EAGER: Tuning Granular Phononic Crystals through Pattern Transformations

这一探索性研究（EAGER）早期概念奖支持基础研究，为可能具有可调谐低频带隙的可模式转换颗粒声子晶体提供知识。声子带隙材料是以声子带隙为特征的复合材料，声子带隙即禁止机械波传播的频率范围。由传统结构材料制成的声子带隙材料在某些高频范围内具有典型的固定窄声子带隙。然而，干扰人体的有害振动和噪声的特征是在较低的频率范围内的宽带频率内容。因此，由于这种知识差距，他们的实用产品尚未出现。这项新研究将开启实用声子带隙材料的可能性。因此，如果这个项目成功，这项研究的结果将使美国制造业受益。此外，PI将为包括代表性不足的少数民族和女学生在内的不同受众设计与模式转变有关的实践活动。通过这些活动，我们的目标是激发学生从事工程方面的职业。这个项目的目的是探索一种模式可转换的二维颗粒晶体的概念验证，其特点是其低频可调声子带隙。目标是基于中心假设，即不稳定性与模式转换引起的带隙可调性密切相关。该假设将通过执行以下具体任务来证明：(1)模式转换机制的识别，(2)识别机制的实验验证，(3)数值声子色散关系的实验验证，以及(4)数值声子色散关系的实验验证。该研究试图采取一种变革性的方法，将传统的不稳定性理论与颗粒声子晶体的未知区域联系起来。不稳定现象几乎与长度尺度无关。因此，本研究的成功完成将对声子带隙材料领域产生重大影响，因为不稳定诱导机制可以用于设计可调谐的颗粒声子晶体，在大范围的长度尺度上使用各种驱动。

This EArly-concept Grant for Exploratory Research (EAGER) award supports fundamental research to provide knowledge for a pattern-transformable granular phononic crystal, which may have tunable low-frequency band-gaps. Phononic band-gap materials are composite materials characterized by phononic band-gaps, i.e., frequency ranges in which the propagation of mechanical waves is prohibited. Phononic band-gap materials made of conventional structural materials possess typically fixed narrow phononic band-gaps in some high-frequency ranges. However, unwanted vibrations and noises disturbing human body are characterized by broadband frequency contents in rather low-frequency ranges. Thus, due to this knowledge gap, their practical products has not appeared yet. This new research will open the possibility of practical phononic band-gap materials. Therefore, if this project succeeds, results from this research will benefit the U.S. manufacturing industry. Furthermore, the PI will design hands-on activities relating to pattern transformations for diverse audiences including under-represented minorities and female students. With these activities, the goal is to stimulate students to pursue a career in engineering.The objective of this project is to explore the proof-of-concept of a pattern-transformable two-dimensional granular crystals, which is characterized by its low-frequency tunable phononic band-gaps. The objective is based on the central hypothesis that instability is closely relating to the pattern-transformation-induced bandgap tunability. The hypothesis will be demonstrated by performing the following specific tasks: (1) identification of pattern transform mechanism, (2) experimental validation of the identified mechanism, (3) numerical phononic dispersion relations, and (4) experimental validation of the numerical phononic dispersion relations. The research attempts to take a transformative approach that links conventional instability theory to an uncharted area of granular phononic crystals. Instability phenomenon is nearly length-scale independent. Therefore, the successful completion of this research could have a significant impact in the field of phononic band-gap materials, because the instability-induced mechanism can be adopted for the design of tunable granular phononic crystals using various actuations in a wide range of length scales.