论文部分内容阅读
应用工业CT(Industrial Computer Tomography,ICT)对路面底基层(水泥稳定碎石层)材料单轴加载细观破裂全过程进行了观测,获得了试件内部裂纹开裂、发展及连通的全过程CT图像。给出了利用DR(Digital Radiography)及CT图像进行试件尺寸测量的方法,计算得到轴向应变及体积应变,获得了全程的应力应变曲线及体积应变曲线,根据曲线把试件变形分为弹性压缩、塑性变形和破坏扩容3个阶段。在弹性压缩阶段,试样各层CT图像灰度均值呈小幅增长趋势,在塑性变形阶段达到极大值后开始减小,在破坏扩容阶段,灰度均值急剧减小;各层CT图像的灰度值方差在弹性压缩及塑性阶段缓慢地呈线性增长,进入破坏扩容阶段,灰度方差迅速增加;把灰度均值极大值和体积应变极小值对应的应力24.81MPa(峰值的83.36%)作为试件裂纹扩展的应力阀值;由CT图像及重构的剖面图像可知,试件破坏时,裂隙不仅在砂浆中沿骨料边缘扩展,还会穿过骨料扩展,裂隙扩展主方向与加载方向平行。
The whole process of meso-fracture of single-axis loading of pavement subbase (cement stabilized macadam) material was observed by Industrial Computer Tomography (ICT), and the whole process of crack initiation, development and connectivity of the specimen was obtained . The method of measuring the specimen size by using DR (Digital Radiography) and CT images is given, the axial strain and volume strain are calculated, and the stress-strain curve and volume strain curve are obtained. According to the curve, the deformation of the specimen is divided into elastic Compression, plastic deformation and destruction of capacity expansion in three stages. In the elastic compression stage, the mean gray values of CT images in all layers of the sample increase slightly, reaching a maximum value in the plastic deformation phase and then decreasing. During the phase of destroying and expanding, the mean gray value decreases sharply; Variance of variance slowly and linearly increased during the period of elastic compression and plasticity, and entered the stage of vandalism and dilatation. The variance of gray level increased rapidly. The stress corresponding to the maximum of gray-scale and the minimum of volumetric strain was 24.81MPa (83.36% of the peak value) As the stress threshold of specimen crack propagation. It can be seen from the CT images and the reconstructed cross-sectional images that the fractures not only expand along the edge of the aggregate in the mortar but also extend through the aggregate, Loading direction parallel.