基于双胞元的颗粒材料应力-应变关系研究

基于细观力学，建立颗粒材料的宏观应力-应变与接触力、接触位移、枝矢量等细观量之间的关系。用改进的Voronoi-Delaunay法对颗粒材料进行几何和物理上划分，得到改进Bagi双胞元体系；以固体胞元为基础，运用牛顿第二定律和Gauss定理提出含有旋转矢量和重力的颗粒材料平均等效应力，避免了颗粒材料的准静态假设；在孔隙胞元区域内利用变形协调条件推导出含有孔隙面矢量等几何变量的颗粒材料平均等效应变。结合文献的二维颗粒材料宏观试验结果验证了双胞元平均等效应力-应变的正确性；在三维情形下，对比双胞元等效应变和最优拟合应变结果，同样验证了基于双胞元的颗粒材料应力-应变关系，因此，该颗粒材料应力-应变关系可以为数值模拟颗粒材料力学行为提供依据。

Stress-strain relationship of granular materials based on two cell systems

Based on granular mesomechanics, this paper sets up the relationship between the macro stress-strain and the mesoscopic quantities including the contact force, contact displacement and branch vector in granular materials. The method of improved Voronoi-Delaunay tessellation for granular materials in geometry and physics is further modified into two cell systems of Bagi. Taking solid cell systems as the basic elements, the average stress tensor that includes particle rotation vector and acceleration of gravity is derived based on Newton’s second law of motion and Gauss theorem. It avoids a static hypothesis. The average strain tensor expression including the void surface vector is derived based on the void cell with compatibility requirement. Two cell systems average equivalent stress-strain is correct combined with the literature of experimental resulting in two dimensions. Compared with two cell systems average equivalent strain and best fitting stress results under three dimensions, granular material stress-strain relationship based on the two cell systems is also validated. Therefore, the granular material stress-strain relationship of the two cell systems provides a theoretical basis for numerical simulation of mechanical properties of granular materials.