普遍性(动力系统)
粒状材料
均方位移
幂律
统计物理学
材料科学
流量(数学)
机械
放松(心理学)
粒子(生态学)
物理
经典力学
流变学
化学
数学
凝聚态物理
地质学
分子动力学
复合材料
海洋学
统计
社会心理学
量子力学
心理学
作者
Binquan Kou,Yixin Cao,Jindong Li,Chengjie Xia,Zhifeng Li,Haipeng Dong,Ang Zhang,Jie Zhang,Walter Kob,Yujie Wang
出处
期刊:Nature
[Springer Nature]
日期:2017-11-01
卷期号:551 (7680): 360-363
被引量:77
摘要
Granular materials such as sand, powders, foams etc. are ubiquitous in our daily life, as well as in industrial and geotechnical applications. Although these disordered systems form stable structures if unperturbed, in practice they do relax because of the presence of unavoidable external influences such as tapping or shear. Often it is tacitly assumed that for granular systems this relaxation dynamics is similar to the one of thermal glass-formers, but in fact experimental difficulties have so far prevented to determine the dynamic properties of three dimensional granular systems on the particle level. This lack of experimental data, combined with the fact that in these systems the motion of the particles involves friction, makes it very challenging to come up with an accurate description of their relaxation dynamics. Here we use X-ray tomography to determine the microscopic relaxation dynamics of hard granular ellipsoids that are subject to an oscillatory shear. We find that the distribution function of the particle displacement can be described by a Gumbel law with a shape parameter that is independent of time and the strain amplitude $\gamma$. Despite this universality, the mean squared displacement of a tagged particle shows power-laws as a function of time with an exponent that depends on $\gamma$ and the time interval considered. We argue that these results are directly related to the existence of the microscopic relaxation mechanisms that involve friction and memory effects. These observations demonstrate that on the particle level the dynamical behavior of granular systems is qualitatively different from the one of thermal glass-formers and instead more similar to the one of complex fluids. Thus we conclude that granular materials can relax even when the driving is weak, an insight which impacts our understanding of the nature of granular solids.
科研通智能强力驱动
Strongly Powered by AbleSci AI