非凸体颗粒材料缓冲性能的离散元模拟

Buffering Capacity of Non-convex Granular Materials Based on Discrete Element Method

采用离散元方法对冲击载荷作用下E形、U形和dolos形(扭转H形)等非凸体颗粒材料的缓冲性能进行数值分析。计算结果表明:与球形颗粒相比,非凸体颗粒材料具有良好的缓冲特性。同时,不同颗粒形状都存在一个临界长宽比R_c,当长宽比R<R_c时,底板的压力峰值随长宽比R的增加而减小;当长宽比R>R_c时,底板的压力峰值变化不再显著并趋于稳定。通过设定不同材料参数分析非凸体颗粒材料能耗散的主要方式,发现非凸体颗粒材料能量耗机制以摩擦耗散为主要方式,非弹性碰撞为次要方式,基本不存在飞溅颗粒耗散能量现象。最后,对颗粒系统在冲击过程中的平均配位数变化进行了讨论,以揭示非凸体颗粒形状对颗粒介质摩擦耗能机制的影响,结果表明,高长宽比的非凸体颗粒在冲击作用下颗粒单元接触更稳定,有利于摩擦力通过滑移诱导能量耗散,这导致非凸体颗粒具有更好的缓冲性能。

Complex systems composed of non-spherical particles are widely present in nature or industry,and their low flow and high interlocking properties under external impact loads cause the energy of the system to be effectively attenuated,thereby achieving buffering.In this paper,the discrete element method was used to numerically analyze the cushioning properties of non-convex granular materials,such as E-,U-and dolos-shaped(twisted H-shaped),under impact load.The calculation results show that the non-convex granular material has good cushioning properties compared with spherical particles.At the same time,there is a critical aspect ratio R c for different particle shapes.At R<Rc,the pressure peak of the bottom plate decreases with an increase of R;at R>Rc,the pressure peak change of the bottom plate is no longer significant and tends to be stable.By analyzing the main energy dissipation modes of non-convex particle materials,it was found that the energy dissipation mechanism of such materials takes friction dissipation as the primary mode and inelastic collision as the secondary mode.Whilst there is basically no phenomenon of splash particles for energy dissipation.The average coordination number change of the particle system during the impact process was discussed to reveal the effect of non-convex particle shape on the frictional energy dissipation mechanism of the granular medium.It is show,that non-convex particles with high aspect ratio keep more steady contact in the process of impact which is beneficial to the energy dissipation by friction through slip,and is major cause of the non-convex particles owning better buffer properties.