Abstract A new development has been proposed to measure the tensile fracture toughness (KIc) of rocks. An innovative configuration of chevron notch was applied acting as a cracked chevron notched direct tension (CCNDT) method to determine the mode I fracture toughness, which also could be suggested as a direct method to specify the tensile fracture toughness. In this method, the initial crack is generally created in the form of a chevron notch by a simple rotary saw, and afterward, the crack is subjected to the direct tensile load. Using the chevron notch in the desired specimen is mainly due to the advantages of the sub-critical crack growth in brittle materials. In the present study, a new expression is proposed to calculate the fracture toughness of CCNDT specimens. Various finite element analyses are performed using different chevron crack geometries to obtain the minimum dimensionless stress intensity factor of the CCNDT specimen. The analytical approach based on Bluhm's slice synthesis method is also implemented for evaluating the minimum dimensionless stress intensity factor of the CCNDT specimens. Furthermore, several experiments are carried out on Hornfels rock using CCNDT and ASTM standard fracture toughness; single-edge notched bend (SENB) tests to verify the proposed CCNDT method. The geometrical parameters of the CCNDT specimens are also provided to meet the plane strain fracturing condition.

中文翻译：

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一种确定岩石I型断裂韧度的裂纹V形缺口直接拉伸法

摘要 测量岩石拉伸断裂韧度 (KIc) 的新进展已被提出。人字形缺口的创新配置被用作裂纹人字形缺口直接拉伸 (CCNDT) 方法来确定 I 型断裂韧性，这也可以作为指定拉伸断裂韧性的直接方法。在这种方法中，初始裂纹通常是通过简单的旋转锯以人字形缺口的形式产生的，然后裂纹受到直接拉伸载荷。在所需试样中使用人字形缺口主要是由于脆性材料中亚临界裂纹扩展的优势。在本研究中，提出了一种新的表达式来计算 CCNDT 试样的断裂韧性。使用不同的 V 形裂纹几何形状进行各种有限元分析，以获得 CCNDT 试样的最小无量纲应力强度因子。还实施了基于 Bluhm 切片合成方法的分析方法，用于评估 CCNDT 试样的最小无量纲应力强度因子。此外，还使用 ​​CCNDT 和 ASTM 标准断裂韧性在 Hornfels 岩石上进行了多项实验；单边缺口弯曲 (SENB) 测试以验证所提出的 CCNDT 方法。还提供了CCNDT试样的几何参数以满足平面应变断裂条件。还实施了切片合成方法来评估 CCNDT 试样的最小无量纲应力强度因子。此外，还使用 ​​CCNDT 和 ASTM 标准断裂韧性在 Hornfels 岩石上进行了多项实验；单边缺口弯曲 (SENB) 测试以验证所提出的 CCNDT 方法。还提供了CCNDT试样的几何参数以满足平面应变断裂条件。还实施了切片合成方法来评估 CCNDT 试样的最小无量纲应力强度因子。此外，还使用 ​​CCNDT 和 ASTM 标准断裂韧性在 Hornfels 岩石上进行了多项实验；单边缺口弯曲 (SENB) 测试以验证所提出的 CCNDT 方法。还提供了CCNDT试样的几何参数以满足平面应变断裂条件。