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利用微焦点工业CT对混凝土试件单轴压缩过程分阶段进行原位扫描,获得相应的系列CT图像。由数字体散斑法(Digital Volumetric Speckle Photography,DVSP)获得了试件内部三维位移场与应变场。混凝土内部非均匀细观结构可以作为散斑结构成为变形信息的载体用于试件内部变形的测量;通过位移场和应变场的分析,揭示了试件内部变形局部化区域的演化及破坏过程,局部化区域与试件最终破坏面位置相一致。根据试件的体积应变随轴向应力的变化曲线分别定义了小于CT尺度微裂隙和CT尺度裂隙的发育点,分别为峰值应力的54.7%和82.0%,这两点同时对应着试件扩容的起始点及塑性变形的起始点。结果表明,DVSP与CT技术相结合能够直观地揭示混凝土试件内部变形局部化产生及发展过程,为三维变形的精细测量及可视化提供了方法。
Using microfocus industrial CT, the uniaxial compression process of concrete specimens was carried out in-situ scanning in stages to obtain the corresponding series of CT images. The 3D displacement field and strain field inside the specimen were obtained by Digital Volumetric Speckle Photography (DVSP). The non-uniform microstructure inside the concrete can be used as the carrier of deformation information in the speckle structure to measure the deformation of the specimen. The analysis of the displacement field and the strain field reveals the evolution and failure process of the localized deformation of the specimen. The localized area is consistent with the final destruction surface of the specimen. According to the curves of volumetric strain and axial stress of specimens, the development points smaller than the CT-scale and CT-scale fractures are respectively defined as 54.7% and 82.0% of the peak stress, which correspond to the expansion of the specimen The starting point and the starting point of plastic deformation. The results show that the combination of DVSP and CT technology can reveal the internal deformation localization and development of concrete specimens intuitively, and provide a method for the precise measurement and visualization of 3D deformation.