Investigating the Use of Ultrasonic Guided Wave Analysis Methods for Detecting and Classifying a Small Notch in a Thin Metallic Plate

Report No. ARL-TR-5432
Authors: Robert F. Anastasi
Date/Pages: February 2011; 22 pages
Abstract: Aircraft and rotorcraft structures are being redesigned with new lower weight materials; however, older metallic structures continue to be used. These older structures need monitoring and characterization of damage for continued operation. The use of ultrasonic guided waves is one nondestructive technique that can be used to interrogate such structures. Typically, large cracks or geometric variations can be found by examining signal amplitude; but smaller damage that can suddenly grow in size and causes serious damage cannot be detected. This work investigates the detection and characterization of such damage where ultrasonic guided waves are transmitted across damage (a notch) in a metallic plate and numerically examined. Data is generated for a rectangular notch of varying depth and position using a finite-difference model and analyzed in time, frequency, and combined time frequency. Results show that a small notch, 0.1 mm deep, cannot be detected using conventional time or frequency domain analysis but can be detected using time-frequency representations.
Distribution: Approved for public release
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Last Update / Reviewed: February 1, 2011