模型粘性粉末的计算机模拟：组装过程和接触规律对低固结状态的影响
Computer simulation of model cohesive powders: influence of assembling procedure and contact laws on low consolidation states
摘要：
用分子动力学模拟研究了一种简单的二维粘性粉末模型的结构和力学性能。微机械成分涉及弹性、摩擦、短程吸引力以及可能的接触中的滚动阻力（RR）。内聚堆积的微观结构根据组装过程而变化，从如果分离的颗粒被直接压缩则相当密集地堆积到如果在压缩之前允许形成大的聚集体则松散得多。关键参数是作用在直径为$a$的颗粒上的施加压力P与最大拉伸接触力F0的比率P*= Pa/F0。在低P* 的最终结构取决于在集群聚集的早期阶段的速度波动的水平。对于RR，在低初速度或大滚动摩擦的极限下，配位数接近2。部队网络通常由小型超静定集群组成，部队数量级为F0，由几乎无应力的刚性臂连接。随着P* 的增长，它迅速重新排列成力链样模式。密度相关性见证了分形结构，与尺寸Df，一些密度相关的斑点大小。WIth RR Df与弹道聚合结果一致，尽管可能存在不同的连接性。一些参数对材料强度的可能影响。
英文摘要：
The structure and mechanical properties of a simple two-dimensional model of a cohesive powder are investigated by molecular dynamics simulations. Micromechanical ingredients involve elasticity, friction, a short range attraction and, possibly, rolling resistance (RR) in contacts. The microstructure of the cohesive packing varies according to the assembling procedure, from rather densely packed if isolated particles are directly compressed to much looser if the formation of large aggregates is allowed prior to compression. A crucial parameter is the ratio P*= Pa/F0 of applied pressure P, acting on grains of diameter $a$, to maximum tensile contact force F0. At low P* the final structure depends on the level of velocity fluctuations at the early stages of cluster aggregation. With RR the coordination number approaches 2 in the limit of low initial velocities or large rolling friction. The force network generally comprises small hyperstatic clusters with forces of the order of F0, joined by nearly unstressed, barely rigid arms. As P* grows, it quickly rearranges into force chain-like patterns. Density correlations witness a fractal structure, with dimension Df, up to some density-dependent blob size. WIth RR Df coincides with the ballistic aggregation result, despite a possibly different connectivity. Possible effects of some parameters on material strength are evoked.
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