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利用分子动力学方法,模拟了5000个表面轻微摩擦(=110-4)的弹性颗粒组成的体系在各向同性压缩过程中的堵塞(jamming)现象,研究了颗粒体系对边壁压强P和对关联函数第一个峰的高度g1随体积分数的变化规律. 结果表明,当体系的体积分数大于临界体积分数c时,P()曲线表现出明显的黏滑(stick-slip)行为,法向的力-力关联函数、切向的力-力关联函数和颗粒的位置-位置关联函数同时发生跳变,说明宏观黏滑现象源自内部的力位形和几何构形的调整. 体系在缓慢增大过程中得到了不同的堵塞态,随着颗粒粒径的缓慢减小,体系得以松弛(unjamming),实现松弛过程并得到相应的c. 对于不同堵塞态,其边壁压强P与-c遵从幂律标度P(-c)0.964.In this paper, the jamming/unjamming processes of the system composed of 5000 elastic disks with small friction =110-4 are simulated by using the molecular dynamics method. The variations of sidewall pressure P and the height of the first peak of the pair correlation function, g1, with packing fraction are studied. The result shows that the P() curve exhibits an obvious stick-slip-like behavior. The normal force-force correlation function, the tangential force-force correlation function, and the position-position correlation function are found to jump simultaneously during the stick-slip process. By relaxing jammed states obtained as the system undergoes the compression process, we observe that the P is related to -c by the power scaling law P(-c)0.964, although the different sidewall pressures corresponds to different values of c.
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Keywords:
- jamming phase diagram/
- pair-correlation function/
- force-force correlation function/
- scaling law
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