Studying V-Notch Stress Intensity Factor by Digital Gradient Sensing Method

The stress intensity factor (SIF) at the V-notch tip of a single-edge-notched polymethyl methacrylate plate was measured by the digital gradient sensing (DGS) method. First, the displacement fields near the V-notch tip of the specimen were recorded using digital image correlation under three-point bending. Second, the stress gradient function of the V-notch tip with unknown SIF was deduced from the Williams series expansion for singular elastic stress fields. Finally, the relationship between the stress gradient and the angular deflection around the V-notch tip was established according to the photoelastic effect. Combined with the theory of linear elastic fracture mechanics, it was derived that the angular deflection of each point can be expressed with the unknown SIF. Considering the unavoidable effects of rigid-body translation and rotation in the experiments, the new angular deflection control equation was derived based on the traditional angular deflection control equation. The SIF was obtained by the least square method. The experimental values calculated by the new control equation were compared with the analytical values. The result shows that the DGS method can accurately measure the SIF at the V-notch tip, which effectively improves the accuracy of SIF.