Plewa Julian, Płońska Małgorzata, Junak Grzegorz
Faculty of Science and Technology, Institute of Materials Engineering, University of Silesia in Katowice, 1a, 75 Pułku Piechoty Str., 41-500 Chorzów, Poland.
Faculty of Materials Engineering, Silesian University of Technology, 44-100 Gliwice, Poland.
Materials (Basel). 2023 Jul 28;16(15):5306. doi: 10.3390/ma16155306.
The paper presents an analysis of rotating rigid unit (RRU) auxetic structures, the special property of which is negative Poisson's ratio. The crucial features of such modified structures are the well-functioning linkages of the square units at their pivot points. This ensures the stable functioning of such structures in tension or compression. The presented geometrical analysis of these auxetic structures may facilitate their adequate construction and allow one to determine the expected values of their expansion as well as the desired porosity. The results are confirmed based on the behaviour of physical models produced by the assembly of square units. The change in the dimensions of the physical models when moving from a closed to an open position is consistent with the predictions of the geometric models. By modifying the well-known 'rotating squares' model, physical structures with auxetic properties are obtained that can be utilised in industrial conditions, where a simultaneous change of linear dimensions is needed-either in compression or in tension. The assembly method may prove efficient in building such structures, given the abilities of assembly robots to regularly arrange the unit cells in lines and rows and to connect them with rings at the designated positions (evenly spaced perforations). The presented auxetic structures might find their potential application in, e.g., expansion joints or structures in which the porosity is mechanically changed, such as mesoscale structures. The tested structures subjected to high compressive forces buckle when the yield strength of the rigid unit material is exceeded.
本文对旋转刚性单元（RRU）拉胀结构进行了分析，其特殊性质是泊松比为负。这种改进结构的关键特征是方形单元在其枢轴点处连接良好。这确保了此类结构在拉伸或压缩时能稳定运行。本文对这些拉胀结构进行的几何分析有助于其合理构建，并能确定其膨胀的预期值以及所需的孔隙率。基于由方形单元组装而成的物理模型的行为，结果得到了证实。当从闭合位置移动到打开位置时，物理模型尺寸的变化与几何模型的预测一致。通过修改著名的“旋转方块”模型，可获得具有拉胀特性的物理结构，这些结构可用于需要线性尺寸同时变化（无论是压缩还是拉伸）的工业条件中。鉴于装配机器人有能力将单元细胞规则地排列成行和列，并在指定位置（等间距穿孔）用环将它们连接起来，这种装配方法在构建此类结构时可能证明是有效的。本文提出的拉胀结构可能会在例如伸缩缝或孔隙率会发生机械变化的结构（如中尺度结构）中找到其潜在应用。当超过刚性单元材料的屈服强度时，承受高压缩力的测试结构会发生屈曲。
