DISPERSION MODE SEPARATION IN ULTRASONIC SIGNAL PROCESSING

This paper report on a technique for the analysis of propagating multimode signals. The method involves a 2-D Fourier transformation of the time history of the waves received at a series of equally spaced positions along the propagation path. The output of the transform being presented using an isometric projection which gives a 3-D view of the wave number dispersion curves. The time history of the waves was obtained by the commercial finite element (FE) code, MARC. The results of numerical studies and the dispersion curves of Lamb waves propagating in the 2.0-mm-thick steel plate are presented. The results are in good agreement with analytical predictions and show the effectiveness of using the 2-D Fourier transform method to identify and measure the amplitudes of individual Lamb modes. Key words: guided waves, Fourier transform