Dynamic fractures occur frequently in geophysical processes and engineering applications. It is thus essential to study crack and failure behaviors, such as crack time-to-initiation, crack growth rate and arrest period under dynamic loading. In this study, impact experiments were implemented by utilizing the single-flawed tunnel specimens under drop-hammer impacts. Four brittle materials, i.e., green sandstone, red sandstone, black sandstone and polymethyl methacrylate, were selected to make single-flawed tunnel specimens. Strain gauges and crack extension gauges were employed to measure the crack extension parameters. The properties of crack growth rate, crack time-to-initiation and arrest period of these four brittle materials were discussed and analyzed. The corresponding numerical simulation was performed by using the commercial software AUTODYN. The numerical results of crack growth rate and crack time-to-initiation agreed with the impact test results. The commercial software ABAQUS was applied to compute the dynamic stress intensity factors. The results show that both the dynamic initiation fracture toughness and the crack growth rate increase with the elastic moduli of these four types of brittle materials under the same loading conditions, whereas the crack time-to-initiation decreases with the increase in elastic moduli of the brittle materials under the same loading conditions.

中文翻译：

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中低速冲击下单缺陷隧道模型断裂特性研究

动态裂缝在地球物理过程和工程应用中经常发生。因此，研究裂纹和破坏行为（如裂纹的起始时间，裂纹的生长速率和动态载荷下的滞留期）至关重要。在这项研究中，冲击试验是通过利用落锤冲击下的单缺陷隧道标本进行的。选择了四种脆性材料，即绿色砂岩，红色砂岩，黑色砂岩和聚甲基丙烯酸甲酯来制作单缺陷隧道标本。使用应变仪和裂纹扩展仪来测量裂纹扩展参数。对这四种脆性材料的裂纹扩展速率，裂纹萌生时间和停止时间的性质进行了讨论和分析。使用商业软件AUTODYN进行相应的数值模拟。裂纹扩展速率和裂纹萌生时间的数值结果与冲击试验结果一致。应用商业软件ABAQUS计算动应力强度因子。结果表明，在相同载荷条件下，这四种类型的脆性材料的动态起始断裂韧性和裂纹扩展速率均随弹性模量的增加而增加，而随着弹性模量的增加，裂纹的起始萌生时间减小。相同载荷条件下的脆性材料。