基于边缘检测和数字图像相关法的疲劳裂纹长度测量方法

针对先进高强钢板存在的显著裂纹闭合现象导致裂纹闭合段难以检测问题,提出一种基于边缘检测和数字图像相关(DIC)技术相结合的疲劳裂纹长度高精度动态测量方法.使用两个相机分别拍摄疲劳裂纹扩展试验过程中裂纹试件两面的裂纹和散斑图像,并对图像进行处理来测量裂纹长度,可检测到传统灰度边缘检测无法检测到的裂纹闭合段,从而提高测量精...

Fatigue Crack Length Measurement Method Based on Edge Detection and DIC

For the difficult detection of crack closure section due to the obvious crack closure phenomenon in advanced high-strength steel plates，a high-precision dynamic measurement method of fatigue crack length based on the combination of edge detection and digital image correlation (DIC) technology is proposed. Two cameras are used to acquire the crack images and speckle images of two sides of the crack specimen during the fatigue crack growth test for processing，which can detect the closed section of the crack which can not be detected by the gray-scale edge detection method，thereby improving measurement accuracy. The fatigue crack growth path is obtained from the crack image by the gray edge detection method, and the crack tip is initially located. Then，the template matching technology is used to map the detected crack path coordinates to the speckle image，and the virtual extensometers are arranged on both sides of the crack tip extension. The opening displacement of virtual extensometer is obtained by DIC. Then the displacement-position curve of extensometer is fitted， the characteristics of the curve are analyzed to obtain the sub-pixel precision abscissa of the fatigue crack tip，and the crack length is accurately calculated. Finally，the results obtained by the edge detection method， the proposed method，and the measuring microscope are compared. The results show that the proposed method has a significant advantage in measurement accuracy compared with the edge detection method. It can be used to effectively detect the closed section of the crack with the measurement accuracy of 8 μm.