混凝土损伤破坏的CT及声发射试验研究

CT and AE test research on concrete damage localization

针对混凝土破坏过程损伤定位的技术难题,对混凝土试样进行了单轴压缩CT扫描试验及声发射损伤定位试验,利用分形理论计算了CT图像的分形维数,建立了基于CT图像及声发射损伤点的损伤变量。研究结果表明:随试件的加载进程,混凝土分形维数和损伤变量变化规律一致,可将混凝土分形维数和损伤变量的快速增大作为混凝土失稳破坏的前兆;综合利用混凝土三维重建图像和声发射损伤图,对混凝土裂缝萌生和演化的全过程进行观察和分析,这为分析混凝土的裂缝萌生损伤过程和定位损伤位置提供了一种新方法。

The relationship between concrete damage localization and concrete damage process were technical problem of many field. CT scanning test and Acoustic Emission(AE) damage localization test on concrete specimens were conducted in the condition of uniaxial compression. The change regulations of concrete porosity, the 3D micromechanical model and the porosity on different loading stages were got with image process technology. Fractal dimension was calculated by using the Fractal Theory, and the damage variable was established based on CT images and AE damage point. The result shows that with the increasing load on the specimens, the change regulations of concrete porosity, pore volume, box-counting dimension and damage variable were the same. The rapid increase of concrete pore volume or fractal dimension and damage variable can be regarded as a sign of unstable failure in concrete. Observing and analyzing the whole process about the appearance and evolution of the cracks in concrete with CT 3D reconstruction images as well as AE damage localization provides a new method for analyzing the process of the damage evolution and damage localization on concrete.