Ultrasonic detection of debond in multi-layer adhesive structure based on wavelet-packet transform

This paper present a wavelet-packet approach for extracting feature from ultrasonic non-destructive evaluation data of a test multi-layer adhesive structure specimen. These features are then used to obtain an estimate of the specimen´s bonded properties. When the multi-layer adhesive structure undergo ultrasonic non-destructive evaluation, echo from interior layers often overlap severely, causing information from individual layers to be obscured or lost completely. A complex-valued mother wavelet based on the impulse response of the test instrumentation system, is used to perform the wavelet-packet transform and separate the overlap echoes. The extracted features displayed are effective to analyze and identify the bonded properties. It is believed that the features extracted via the method outlined in this paper provide considerable promise in the area of the test of multi-layered bonded structure.