Coste Christophe, Gilles Bruno
INSP, Université Pierre et Marie Curie-Paris 6, Université Denis Diderot -Paris 7, CNRS, UMR 7588, Campus Boucicaut, Paris, France.
Phys Rev E Stat Nonlin Soft Matter Phys. 2008 Feb;77(2 Pt 1):021302. doi: 10.1103/PhysRevE.77.021302. Epub 2008 Feb 7.
We report on acoustic wave propagation in a regular array of nominally identical beads under isotropic static stress. The weak polydispersity of the beads makes the contact lattice random. Time-frequency analysis of the acoustic signal is performed and allows measurement of the full lattice dispersion relation. Comparison with the theoretical prediction for a perfect triangular lattice gives an indication of the level of randomness in the contact lattice. The results extend, in a consistent way, a previous study restricted to long wavelength propagation [B. Gilles and C. Coste, Phys. Rev. Lett. 90, 174302 (2003)]: The contact lattice is ordered by increasing the stress, and the smaller the wavelength, the higher the stress required to get regular lattice behavior. Measurements involving ballistic propagation of the coherent wave, whatever its frequency, evidence reversible lattice behavior under compression and/or decompression. Nevertheless, correlations of short wavelength incoherent waves are a sensitive probe of disorder, and allow us to exhibit a small irreversible evolution of the lattice.
我们报告了在各向同性静应力下，标称相同的珠子的规则阵列中的声波传播情况。珠子的弱多分散性使得接触晶格具有随机性。对声信号进行时频分析，从而能够测量完整的晶格色散关系。与完美三角晶格的理论预测进行比较，可得出接触晶格的随机程度。这些结果以一种连贯的方式扩展了先前一项仅限于长波长传播的研究 [B. 吉尔斯和 C. 科斯特，《物理评论快报》90, 174302 (2003)]：通过增加应力可使接触晶格有序化，且波长越小，要获得规则晶格行为所需的应力就越高。涉及相干波弹道传播的测量，无论其频率如何，都证明了在压缩和/或减压下晶格行为是可逆的。然而，短波长非相干波的相关性是无序的敏感探测器，使我们能够展现出晶格的微小不可逆演化。
