Departamento de Fisica Aplicada, Universidade de Vigo, E. T. S. Enxeneiros Industriais, Campus Universitario, E36310 Vigo, Spain.
J Acoust Soc Am. 2010 Apr;127(4):2210-9. doi: 10.1121/1.3327795.
A method for the measurement of the phase and group velocities of guided acoustic waves is presented. For this purpose, a unique capability of a self-developed double-pulsed TV holography system to create movies of the propagation of guided acoustic wavetrains is used. Thereby, the experimental visualization of the evolution of Lamb and Rayleigh wavetrains in aluminum plates is shown, including several movies that illustrate different dispersive behaviors. Each movie shows the propagation of a narrowband wavetrain with a central frequency in the order of 1 MHz that consists of a carrier moving with the phase velocity, modulated by an envelope moving with the group velocity. Each snapshot is a two-dimensional map of the instantaneous out-of-plane displacement field of the surface points of the plate, with amplitudes in the order of several nanometers, acquired with the double-pulsed TV holography system. Then, by repeating the acquisition with successively increasing delays between the generation and detection instants, a sequence of maps is obtained from which a movie is composed. The phase and group velocities of the waves are accurately measured from the movies, yielding values that match well with the reference values for the same plates obtained from independent measurements.
本文提出了一种测量导波相速度和群速度的方法。为此，利用自行研制的双脉冲电视全息系统独特的产生导声波列传播电影的能力。由此，实验可视化了在铝板中兰姆波和瑞利波的演化，包括几个说明不同色散行为的电影。每个电影显示了一个窄带波列的传播，其中心频率约为 1MHz，由以相速度运动的载波和以群速度运动的包络调制而成。每个快照是板表面点的瞬时离面位移场的二维图，幅度约为几个纳米，用双脉冲电视全息系统获得。然后，通过在产生和探测瞬间之间成功地重复采集，从获得的一系列图谱中组成一个电影。从电影中准确测量了波的相速度和群速度，得到的值与从独立测量获得的相同板的参考值吻合良好。
