Zhou J, Long S, Wang Q, Dinsmore A D
Department of Physics, University of Massachusetts, Hasbrouck Laboratory 411, 666 North Pleasant Street, Amherst, MA 01003, USA.
Science. 2006 Jun 16;312(5780):1631-3. doi: 10.1126/science.1125151.
We present systematic and detailed measurements of interparticle contact forces inside three-dimensional piles of frictionless liquid droplets. We measured long-range chainlike correlations of the directions and magnitudes of large forces, thereby establishing the presence of force chains in three dimensions. Our correlation definition provides a chain persistence length of 10 mean droplet diameters, decreasing as load is applied to the pile. We also measured the angles between contacts and showed that the chainlike arrangement arises from the balance of forces. Moreover, we found that piles whose height was comparable to the chain persistence length exhibited substantially greater strain hardening than did tall piles, which we attributed to the force chains. Together, the results establish a connection between the microscopic force network and the elastic response of meso- or macroscopic granular piles. The conclusions drawn here should be relevant in jammed systems generally, including concentrated emulsions and piles of sand or other heavy particles.
我们展示了对无摩擦液滴三维堆积内部颗粒间接触力的系统且详细的测量。我们测量了大力的方向和大小的长程链状相关性，从而确定了三维中力链的存在。我们的相关性定义给出了一个10个平均液滴直径的链持续长度，随着对堆积施加负载而减小。我们还测量了接触之间的角度，并表明链状排列源于力的平衡。此外，我们发现高度与链持续长度相当的堆积比高堆积表现出显著更大的应变硬化，我们将其归因于力链。这些结果共同建立了微观力网络与中观或宏观颗粒堆积的弹性响应之间的联系。这里得出的结论通常应适用于堵塞系统，包括浓缩乳液以及沙子或其他重颗粒的堆积。
