摘要
采用离散元(DEM)数值方法结合物理实验,分别实现了单一尺寸硬球在三维(3D)间歇振动及批量加料条件下堆积的有序化(结晶),通过对晶体的结构表征、数值仿真中的微观性能如配位数(CN)、径向分布函数(RDF)、角分布函数(ADF)、Voronoi/Delaunay孔的尺寸分布、力的网络分析以及晶体形成过程中的动力学分析,得出如下结论:(1)数值仿真和物理实验中所获得的均为{111}取向FCC晶体,晶体中粒子的最大堆积密度可达0.74;(2)晶体中粒子的配位数分布在CN=12处出现峰值,表明每个粒子具有12个近邻;RDF和ADF分布表明堆积粒子之间分别在径向具有长程相关性及角度上具有相关性,这是晶态结构的典型特征;Voronoi/Delaunay孔的尺寸分布与非晶态相比表现为高且窄的曲线,且向左移,表明所获得的硬球晶中孔隙很小且分布均匀;粒子间力的网络更直观地表明了晶体的结构,同时还指出在FCC硬球晶中分别存在着面内的力和面间的力,其中后者小于前者;(3)晶体形成过程中的速度场和力场等动力学信息的变化表明粒子在堆积过程中一旦形成有序,它将作为一个整体运动,并为后续粒子的有序化提供模板,起到了结晶的晶核的作用.
In this paper, the ordering （ Crystallization ） of mono - sized sphere packing under three - dimensional （3D） interval vibration and batch- wised feeding was studied with numerical discrete element method （DEM） combined with the physical experiments. Through the characterization on the crystalline structure and the analysis on the micro -properties obtained numerically such as coordination number （CN） , radial distribution function （RDF） , angular distribution function （ ADF ） , Voronoi/Delaunay void size distribution, force network and the dynamics formed during ordering, following conclusions can be drawn： （1） The crystalline obtained both numerically and physically all indicates { 111 } - oriented FCC structure, where the maximum packing density can reach 0. 74 ; （ 2 ） There is a peak at CN -- 12 in the coordination number distribution curve, which implies that each particle in the hard sphere crystal has 12 neighbors in contact; the distributions for RDF and ADF show the long range correlation in radial distance and angle correlation among particles, which are the typical characteristics of the crystalline structure; the Voronoi/Delaunay void size distribution indicates the higher and narrower curve shifting to the left compared with non -crystal state, which means that the voids in crystalline structure are small and uniform; the force network among particles can identify the crystalline structure more intuitively, meanwhile, it＇ s also indicated that the in - plane forces and inter- plane forces coexist in the crystal, and the latter is smaller than the former; （3） The variation of dynamic information such as the velocity field and the force field all indicates that once the ordered structure formed during crystallization, it will move as a whole part, which served as the template for the other particles, i. e. as the nucleus in the crystallization.
出处
《材料与冶金学报》
CAS
2011年第4期318-324,共7页
Journal of Materials and Metallurgy
基金
国家自然基金(50974040)
中央高校基本科研业务费(N100402009)
澳大利亚研究委员会基金(DP0665276)
关键词
颗粒堆积
致密化
振动
离散元模拟
硬球晶
particle packing
densification
vibration
DEM simulation
hard sphere crystal
