基于CT试验的混凝土细观破裂过程研究

发布时间：2018-04-01 19:17

本文选题：混凝土　切入点：CT试验　出处：《河北农业大学》2015年硕士论文

【摘要】：随着社会经济的高速发展,混凝土越来越多的应用于社会经济的基础建设中,由于混凝土自身力学性能的复杂性以及施工条件的多变性,混凝土的破裂行为日益受到人们的关注,因此研究混凝土的破裂过程显得尤为重要。本文将试验研究和理论分析相结合,对混凝土的破裂现象、破裂过程和破裂机理进行了理论和试验研究。利用中国矿业大学(北京)国家重点实验室中的ACTIS300-320/225X射线工业CT检测系统以及3000KN超高刚性伺服试验机,对混凝土试样在单轴压缩条件下的裂纹扩展过程进行了CT扫描综合试验。借助非线性分形理论,对混凝土试样内部初始损伤及裂纹扩展的分布特征进行了分形描述,得到CT图像计盒维数的快速上升预示材料即将进入破坏阶段的研究结论。本文的主要研究内容如下:(1)对混凝土的破裂现象、破裂过程和破裂机理进行了理论上的综合分析。对于混凝土裂纹的扩展机理研究应该从细观层次来进行分析是比较合适的,利用CT技术对混凝土试样进行单轴压缩荷载作用下的CT试验,对混凝土内部的萌生、开裂、贯通直至破坏的过程进行CT描述。(2)在单轴压缩条件下对混凝土试样进行了CT扫描实验,获得了单轴压缩荷条件下不同应力阶段混凝土试样微孔洞或者微裂纹发展过程的CT图像。通过对CT图像进行三维重建,对单轴压缩荷载作用下混凝土内部微裂纹的萌生、开裂、贯通直至破坏的过程进行CT描述。(3)通过得到的混凝土试样CT图像进行了边缘检测分析,利用多种边缘检测算子程序提取混凝土试样CT图像的边缘信息,通过这种方法来进行描述混凝土的开裂行为。(4)利用非线性分形几何理论的基本原理和方法,将混凝土试样内部初始损伤以及微裂纹扩展的分布及其微裂纹从萌生、扩展、贯通直到破坏的过程进行了分形描述并计算了各个应力阶段混凝土试样损伤的分形维数。在混凝土损伤稳定发展阶段,混凝土裂纹损伤计盒维数基本上是随着应力水平的增加而增大。
[Abstract]:With the rapid development of social economy, concrete is more and more used in the basic construction of social economy. Due to the complexity of the mechanical properties of concrete and the variability of construction conditions, People pay more and more attention to the rupture behavior of concrete, so it is very important to study the rupture process of concrete. The rupture process and fracture mechanism are studied theoretically and experimentally. The ACTIS300-320/225X X-ray industrial CT testing system and the 3000KN ultra-rigid servo testing machine are used in the State key Laboratory of China University of Mining and Technology (Beijing). The crack propagation process of concrete specimen under uniaxial compression is tested by CT scan. The distribution of initial damage and crack propagation in concrete specimen is described by means of nonlinear fractal theory. The conclusion that the rapid increase of box dimension in CT image indicates that the material is about to enter the stage of failure is obtained. The main contents of this paper are as follows: 1) the cracking phenomenon of concrete. The fracture process and fracture mechanism are analyzed in theory. It is appropriate to study the crack propagation mechanism of concrete from the meso level. The CT test of concrete specimen under uniaxial compression load was carried out by using CT technique, and the internal initiation and cracking of concrete were carried out. The CT scanning experiments were carried out on concrete samples under uniaxial compression. The CT images of microvoid or microcrack development of concrete samples under uniaxial compression loading are obtained. By 3D reconstruction of CT images, the initiation and cracking of microcracks in concrete under uniaxial compression loading are studied. Through the process of failure, CT description. 3) through the obtained CT images of concrete samples for edge detection analysis, using a variety of edge detection subroutine to extract the edge information of concrete samples CT images, This method is used to describe the cracking behavior of concrete. (4) based on the basic principles and methods of nonlinear fractal geometry theory, the initial damage and the distribution of microcracks in concrete specimens and the distribution of microcracks are derived from the initiation and propagation of microcracks. The fractal dimension of concrete specimen damage in each stress stage is calculated by fractal description of the process from through to failure. In the stage of steady development of concrete damage, the fractal dimension of concrete damage is calculated. The box dimension of concrete crack damage meter increases with the increase of stress level.
【学位授予单位】：河北农业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

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