Global and Local Fracture Behavior in a Brittle Solid with a Set of Pre-Existing Small-Scale Cracks
Global and Local Fracture Behavior in a Brittle Solid with a Set of Pre-Existing Small-Scale Cracks
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具有一组预先存在的小规模裂纹的脆性固体中的整体和局部断裂行为
DOI：
10.1016/j.prostr.2022.01.101
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
and K. Nagasawa
中科院分区：
文献类型：
--
作者：
Uenishi;K.;and K. Nagasawa
为了理解复杂地震活动的机制，不仅需要对大尺度物质行为进行全局观测，还需要对较小尺度裂缝进行更多的局部追踪。因此，在本研究中，通过使用动态光弹性技术，在具有一组预先存在的小规模平行断裂区域的二维线弹性脆性试样中对断裂和波的演化进行实验追踪。通过数字激光切割机制备小规模断裂区域或裂缝，模拟大规模地质正断层面。我们使用高速摄像机进行的实验观察以及有限差分数值模拟表明，全局和局部断裂行为很大程度上取决于平行裂纹组的初始倾斜角和分布模式。在预先存在的裂纹相对于拉伸试验机施加的准静态外部载荷更垂直倾斜的情况下，主裂纹动态发展，然后次要裂纹出现在距主裂纹时空较远的距离处。次要裂缝也动态地延伸到与主裂缝相反的方向。另一方面，在倾角较小的情况下，主裂缝趋于准静态演化。然而，在这两种情况下，我们发现在具有许多小规模裂纹的脆性固体中，断裂可以毫无困难地被阻止和跳跃，这意味着这种小规模裂纹可能在地震事件集群的产生中发挥重要作用。
For understanding the mechanics of complicated seismic activities, not only global observations of large-scale material behavior but also more local tracing of smaller-scale fractures is needed. In this study, therefore, by using the technique of dynamic photoelasticity, the evolution of fractures and waves is experimentally traced in a two-dimensional linear elastic brittle specimen that has a set of pre-existing small-scale parallel fracture regions. The small-scale fracture regions or cracks, modeling a large-scale geological normal fault plane, are prepared by a digital laser cutter. Our experimental observations with a high-speed video camera, together with finite difference numerical simulations, indicate that the global and local fracture behavior significantly depends on the initial inclination angle and distribution pattern of the set of parallel cracks. In the case of pre-existing cracks that are more vertically inclined with respect to the quasi-static external load applied by a tensile testing machine, the main fracture develops dynamically and then the secondary fractures appear at spatiotemporally remote distances from the main fracture. The secondary fractures extend also dynamically, into the direction opposite to the main fracture. On the other hand, in the case of smaller inclination angles, the main fracture tends to evolve quasi-statically. Nevertheless, in both cases, it is found that fracture can be arrested and jump without difficulties in a brittle solid having a number of small-scale cracks, which implies that such small-scale cracks may play an important part in the generation of a cluster of seismic events.