Ding Weihua, Zhu Lin, Li Hu, Lei Man, Yang Fan, Qin Junrong, Li Aiguo
State Key Laboratory of Eco-Hydraulics in Northwest Arid Region, Xi'an University of Technology, Xi'an 710048, China.
School of Civil Engineering and Architecture, Xi'an University of Technology, Xi'an 710048, China.
Materials (Basel). 2022 Aug 16;15(16):5640. doi: 10.3390/ma15165640.
To achieve more accurate prediction of the potential failure location and to conduct a deeper analysis of the failure mechanism of concrete constructions, it is critical to probe the evolution process of internal meso-cracks that bear various intensities of load. While a computer Tomography (CT) test provides a non-destructive detection technique for obtaining the internal meso-damage state of concrete, traditional image processing and Digital Image Correlation (DIC) are ineffective in extracting meso-damage information from concrete CT images. On the other hand, by observing the shape change law of concrete's internal holes under load, it is proposed to use the hole roundness and area fraction formula, developed based on the stereology principle and morphology, to characterize and predict the potential failure location. Four features particularly addressed include the CT image as a whole, image equal partitioning, crack and non-crack areas, and representative holes. The approach is to explore the variation law of critical hole shape parameters, especially the hole roundness under different loading stages, and analyze the relationship between the change in hole shapes and the final macro-crack positions. It is found that compared with the average area fraction, the average hole roundness value of cross section images is more sensitive to the change in stress. In both uniform partitioning and non-uniform partitioning, the average hole roundness value near the final macro-crack location exhibits an increase trend with the stress, while the smoothing effect caused by the hole roundness averaging always exists. Near the final macro-crack location, the roundness of each individual hole is positively associated with the stress, while away from the final macro-crack location such a relation may not be observed. This trend expounds the evolution process of meso-damage in concrete, and the finding can be used to predict the accurate locations of macro-cracks.
为了更准确地预测混凝土结构潜在的破坏位置，并对其破坏机理进行更深入的分析，探究承受不同荷载强度的内部细观裂缝的演化过程至关重要。虽然计算机断层扫描（CT）测试提供了一种获取混凝土内部细观损伤状态的无损检测技术，但传统图像处理和数字图像相关（DIC）技术在从混凝土CT图像中提取细观损伤信息方面效果不佳。另一方面，通过观察混凝土内部孔洞在荷载作用下的形状变化规律，提出利用基于体视学原理和形态学开发的孔洞圆度和面积分数公式来表征和预测潜在的破坏位置。特别关注的四个特征包括整体CT图像、图像等分区、裂缝和非裂缝区域以及代表性孔洞。该方法是探索关键孔洞形状参数的变化规律，特别是不同加载阶段下的孔洞圆度，并分析孔洞形状变化与最终宏观裂缝位置之间的关系。研究发现，与平均面积分数相比，横截面图像的平均孔洞圆度值对应力变化更敏感。在均匀分区和非均匀分区中，最终宏观裂缝位置附近的平均孔洞圆度值均随应力呈现增加趋势，而孔洞圆度平均化所产生的平滑效应始终存在。在最终宏观裂缝位置附近，各个孔洞的圆度与应力呈正相关，而在远离最终宏观裂缝位置时可能观察不到这种关系。这一趋势阐述了混凝土中细观损伤的演化过程，该发现可用于预测宏观裂缝的准确位置。
