Lamb Wave Polarization Techniques for Structural Damage Localization and Quantification
Final rept. Jan-Aug 2011
ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD VEHICLE TECHNOLOGY DIRECTORATE
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U.S. Army rotorcraft and land-based vehicles develop induced structural damage that requires robust damage diagnostics that characterize these real-time defects. This report investigates one such method based on polarization of guided waves. Initially, an analytical description of polarized Lamb wave components that yield an elliptical, rotated profile of the particle trajectory is provided. A damage localization technique is shown to utilize the elliptical orientation as a damage identification parameter for guided wave structural interrogation techniques. In addition, a damage quantification technique incorporates spatially integrated multiple component mode coefficients that are formulated in the frequency-spatial domain with the intent to better characterize wave reflections and mode conversions. The techniques are applied to finite-element FE models of aluminum and composite armor-like structures. Trends from the two-dimensional FE numerical studies are verified by a threedimensional scanning laser vibrometry test setup for the undamaged case. Recommendations of implementing the polarization techniques for damage localization and quantification on Army platforms are given.
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