颗粒形状对颗粒材料力学行为影响的数值研究
Polygons vs. clumps of discs: a numerical study of the influence of grain shape on the mechanical behaviour of granular materials
摘要：
我们进行了一系列的数值垂直压缩试验的二维颗粒材料组件使用离散元代码和研究结果方面的颗粒形状。样品由5，000个颗粒组成，这些颗粒由3个重叠的圆盘（团块-具有凹面的颗粒）或六边多边形（凸面颗粒）制成。这两种颗粒类型具有相似的外部包络，其是几何参数$α$的函数。在本文中，所应用的数值计算程序是简要介绍其次所使用的颗粒模型的描述。对密实和松散颗粒集合体在各向同性载荷作用下的力学行为进行了观察和分析。在经典的常侧向应力垂直压缩试验（双轴试验）的框架下，研究了数值颗粒试样的力学响应。具有不同晶粒形状的致密和松散样品的宏观响应的比较表明，当$α$被认为是一个参数时，它因此是一个相关变量，用于增加致密样品的机械性能。当$α$被认为是与完美球度的包络偏差时，它可以控制大应变的机械性能。最后，我们提出了一些关于变形样品的运动学的评论：虽然一些多边形样品进行垂直压缩呈现大的损伤区（任何多边形形状），致密的块状样品总是表现出薄的反射剪切带。这篇论文是作为CEGEO研究项目的一部分编写的www.granuloscience.com
英文摘要：
We performed a series of numerical vertical compression tests on assemblies of 2D granular material using a Discrete Element code and studied the results with regard to the grain shape. The samples consist of 5,000 grains made from either 3 overlapping discs (clumps - grains with concavities) or six-edged polygons (convex grains). These two grain type have similar external envelopes, which is a function of a geometrical parameter $α$. In this paper, the numerical procedure applied is briefly presented followed by the description of the granular model used. Observations and mechanical analysis of dense and loose granular assemblies under isotropic loading are made. The mechanical response of our numerical granular samples is studied in the framework of the classical vertical compression test with constant lateral stress (biaxial test). The comparison of macroscopic responses of dense and loose samples with various grain shapes shows that when $α$ is considered a concavity parameter, it is therefore a relevant variable for increasing mechanical performances of dense samples. When $α$ is considered an envelope deviation from perfect sphericity, it can control mechanical performances for large strains. Finally, we present some remarks concerning the kinematics of the deformed samples: while some polygon samples subjected to a vertical compression present large damage zones (any polygon shape), dense samples made of clumps always exhibit thin reflecting shear bands. This paper was written as part of a CEGEO research project www.granuloscience.com
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