Multi-site damage localization in anisotropic plate-like structures using an active guidedwave structural health monitoring system

Abstract

A new approach for structural health monitoring using guided waves in plate-like structureshas been developed. In contrast to previous approaches, which mainly focused on isotropicor quasi-isotropic plates, the proposed algorithm does not assume any simplificationsregarding anisotropic wave propagation. Thus, it can be used to improve the probability ofdetection.In this paper the mathematical background for damage localization in anisotropic plateswill be introduced. This is an extension of the widely known ellipse method. The formalismis based on a distributed sensor network, where each piezoelectric sensor acts in turn as anactuator. The automatic extraction of the onset time of the first waveform in thedifferential signal in combination with a statistical post-processing via a two-dimensionalprobability density function and the application of the expectation-maximization algorithmallows a completely automatic localization procedure. Thus, multiple damages can beidentified at the same time.The present study uses ultrasonic signals provided by the spectral element method. Thissimulation approach shows good agreement with experimental measurements. A local linearneural network is used to model the nonlinear dispersion curves. The benefit of using aneural network approach is to increase the angular resolution that results from the sparsesensor network. Furthermore, it can be used to shorten the computational time for thedamage localization procedure.