粗粒料多边形表征及二维FEM/DEM分析

考虑到颗粒形状对粗粒料的力学特性有重大影响，提出了一种新的表征颗粒形状的方法，即在椭圆上随机选取一系列点连接成多边形颗粒，表征狭长扁平的颗粒。新方法较圆上取点的方法能代表更多类型的颗粒形状，适用范围更广。提出了一种新的粗粒料投放算法，即先缩小颗粒，然采用随机算法将缩小的颗粒投放至给定区域，对颗粒划分好网格后，将颗粒放大到原来的大小，然后采用有限元-离散元(FEM/DEM)方法计算稳定后即生成了相应的试样。通过将上述颗粒生成及投放算法与FEM/DEM结合，应用于粗粒料的数值模拟。分析表明，FEM/DEM是研究粗粒料力学性质的较好方法，对复杂的颗粒形状也可简单建模，且因在颗粒内部划分了有限元网格，复杂的接触判断及接触力计算转化为标准统一的三角形和三角形之间的接触判断及接触力计算，所有的计算均可标准化、统一化。同时因为颗粒是可以变形的，依然保留了连续介质力学中应力和应变的概念，无须像PFC那样需通过测量圆来间接表示某点的应力、应变。最后，通过粗粒料的侧限压缩试验的数值模拟，展现了文中提出的一整套解决方案在模拟粗粒料方面的巨大潜力。

Polygon characterization of coarse aggregate and two-dimensional combined finite discrete element method analysis

Considering that the shapes of particles have an important impact on the mechanical properties of the coarse aggregate, this paper proposes a new method for characterizing particle shapes. The method randomly selects a series of points on ellipse; then those points are connected to form polygon particles. The new method can represent more types of particle shapes than old method that access points on the circle, applies more broadly, can characterize the narrow flat particles. In addition, a new algorithm of particle delivery is proposed, which is to reduce the particle; then the reduced particles are put to the given area randomly. After the particle was meshed by triangular element, the reduced particles was enlarge to the original size. Afterwards, using finite combined finite-discrete element method(FEM/DEM) to calculating equilibrium state, a sample that meet given void ratio was generated. Then the particle generation algorithm above and FEM/DEM was combined, the FEM/DEM method is applied to coarse aggregate numerical simulation, the analysis shows, FEM/DEM is a great way to study the mechanical properties of coarse aggregate. The complex particle shape can also be modeling simply, because the particles was meshed into the triangle finite element, complex contact judgments and the contact force calculation can be transformed into a standard uniform contact judgments and contact force calculations between triangles, all calculations can be standardization and unification. At the same time, particles can be deformed, the concept of stress and strain that belong to the continuum mechanics was still retains, rather than PFC which stress and strain of a point was expressed indirectly by the measuring circle. Finally, by confined compression test numerical simulations of coarse aggregate show enormous potential of the proposed set of solutions in the simulation coarse aggregate.