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  

Fatigue Crack Length Measurement Method Based on Edge Detection and DIC

作　　者：黄心畏 单晓锋 高红俐[1,2] 王晨[1,2] HUANG Xinwei;SHAN Xiaofeng;GAO Hongli;WANG Chen(School of Mechanical Engineering,Zhejiang University of Technology,Hangzhou 310023,Zhejiang,China;Key Laboratory of Special Purpose Equipment and Advanced Processing Technology of Ministry of Education,Zhejiang University of Technology,Hangzhou 310023,Zhejiang,Chin)

机构地区：[1]浙江工业大学机械工程学院,浙江杭州310023 [2]浙江工业大学特种装备制造与先进加工技术教育部重点实验室,浙江杭州310023

出　　处：《兵工学报》2022年第4期940-951,共12页Acta Armamentarii

基　　金：浙江省基础公益研究计划项目(LGG22E050039)。

摘　　要：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,从而提高测量精度。通过灰度边缘检测在裂纹图像中得到裂纹扩展路径,并对裂纹尖端进行初定位,结合模板匹配将裂纹路径坐标映射到散斑图像中,并在裂纹初尖端延伸段布置虚拟引伸计,利用DIC技术求得虚拟引伸计张开量。拟合引伸计张量- 位置曲线,分析曲线特征得到疲劳裂纹尖端亚像素精度横坐标,进而精确计算出裂纹长度。将边缘检测法、该方法、测量显微镜测量得到的结果进行对比,结果表明,该方法在测量精度上有显著优势,可有效检测出裂纹闭合段,测量精度可达8 μm。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.

关 键 词：疲劳裂纹 裂纹长度测量 边缘检测 数字图像相关法 裂纹闭合 虚拟引伸计 

分 类 号：TP399[自动化与计算机技术—计算机应用技术]