混凝土单轴压缩及单轴拉伸破坏过程的细观数值试验及CT验证

发布时间：2018-05-26 01:23

本文选题：ABAQUS + CT试验　；参考：《长安大学》2017年硕士论文

【摘要】：混凝土材料在动荷载作用下,会导致其的力学性能发生很大的变化,其破坏过程是一个非常复杂的非线性材料损伤过程。本文利用细观力学、随机数学方法和数值计算理论相结合,来分析混凝土试件在冲击荷载作用的变形、损伤和破坏过程。利用有限元软件ABAQUS对混凝土试件在不同加载速率和不同加载幅值下受到冲击荷载作用下的单轴受压和单轴拉伸破坏的数值模拟,研究不同加载速率以及加载幅值对混凝土强度的影响。利用CT技术能够观察混凝土材料中裂纹的萌生、发展以及最终贯通破坏过程,通过对比数值计算结果与CT试验结果,总结混凝土材料的破坏机理和破坏形态。本文通过数值模拟和CT试验分析,研究成果如下:(1)在不同加载速率下的冲击荷载条件下,对混凝土试件的单轴受压模拟时,速率越大,其强度也会增大。当速率提高2.5倍时,试件的平均强度提高了2%;当加载速率提高4倍时,试件的平均强度提高了7.3%。对混凝土试件的单轴拉伸模拟时,当速率提高2.5倍时,试件的平均强度提高了53%;当加载速率提高4倍时,试件的平均强度提高了57%。(2)在不同加载幅值下的冲击荷载条件下,对混凝土试件的单轴受压模拟时,我们发现,混凝土的强度随着加载幅值的增大而增大。当加载幅值提高2倍时,平均强度提高了2.6%。当加载幅值提高3倍时,试件的平均强度提高了5.6%。(3)对于在不同加载速率以及不同加载幅值条件下的单轴受压模拟,我们得知,混凝土的破坏最开始是从界面层发生的,即界面层的强度最低。产生的裂纹随着外荷载的增大向砂浆层发展,最后直至裂纹贯穿整个混凝土试件。破坏形式为呈45度的剪切破坏。对于不同加载速率下的单轴拉伸模拟时,我们通过分析数值计算结果发现,其破坏是在混凝土试件底部形成一条贯穿横截面的宏观裂纹。(4)通过对比混凝土试件在冲击荷载作用下的单轴受压和单轴拉伸数值模拟损伤云图与CT试验获得的CT图像,我们总结,两种方式下混凝土破坏裂纹的发展及破坏形态与CT试验结果比较相近,验证了本文对混凝土进行单轴受压和单轴拉伸数值模拟的可行性。
[Abstract]:Under dynamic load, the mechanical properties of concrete material will change greatly, and the damage process of concrete material is a very complicated nonlinear material damage process. In this paper, the deformation, damage and failure process of concrete specimens under impact load are analyzed by means of the combination of meso-mechanics, stochastic mathematical method and numerical calculation theory. The finite element software ABAQUS is used to simulate the uniaxial compression and uniaxial tensile failure of concrete specimens under different loading rates and different loading amplitudes. The effects of different loading rates and loading amplitude on the strength of concrete are studied. The crack initiation, development and ultimate penetrating failure process in concrete can be observed by using CT technique. The failure mechanism and failure pattern of concrete material are summarized by comparing the numerical results with the results of CT test. Through numerical simulation and CT test analysis, the research results are as follows: 1) under different loading rates, the strength of concrete specimen under uniaxial compression will increase with the increase of the rate. The average strength of the specimen was increased by 2. 5 times when the loading rate was increased by 2. 5 times, and by 7. 3% when the loading rate was 4 times higher. In uniaxial tensile simulation of concrete specimens, the average strength of concrete specimens increases by 53 when the rate increases by 2.5 times, and when the loading rate increases by 4 times, the average strength of specimens increases by 57% under different loading amplitudes. Under uniaxial compression simulation of concrete specimens, it is found that the strength of concrete increases with the increase of loading amplitude. When the loading amplitude is increased by 2 times, the average strength is increased by 2.6 times. When the loading amplitude is increased by three times, the average strength of the specimen is increased by 5.60.The uniaxial compression simulation under different loading rates and different loading amplitudes shows that the failure of concrete begins from the interface layer. That is, the interfacial layer has the lowest strength. The resulting crack develops to the mortar layer with the increase of the external load, and finally the crack runs through the whole concrete specimen. The failure form is 45 degrees shear failure. For uniaxial tensile simulation at different loading rates, we find that, The failure is to form a macroscopic crack at the bottom of the concrete specimen. (4) by comparing the uniaxial compression and uniaxial tension of the concrete specimen under impact load, the damage cloud diagram and the CT image obtained by the CT test are simulated. We conclude that the development and failure pattern of concrete failure crack in two ways are close to the results of CT test, which verifies the feasibility of uniaxial compression and uniaxial tensile numerical simulation of concrete in this paper.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU528

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