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为了能定量地利用CT数资源研究混凝土静动力强度特性及裂纹演化规律,利用适合CT扫描仪的便携式动力加载设备,对圆柱体混凝土试样进行单轴静动力拉伸CT试验,并利用编制的差分盒维数计算程序计算CT扫描断面的分形维数,以此为基础从细观层面上比较分析混凝土静动单轴拉伸强度特性、受力破坏机制及裂纹分形特征。结果表明:静力拉伸荷载条件下混凝土破坏时裂纹扩展速度慢,破裂面粗糙曲折,裂纹绕着骨料追随最薄弱界面发展;动力拉伸时裂纹扩展速度快,破裂面较平直,裂纹切割骨料追随能量释放最快路径发展;静动力拉伸CT扫描断面分形特征明显,分形维数随裂纹扩展成规律发展,能较好地反映出混凝土材料损伤裂纹的演化规律,可以定量表述试样的破损程度,可作为裂纹演化的定量参数。
In order to quantitatively use the CT resources to study the static and dynamic strength characteristics of concrete and the evolution of cracks, a uniaxial static and dynamic tensile CT test on cylindrical concrete specimens was carried out by using portable power loading equipment suitable for CT scanner. Differential box dimension calculation program to calculate the fractal dimension of CT scan section, based on which the comparative analysis of the static and dynamic uniaxial tensile strength of concrete, the mechanical failure mechanism and the fractal characteristics of fractures are carried out. The results show that the crack propagation speed is slow, the fracture surface is rough and tortuous when the concrete is damaged under static tensile load, the crack develops along the aggregate following the weakest interface, the crack propagation speed is fast, the crack surface is straight and the crack is cracked The cutting aggregate follows the fastest path of energy release. The fractal characteristics of the CT scanning cross-section under static and dynamic tension are obvious. The fractal dimension develops with the crack growth law, which can well reflect the evolution law of the damage crack of the concrete material. The degree of damage can be used as a quantitative parameter for the evolution of cracks.