Cloaking Mechanical Waves

该项目探索了声音和振动的隐形。斗篷包裹着物体，使声波或振动波绕过物体。2006年，隐形出现在现场，第一次展示了一种可以隐身电磁微波的设备。声波隐身还处于初级阶段，甚至还不清楚是否有可能隐身弹性波。本课题将通过理论和仿真相结合的方法来解决这些问题。第一个目标是彻底了解声学斗篷，重点是所谓的五模超材料。它们像橡胶或水一样容易剪切，但与流体静力学相比，它们具有支持双轴应力状态的不同寻常的特性。主要目标，弹性动力学隐形，将首先考虑一种能够模拟较厚的正常固体层的波特性的超材料层。将使用涉及坐标和规范变换的数学关系，并将研究更复杂的柱面和球面结构。最终目标是一个真实的瑞利波隐形模型。更长期的社会效益将是减少振动和噪音的增强技术，以及在敏感区域和物体周围引导破坏性机械波能的方法，例如保护建筑物免受地震地面运动的影响。该项目将包括一场面向工程学荣誉新生的研讨会，主题为超材料、隐形和未来技术。本科生将明确参与这项研究，这是在目前针对高年级学生的一个项目的基础上进行的。一个用外行术语解释斗篷的网页将得到加强。

The project explores cloaking of sound and vibration. A cloak surrounds an object so that it causes waves of sound or vibration to bypass the object. Cloaking appeared on the scene in 2006 with the first demonstration of a device that can cloak electromagnetic microwaves. Acoustic cloaking is in its infancy, and it is not even clear whether cloaking of elastic waves is possible. This project will address these questions through theory and simulation. The first goal is a thorough understanding of acoustic cloaks, focusing on so-called pentamode metamaterials. These are easily sheared, like rubber or water, but have the unusual property that they support a biaxial state of stress, as compared with hydrostatic. The main objective, elastodynamic cloaking, will first consider a metamaterial layer capable of emulating the wave properties of a thicker layer of normal solid. Mathematical relations involving coordinate and gauge transformations will be used, and more complicated cylindrical and spherical structures will be studied. The final goal is a realistic model of Rayleigh wave cloaking. Longer term societal benefits will be enhanced technology for reducing vibration and noise, and methods to channel destructive mechanical wave energy around sensitive areas and objects, such as shielding buildings from earthquake ground motion. The project will include a seminar for honors engineering freshmen on the subject of metamaterials, cloaking, and futuristic technology. Undergraduates will be explicitly involved in the research, building on a current project for seniors. A web-page explaining cloaking in layperson terms will be enhanced.