Abstract Auxetics are structures and materials with a negative Poisson's ratio, meaning they contract in the direction perpendicular to the applied force under a compressive load. This phenomenon can lead to increased energy absorption, among other favourable parameters to protect against impulsive loadings. In this research, a structure with alternating oval perforations was investigated which gives rise to an auxetic geometry, referred to as an ‘auxetic oval’ design within this paper. Quasi-static (strain rate = 0.001/s) and dynamic (strain rate = 100/s) experiments have been conducted on small-scale specimens, manufactured using subtractive fabrication (laser cutting). Different design criteria were examined to understand the mechanisms behind the energy absorption of the auxetic structures. A modified version of the energy efficiency method was developed to determine the densification strain of the auxetics. A shift from strain-softening to strain-hardening behaviour is seen as the number of cell layers increases, with the perfectly-plastic response ideal for energy absorbing structures. Inertia effects are present in the dynamic tests, showing an increase in plateau stress for several of the designs. The quasi-static and dynamic responses are fundamentally identical, meaning that the performance of the auxetics do not change under the range of strain rates examined. Digital image correlation has been successfully utilised in the analysis process. This includes confirmation of the mechanism giving rise to the auxetic behaviour (rigid rotating squares) and the calculation of the negative Poisson's ratio. Strain fields have been examined showing the regions of energy dissipation. Based on these results the auxetic oval design experiences bending dominated behaviour. Finally, a unique design has been developed, dubbed the ‘Hybrid Auxetic Oval’, which shows favourable behaviour compared to the equivalent base auxetic oval design by mitigating the effects of fracture.

中文翻译：

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通过准静态和动态实验研究用于能量吸收的拉胀椭圆形结构

摘要 拉胀是具有负泊松比的结构和材料，这意味着它们在压缩载荷下沿垂直于施加的力的方向收缩。这种现象会导致能量吸收增加，以及防止脉冲负载的其他有利参数。在这项研究中，研究了一种具有交替椭圆形穿孔的结构，该结构产生了拉胀几何形状，在本文中称为“拉胀椭圆形”设计。准静态（应变率 = 0.001/s）和动态（应变率 = 100/s）实验已对使用减法制造（激光切割）制造的小规模试样进行。检查了不同的设计标准，以了解拉胀结构能量吸收背后的机制。开发了一种改进的能效方法来确定拉胀剂的致密化应变。随着细胞层数量的增加，从应变软化到应变硬化行为的转变被视为能量吸收结构的理想塑性响应。动态测试中存在惯性效应，表明几个设计的平台应力增加。准静态和动态响应从根本上是相同的，这意味着拉胀的性能在检查的应变率范围内不会改变。数字图像相关已成功地用于分析过程。这包括确认引起拉胀行为（刚性旋转方块）的机制和负泊松比的计算。已经检查了应变场，显示了能量耗散区域。基于这些结果，拉胀椭圆形设计经历弯曲主导行为。最后，开发了一种独特的设计，称为“混合拉胀椭圆形”，与等效的基础拉胀椭圆形设计相比，它通过减轻断裂的影响显示出良好的性能。