An automatic discontinuous deformation measurement (DDM) approach was proposed to evaluate full-field deformations during the crack propagation process based on the digital image correlation (DIC) method. The color speckle pattern and crack identification procedure were applied at first in the DDM approach to obtain the region of interest (ROI) in the speckle images, the DIC analysis was then used to obtain the full-field displacements and strains of the cracked body. Three tests, the uniaxial tensile test (aluminum foil), the three-point bending and the four-point bending fracture tests (steel fiber reinforced cement-based composites), were conducted to validate the accuracy and reliability of the DDM approach. The experimental results demonstrated that the ROI images can be formed automatically, the evolution of the full-field displacements and strains were effectively obtained. Meanwhile, the DDM approach is applicable to the situations with single or multiple growing cracks. The crack mouth opening displacement values obtained by the DDM approach are agreed well with that obtained by the crack displacement clip gauge.

中文翻译：

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一种基于数字图像相关法测量不连续变形场的新方法

基于数字图像相关（DIC）方法，提出了一种自动不连续变形测量（DDM）方法来评估裂纹扩展过程中的全场变形。在 DDM 方法中首先应用彩色散斑图案和裂纹识别程序以获得散斑图像中的感兴趣区域（ROI），然后使用 DIC 分析获得裂纹体的全场位移和应变。进行了三项试验，即单轴拉伸试验（铝箔）、三点弯曲试验和四点弯曲断裂试验（钢纤维增强水泥基复合材料），以验证 DDM 方法的准确性和可靠性。实验结果表明，ROI图像可以自动形成，有效地获得了全场位移和应变的演变。同时，DDM 方法适用于单个或多个裂纹扩展的情况。用 DDM 方法得到的裂纹口张开位移值与用裂纹位移夹规得到的值吻合得很好。