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: 1505125
• 负责人: Douglas Holmes
• 金额: $ 29.46万
• 依托单位: Trustees of Boston 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: 2014-08-18 至 2018-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1505125&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.

当结构捕捉到替代形状时（例如在大风天的雨伞的倒置）通常会永久丢失其结构和物质完整性。但是，许多软结构能够扭转两种形状之间的变化。这为设计动态和适应能力的工程结构提供了一个有趣的机会。金星捕蝇器的快速叶子闭合是捕捉如何提供自然界功能的一个例子。该奖项支持有关结构不稳定性机制的基本研究。特别是，它考虑了能够将变形转换为能量的高级和活性材料制成的结构。它的结果将有助于工程师设计使用不稳定性作为功能而不是故障的工程师，从而实现了在短时间内易于改变形状的结构，在此过程中转换和存储能量。此类结构在美国行业中具有对自动电源需求的应用。 由于在“跳碟”和“ Popper”玩具中使用了捕捉结构，并以可听见的流行音乐跳来跳去，因此这项研究将有助于增加公众对科学的兴趣。许多柔软的，细长的结构能够通过快速弹性不稳定在两个稳定的配置之间迅速改变。这项研究将建立用于外壳双重性的机械和几何标准。它将确定壳几何形状对快照速度的影响，后扣振动以及不对称壳耗散的速度。将检查材料特性的效果，以理解壳的自动弹跳，即暂时双重的结构。研究团队将从电动材料中准备贝壳。这将使研究团队能够在不稳定性过程中对壳体内壳的面内应变进行新颖的测量。这些测量结果将为壳结构理论提供重要的实验见解。最后，介电弹性壳还将提供一种自然的手段，用于在瞬间变形过程中收获能量。研究团队将进一步发展眨眼，这是一项创新的计划，它向学生介绍了我们眼睛经常错过的快速发展科学。该计划将使用玩具Poppers的机制作为研究牛顿运动定律的一种方式。该计划的实施以及随后创建相关的在线视频内容，将为学生和公众提供机会，以实现力学研究在应对当前技术挑战方面的重要性。