用数字梯度敏感法(DGS)测量了聚甲基丙烯酸甲酯(PMMA)板的张开型应力强度因子(SIF)。用DGS方法测量了PMMA板裂纹附近应力集中区的应力梯度（或偏转角）。此方法先用数字图像相关法(DIC)测量了透明试件裂纹尖端附近的全场位移，再根据光弹效应获得光线在透明固体应力集中区的全场偏转角，在平面应力条件下，偏转角可以与应力梯度建立联系从而获得应力集中区的应力梯度。由应力梯度场测量了裂纹尖端的应力强度因子。在应力强度因子的求解过程中提出了一种迭代最小二乘拟合应力梯度场的方法，此方法可同时得出应力强度因子与裂纹尖端位置。将实验结果与理论值进行了比较，结果显示数字梯度敏感方法准确地测量了复合型应力强度因子。

This paper focuses on the application of digital gradient sensing (DGS) method to the determination of stress intensity factors (SIFs) for cracks in polymethyl methacrylate (PMMA). First，the full-field displacement fields of the test sample are recordedusing digital image correlation (DIC), and then the angular deflections of light rays propagating through the material are obtained based on the elasto-optical effect exhibited by transparent materials subjected to non-uniform state of stress. Under plane stress conditions, the deflections of light rays can be related to two orthogonal in-plane stress gradients. In this way, the stress gradients near the crack on PMMA plates are quantified, and then cracktip SIFs are extracted from DGS Measurements using the method of nonlinear least-squares proposed. With the obtained SIFs, crack tip location is determined simultaneously. For validation, the SIF determined is compared with theoretical results, confirming the effectiveness and accuracy of the proposed technique. Therefore, it DGS method is a practical and effective tool for SIF measurement.