Abstract Fracture loads of engineering components with blunt notches cannot be evaluated by the linear elastic fracture mechanics (LEFM) due to no stress singularity. In this study, an approach to determining stress fields and notch stress intensity factors (NSIFs) at blunt V-notches is developed using the photoelastic technique. To solve the nonlinear governing equations of the NSIFs derived from the Filippi’s stress equation, the overdeterministic least squares method combined with the Newton-Raphson method is applied. The NSIFs for a series of three-point-bending specimens with a blunt V-notch up to fracture are evaluated for different notch angles, tip radii, and notch lengths under mode I loading conditions. It is observed that the NSIFs obtained from photoelastic measurements agree well with the numerical values, and the notch fracture toughness is accordant to the mean stress (MS) criterion. The experimental results will be useful for the fracture characterization and strength evaluation of engineering components with complex notches.

中文翻译：

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钝V形缺口应力场和缺口应力强度因子的光弹性评价

摘要 由于没有应力奇异性，线弹性断裂力学（LEFM）无法评估钝缺口工程构件的断裂载荷。在这项研究中，使用光弹性技术开发了一种确定钝 V 形缺口处的应力场和缺口应力强度因子 (NSIF) 的方法。为了求解由 Filippi 应力方程导出的 NSIF 的非线性控制方程，应用了与 Newton-Raphson 方法相结合的超确定性最小二乘法。在模式 I 加载条件下，针对不同的缺口角度、尖端半径和缺口长度，评估了一系列具有钝 V 形缺口直至断裂的三点弯曲试样的 NSIF。观察到从光弹性测量获得的 NSIFs 与数值吻合良好，缺口断裂韧性符合平均应力（MS）准则。实验结果将有助于复杂缺口工程构件的断裂表征和强度评估。