Snapping Shells: Coupling Geometry, Dynamics, and Materials to Harvest Energy through Instability

当一个结构突然变成另一种形状时——就像在刮风的日子里一把雨伞的倒置——它的结构和材料的完整性往往会永久丧失。然而，许多软结构能够逆转两种形状之间的变化。这为设计动态和适应性强的工程结构提供了一个迷人的机会。捕蝇草的叶子迅速闭合是一个例子，说明了捕捉在自然界中是如何提供功能的。该奖项支持结构失稳力学的基础研究。特别是，它考虑了由先进和活性材料制成的结构，这些材料能够将变形转化为能量。其结果将帮助工程师设计出将不稳定性作为特征而不是故障的系统，从而使结构在短时间内容易且可预测地改变形状，并在此过程中转换和存储能量。这种结构在需要自主电源的美国工业中有应用。由于“弹跳盘”和“弹跳弹”玩具中使用的弹跳结构带来了巨大的乐趣，因此这项研究将有助于提高公众对科学的兴趣。许多柔软的、细长的结构能够在两种稳定的结构之间通过弹跳不稳定性快速变化。本研究将建立壳双稳定性的力学和几何准则。它将决定壳的几何形状对弹通速度的影响，弹通后的振动，以及非对称到对称的壳耗散率。材料性质的影响将被检查，以了解自激弹壳，结构是暂时双稳态的反弹。研究小组将用一种电活性材料制备外壳。这将使研究小组能够在不稳定期间对壳体的平面内应变进行新的测量。这些测量将为壳结构理论提供重要的实验见解。最后，介电弹性体壳也将提供一种自然的手段，以收集能量，在弹性体变形。研究团队将进一步开发BLINK，这一创新项目将向学生介绍我们的眼睛经常错过的快速发展的科学。该项目将以学生使用玩具爆竹的力学作为研究牛顿运动定律的一种方式而告终。该计划的实施，以及随后相关在线视频内容的创建，将为学生和公众提供机会，让他们认识到力学研究在应对当前技术挑战方面的重要性。

When a structure snaps to an alternate shape -- like the inversion of an umbrella on a windy day -- its structural and material integrity are often permanently lost. Many soft structures, however, are able to reverse the change between two shapes. This presents a fascinating opportunity to design dynamic and adaptable engineering structures. The rapid leaf closure of the Venus flytrap is an example of how snapping provides functionality in nature. This award supports fundamental research on the mechanics of instabilities in structures. In particular, it considers structures made of advanced and active materials which are capable of converting deformation into energy. Its results will help engineers design systems that use instabilities as a feature rather than a fault, thereby enabling structures that easily and predictably change shape over a short timescale, converting and storing energy in the process. Such structures have applications in U.S. industries with needs for autonomous power sources. Since snapping structures have been employed with great amusement in the `jumping disc' and `popper' toys that jump with an audible pop, this research will help increase public interest in science. Many soft, slender structures are able to rapidly change between two stable configurations by a snap-through elastic instability. This research will establish the mechanical and geometric criteria for shell bistability. It will determine the effect of shell geometry on the speed of snap-through, the post-snap vibrations, and the rate of asymmetric-to-symmetric shell dissipation. The effect of material properties will be examined to understand the self-actuated snap-back of shells, structures that are temporarily bistable. The research team will prepare shells out of an electrically active material. This will allow the research team to conduct novel measurements of the in-plane strain in shells during instability. These measurements will contribute important experimental insight to the theory of shell structures. Finally, the dielectric elastomeric shells will also offer a natural means for harvesting energy during the snap-through deformation. The research team will further develop BLINK, the innovative program that introduces students to the fast-moving science that our eyes often miss. The program will culminate with students using the mechanics of toy poppers as a way to study Newton's laws of motion. The implementation of this program, and subsequent creation of relevant online video content, will provide opportunities for students and the general public to realize the importance of mechanics research in answering current technological challenges.