-10-22
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