Abstract In this paper, the crack initiation angle is studied experimentally and theoretically in sharp V-notched specimens subjected to mode I loading. Some experiments are performed on the V-notched compact tension (CT) and double cantilever beam (DCB) specimens made of polymethylmetacrylate (PMMA) with two different notch opening angles. It is demonstrated that although symmetry exists in both geometry and loading of the specimens, the initiated crack would not be necessarily along the notch bisector line. Hence, a proper theory is necessary for predicting the crack initiation angle. An attempt is then made to generalize the conventional strain energy density (SED) criterion by considering the first non-singular term in the fracture model. It is shown that the first non-singular stress term has a significant role in predicting both the crack initiation angle and the notch fracture resistance. Moreover, the results of theoretical predictions when the first non-singular term is taken into account have reasonable consistency with the experimental data.

中文翻译：

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尖锐 V 形缺口中的裂纹分叉

摘要 本文通过实验和理论研究了I型载荷作用下尖锐V型缺口试样的裂纹萌生角。一些实验是在由聚甲基丙烯酸甲酯 (PMMA) 制成的 V 型缺口紧凑张力 (CT) 和双悬臂梁 (DCB) 试样上进行的，具有两种不同的缺口开口角度。结果表明，尽管试样的几何形状和载荷均存在对称性，但起始裂纹不一定沿着缺口平分线。因此，需要一个合适的理论来预测裂纹萌生角。然后尝试通过考虑断裂模型中的第一个非奇异项来推广常规应变能密度 (SED) 准则。结果表明，第一个非奇异应力项在预测裂纹起始角和缺口断裂阻力方面具有重要作用。此外，考虑第一个非奇异项时的理论预测结果与实验数据具有合理的一致性。