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Analyzes of Fracture Process Zone by AE and Constitution of its Numerical Model

断裂过程区的声发射分析及其数值模型的建立

基本信息

批准号：
06650493
负责人：
NIISEKI Shigeru
金额：
$ 1.09万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06650493/
关键词：
Concrete Mortar Fracture Process Zone 3-D AE Source Location AE Wave Form Analysis Continuum Damage Theory AE Event Controlled Loading 岩質材料 3次元AE位置標定仮想クラックモデル損傷発展側

项目摘要

It is generally recognized that the fracture process zone is composed of a microcracking zone including very many microcracks and bridging zone with cohesive stress. However, lengths, widths and shapes of these zones in concrete and mortar have not been clarified.To identify the microcracking zones in concrete and mortar specimens, we used the loading method controlled by the AE event count rate in near the maximum load and strain softening-region and three-dimensional AE source location. The dimensions of concrete and mortar specimens are 150 mm high, 94 mm thick and 550 wide. The maximum grain sizes of aggregate in these specimens are 15 and 5 mm respectively. As a result of identification, the average lengths of microcracking zones in concrete and mortar were 51 and 61 mm respectively, and their average widths were 71 and 57 mm respectively. In addition, by penetration of dye, we identified that the bridging zones in concrete and mortar specimens were 54 and 31 mm. From the above results, the total lengths of fracture process zones in concrete and mortar specimens were 105 and 92 mm.Based on the statistical distributions of directions of microcrack surfaces obtained by the AE waveform analysis, we formulated an anisotropic continuum damage theory. Then, by this theory and the finite element method, we constituted a numerical model of the fracture process zone, and analyzed crack growth in the three-point bending test. Compared with experimental results, the extent of various damage levels of the fracture process zone was fairly good, but the maximum load-displacement curve was not satisfactory.

一般认为断裂过程区由含有大量微裂纹的微裂纹区和具有内聚应力的桥接区组成。然而，混凝土和砂浆中这些区域的长度、宽度和形状尚未明确。为了识别混凝土和砂浆试件中的微裂纹区域，我们采用了由最大荷载和应变软化区附近的声发射事件计数率和三维声发射源位置控制的加载方法。混凝土和砂浆试件的尺寸为高150毫米、厚94毫米、宽550毫米。这些样本中骨料的最大粒径分别为15 和5 毫米。鉴定结果，混凝土和砂浆中微裂纹区的平均长度分别为51和61 mm，平均宽度分别为71和57 mm。此外，通过染料的渗透，我们确定混凝土和砂浆样本中的桥接区域分别为 54 毫米和 31 毫米。由以上结果可知，混凝土和砂浆试件断裂过程区的总长度分别为105和92mm。根据AE波形分析得到的微裂纹表面方向的统计分布，我们建立了各向异性连续介质损伤理论。然后，利用该理论和有限元方法，构建了断裂过程区的数值模型，并对三点弯曲试验中裂纹的扩展进行了分析。与实验结果相比，断裂过程区各损伤程度程度较好，但最大载荷-位移曲线不理想。