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借助CT扫描获得了压缩破坏过程混凝土材料的内部密度分布特征,对CT图像进行分区讨论,通过分析微裂纹演化所引起的灰度变化,采用分形Rd指标来描述分区位置线上灰度变化及统计规律,并基于Rd指标定义了一个损伤变量.研究表明:1)所有位置线上灰度变化的Rd总值随荷载增大呈二次减小规律,这是微裂纹演化的不断局部化所致;2)不同的荷载阶段Rd值变化不同,荷载水平从零增大到0.6时,所有位置线上灰度变化的Rd值都下降较快,从0.6到0.9的过程,各位置线上Rd值上下波动;从0.9到主裂纹贯通,大部分位置线Rd值减小,靠近贯通区域的位置线上Rd值则略有增大;3)定义的损伤度与荷载成二次增大关系,这与实际相符较好.
By CT scanning, the internal density distribution characteristics of concrete during compression failure process were obtained. The CT images were divided and discussed. The grayscale changes caused by microcrack evolution were analyzed. The fractal Rd index Law and a damage variable is defined based on the Rd index.Research shows that: 1) The total Rd value of the gray-level changes in all the locations decreases quadratically with the increase of load, which is caused by the continuous localization of microcrack evolution ; 2) The values of Rd vary with different loading stages. The Rd values of gray values of all the positions decrease rapidly when the loading level increases from zero to 0.6. From 0.6 to 0.9, the values of Rd Fluctuating; from 0.9 to the main crack through, most of the location line Rd value decreases, near the through-site location line Rd value increases slightly; 3) The defined damage degree and the load into a second increase, which Good match with the actual.