Løvoll G, Måløy K J, Flekkøy E G
Department of Physics, University of Oslo, P.O. Box 1048, Blindern, 0316 Oslo 3, Norway.
Phys Rev E Stat Phys Plasmas Fluids Relat Interdiscip Topics. 1999 Nov;60(5 Pt B):5872-8. doi: 10.1103/physreve.60.5872.
A method for measuring normal forces under a granular packing is introduced. A high precision electronic balance is used to measure normal forces on individual beads at the bottom of a granular material. Due to the high sensitivity of this setup the normal forces on individual beads without applying any external load on the system were measured. From these measurements the distribution of forces, the response to small perturbations at grain level and the spatial correlation between normal forces were investigated at the bottom of the packing. The distribution function is consistent with a power law with an exponent alpha=0.3 for small forces. At large forces a crossover to an exponential decay is observed with a decay constant beta=1.8. Small amplitude spatial correlations were observed in the normal forces at the bottom of the pile, and the radial pressure distribution was dependent of the different filling procedures. Finally we report on systematic relaxations in the measured weight as a function of time on single grains at the bottom of the packing after perturbing the system.
介绍了一种测量颗粒堆积下法向力的方法。使用高精度电子天平测量颗粒材料底部单个珠子上的法向力。由于该装置的高灵敏度，在未对系统施加任何外部负载的情况下测量了单个珠子上的法向力。通过这些测量，研究了堆积底部的力分布、颗粒水平上对小扰动的响应以及法向力之间的空间相关性。对于小力，分布函数与指数α = 0.3的幂律一致。在大力时，观察到向指数衰减的转变，衰减常数β = 1.8。在堆底部的法向力中观察到小幅度的空间相关性，并且径向压力分布取决于不同的填充程序。最后，我们报告了在对系统进行扰动后，测量的堆积底部单个颗粒重量随时间的系统弛豫情况。
