This paper presents the results of an experimental study on the dynamic fracture behaviour of 3D printed rock-like disc specimens with various pre-existing flaw configurations under high strain rate loading. The 3D printing technology is utilized to prepare disc specimens containing a single or a pair of unfilled or filled flaws. A split Hopkinson pressure bar is employed to generate high rate loading on the specimens, while the digital image correlation (DIC) technique is adopted to determine the type of new cracks, and their initiation, propagation paths and coalescence types. The results show that the dynamic strengths of the 3D printed specimens are higher than the quasi-static ones. When under high strain rate loading, not only can the specimens with filled flaws carry more load than the corresponding specimens with an unfilled flaw, but also their cracking pattern is different as compared to the unfilled flaw counterpart. It is interesting to note that the dynamic peak loads are not dependent on the flaw inclination angle, while the quasi-static peak loads show obvious flaw inclination angle dependence. Moreover, DIC results reveal that under some specific flaw configurations, the filling material undergoes shear strain concentration and a shear band develops inside the filled flaws. Overall this study confirms the strong effects of the flaw configurations and filling material on the deformation and crack patterns of the 3D printed rock-like materials under impact loading.

中文翻译：

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3D打印类岩石材料在冲击下动态断裂模式的数字图像相关实验研究

本文介绍了在高应变率载荷下具有各种预先存在的缺陷配置的 3D 打印类岩石圆盘试样的动态断裂行为的实验研究结果。3D 打印技术用于制备包含单个或一对未填充或填充缺陷的圆盘样本。采用分裂式霍普金森压力棒在试样上产生高速率载荷，同时采用数字图像相关（DIC）技术确定新裂纹的类型，以及它们的萌生、传播路径和聚结类型。结果表明，3D打印试样的动态强度高于准静态试样。在高应变率载荷下，不仅带有填充缺陷的试样比相应的带有未填充缺陷的试样承载更多的载荷，但与未填充的缺陷对应物相比，它们的开裂模式也不同。有趣的是，动态峰值载荷不依赖于缺陷倾角，而准静态峰值载荷显示出明显的缺陷倾角依赖性。此外，DIC 结果表明，在某些特定的缺陷配置下，填充材料会经历剪切应变集中，并且在填充的缺陷内部形成剪切带。总的来说，这项研究证实了缺陷配置和填充材料对 3D 打印类岩石材料在冲击载荷下的变形和裂纹模式的强烈影响。而准静态峰值载荷表现出明显的缺陷倾角依赖性。此外，DIC 结果表明，在某些特定的缺陷配置下，填充材料会经历剪切应变集中，并且在填充的缺陷内部形成剪切带。总的来说，这项研究证实了缺陷配置和填充材料对 3D 打印类岩石材料在冲击载荷下的变形和裂纹模式的强烈影响。而准静态峰值载荷表现出明显的缺陷倾角依赖性。此外，DIC 结果表明，在某些特定的缺陷配置下，填充材料会经历剪切应变集中，并且在填充的缺陷内部形成剪切带。总的来说，这项研究证实了缺陷配置和填充材料对 3D 打印类岩石材料在冲击载荷下的变形和裂纹模式的强烈影响。