界面强度对混凝土拉伸断裂影响的数值模拟

Digital Simulation of Influence of Tensile Strength of Interfacial Transition Zone on Tensile Fracturing Process of Concrete

采用数字图像的处理手段表征混凝土的三相(基质、骨料、界面过渡区)细观结构,获取混凝土界面过渡区的形状与分布,并引入到原有材料破坏过程分析(MFPA2D)系统中,建立了能反映混凝土真实细观结构的数值模型,并应用该模型模拟了界面强度对混凝土拉伸断裂过程的影响.研究表明,当界面过渡区强度较低时,混凝土的断裂过程表现为界面过渡区中萌生的局部裂纹相互作用、桥接贯通的过程;界面强度与抗拉强度之间存在非线性关系,界面强度的提高增大了混凝土的延性,导致单轴拉伸荷载作用下混凝土试件的宏观断裂模式由单一贯通裂纹向多条非贯通裂纹过渡;模拟结果与试验结果比较吻合.

Digital image processing methods were employed to characterize the three-phase microstructures of concrete consisting of mortar matrix, coarse aggregate and interfacial transition zone（ITZ）. The distribution and shape of ITZ were obtained digitally. The characterized microstructure was incorporated into material failure process analysis（MFPA^2D） system, and the numerical model of concrete was established which took into account the real heterogeneity of concrete. The influence of tensile strength of ITZ on tensile fracturing process was studied using this model according to a surface image of concrete with certain proportioning. The results show that if the tensile strength of ITZ is low, in the fracturing process of concrete the mierocracks initiated in ITZ interact with each other, then propagate and coalesce. With the tensile strength of ITZ increasing, fractured modes of concrete under uniaxial tensile loading transit from sin- gle coalescent crack to multiple non-coalescent cracks and the ductility of concrete is enhanced. The relation between the tensile strength of ITZ and that of concrete is non-linear. The simulation results agree well with experimental results.