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采用数字图像相关(DIC)方法研究了混凝土材料的压缩破坏。在压缩实验前,将混凝土外表层切除,裸露的细观形貌可以作为DIC技术中的自然散斑场。采用高分辨CCD进行表面图像采集,通过DIC技术处理后可以获得压缩破坏过程中的应变场分布。两端无约束的混凝土压缩破坏符合第二强度理论(最大拉应变强度理论),因此本文分析了混凝土压缩破坏前垂直荷载方向的拉应变场的分布规律。实验结果表明,在压缩破坏发生前,拉应变已经出现应变集中的现象,并且该应变集中与混凝土最后的压缩破坏形态有关。从细观形貌来看,混凝土破坏前的最大拉应变往往出现在骨料上,导致骨料内部开裂或者骨料边界开裂。本文研究结果表明,DIC技术可以提前预测出混凝土破坏的位置,适用于混凝土结构破坏的监测。
The digital image correlation (DIC) method was used to study the compression failure of concrete materials. Before the compression experiment, the concrete outer surface is cut off, and the exposed micromorphology can be used as a natural speckle field in DIC technology. Using high-resolution CCD for surface image acquisition, the strain field distribution during compression failure can be obtained after DIC processing. The unconstrained concrete compression failure at both ends accords with the second strength theory (maximum tensile strength theory). Therefore, the distribution law of tensile strain field in the vertical load direction before concrete compression failure is analyzed in this paper. The experimental results show that there is a phenomenon of strain concentration in the tensile strain before the compression failure occurs, and the strain concentration is related to the final compression failure mode of the concrete. In terms of mesoscopic morphology, the maximum tensile strain before concrete failure often appears on aggregate, leading to internal cracking of aggregate or cracking of aggregate boundaries. The results of this paper show that DIC can predict the location of concrete failure in advance and is suitable for the monitoring of concrete structure failure.