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Hybrid Coherent/Incoherent Beam Forming Diagnostic Approach to Naval Assets

S. S. KESSLER, E. B. FLYNN, M. D. TODD

Abstract


This paper presents a hybrid diagnostic algorithm that leverages a novel piezoelectric-based damage-localization method using ultrasonic waves. The goal of the present research was to monitor a Navy established “challenge problemâ€â€”a large (1.8 x 0.9 m) aluminum plate with several geometric features such as cutouts and bolted doublers, which tend to confound most guided wave methods. The algorithms used were a hybrid collection of functions making use of both coherent and incoherent information in the data. Data for each sensor is processed separately, then ultimately summed in a weighted fashion across the test structure. Further logic is also deployed to eliminate anomalies and invalid features. Generally, this process is analogous to active sonar. Damage ("targets") are detected and/or localized by generating ultrasonic elastic waves and observing how they bounce off of potential targets. Because a test structure is arguably far more complex than the open ocean, producing potentially far more "false targets", this approach takes advantage of embedding probabilistic models into the wave propagation/scattering process so that likelihood-based judgments can be made about the damage targets. These judgments may be understood in appropriate performance terms—probability of detection, probability of localization, etc.— which directly supports the uncertainty quantification needed for decision-making.

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