Two-dimensional Gabor analysis of space–time transient Lamb waves using Laser ultrasonic investigation

Abstract

Laser generation/detection methods allow the investigation of ultrasonic transient phenomena in both space and time dimensions. Used for the experimental investigation of surface wave propagation along a one-dimensional medium, laser ultrasonics leads to two-dimensional (2D) space–time signal collections. In order to extract the wave propagation information, the classical high resolution signal processing methods or 2D Fourier transforms are not suitable to identify the transient and local aspect of wave propagation and mode conversion. In order to quantify these transient aspects in the space–time-wave number–frequency domains, the 2D Gabor transform is introduced. Its potential for the identification of the local and transient complex wave numbers is illustrated on the propagation of Lamb waves on a plane limited plate. The mode conversion sequences are clearly identified in the space–time–wave number-frequency planes. The experimental results are in good agreement whith the numerical simulations.