The dynamic tensile stress-strain behaviour is desirable in evaluating the stability of geo-structures subjected to dynamic loading. However, the dynamic direct pull test is rather difficult to conduct due to experimentation difficulties; its common alternative the traditional Brazilian disc (BD) test cannot provide the stress-strain curve. This work proposes a method to obtain the dynamic tensile stress-strain curve of rocks based on the modified dynamic BD test using a split Hopkinson pressure bar (SHPB) system in combination with a high-speed camera. The stress history of the disc center is obtained following the ISRM suggested method on rock dynamic tests, while its strain history is estimated using the digital image correlation (DIC) technique. Due to the rock heterogeneity, a small rectangular sensing region (RSR) enclosing the disc center is chosen and the average strain of RSR is used to estimate the strain of the disc center. As compared with the conventional strain gauge method, the strain calculation method in this work has many advantages, including non-contact measurement and high accuracy. The proposed method is thus more reliable and can be readily applied for determining dynamic tensile stress-strain curves of rocks.

中文翻译：

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一种获取岩石动态拉伸应力-应变曲线的新方法

动态拉应力-应变行为是评估动态荷载作用下的地质结构稳定性的理想方法。但是，由于实验困难，动态直接拉力测试相当困难。它是传统的巴西圆盘（BD）测试的常见替代方法，无法提供应力-应变曲线。这项工作提出了一种方法，该方法基于改进的动态BD测试，使用分裂的Hopkinson压力杆（SHPB）系统结合高速相机来获得岩石的动态拉伸应力-应变曲线。圆盘中心的应力历史是根据ISRM建议的岩石动力学测试方法获得的，而其应变历史是使用数字图像相关（DIC）技术估算的。由于岩石的异质性，选择一个围绕圆盘中心的小矩形感应区域（RSR），并将RSR的平均应变用于估算圆盘中心的应变。与传统的应变仪方法相比，这项工作中的应变计算方法具有许多优点，包括非接触式测量和高精度。因此，所提出的方法更加可靠，并且可以容易地应用于确定岩石的动态拉伸应力-应变曲线。