Rate effect on crack propagation measurement results with crack propagation gauge, digital image correlation, and visual methods
Rate effect on crack propagation measurement results with crack propagation gauge, digital image correlation, and visual methods
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DOI：
10.1016/j.engfracmech.2019.106537
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发表时间：
2019-10-01
影响因子：
5.4
通讯作者：
Zhao, Jian
中科院分区：
文献类型：
--
作者：
Ju, Minghe;Li, Jianchun;Zhao, Jian
通过一个实例研究确定了裂纹扩展仪（CPG）、数字图像相关（DIC）和可视化方法测量动态岩石裂纹扩展的速率相关测量间隙。采用改进的分离式Hopkinson压杆系统，对红砂岩进行了不同裂纹扩展速度的动态缺口半圆弯曲（NSCB）试验。从初始裂纹时间的观点来看，DIC中2%的法向应变阈值在低CPV下有效地获得CPG和DIC方法之间的匹配。然而，在DIC中选择2%-5%的正常菌株是可能影响CPG和Visual方法的结果的关键因素，其中就峰值CPV而言，CPV较低，而对于CPV较高的病例，推荐使用2%-3%的正常菌株。此外，CPG、Visual和DIC技术的等效裂纹速度相关应变阈值（t（i）（DIC）等于t（i）（CPG），t（i）（DIC）等于t（i）（Visual））与CPV呈线性拟合。DIC和目视方法之间的测量间隙比DIC和CPG方法之间的测量间隙窄。红砂岩CPG的临界初始开裂时间需要约500 m/s的CPV条件。这些差距提出了一个潜在的解释与CPV的断裂过程区的变化，并随后建议三个建议的实验结果的基础上，以帮助其他实验结果的解释。
The rate-dependent measurement gaps among the crack propagation gauge (CPG), digital image correlation (DIC), and Visual methods for measuring dynamic rock crack propagation were determined using a case study. Dynamic notched semi-circular bending (NSCB) tests of a rock material, namely, red sandstone, were conducted using a modified split Hopkinson pressure bar system to form different crack propagating velocities (CPVs). From the viewpoint of the initial crack time, a normal strain threshold of 2% in the DIC was effective in obtaining a match between the CPG and DIC methods at a low CPV. However, the selected 2%-5% normal strains in the DIC were pivotal factors that could compromise the results from the CPG and Visual methods with a low CPV in terms of the peak CPV, whereas 2%-3% normal strains were recommended for cases with a high CPV. In addition, the equivalent crack-velocity-dependent strain thresholds (t(i)(DIC) equal to t(i)(CPG) and t(i)(DIC) equal to t(i)(Visual)) for the CPG, Visual, and DIC techniques displayed a linear fit with the CPV. The measurement gap between the DIC and Visual methods was narrower than the measurement gap between the DIC and CPG methods. The critical initial crack time of CPG for red sandstone needed the condition of a CPV of approximately 500 m/s. A potential explanation for these gaps was proposed in terms of the changes in the fracture process zone with CPV, and three suggestions were subsequently recommended based on the experimental results to aid in the interpretation of other experimental results.