Multi-wave-mode,multi-frequency detectors for guided wave interrogation of plate structures

Abstract

The detection and localization of damage using an array of closely spaced transducers is investigated theoretically and experimentally using single- and multiple-mode guided wave active sensing models. Detectors are derived using a generalized likelihood ratio approach assuming that amplitude, absolute phase, and source location of a scattered wave are unknown, while frequency, group velocity, and phase velocity are known. Theoretical detection performance for processing with each detector is derived and related to the energy-to-noise ratio of a scattered mode as a metric of determining when processing with multiple modes provides increased performance over processing with a single mode. Experimentally, detectors are implemented to detect scattering from a small mass glued to the surface of an aluminum plate with a 7 × 7 array of transducers. Relative detection and localization performance is compared through receiver operating characteristic curves and histograms of distance from true damage location for 1000 no-damage and damaged measurements. A single-mode, multi-frequency detector is shown to have the best detection and localization performance for the tested damage scenarios.

Keywords

Guided ultrasonic waves Lamb waves generalized likelihood ratio test detection theory plate structures

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