Carlevaro C M, Pugnaloni L A
Instituto de Física de Líquidos y Sistemas Biológicos (CONICET La Plata, UNLP), La Plata, Argentina.
Eur Phys J E Soft Matter. 2012 Jun;35(6):44. doi: 10.1140/epje/i2012-12044-7. Epub 2012 Jun 13.
Assemblies of granular particles mechanically stable under their own weight contain arches. These are structural units identified as sets of mutually stable grains. It is generally assumed that these arches shield the weight above them and should bear most of the stress in the system. We test such hypothesis by studying the stress born by in-arch and out-of-arch grains. We show that, indeed, particles in arches withstand larger stresses. In particular, the isotropic stress tends to be larger for in-arch grains whereas the anisotropic component is marginally distinguishable between the two types of particles. The contact force distributions demonstrate that an exponential tail (compatible with the maximization of entropy under no extra constraints) is followed only by the out-of-arch contacts. In-arch contacts seem to be compatible with a Gaussian distribution consistent with a recently introduced approach that takes into account constraints imposed by the local force balance on grains.
在自身重量作用下机械稳定的颗粒集合体包含拱结构。这些是被识别为相互稳定颗粒组的结构单元。通常认为这些拱结构支撑着其上方的重量，并且应该承受系统中的大部分应力。我们通过研究拱内颗粒和拱外颗粒所承受的应力来检验这一假设。我们表明，确实，拱内颗粒承受更大的应力。特别是，拱内颗粒的各向同性应力往往更大，而两种类型颗粒之间的各向异性分量则略有差异。接触力分布表明，只有拱外接触遵循指数尾部（与无额外约束下的熵最大化相一致）。拱内接触似乎与高斯分布相一致，这与最近引入的一种方法一致，该方法考虑了局部力平衡对颗粒施加的约束。
