Numerical Simulation of Fracture Initiation in Barre Granite using an Experimentally Validated XFEM Model
Numerical Simulation of Fracture Initiation in Barre Granite using an Experimentally Validated XFEM Model
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：在存在裂缝的脆性岩石中，破裂会在裂缝尖端周围形成一个重要的非线性区域，称为断裂过程区。各种实验和数值研究表明，裂纹尖端张开位移(CTOD)和断裂能等裂纹尖端参数对表征断裂过程区是至关重要的。本文采用扩展有限元方法和粘聚区模型对中心缺口岩石试件在三点弯曲下的断裂过程进行了数值模拟。首先根据中心缺口Barre花岗岩试件的三点弯曲试验结果，估算了CZM的输入参数，如弹性裂纹张开位移和临界裂纹张开位移。利用二维数字图像相关技术测量了位移，并用于表征断裂过程区的演化和估计粘聚区模型的参数。数值模拟结果表明，CZM模型能较好地预测从裂纹萌生到宏观裂纹扩展的三个阶段，与实验数据吻合较好。
: Fracturing in brittle rocks with an existing crack results in the development of a significant nonlinear region surrounding the crack tip called the fracture process zone. Various experimental and numerical studies have shown that the crack tip parameters such as the crack tip opening displacement (CTOD) and the fracture energy are critically important in characterizing the fracture process zone. In this study, numerical simulations of rock specimens with a center notch subjected to three-point bending were conducted using the extended finite element method (XFEM) along with the cohesive zone model (CZM) to account for fracture process zone. The input parameters of CZM such as the elastic and critical crack opening displacements were first estimated based on the results of three-point bending tests on the center notched Barre granite specimens. Displacements were measured using the two dimensional digital image correlation technique and used to characterize the evolution of the fracture process zone and estimate the parameters of the cohesive zone model. The results from the numerical simulations showed that CZM provided a good agreement with experimental data as it predicted all three stages of cracking from fracture process initiation to macro-crack growth.