江苏科技大学硕士学位论文基于细观层次的混凝土数值模拟研究姓名：杨冠颖申请学位级别：硕士专业：结构工程指导教师：俞铭华;黄海燕20080304学 号： 05010207 05010207 摘 要： 在一定的试验基础上，采用数值模拟方法研究混凝土断裂破坏的全过程，可以为改善混凝土的力学性能和研制高性能混凝土材料提供力学依据。此外，数值模拟方法有利于解释试验中发生的一些断裂现象，为改善试验设计提供有益参考，在证明数值模拟方法可靠和有效的前提下，可以取代部分试验，节省大量的人力和物力。利用数值模拟方法对混凝土材料的力学性能进行研究具有重大的意义。 本文根据细观力学理论，将混凝土看成是由骨料、水泥砂浆及其二者之间的粘结界面组成的非均质复合材料，采用非线性有限单元法，在自编软件和商业软件的基础上，对三级配混凝土试件的轴向压缩、拉伸直至破坏的过程进行了数值模拟，对试件细观损伤和宏观破坏之间的联系进行了初步探讨。 根据三级配混凝土骨料的实际配比及 Walraven 公式，计算出混凝土试件中各种粒径骨料的数目，根据蒙特卡罗方法随机确定骨料的空间位置，使用 VC+编制了可视化程序，提出了混凝土任意形状骨料及其界面层的二维生成算法。在该算法的基础上，对 AutoCAD 进行二次开发，生成了具有任意形状骨料及界面层的二维混凝土试件几何模型，该模型能很好地模拟人工骨料和再生骨料，为进一步进行有限元分析奠定了良好的基础。 采用 Advancing Front 方法对随机骨料模型进行网格剖分，网格剖分严格按骨料、界面和砂浆分别进行。 对三级配混凝土试件在单轴荷载作用下的响应进行了数值模拟分析，计算结果表明界面是试件的薄弱环节，试件的微裂纹首先出现在界面单元上，然后向相邻砂浆单元扩张，微裂纹不断扩展、合并，最终导致试件破坏。这表明：混凝土材料的宏观力学性能受其细观结构的控制， 混凝土试件的宏观破坏是细观尺度上的损伤行为和断裂行为的累积和发展的结果， 细观层次的破坏和损伤是宏观破坏的内因和基础。 数值模拟结果与试验结果的一致性表明， 采用随机骨料随机参数模型从细观层次上研究混凝土的损伤、开裂，从而找出混凝土细观损伤和宏观破坏之间联系的方法是可行的。通过本文研究可知，界面是试件的薄弱环节，混凝土的损伤和开裂都是最先发生在界面上，随着界面的开裂，裂纹逐渐扩展，从而导致试件的破坏，即混凝土的细观损伤是宏观破坏的内因和基础，而试件的宏观破坏是细观损伤的累积和发展。混凝土的力学性能主要与粘结界面的力学性能及骨料的最大粒径有关， 界面裂纹几乎是同时在大、小骨料颗粒的界面上引发，并随着应力的增大而增大。 对于单轴受拉试件，随着界面强度的提高，试件的承载能力逐渐提高；随着界面软化模量的增大，下降段逐渐变陡，但下降段对软化模量的变化不是太敏感。随着界面厚度的增加，试件的荷载位移曲线出现非线性行为的时间逐渐滞后，但试件破坏时的极限承载力逐渐减小，且界面厚度对材料非线性段的力学性能有一定的影响。 最后，进一步开发生成了三维混凝土模型的算法及程序，实现了三维混凝土随机骨料模型的建立。 二维和三维混凝土随机模型的建立及二维数值模型的分析表明本文生成模型的方法是可行的，分析思路是正确的，结果是合理的。 关键词：关键词：三级配混凝土；任意形状骨料；随机骨料模型；数值模拟；细观损伤 ABSTRACT： Based on certain experimentation, using the numerical simulation method to research the whole course of rupture damage of concrete, which can support mechanical reference for the improvement of concretes mechanical capability and the develop of high-capability concrete material. Besides, numerical simulation method is propitious to explain some rupture phenomena happening in the experimentation and can support helpful reference for the improvement of experimentation, under the precondition of credibility and availability of the numerical simulation method, it can replace some experimentations and save a great deal of manpower and material resources. It has signality to make use of the numerical simulation method to research the mechanical capability of concrete material. In this paper, based on the meso-mechanics theory, concrete was taken as three-phase composites, which consists of aggregate, mortar matrix and bond between matrix and aggregate. With nonlinear finite element method, the numerical simulation of mechanical performance and failure process was studied for the uniaxial compress and pull of three-graded-concrete specimen based on self-programme and commercial software, and the relation of meso-damage and macro-failure were simply discussed. The number of all kinds of aggregate was decided according to the actual gradation of aggregate of three-graded-concrete and Walraven formula. The location of aggregate was random generated by Monte Carlo method, a visual program was designed by VC+, 2-D generation algorithm for concrete aggregate of arbitrary shape and its bond layer was advised. Based on the algorithm, a geometrical model was built using AutoCAD software on its second development, the artificial or regenerated aggregates model can be simulated by these models, which settle a groundwork for the next finite element analysis. The mesh division of aggregate, bond and mortar a finite element mesh model matrix was carried out respectively by Advancing Front method. The response happened on the three-graded-concrete specimen under the uniaxial load has been simulated, the results indicate that the bond is weak links, the meso-cracks appears in the bond first before they enter the mortar matrix, then the specimen failed because of the expand, combination of meso-cracks. This show that the macro-mechanical-performance of concrete material is controlled by its meso-structure, the macro-failure of concrete specimen is the cumulation and result of damages and fracture in meso-scale, meso-damage is the intrinsic factor and base of macro-failure. The consistency between numerical simulation result and experimentation result indicate that, using random aggregate random parameters model to research the damage and craze of concrete on meso-level, which is a feasible method to find the connection between the meso-damage and macro-failure of concrete. From this paper, some conclusion can be reached: bond is the weakness of the specimen, concrete damage and craze happens first on bond, as the bond craze, cracks expand gradually, consequently lead to the failure of the specimen, that is, concretes meso-damage is the intrinsic factor and the base of the macro-failure, specimens macro-failure is the cumulation and development of the meso-damage. The mechanical capability of concrete is mainly related to the mechanical capability of bond and the biggest diameter of aggregate, bond crack almost solicitation synchronously on the bond of the big and small aggregate and aggrandize as the stresss aggrandizement. For uniaxial tensile specimen,