The effects of geometrical constraints on the fracture initiation location and the fracture strength are evaluated in U‐notched specimens using theoretical and experimental analyses. It is proven that high geometrical constraints in pure mode I loading of geometrically symmetric U‐notched specimens can result in occurrence of the maximum tangential stress (MTS) at two symmetric points on both sides of the notch bisector line. The experiments also indicated that the fracture takes place from a direction that is not along the notch bisector line. The experimental results are then examined theoretically through a stress‐based brittle fracture criterion. Because the conventional MTS criterion was poor to predict the onset of fracture properly, an attempt is made to use the generalized MTS (GMTS) criterion by considering the higher order terms in the fracture model. It is shown that the GMTS criterion gives very good predictions for experimentally obtained values of crack initiation angle and notch fracture resistance.

中文翻译：

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几何形状对U型缺口试样I型脆性断裂的影响

使用理论和实验分析，在U形缺口样品中评估几何约束对断裂起始位置和断裂强度的影响。事实证明，在几何对称的U型缺口试样的纯模式I加载中，较高的几何约束会导致在缺口等分线两侧的两个对称点处出现最大切向应力（MTS）。实验还表明，断裂发生在不沿着缺口等分线的方向。然后，通过基于应力的脆性断裂准则从理论上检验了实验结果。由于常规的MTS标准很难正确预测骨折的发生，通过考虑裂缝模型中的高阶项，尝试使用广义MTS（GMTS）准则。结果表明，GMTS准则对于通过实验获得的裂纹萌生角和缺口抗裂性的值给出了很好的预测。