We propose an asymmetric viscoelastic metamaterial constructed from a unit with two distinct resonators selected to isolate elastic waves in a large coupled locally resonant bandgap (LRBG) and simultaneously realize designed unidirectional zero reflection (UZR). A generalized Maxwell model, as opposed to a Kelvin–Voigt model or standard linear solid model, is adopted to more accurately describe actual linearly viscoelastic mechanical response in both the epoxy and rubber components over the frequency range of application. The analysis of the band structure of this asymmetric viscoelastic matamaterial shows that there is a quasi-bandgap formed between the two LRGBs when they are close, allowing a broadening of the bandwidth of wave isolation. Interface response theory and finite element methods are used to show that the quasi-bandgap forms in the frequency domain for both discrete and continuous metamaterials. Exploiting this asymmetric viscoelastic metamaterial, an exceptional point with UZR for longitudinal waves in the non-Hermitian system is achieved by tuning the masses of two oscillators in the unit. The proposed multifunctional metamaterial may have significant potential in vibration/wave control and guided wave based non-destructive testing.

我们提出了一种非对称粘弹性超材料，由一个单元构成，该单元具有两个不同的谐振器，用于隔离大耦合局部谐振带隙 (LRBG) 中的弹性波，同时实现设计的单向零反射 (UZR)。与 Kelvin-Voigt 模型或标准线性实体模型相反，广义 Maxwell 模型被用来更准确地描述环氧树脂和橡胶组件在应用频率范围内的实际线性粘弹性机械响应。对这种非对称粘弹性材料的能带结构的分析表明，当它们靠近时，两个 LRGB 之间会形成准带隙，从而扩大了波隔离的带宽。界面响应理论和有限元方法用于显示离散和连续超材料在频域中的准带隙形式。利用这种不对称的粘弹性超材料，通过调整单元中两个振荡器的质量，可以实现非厄米系统中纵波的 UZR 特殊点。所提出的多功能超材料可能在振动/波控制和基于导波的无损检测方面具有巨大潜力。