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

折断壳：耦合几何、动力学和材料，通过不稳定性获取能量

• 批准号: 1435607
• 负责人: Douglas Holmes
• 金额: $ 29.46万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-08-15 至 2014-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1435607&HistoricalAwards=false
• 关键词: Snapping; Shells; Coupling; Geometry; Dynamics

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.

当一种结构突然变成另一种形状时--就像在刮风的日子里把伞翻过来一样--它的结构和材料的完整性通常会永久性地丧失。然而，许多软结构能够逆转两个形状之间的变化。这为设计动态和适应性强的工程结构提供了一个极好的机会。捕蝇器的叶子快速闭合就是捕捉在自然界中提供功能的一个例子。该奖项支持结构中不稳定力学的基础研究。特别是，它考虑了由先进和活性材料制成的能够将变形转化为能量的结构。它的结果将帮助工程师设计将不稳定作为特征而不是故障的系统，从而使结构能够在短时间尺度内轻松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行业中有应用。这项研究将有助于提高公众对科学的兴趣，因为在“跳盘”和“爆竹”玩具中使用抓拍结构非常有趣，这些玩具可以听到砰的一声跳跃。许多柔软、细长的结构能够通过快速弹性不稳定在两种稳定构型之间快速变化。本研究将建立壳体双稳的力学和几何判据。它将决定壳的几何形状对突跃速度、突跃后的振动以及非对称到对称的壳的耗散率的影响。将研究材料特性的影响，以了解壳的自启动回跳，即暂时双稳的结构。研究小组将用一种具有电活性的材料来准备外壳。这将使研究小组能够对壳体在失稳期间的面内应变进行新的测量。这些测量结果将为壳体结构理论提供重要的实验依据。最后，电介质弹性体外壳还将提供一种在突跃变形过程中获取能量的自然方法。研究团队将进一步开发BLINK，这是一个创新的项目，向学生介绍我们经常错过的快速发展的科学。该计划的高潮将是学生使用玩具弹射器的力学作为学习牛顿运动定律的一种方式。该计划的实施，以及随后相关在线视频内容的创建，将为学生和普通公众提供机会，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。