在剪切颗粒材料中的力网络的对数速率依赖性
1Department of Physics & Center for Nonlinear and Complex Systems, Duke University, Durham, North Carolina 27708-0305, USA.
Nature
|February 28, 2003
概括
缓慢切割的颗粒物材料显示了取决于切割速率的应力,导致不可逆转的变形. 这项研究揭示了对算数速率的依赖性和缓慢的集体放松机制,用于加强颗粒流.
科学领域:
- 颗粒状材料的物理学 颗粒状材料的物理学
- 密集颗粒流的风学.
- 无序系统的统计力学.
背景情况:
- 颗粒流的传统模型通常假设应力是独立于剪切率的.
- 然而,像固体对固体摩擦和地质过程这样的现象表现出对数直线速率的依赖.
- 这表明需要更仔细地研究颗粒系统中的速率效应.
研究的目的:
- 在颗粒系统中研究剪切速率和内部应力之间的关系.
- 为了确定颗粒应力是否表现出速率依赖,特别是对数依赖.
- 探索剪切速率对力网和应力放松动态的影响.
主要方法:
- 在缓慢剪切下利用光弹性盘的二维系统.
- 采用光弹性来测量颗粒级的力.
- 分析了塑性和弹性变形的应力时间平均行为.
主要成果:
- 平均应力显示了塑性 (不可逆转) 变形对剪切速率的对数依赖.
- 弹性 (可逆) 变形没有明显的速率依赖.
- 增加的剪速增强了力网络,增强了应力波动,并改变了应力事件分布.
结论:
- 颗粒应力取决于不可逆转变形的剪切速率,遵循对数关系.
- 该系统表现出压力网络的缓慢集体放松,提供了依赖速度的强化机制.
- 行为质量上类似于增加密度效应,突出了网络重组的作用.
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