纤维混凝土细观结构及破裂过程数值模拟研究

发布时间：2018-05-15 04:24

本文选题：纤维混凝土 + 随机骨料模型　；参考：《长安大学》2014年硕士论文

【摘要】：纤维混凝土具有高延性和高韧性优点，在土木工程等领域中得到广泛的应用，但目前研究仍以宏观试验和定性分析为主，缺乏成熟的细观力学模型，对其细观力学性能与宏观力学行为之间关联性的研究仍较少见。本文从细观角度出发，采用细观损伤力学理论和数值模拟技术，建立纤维混凝土细观力学模型，探究纤维混凝土损伤与断裂过程中裂纹扩展规律以及损伤与断裂机制问题。本文首先在细观层次上把纤维混凝土看作是由粗集料、硬化纤维砂浆基体和两者之间界面过渡区所组成的三相非均匀复合材料，，基于Monte-Carlo随机抽样方法，分析了混凝土内部不同骨料的形状几何信息，提出了混凝土骨料随机投放算法，建立了基于不同骨料含量和不同骨料形状的纤维混凝土细观结构数值模型。基于分水岭分割等图像处理技术对纤维混凝土随机截面进行了数字图像处理和分析，通过矢量转换技术建立了基于纤维混凝土真实骨料分布的细观结构模型。利用粗集料的圆度、针状系数和Blaschke系数等参数定量分析了混凝土内部粗集料的形状特征，并利用粗集料主轴倾角和级配这两个指标定量分析了混凝土内部粗集料的空间分布特征。从混凝土材料的细观结构入手，通过室内力学性能试验和细观损伤理论研究，建立了适合描述三相细观介质力学特征的本构关系。利用有限元技术对纤维混凝土单轴受压和弯拉试验进行了数值模拟，模拟结果能够较好地反应出纤维混凝土在不同受力状态下的应力应变特点以及损伤与断裂过程。采用细观数值模拟试验分析了粗集料形状和粗集料含量对纤维混凝土力学性能的影响。分析结果表明，粗集料形状对纤维混凝土弯拉强度的影响大于抗压强度；粗集料含量的增加显著地提高纤维混凝土的抗压和抗弯拉强度，且粗集料含量增加一定程度上增大了纤维混凝土脆性破坏概率。
[Abstract]:Fiber concrete has the advantages of high ductility and high toughness , and is widely used in the fields of civil engineering and other fields . However , the present research is still mainly based on macro - test and qualitative analysis .

In this paper , the fiber concrete is regarded as a three - phase non - uniform composite material composed of coarse aggregate , hardened fiber mortar matrix and interface transition area between them . Based on Monte - Carlo random sampling method , the shape geometry information of different aggregate inside the concrete is analyzed , the random throwing algorithm of concrete aggregate is put forward , and the numerical model of fiber concrete meso - structure based on different aggregate content and different aggregate shapes is established .

Based on watershed segmentation and other image processing techniques , the random section of fiber concrete is subjected to digital image processing and analysis , and a meso - structure model based on the real aggregate distribution of fiber - concrete is established through vector conversion technology . The shape characteristics of coarse aggregate in concrete are analyzed quantitatively by using the parameters such as roundness , needle - like coefficient of coarse aggregate and Blakeske coefficient , and the spatial distribution characteristics of coarse aggregate in concrete are analyzed quantitatively by using the inclination angle and gradation of coarse aggregate .

Based on the meso - structure of concrete material , this paper has established the constitutive relation suitable for describing the mechanical characteristics of three - phase meso - mesoscopic medium by means of indoor mechanical property test and meso - view damage theory . The finite element technique is used to simulate the uniaxial compression and bending test of fiber concrete . The simulation results can reflect the stress - strain characteristics and damage and fracture process of fiber concrete under different stress states .

The influence of coarse aggregate shape and coarse aggregate content on the mechanical properties of fiber concrete is analyzed by means of numerical simulation test . The results show that the influence of coarse aggregate shape on the flexural strength of fiber concrete is greater than that of compressive strength ;
The increase of coarse aggregate content significantly increases the compressive strength and flexural tensile strength of fiber concrete , and increases the probability of brittle failure of fiber concrete to some extent .

【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU528

【参考文献】