基于星形拉胀结构的声学超材料双负特性形成机制与调控规律研究

Sonic metamaterials have a wide range of application in wave control and super-resolution imaging, and are favored for several unique and advantageous properties. The structures of currently existing double-negative sonic metamaterials are highly complex, as they are composed of various materials, which limits their design function and application in practice – it is quite desirable, as such, to realize double-negative features by single materials simple in structure. Due to unique concave configurations and various resonances, star-shaped auxetic structures readily form band gaps and show superior material properties; as such they are considered ideal structures for single-phase metamaterials. In this proposal, single-phase metamaterials are designed based on star-shaped structure. It may be feasible to design an acoustic flat lens with single-phase metamaterials by establishing a numerical model for star-shaped auxetic structures and conducting a series of experiments to determine the effects of the metamaterial’s structural parameters; this should include ascertaining the internal mechanical mechanisms among the structures, deformation behavior, and extraordinary properties, as well as investigating the formation and regulatory mechanisms of the double-negative characteristics. This research helps to reveal the formation and regulatory mechanisms of double-negative characteristics from the structural level, and helps solve problems related to structural optimization and design of single-phase acoustic devices.

由于奇异的物理特性，声学超材料在波定向控制与超分辨成像等领域有着广泛的应用前景。目前双负声学超材料结构构型通常较为复杂，需要多种材料复合而成，不利于功能设计与实际应用。如何利用简单结构的单相材料实现双负特性，是声学超材料研究中急需解决的关键科学问题。星形拉胀结构具有特殊的内凹构型，包含多种共振形式，有利于低频带隙及超常声学属性的形成，是单相材料实现双负特性的理想结构。本项目拟利用星形拉胀结构开展单相双负声学超材料的设计研究，通过构建数值分析模型并结合实验，分析结构参数对超材料属性的影响规律，研究结构—变形—超常属性内在关联的力学本质，探明双负特性形成机制，在此基础上设计出可实现亚波长成像的平板型透镜。本项目的研究从结构层面更好的揭示双负特性形成与调控机制，并且有助于解决声学超材料结构优化和器件设计中的实际问题。

星形结构具有特殊的内凹构型，包含多种共振形式，有利于低频带隙及超常声学属性的形成，是单相材料实现双负特性的理想结构。本项目通过有限元数值分析并结合实验重点开展星形结构声学超材料带隙及双负特性形成机制研究，研究结果表明该结构能在低频产生较宽的带隙，与传统结构超材料的共振形式不同，其带隙源于丰富的弯曲模态，结构形式更为简单。此外，由于这些丰富的弯曲模态形成的杂化态，使其在可以在特定频率范围内实现双负特性与负折射的反常色散效应。基于双负特性，利用星形结构设计了新型声波超透镜，它可以实现对声波的超分辨成像，成像分辨率可达0.39λ，这为单相双负声学超材料的设计与制备提供了新的思路，也为声学超材料在波定向控制与超分辨成像等领域的应用奠定了基础。

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