颗粒材料内部滑动变形局部化的离散元模拟

DEM simulations on localized slide slide edformation of granular materials

颗粒材料在加载过程中表现出非常复杂的变形性质。在微观尺度上,单个颗粒的运动、单个孔隙胞元内的变形都是非均匀的,但也不是完全随机、没有规律可循的,而是呈现一定结构性的分布,如微带、剪切带等。本文用基于孔隙胞元的离散元方法对颗粒体进行双轴加载数值试验,模拟了以滑动变形表征的变形局部化现象。数值结果发现,对应加载过程中的不同阶段,滑动变形存在几种不同的变形局部化形式。同时,在加载过程中颗粒体内部一直都存在与平均滑动变形方向相反的负滑动现象,这说明在速度梯度场不连续的区域同时存在弹性卸载和塑性流动。

Granular materials exhibit very complex behavior under external load. In the micro-scale the motion or deformation of the individual particle and void cell are nonuniform but not random or unrelated. The localized deformation structures appear as micro-bands of small strain and shear bands of large strain. In this paper, quasi-static biaxial compression test is carried out to investigate the structured deformation pattern in microscale using discrete element method （DEM）. Localized deformation is found from slide deformation in void cells at the initial stage, the peak state and the soften stage. During the biaxial compression, the negative slip occurs in the neighboring regions of elastic unloading and plastic flow along a plane of discontinuity in the velocity gradient field.