Magnetic actuation and transition shapes of a bistable spherical cap

Multistable shells have been proposed for a variety of applications; however, their actuation is almost exclusively addressed through embedded piezoelectric patches. Additional actuation techniques are needed for applications requiring high strains or where remote actuation is desirable. Part of the reason for the lack of research in this area is the absence of appropriate models describing the detailed deformation and energetics of such shells. This work presents a bistable spherical cap made of iron carbonyl-infused polydimethylsiloxane. The magnetizable structure can be actuated remotely through permanent magnets while the transition is recorded with a high-speed camera. Moreover, the experiment is reproduced in a finite element (FE) dynamic model for comparison with the physical observations. High-speed footage of the physical cap inversion together with the FE modeling gives valuable insight on preferable intermediate geometries. Both methods return similar values for the magnetic field strength required for the snap-through. High-strain multistable spherical cap transformation is demonstrated, based on informed material selection. We discover that non-axisymmetric transition shapes are preferred in intermediate geometries by bistable spherical caps. We develop the methods for design and analysis of such actuators, including the feasibility of remote actuation methods for multistable shells.多稳态壳体已被提出用于多种应用场景，但目前其驱动方式几乎仅通过嵌入式压电贴片实现。对于需要高应变或期望实现远程驱动的应用而言，亟需开发额外的驱动技术。该领域研究匮乏的部分原因在于，尚无合适的模型可用于描述这类壳体的详细变形与能量特性。本研究提出了一种由浸渍羰基铁的聚二甲基硅氧烷（polydimethylsiloxane, PDMS）制备的双稳态球冠结构。该可磁化结构可通过永磁体实现远程驱动，其形态转变过程可通过高速相机记录。此外，本研究通过有限元（finite element, FE）动力学模型复现了该实验，以与物理观测结果进行对比。物理壳体反转的高速影像与有限元建模结果，可为优选的中间几何构型提供重要参考依据。两种方法得到的实现突跳所需的磁场强度数值相近。基于合理的材料选型，本研究实现了高应变异多稳态球冠的形态转变。研究发现，在中间几何构型下，双稳态球冠更倾向于呈现非轴对称的转变形态。本研究还提出了这类驱动器的设计与分析方法，包括多稳态壳体远程驱动方案的可行性分析。