Detection and localization of small notches in plates using Lamb waves

The interaction of the first antisymmetric (a o) Lamb wave in an aluminum plate with small surface notches (> 25% of the plate thickness) is investigated. The study is motivated by the need for real-time, early detection of cracks in plate-like structures. The experimental procedure uses a piezoelectric pinducer point source to generate and a laser Doppler vibrometer to detect Lamb waves in the plate. A spectrogram of the measured plate motion is used to isolate a nondispersive portion of the a o Lamb mode from the rest of the signal for use in the notch detection algorithm. An efficient algorithm uses information about the notch reflected energy to locate the notch and to calculate a reflection coefficient. An estimate of the smallest detectable notch is made based on the experimental reflection coefficient vs. notch depth characteristic and the noise floor. A finite element model of the plate is used to verify the experimental results.

Detection and localization of small notches in plates using Lamb waves Conference Paper