Actuation of kagome lattice structures
Actuation of kagome lattice structures
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kagome晶格结构的驱动
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
S. Guest
中科院分区：
文献类型：
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作者：
A. Leung;D. Symons;S. Guest
可果美晶格已被证明有希望作为主动结构的基础，其形状可以通过替代晶格的一些杆的线性致动器来改变。作为一个初步的检查，本文探讨了单一的驱动杆在一个大的二维kagome格子的效果。以前的工作已经表明，有趣的属性的可果美晶格依赖于与致动直杆共线的杆，但也表明，致动导致这些杆弯曲，因此，本文探讨了结构的几何非线性响应。数值结果表明，由于几何非线性效应的影响，结构的驱动刚度比线性模型预测的要小，而结构的峰值弹性应变却增大了。单个的致动器取代了桁架的一些构件：改变这些致动器的长度会改变结构的宏观形状。在二维空间中，戈薇桁架（图1）已被证明是这些结构的一个有前途的解决方案。3它已被证明是少数具有最佳无源刚度的周期性、平面、单长度尺度晶格拓扑结构之一。同时，如果被认为是销连接的，则任何杆件都可以无阻力地被致动。虽然实际的微尺度结构将必然是刚性连接的，但是如果构件是细长的，则对来自杆弯曲的致动的附加阻力是小的。因此，刚性连接的平面Kagome晶格具有用于高权威形状变形结构的所需性质;即被动刚度和低致动阻力。作为初步的研究，本文将检查一个单一的驱动杆在一个大型的二维可果美格子的效果，并将考虑如何stockiness，s，成员影响的响应。紧密度是每个杆的纵横比的无量纲度量，定义为横截面的平面内回转半径k与构件长度L的比率。实际结构的s在0.005至0.05的范围内，这是本文研究的范围。以前的工作4已经检查了所需的能量驱动一个单一的酒吧在一个大的二维晶格考虑各种线性分析和计算模型。然而，可果美晶格的特殊性质取决于其几何形状，并且致动施加大的几何变形。因此，本文建立在以前的工作，考虑结构的几何非线性响应。将考虑结构对致动的阻力，以及材料屈服对致动的限制;将针对材料屈服应变的各种值计算极限致动应变。本文的结构如下。第二节将描述所使用的计算模型，第三节将描述可果美晶格对单个杆的致动的响应的一些通用特征。第四节然后继续探索的建立力的被致动的成员，因为该酒吧是致动的。第五节探讨了由于施加的驱动而在结构中任何地方的峰值弹性应变，并示出了驱动应变如何受到结构屈服的限制，以改变坚固性和屈服应变的值。
The kagome lattice has been shown to have promise as the basis of active structures, whose shape can be changed by linear actuators that replace some of the bars of the lattice. As a preliminary examination, this paper examines the effect of the actuation of a single bar in a large two-dimensional kagome lat- tice. Previous work has shown that interesting properties of the kagome lattice depend on the bars that are co-linear with the actuated bar being straight, but has also shown that actuation causes these bars to bend; this paper therefore explores the geometrically non-linear response of the structure. Numerical re- sults show that due to geometrically non-linear effects, the actuation stiffness is reduced from that predicted by linear models, while the peak elastic strain in the structure is increased. Individual actuators replace some of the members of the truss: altering the length of these actuators changes the macroscopic shape of the structure. In two dimensions, the kagome truss (Fig. 1) has been shown to be a promising solution for these structures. 3 It has been shown to be one of the few periodic, planar, single length scale lattice topologies that has optimal passive stiffness. At the same time, if considered as pin-jointed, any bar can be actuated without resistance. Although practical micro-scale structures will necessarily be rigid-jointed, the additional resistance to actuation from bar bending is small providing that the members are slender. The rigid- jointed planar Kagome lattice therefore has the required properties for use in high authority shape morphing structures; namely passive stiffness and low resistance to actuation. As a preliminary investigation, this paper will examine the effect of the actuation of a single bar in a large two-dimensional kagome lattice, and will consider how the stockiness, s, of the members affects the response. The stockiness is a non-dimensional measure of the aspect ratio of each bar, defined as the ratio of the in-plane radius of gyration of the cross-section, k, to the length of the member, L. Practical structures have s in the range from 0.005 to 0.05, which is the range investigated here. Previous work 4 has examined the energy required to actuate a single bar in a large two-dimensional lattice by considering various linear analytical and computational models. However, the special properties of the kagome lattice are dependent on its geometry, and actuation imposes large geometric deformations. This paper therefore builds on the previous work by considering the geometrically non-linear response of the structure. The resistance of the structure to actuation will be considered, as well as the limitation on actuation imposed by material yield; the limiting actuation strain will be calculated for various values of material yield strain. The paper is structured as follows. Section II will describe the computational model used, and Section III will describe some generic features of the response of the kagome lattice to the actuation of a single bar. Section IV then goes on to explore the build-up of force in the actuated member as the bar is actuated. Section V explores the peak elastic strain anywhere in the structure due to the imposed actuation, and shows how the actuation strain is limited by yielding of the structure for varying values of stockiness and yield strain.