颗粒物质局部化行为的细观研究
发布时间：2018-08-02 14:03
【摘要】：颗粒物质是在自然界和工程建设中广泛存在的一种物质类型，近百年来得到了广泛而深入地研究。颗粒物质在形成过程中内部形成不同的细观组织结构，这些细观结构对体系的整体稳定性产生巨大影响。从颗粒角度出发，研究颗粒接触形成的细观结构（如力链网络）、动力学过程及其与宏观力学性质之间关系是细观研究的主要思路，，这方面工作是工程建设及地质散体灾害防治关键技术的理论基础。 通过光弹实验方法可以观察二维静力触探试验过程中力链网络的演化规律。利用图形处理和基于条纹光强梯度的拟合方法，获取实验过程中颗粒圆心位置，以及颗粒所受力的大小，得到加载过程中内部力链网络的形态。采用颗粒流商业软件PFC (Particle Flow Code)对相同加载条件下的颗粒试样进行了数值模拟，所得结果与光弹实验中观察到的力链网络吻合较好。分析表明，颗粒体系在外荷载作用下内部存在着形态各异的力链网络，力链网络的主要分布方向与体系主应力的方向相同，在外荷载作用下力链网络呈现复杂的局部化行为。 文章的重点是，提出了基于单颗粒的非仿射应变率的概念，来量化局部化行为。分析了双轴压缩、静力触探、混凝土立方体抗压强度以及混凝土圆盘劈拉试验过程中内部非仿射应变率的空间分布；利用小波方法分析了非仿射应变率较大颗粒的空间关联；引入统计的概念，建立非仿射应变率概率分布演化方程，利用这个演化方程很好的描述了双轴压缩试验过程中局部化的演化过程。 将离散元（Discrete Element Method, DEM）串行程序引入并行自适应结构网格应用支撑软件框架（J Adaptive Structured Mesh applications Infrastructure,Jasmin），开展了颗粒物质大规模并行数值模拟，计算了颗粒膨胀过程和三轴压缩试验，分析了力链网络、局部体积分数、局部应力等参数的不均匀化。数值模拟结果显示，颗粒体系内部存在着很强的局部化现象，通过后处理程序，可以很清晰的观察颗粒体系内部的局部化现象，且随着体系越来越密实，内部不均匀性逐渐下降。同时，我们发现当颗粒体系在达到堵塞（Jamming）状态之后，边壁压力增量、配位数增量以及平均局部应力与体积分数的增量形成很好的指数关系。
[Abstract]:Granular matter is a kind of material widely existing in nature and engineering construction, which has been studied extensively and deeply in the last hundred years. In the process of the formation of granular matter, different microstructures are formed, which have a great influence on the overall stability of the system. From the point of view of particles, the main idea of mesoscopic research is to study the meso-structure (such as force chain network) formed by particle contact, and the dynamic process and its relationship with macroscopic mechanical properties. This work is the theoretical basis of engineering construction and the key technology of geological bulk disaster prevention. The evolution of the force chain network during the two dimensional static penetration test can be observed by the photoelastic experimental method. By using the graphic processing and fitting method based on the fringe intensity gradient, the position of the center of the particle and the size of the force acting on the particle during the experiment are obtained, and the shape of the internal force chain network during the loading process is obtained. The particle flow commercial software PFC (Particle Flow Code) is used to simulate the particle samples under the same loading conditions. The results are in good agreement with the force chain network observed in the photoelastic experiments. The analysis shows that there are different forms of force chain network in particle system under external load, and the main distribution direction of force chain network is the same as that of system principal stress, and the force chain network presents complex localization behavior under external load. The emphasis of this paper is that the concept of non-affine strain rate based on single particle is proposed to quantify the localization behavior. The spatial distribution of biaxial compression, static penetration, concrete cube compressive strength and internal non-affine strain rate during splitting tensile test of concrete disk is analyzed, and the spatial correlation of large non-affine strain rate particles is analyzed by wavelet method. By introducing the concept of statistics, the evolution equation of probability distribution of non-affine strain rate is established. The evolution process of localization in biaxial compression test is well described by using this evolution equation. The discrete element (Discrete Element Method, DEM) serial program is introduced into the parallel adaptive grid application support software framework (J Adaptive Structured Mesh applications Infrastructure Jasmin). A large-scale parallel numerical simulation of granular matter is carried out, and the particle expansion process and triaxial compression test are calculated. The inhomogeneity of some parameters, such as force chain network, local volume fraction and local stress, is analyzed. The numerical simulation results show that there is a strong localization phenomenon in the particle system. Through the post-processing program, the localization phenomenon in the particle system can be observed clearly, and as the system becomes more and more dense, The internal inhomogeneity decreases gradually. At the same time, we find that the increment of side wall pressure, coordination number, average local stress and volume fraction have a good exponential relationship when the particle system reaches the (Jamming) state.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：O347.7;TU4
本文编号：2159671
[Abstract]:Granular matter is a kind of material widely existing in nature and engineering construction, which has been studied extensively and deeply in the last hundred years. In the process of the formation of granular matter, different microstructures are formed, which have a great influence on the overall stability of the system. From the point of view of particles, the main idea of mesoscopic research is to study the meso-structure (such as force chain network) formed by particle contact, and the dynamic process and its relationship with macroscopic mechanical properties. This work is the theoretical basis of engineering construction and the key technology of geological bulk disaster prevention. The evolution of the force chain network during the two dimensional static penetration test can be observed by the photoelastic experimental method. By using the graphic processing and fitting method based on the fringe intensity gradient, the position of the center of the particle and the size of the force acting on the particle during the experiment are obtained, and the shape of the internal force chain network during the loading process is obtained. The particle flow commercial software PFC (Particle Flow Code) is used to simulate the particle samples under the same loading conditions. The results are in good agreement with the force chain network observed in the photoelastic experiments. The analysis shows that there are different forms of force chain network in particle system under external load, and the main distribution direction of force chain network is the same as that of system principal stress, and the force chain network presents complex localization behavior under external load. The emphasis of this paper is that the concept of non-affine strain rate based on single particle is proposed to quantify the localization behavior. The spatial distribution of biaxial compression, static penetration, concrete cube compressive strength and internal non-affine strain rate during splitting tensile test of concrete disk is analyzed, and the spatial correlation of large non-affine strain rate particles is analyzed by wavelet method. By introducing the concept of statistics, the evolution equation of probability distribution of non-affine strain rate is established. The evolution process of localization in biaxial compression test is well described by using this evolution equation. The discrete element (Discrete Element Method, DEM) serial program is introduced into the parallel adaptive grid application support software framework (J Adaptive Structured Mesh applications Infrastructure Jasmin). A large-scale parallel numerical simulation of granular matter is carried out, and the particle expansion process and triaxial compression test are calculated. The inhomogeneity of some parameters, such as force chain network, local volume fraction and local stress, is analyzed. The numerical simulation results show that there is a strong localization phenomenon in the particle system. Through the post-processing program, the localization phenomenon in the particle system can be observed clearly, and as the system becomes more and more dense, The internal inhomogeneity decreases gradually. At the same time, we find that the increment of side wall pressure, coordination number, average local stress and volume fraction have a good exponential relationship when the particle system reaches the (Jamming) state.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2013
【分类号】：O347.7;TU4
【参考文献】
相关期刊论文 前8条
1 李静海;董元吉;郭慕孙;;颗粒——流体两相流数学模型 Ⅰ.多尺度作用模型和能量最小方法[J];化工冶金;1988年01期
2 李静海;董元吉;郭慕孙;;颗粒——流体两相流数学模型 Ⅱ、能量传递和流型过渡[J];化工冶金;1988年01期
3 耿丽;黄志强;苗雨;;粗粒土三轴试验的细观模拟[J];土木工程与管理学报;2011年04期
4 苗天德;宜晨虹;齐艳丽;慕青松;刘源;;集中力作用下球形颗粒六角密排堆积体的传力研究[J];物理学报;2007年08期
5 孙其诚;王光谦;;静态堆积颗粒中的力链分布[J];物理学报;2008年08期
6 孙其诚;金峰;;颗粒物质的多尺度结构及其研究框架[J];物理;2009年04期
7 邵磊;迟世春;贾宇峰;;堆石料大三轴试验的细观模拟[J];岩土力学;2009年S1期
8 李静海,郭慕孙;过程工程量化的科学途径——多尺度法[J];自然科学进展;1999年12期
本文编号：2159671
本文链接：https://www.wllwen.com/kejilunwen/sgjslw/2159671.html
