Boltachev G Sh, Lukyashin K E, Shitov V A, Volkov N B
Institute of Electrophysics, Ural Branch of Russian Academy of Sciences, Amundsen Street 106, 620016 Ekaterinburg, Russia.
Phys Rev E Stat Nonlin Soft Matter Phys. 2013 Jul;88(1):012209. doi: 10.1103/PhysRevE.88.012209. Epub 2013 Jul 29.
In order to describe and to study the processes of cold compaction within the discrete element method a three-dimensional model of nanosized powder is developed. The elastic forces of repulsion, the tangential forces of "friction" (Cattaneo-Mindlin), and the dispersion forces of attraction (van der Waals-Hamaker), as well as the formation and destruction of hard bonds between the individual particles are taken into account. The monosized powders with the size of particles in the range 10-40 nm are simulated. The simulation results are compared to the experimental data of the alumina nanopowders compaction. It is shown that the model allows us to reproduce experimental data reliably and, in particular, describes the size effect in the compaction processes. A number of different external loading conditions is used in order to perform the theoretical and experimental researches. The uniaxial compaction (the closed-die compaction), the biaxial (radial) compaction, and the isotropic compaction (the cold isostatic pressing) are studied. The real and computed results are in a good agreement with each other. They reveal a weak sensitivity of the oxide nanopowders to the loading condition (compaction geometry). The application of the continuum theory of the plastically hardening porous body, which is usually used for the description of powders, is discussed.
为了在离散元方法中描述和研究冷压实过程，建立了纳米粉末的三维模型。考虑了排斥弹性力、“摩擦”切向力（卡塔尼奥 - 明德林力）、吸引色散力（范德华 - 哈马克力）以及单个颗粒之间硬键的形成和破坏。模拟了粒径范围为10 - 40 nm的单尺寸粉末。将模拟结果与氧化铝纳米粉末压实的实验数据进行了比较。结果表明，该模型能够可靠地再现实验数据，特别是描述了压实过程中的尺寸效应。为了进行理论和实验研究，采用了多种不同的外部加载条件。研究了单轴压实（闭模压实）、双轴（径向）压实和各向同性压实（冷等静压）。实际结果与计算结果吻合良好。它们揭示了氧化物纳米粉末对加载条件（压实几何形状）的敏感性较弱。还讨论了通常用于描述粉末的塑性硬化多孔体连续介质理论的应用。
