Tournat V, Inserra C, Gusev V
Laboratoire d'Acoustique de l'Université du Maine, UMR-CNRS 6613, Université du Maine, Avenue Olivier Messiaen, 72085 Le Mans CEDEX 9, France.
Ultrasonics. 2008 Nov;48(6-7):492-7. doi: 10.1016/j.ultras.2008.03.014. Epub 2008 Apr 7.
Due to disorder, contacts between beads in stressed granular assemblages are not equally loaded. There exists a distribution of contact static loads, containing weakly loaded contacts (the weak contacts) and strongly loaded contacts (the strong contacts involved in the so-called force chains). For an elastic periodic excitation with a given deformation amplitude, the weakest contacts are supposed to clap (periodically open and close) due to the action of the acoustic wave. When increasing the acoustic amplitude, more and more contacts are clapping, progressively producing a non classical spectral signature. Presented spectra have been observed in a laboratory scale experiment, where two frequencies were initially launched in the medium. Results are obtained for increasing pump wave amplitudes and different frequency pairs. These experimental results are in good agreement with a model derived from the Hertz theory of contacts with possibility of clapping.
由于无序性，受压颗粒集合体中珠子之间的接触并非均匀受力。存在接触静载荷分布，其中包含受力较弱的接触（弱接触）和受力较强的接触（参与所谓力链的强接触）。对于具有给定变形幅度的弹性周期激励，由于声波的作用，最弱的接触预计会发生拍击（周期性地打开和关闭）。当增加声波幅度时，越来越多的接触会发生拍击，逐渐产生非经典的频谱特征。在实验室规模的实验中观察到了所呈现的频谱，实验中最初在介质中发射了两个频率。得到了泵浦波幅度增加以及不同频率对的结果。这些实验结果与从赫兹接触理论推导并考虑拍击可能性的模型高度吻合。
