论文标题
颗粒状柱中的起伏的压缩和多阶段放松，由灰尘颗粒或玻璃珠组成
Undulating compression and multi-stage relaxation in a granular column consisting of dust particles or glass beads
论文作者
论文摘要
为了从根本上表征粒度物质中层次结构的影响，对限制在圆柱形细胞中的灰尘颗粒和玻璃珠进行了一组压缩 - 放松测试。两种晶粒的典型直径约为1〜mm。但是，灰尘颗粒是通过绑定小（$ \ sim 5 $〜{\ textmu} m）玻璃珠来产生的。用活塞压缩颗粒柱，直到达到20 〜n的最大负载力，并具有恒定压缩率$ v $（$ 0.17 \ leq v \ leq 2000 $〜{\ textmu} m〜s $ s $^{ - 1} $）。之后，停止活塞并量化了放松过程。从实验结果中，我们发现压缩力$ f $非线性随着压缩冲程$ z $的增加而增加，具体取决于颗粒。此外，分别在$ f（z）$的灰尘颗粒和玻璃珠上观察到周期性起伏和突然的力量。弛豫过程的特征是应力的指数衰减，然后是对数依赖性的两种粒子。这些实验发现是本研究的重点。为了了解管理压缩力学的基本物理学，我们假设了$ f（z）$的经验形式； $ f \ propto z^α$用于灰尘粒子和$ f \ propto \ exp（z/z_g）$ for玻璃珠（$α= 2.4 $和$ z_g = 70 $〜{\ textmu} m）。然后，我们发现，周期性起伏和力降低的礼貌与平均压缩力的降低相同，即灰尘颗粒中的功率定律和玻璃珠中的指数相同。此外，随着$ v $的压缩，起伏的幅度和波长下降。根据实验结果以及灰尘颗粒和玻璃珠之间的差异，我们还讨论了工程领域中使用的颗粒状压缩模型的起源以及物理含义。
For fundamentally characterizing the effect of hierarchical structure in granular matter, a set of compression-relaxation tests for dust particles and glass beads confined in a cylindrical cell was performed. Typical diameter of both grains is approximately 1~mm. However, dust particles are produced by binding tiny ($\sim 5$~{\textmu}m) glass beads. The granular columns were compressed with a piston until reaching a maximum load force of 20~N with a constant compression rate $v$ ($0.17 \leq v \leq 2000$~{\textmu}m~s$^{-1}$). After that, the piston was stopped and the relaxation process was quantified. From the experimental results, we found that the compression force $F$ nonlinearly increases with the increase of compression stroke $z$ depending on particles. Besides, periodic undulation and sudden force drops were observed on $F(z)$ in dust particles and glass beads, respectively. The relaxation process was characterized by an exponential decay of stress followed by a logarithmic dependence one in both kinds of particles. These experimental findings are the main point in this study. To understand the underlying physics governing the compression mechanics, we assumed empirical forms of $F(z)$; $F\propto z^α$ for dust particles and $F \propto \exp(z/z_G)$ for glass beads ($α=2.4$ and $z_G=70$~{\textmu}m). Then, we found that the growing manners of periodic undulation and force drops were identical to those of mean compression forces, i.e., power law in dust particles and exponential in glass beads. In addition, the undulation amplitude and wavelength decreased as $v$ increased in dust-particles compression. On the basis of experimental results and the difference between dust particles and glass beads, we also discuss the origin of undulation and the physical meaning of granular-compression models used in engineering fields.
