In this paper, the coherent gradient sensing (CGS) method is extended to study the local stress fields and fracture behavior of a blunt V-notch tip. First, the optical governing equations of the CGS method are derived based on Filippi’s stress equation for blunt V-notches and the concept of the notch stress intensity factor (NSIF). Moreover, the CGS fringe patterns in the vicinity of the blunt V-notch tip with different opening angles and notch radii are theoretically synthesized. Next, the fracture property of a blunt V-notch is experimentally studied using a series of three-point-bending polymethyl methacrylate (PMMA) specimens with different geometrical configurations. Finally, the generalized NSIFs up to the initiation of a fracture are evaluated using the proposed CGS method. The CGS fringe patterns in the experimental results exhibit a reasonable agreement with the theoretical fitted fringes, and the NSIFs and notch fracture toughness at the blunt V-notch tip are consistent with those obtained in previous theoretical studies and finite element simulations.

在本文中，相干梯度传感（CGS）方法被扩展用于研究钝V形缺口尖端的局部应力场和断裂行为。首先，基于Filippi的钝V型缺口应力方程和缺口应力强度因子（NSIF）的概念，推导了CGS方法的光学控制方程。此外，理论上合成了具有不同张角和缺口半径的钝V形缺口尖端附近的CGS条纹图案。接下来，使用一系列具有不同几何构型的三点弯曲聚甲基丙烯酸甲酯（PMMA）标本，通过实验研究了钝V形缺口的断裂特性。最后，使用提出的CGS方法评估直至骨折开始的广义NSIF。