RAPID CALCULATION OF LAMB WAVES IN PLATES DUE TO LOCALIZED SOURCES Dawei Guo and Ajit Mal Mechanical and Aerospace Engineering Department University of California, Los Angeles, CA 90095-1597 INTRODUCTION Waveform based acoustic emission (AE) analysis is an emerging technique for nondestructive monitoring of the integrity of structures in service. In contrast to conventional AE studies, a detailed understanding of wave propagation is required in order to correlate the information from detected AE signals to their sources representing various failure modes. AE source characterization can be carried out by using the sensor output waveform, identifying unknown signals and evaluating their significance, and correlating identified signals to the failure modes. This requires efficient evaluation of the surface response due to each elementary microfracture source (represented by moment tensor components) in the plate. Guided wave propagation in isotropic plates has been studied extensively in the literature using a variety of techniques [see, e. g., 1] In all cases the calculation of the surface response is rather complicated and may not be automatically realized for an arbitrary source-receiver configuration. Wave motion in anisotropic plates is much more complicated due to their anisotropy. For plates with general anisotropy, 2- and 3-dimensional models have been studied in detail [2-6]. Although the solution to general three-dimensional cases can, in principle, be constructed by applying the global matrix method, the computational effort for realistic geometries and source types can be enormous. In this paper, a method for rapid calculation of the guided wave components of isotropic and anisotropic plates due to localized surface sources is described. This method can be easily extended to deal with internal microfracture events. MATHEMATICAL MODELING The surface response of a plate due to an interior displacement discontinuity source can be written in the frequency domain as (1) Review of Progress in Quantitative Nondestructive Evaluation, Vol 17 Edited by D.O. Thompson and D.E. Chimenti, Plentml Press, New York, 1998 485