Tournat V, Gusev V E
LAUM, CNRS, Université du Maine, Avenue O. Messiaen, 72085 Le Mans, France.
Phys Rev E Stat Nonlin Soft Matter Phys. 2009 Jul;80(1 Pt 1):011306. doi: 10.1103/PhysRevE.80.011306. Epub 2009 Jul 17.
Experimental results and their interpretations are presented on the nonlinear acoustic effects of multiple scattered elastic waves in unconsolidated granular media. Short wave packets with a central frequency higher than the so-called cutoff frequency of the medium are emitted at one side of the statically stressed slab of glass beads, and received at the other side after multiple-scattering and nonlinear elastic effects. Typical signals are strongly distorted compared to their initially radiated shape both due to nonlinearity and scattering. It is shown that acoustic waves with a deformation amplitude much lower than the mean static deformation of the contacts in the medium can modify the elastic properties of the medium. This addresses the problem of acoustic wave action on granular matter during and after acoustic excitation, which is necessary to understand in the nondestructive testing of the elastic properties of granular media by acoustic methods. Coda signal analysis is shown to be a powerful time-resolved tool in monitoring slight modifications in the elastic response of an unconsolidated granular structure.
本文展示了关于松散颗粒介质中多次散射弹性波的非线性声学效应的实验结果及其解释。在静态应力作用下的玻璃珠平板一侧发射中心频率高于介质所谓截止频率的短波包，经过多次散射和非线性弹性效应后在另一侧接收。与初始辐射形状相比，典型信号由于非线性和散射而严重失真。结果表明，变形幅度远低于介质中接触点平均静态变形的声波可以改变介质的弹性特性。这解决了声激发期间及之后声波对颗粒物质作用的问题，这对于通过声学方法无损检测颗粒介质的弹性特性而言是必须理解的。结果表明，尾波信号分析是监测松散颗粒结构弹性响应微小变化的强大时间分辨工具。
