基于数字图像处理的沥青混合料蠕变剪切微观性能研究

发布时间：2018-07-02 07:14

本文选题：沥青混合料 + 数字图像处理技术　；参考：《长沙理工大学》2015年硕士论文

【摘要】：目前,沥青混合料抗剪切性能不足和重载交通在沥青层内产生了很大的剪应力,使得沥青路面产生失稳型车辙、荷载型裂缝等破坏。因此本文利用数字图像处理技术开展室内荷载条件下沥青混合料微观蠕变剪切破坏的形式与机理研究。运用数字图像处理技术分析混合料破坏前后不同级配内部各层面孔隙率、CT数、损伤变量的变化规律并进行分形分析。还考察内部粗颗粒破坏前后运动轨迹,后运用有限元软件来验证运用数字图像做数值模拟的适用性。运用数字图像处理技术将SPT蠕变试验剪切破坏前后CT图像进行二值化,计算出空隙率,试件剪切破坏多发生在其初始空隙分布较密集处。各级配试件初始CT数呈现“两头大,中间小”的规律,这跟空隙率分布规律相对应。CT数大小与密度成正比,剪切破坏后试件空隙率较大的中间层CT数下降更为明显。损伤变量最大值出现在空隙率比较大的试件中部,即剪切破坏较严重,AC-13级配的损伤变量均高于SMA-13级配,得出SMA-13级配抗蠕变剪切性能更强。沥青混合料蠕变剪切破坏前后过程具有分形特征。分析了粗颗粒破坏前后的轨迹,其中试验前后颗粒平动位移量平均值和离散性能,级配AC-13大于SMA-13,两级配位移量在试件中间层位较大;位移平动角整体均值和标准差级配AC-13大于SMA-13。剪切破坏后转动轨迹即主轴方向变化,级配AC-13比SMA-13主轴方向波动稍大一点;级配AC-13颗粒主轴方向的统一性大于SMA-13,SMA-13有更多的颗粒趋于水平排列;中间层位的主轴方向破坏前后差值比其它层略大,破坏极不均匀。同样验证了级配SMA-13抗剪切的性能大于AC-13。通过ABAQUS数值模拟劈裂试验,发现均质二维试样的应力分布皆比较有规律,而借助数字图像处理技术重构的二维非均值试样劈裂试验相关应力参数分布极不均匀,这跟实际的劈裂试验混合料受力情况相符合。应力集中因子能很好地反映沥青混合料的力学性能,从而验证了DIP-FEM方法的适用性。
[Abstract]:At present, the lack of anti shear performance of asphalt mixture and heavy load traffic have produced great shear stress in the asphalt layer, which causes the asphalt pavement to produce unstable rutting and load type cracks. Therefore, this paper uses digital image processing technology to carry out the study of the form and mechanism of the micro creep shear failure of asphalt mixture under indoor load conditions. The digital image processing technology is used to analyze the porosity, the CT number, the variation of the damage variable and the fractal analysis of the different gradations of the different gradations before and after the damage of the mixture. The motion trajectory of the internal coarse particles before and after the destruction is also investigated. Then the applicability of the numerical simulation using the digital image is verified by the finite element software. The two values of the CT image before and after the shear failure of the SPT creep test are calculated by the technology, and the void fraction is calculated. The shear failure of the specimen is mostly in the dense initial gap distribution. The initial CT number of the specimens at all levels presents the law of "two heads and the middle", which is proportional to the size of the void ratio and the density of the.CT and the shear failure. The CT number of the middle layer in the middle layer is more obvious. The maximum damage variable appears in the middle part of the specimen with larger void ratio, that is, the shear failure is more serious, and the damage variable of the AC-13 gradation is higher than that of the SMA-13 gradation. It is concluded that the creep shear performance of the SMA-13 gradation is stronger. The process of the asphalt mixture before and after the creep shear failure is divided. The trajectory of the coarse particle before and after the damage is analyzed, in which the average and discrete performance of the particle translational displacement before and after the test, the gradation AC-13 is greater than SMA-13, the two gradation displacement is larger in the middle layer of the specimen; the overall mean of the displacement translational angle and the standard difference gradation AC-13 are larger than the rotation path of the spindle after the shear failure, that is, the change of the main axis direction. AC-13 is slightly larger than the SMA-13 spindle direction, and the uniformity of the spindle direction of the graded AC-13 particles is greater than that of SMA-13, and more particles in SMA-13 tend to be horizontally arranged, and the difference value of the main axis direction before and after failure is slightly larger than the other layers, and the damage is extremely uneven. It is also verified that the anti shear performance of the grade SMA-13 is greater than that of AC-13. through ABAQUS. It is found that the stress distribution of homogeneous two dimensional specimens are all regular, and the distribution of related stress parameters of two dimensional non mean sample splitting test reconstructed by digital image processing technology is very uneven, which coincide with the actual stress condition of the actual split test. The stress concentration factor can reflect the asphalt mixture well. The applicability of the DIP-FEM method is verified by the mechanical properties of the aggregate.
【学位授予单位】：长沙理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U414;TP391.41

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