图像处理技术在疲劳裂纹长度测量中的应用

研究材料的疲劳断裂特性，对产品结构设计和寿命预估计具有重要意义。试验中常需测量裂纹扩展长度，以确定裂纹长度与循环载荷次数的关系。在多孔铝合金板疲劳试验过程中，采用先进的图像数据采集和处理技术来测定疲劳裂纹的实际长度，拍摄不同循环次数下疲劳裂纹扩展的CCD图像；基于MATLAB软件，采用OTSU算法和形态学方法，把CCD图像转换成二值图并进行细化处理，得到裂纹扩展骨架图；用链码方法计算出裂纹像素长度，最后根据标定系数便可获得裂纹的实际长度。与显微镜测量裂纹方法比较，该方法具有精度高、非接触、可保存裂纹扩展状态等特点。

Application of Digital Image to Processing Technique Fatigue Crack Growth Measurement

Research on the fatigue failure characteristic of material is of great significance to products＇ structure design and life prediction. In the test, using advanced technology of digital image processing to measure fatigue crack length, which aiming to determine the relationship between fatigue crack length and number of circle load ing. Fatigue test is carried out for multihole aluminum alloy specimens by using MTS testing machine. Firstly, the fatigue crack growth images under different cyclic numbers are extracted. Secondly, the binary images are obtained by using the method of OTSU, and the crack is thinned by morphological method and the fatigue crack framework is gained. Finally the pixel lengths of crack framework are calculated by chain code method and the real crack lengths are acquired by measuring the calibration coefficient. Comparing with measuring crack method of microscope, the method of digital image processing is more accurate, non-contact. The crack growth state can be saved by using this method.