冲击荷载下混凝土损伤裂纹的分形实验

Fractal experiment of damaged concrete under impact loading

采用分离式Hopkinson压杆实验装置,对混凝土材料在冲击荷载下的动态单轴压应力极限值及裂纹分形维数值进行了研究.依据盒维数计算原理,设计了基于Matlab的数字图像盒维数计算程式,建立了一种数字图像盒维数简易算法.实验结果表明,冲击荷载条件下,混凝土表面裂纹具有很好的分形特性,分维是表征混凝土破坏程度的一个定量参数,并用分形维数对混凝土试块的单轴动态抗压强度极限值和应变率进行定量描述,拟合了试块动态单轴压应力极限值与其对应的分形维数的定量关系.为探索混凝土表面裂纹图形的分形特征与其承受的动荷载之间的内在规律,提供了一条新的研究思路.

Researches were carried on extreme of concrete dynamic uniaxial compression stress and crack fractal dimension,by using the split Hopkinson pressure bar（SHPB） device.Basing on the box-counting dimension calculation method,Matlab calculating functions of 2D digital image box-counting dimension were actualized and a direct computational method of 2D digital image box-counting dimension was achieved.Experimental results indicate that under impact loading,the surface crack distribution of damaged concrete exhibits fractal properties and can be used as a description parameter of concrete damage degree.Quantitative description of extreme of dynamic uniaxial compression stress and fractal dimension was tried according to the experiment.Results of the experiment offer a new research thinking of inherent laws between concrete surface crack and pressure state.