Abstract The aim of this paper is to present a new approach for predicting the mixed-mode fracture resistance of rock-type specimens containing U-shaped notches. The new approach is a modified form of maximum tangential stress (MTS) criterion which states the fracture takes place when the maximum tangential stress at the critical distance from the notch border attains critical value. The critical distance in rock-type specimen is relatively large and the formulations presented in the conventional MTS for characterizing the tangential stress component cannot provide good estimates. Therefore, the modified MTS (MTS-FEM) criterion proposes that the value of maximum tangential stress at the critical distance is determined directly from finite element analysis. Several mixed-mode fracture tests were conducted on the Brazilian disks weakened by central U notches in order to evaluate the MTS-FEM criterion. The comparison between the fracture loads obtained from experiments and those predicted by the MTS-FEM criterion shows that the MTS-FEM criterion can provide good estimates for fracture loads of rock-type U-notched samples under mixed mode loading.

中文翻译：

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混合模式 I/II 加载下岩石型 U 型缺口试样的实验和理论断裂评估

摘要 本文的目的是提出一种预测含有 U 形缺口的岩石型试样的混合模式断裂阻力的新方法。新方法是最大切向应力 (MTS) 准则的一种改进形式，该准则指出，当距缺口边界的临界距离处的最大切向应力达到临界值时，就会发生断裂。岩石型试样的临界距离相对较大，传统 MTS 中​​用于表征切向应力分量的公式无法提供良好的估计。因此，修正的 MTS (MTS-FEM) 准则提出临界距离处的最大切向应力值由有限元分析直接确定。为了评估 MTS-FEM 标准，在被中央 U 形缺口削弱的巴西圆盘上进行了几次混合模式断裂试验。通过实验获得的断裂载荷与 MTS-FEM 准则预测的断裂载荷之间的比较表明，MTS-FEM 准则可以很好地估计混合模式载荷下岩石型 U 型缺口样品的断裂载荷。