Location of pointlike acoustic emission sources in anisotropic plates

Abstract

In this paper is described a method by which a pointlike source of acoustic emission can be located in an anisotropic plate. The method is applicable for a source in an anisotropic solid of arbitrary symmetry as long as the principal acoustic axes of the material are known a priori. It is shown that from the time-of-flight differences of particular features in the waveforms detected by any pair of sensors, a set of nonlinear transcendental equations can be formed in which the coefficient of each term in the equations is related to the time-of-flight differences, the geometrical parameters of the array, and the wave speeds of quasiwaves propagating along each source/receiver path. For waves propagating in principal planes, the analytical expressions for the wave speed values are used. Extension to nonprincipal planes is obtained by computing the eigenvalues of the Green–Christoffel tensor. Determination of the optimum location of the source is found by minimizing the Euclidean functional associated with the set of transcendental nonlinear equations. The results obtained with numerical simulations of two- and three-dimensional source-location problems are presented to illustrate several characteristic features of the solution. Also shown are the results of two-dimensional source-location measurements made on specimens of a unidirectional fiber-glass-reinforced composite material. The results demonstrate the efficiency of the algorithm in locating a source of emission.