Abstract Graded chiral auxetic cellular metal structures were produced from copper alloy powder using Selective Electron Beam Melting (SEBM) technique and tested under compressive and shear loading conditions. The predesigned geometry of chiral structures has a variable chiral amplitude through the length of the specimens, which results in graded porosity of the analyzed auxetic structures. The deformation mechanisms and mechanical response were evaluated with compression and shear testing at two loading velocities. The infrared thermography has been used to track the evolution of plastic deformation in the specimens. The deformation process under compression loading starts in the area with the largest chiral amplitude and then continues through the whole height of the specimen. The shear loading shows two significantly different groups of responses, which are affected by local defects causing the start of failure in different parts of structure. The results of experimental testing were further used for validation of developed finite element models of chiral structures. The influence of graded porosity on the mechanical response of chiral structures was evaluated with parametric computational simulations and compared to the non-graded structure with constant chiral amplitude and same weight. The non-graded auxetic structure offers a stiffer response due to deformation uniformly distributed through the height of the specimens but fails abruptly at lower strains.

中文翻译：

---

分级手性拉胀结构的压缩和剪切行为

摘要 使用选择性电子束熔化 (SEBM) 技术从铜合金粉末制备分级手性拉胀蜂窝金属结构，并在压缩和剪切载荷条件下进行测试。预先设计的手性结构几何形状在整个试样的长度上具有可变的手性振幅，这导致所分析的拉胀结构的孔隙度分级。变形机制和机械响应通过压缩和剪切测试在两种加载速度下进行评估。红外热成像已被用于跟踪试样中塑性变形的演变。压缩载荷下的变形过程从手征幅度最大的区域开始，然后继续贯穿整个试样高度。剪切载荷显示出两组明显不同的响应，它们受局部缺陷的影响，导致结构不同部分开始失效。实验测试的结果进一步用于验证开发的手性结构有限元模型。梯度孔隙率对手性结构力学响应的影响通过参数计算模拟进行评估，并与具有恒定手性振幅和相同重量的非梯度结构进行比较。由于变形均匀分布在试样的高度上，非分级拉胀结构提供了更硬的响应，但在较低的应变下突然失效。实验测试的结果进一步用于验证开发的手性结构有限元模型。梯度孔隙率对手性结构力学响应的影响通过参数计算模拟进行评估，并与具有恒定手性振幅和相同重量的非梯度结构进行比较。由于变形均匀分布在试样的高度上，非分级拉胀结构提供了更硬的响应，但在较低的应变下突然失效。实验测试的结果进一步用于验证开发的手性结构有限元模型。梯度孔隙率对手性结构力学响应的影响通过参数计算模拟进行评估，并与具有恒定手性振幅和相同重量的非梯度结构进行比较。由于变形均匀分布在试样的高度上，非分级拉胀结构提供了更硬的响应，但在较低的应变下突然失效。