Elhanaoui Abdelkader, Aassif Elhoucein, Maze Gérard, Décultot Dominique
Ultrasonics. 2016 Feb;65:131-6. doi: 10.1016/j.ultras.2015.10.010.
The present paper studies the acoustic signal backscattered by an air-filled copper–solid polymer two-layer cylindrical tube immersed in water. The work is done from the calculation of the backscattered pressure, an inverse Fourier Transform, which allows us to obtain an impulse signal. Smoothed pseudo Wigner–Ville and Concentrated spectrogram representations have been chosen to analyze the scattering phenomenon. For reduced frequencies ranging from 0.1 to 200, the resonance trajectories and time–frequency images have shown the presence of the guided waves. The bifurcation of the A0 wave into the A0(-) and the A0(+) waves has also been observed. The authors provide the phase and the group velocities of guided waves and investigate the differences between curves. The findings are then compared with those obtained for the copper and the solid polymer one-layer cylindrical tubes. Group velocity values have also been extracted from smoothed pseudo Wigner–Ville and Concentrated spectrogram time–frequency images. A good agreement with the theory has, therefore, been observed. The study of acoustic backscattering by a copper–solid polymer two-layer tube has revealed the interaction and the coupling of guided waves, specially the presence of a pseudo A1 wave; which is a very interesting, remarkable phenomenon.
本文研究了浸没在水中的充气铜 - 固体聚合物双层圆柱形管反向散射的声信号。这项工作是通过计算反向散射压力（一种逆傅里叶变换）来完成的，它使我们能够获得一个脉冲信号。已选择平滑伪维格纳 - 维尔分布和集中频谱图表示来分析散射现象。对于0.1至200的约化频率，共振轨迹和时频图像显示了导波的存在。还观察到A0波分叉为A0(-)波和A0(+)波。作者给出了导波的相速度和群速度，并研究了曲线之间的差异。然后将这些结果与铜和固体聚合物单层圆柱形管的结果进行比较。群速度值也已从平滑伪维格纳 - 维尔分布和集中频谱图时频图像中提取。因此，观察到与理论有很好的一致性。对铜 - 固体聚合物双层管声反向散射的研究揭示了导波的相互作用和耦合，特别是伪A1波的存在；这是一个非常有趣且显著的现象。
