Nonlinear Acoustic Meta-Materials for Wave Propagation Management and Control

该研究探索了周期性元材料中的非线性声子行为，旨在开发具有新颖功能、增强性能和自适应可调性的低功率波基器件。具有周期性微结构的声子超材料表现出非凡的波特性，如带隙、响应方向性、左旋性和负声折射，所有这些都可以用于设计在广泛频率和长度尺度上工作的声学器件。随着设备的小型化，非线性行为成为常态，而不是例外，正如用于描述小规模相互作用的复杂势所见证的那样。本研究探讨了非线性对色散特性、带隙和方向性的影响，并特别探讨了非线性作为实现新功能的手段，丰富了周期介质的设计空间。硬化和软化效应、正常响应模式与剪切响应模式、振幅相关色散以及超谐波和次谐波的存在实际上可能对给定介质的导波特性产生积极影响，并可能被用来实现波特性的可调性。分析和计算技术将制定，以研究非线性声子系统的非线性性质，并预测其波动力学效应。所开发的工具将能够设计具有可控带宽的可调谐通带滤波器和能够将声能定向和聚焦到特定方向的声学超材料。将这些概念应用于滤波器、波导、逻辑端口和执行各种基于声学的信号处理功能的超声波换能器阵列是非常有吸引力的，特别是在电子设备受到严重功率限制的频率下。该项目预计将显著推进非线性超材料波动力学一般领域的知识和理解，这将对开发用于通信系统（移动电话、GPS设备等）的高频可调谐设备、噪声隔离、能量定向材料、用于医疗设备的可调谐超声波、可调谐声学麦克风和接收器以及声波束形成器非常重要。

The research explores nonlinear phononic behavior in periodic meta-materials, with the intent of enabling the development of low-power wave-based devices with novel functionality, enhanced performance, and adaptive tunability. Phononic meta-materials with periodic microstructures exhibit extraordinary wave properties such as band-gaps, response directionality, left-handedness, and negative acoustic refraction, all of which can be employed for the design of acoustic devices operating over a broad range of frequencies and length scales. As devices miniaturize, nonlinear behavior becomes the norm and not the exception, as witnessed in part by the complex potentials used to describe small-scale interactions. This research investigates the effects of nonlinearities on dispersion characteristics, band-gaps, and directionality and specifically explores nonlinearities as means to achieve novel functionalities that enrich the design space of periodic media. Stiffening and softening effects, normal versus shear modes of response, amplitude-dependent dispersion, and the presence of super- and sub-harmonics may in fact positively affect the wave guiding characteristics of a given medium and may be exploited to achieve tunability of the wave properties. Analytical and computational techniques will be formulated to investigate the nature of nonlinearities in nonlinear phononic systems, and to predict their wave mechanics effects.The developed tools will enable the design of tunable pass-band filters with controllable bandwidth and of acoustic meta-materials capable of directing and focusing the acoustic energy towards specific directions. The application of these concepts to filters, waveguides, logic ports, and ultrasonic transducer arrays which perform a variety of acoustics-based signal processing functions is very attractive particularly at frequencies where electronics suffer from severe power limitations. The project is expected to significantly advance knowledge and understanding in the general area of nonlinear meta-material wave mechanics, which will be important for the development of high-frequency, tunable devices for use in communication systems (mobile phones, GPS units, etc.), noise isolation, energy-directing materials, tunable ultrasound for medical devices, tunable acoustic microphones and receivers, and acoustic beamformers.