混凝土CT图像中等效裂纹区域的定量分析

Quantitative analysis of equivalent crack region in CT images of concrete

从细观尺度观察,混凝土材料可看作由骨料、砂浆及其结合面构成的不均匀复合材料。为研究加载时裂纹在混凝土内部结构中扩展的过程,采用X射线CT扫描技术获得单轴动载条件下混凝土破裂过程的系列CT图像。对于CT图像中裂纹信息的提取,传统的方法是将CT图像中的低密度区作为裂纹区域,无法准确地识别裂纹和判定裂纹具体形态。本文根据差值CT图像是否出现线状或环状影像判断裂纹的存在。通过变换差值CT图像中像素值的阈值范围分析裂纹的分布特点。根据CT物理原理确定等效裂纹区域。探讨了混凝土CT图像中裂纹及其形态的判定时存在的问题。

In view of the meso-mechanism, concrete can be regarded as a heterogeneous composite material consisting of aggregates, mortar and interfaces. In order to investigate the crack propagation in the inner structure of concrete under loading, a series of CT images about the fracture evolution process of concrete under a uni-axial dynamic loading condition was obtained by applying the X-ray CT technique. The traditional method of collecting crack information in CT images is to define the low density region in the CT images as the cracks. But the cracks would not be truly identified and the specific shape of the cracks would not be clearly determined. This paper presents a method of determining cracks according to linear or circular shadows whether or not appearing in the minus image between CT images. The characteristics of distributional region of cracks are also analyzed by means of changing threshold value. Then, the equivalent crack region can be determined based on the CT physics theory. Finally, a few issues about crack determination criterion and crack locations are discussed.