Force networks and jamming in shear-deformed sphere packings.
Force networks and jamming in shear-deformed sphere packings.
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剪切变形球填料中的力网络和干扰。
DOI：
10.1103/physreve.99.012123
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
S. Sastry
中科院分区：
文献类型：
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作者：
H. A. Vinutha;S. Sastry
在温度、密度或颗粒无序组装中施加的应力变化时出现的刚性在玻璃形成体、凝胶、泡沫和颗粒物质等各种软物质中引起了人们的兴趣。摩擦颗粒的剪切堵塞呈现出一种有趣的特殊情况，其中剪切应力的应用导致刚性而不是损失。抵抗剪切变形的自组织结构的形成提供了一幅有吸引力的剪切干扰几何图，但该图尚未完全开发，并且没有与无摩擦系统中的刚性思想很好地结合。利用观察结果，即使在没有摩擦的情况下，非热剪切球组件也会产生剪切干扰所需的结构特征[H. A. Vinutha 和 S. Sastry，《自然物理学》12, 578 (2016)1745-247310.1038/nphys3658]，我们通过计算分析了此类组件中的干扰条件。求解其接触几何形状的力和扭矩平衡条件，我们显示并通过摩擦模拟进行验证，在有限和无限摩擦的干扰下，平均接触数 Z 等于 D+1（空间维度 D=2,3），高于“随机松散堆积”极限密度，与之前的摩擦干扰分析不同。我们证明剪切干扰阈值满足最近提出的无摩擦系统干扰的边际稳定性条件。沿着研究共价玻璃的思路，我们对 D=2 进行刚性渗流分析，发现刚性渗流先于剪切干扰，然而，这与过度约束区域的渗流一致，导致识别出类似于在共价玻璃中观察到的中间相的状态。总之，这些结果提供了剪切干扰的几何描述，与无摩擦系统中的干扰、刚性和玻璃化转变的分析密切相关，从而有助于对不同无序物质中的干扰现象学进行统一的描述。
The emergence of rigidity upon changes of temperature, density, or applied stresses in disordered assemblies of particles is of interest in a wide range of soft matter, from glass formers, gels, foams, and granular matter. Shear jamming of frictional grains presents an interesting special case wherein the application of shear stress leads to rigidity rather than its loss. The formation of self-organized structures that resist shear deformation offers an appealing geometric picture of shear jamming, which nevertheless is incompletely developed, and not well integrated with ideas concerning rigidity in frictionless systems. Exploiting the observation that athermally sheared sphere assemblies develop structural features necessary for shear jamming even in the absence of friction [H. A. Vinutha and S. Sastry, Nature Physics 12, 578 (2016)1745-247310.1038/nphys3658], we analyze conditions for jamming in such assemblies computationally. Solving force and torque balance conditions for their contact geometry, we show, and validate with frictional simulations, that the mean contact number Z equals D+1 (for spatial dimension D=2,3) at jamming for both finite and infinite friction, above the "random loose packing" limit density, at variance with previous analyses of frictional jamming. We show that the shear jamming threshold satisfies the marginal stability condition recently proposed for jamming in frictionless systems. Along lines explored in studying covalent glasses, we perform rigidity percolation analysis for D=2 and find that rigidity percolation precedes shear jamming, which, however, coincides with the percolation of over-constrained regions, leading to the identification of a regime analogous to the intermediate phase observed in covalent glasses. Together, these results provide a geometric description of shear jamming that relate closely with analyses of jamming, rigidity, and the glass transition in frictionless systems, and thus help develop a unified description of jamming phenomenology in diverse disordered matter.