Wavelet-transform-based method of analysis for Lamb-wave ultrasonic NDE signals

We present a new acoustic nondestructive testing method which uses Lamb waves as the probe. These waves are generated and received by an electromagnetic acoustic transducer (EMAT). The position of flaws in the structure under test is computed from the time of arrival of main peak of the reflected signal. Due to the noisy nature of the received signal, we use a wavelet transform algorithm to extract the required time information. The main advantage of such a multi-scale method of signal analysis is to be suitable for detection peak problems especially in highly noisy environment. We explain how we proceed to do the feature extraction and proposed two methods for reconstructing the image of the inspected structure. Results of real-world ultrasonic Lamb wave signal analysis are presented, including the case of synthetic and experimental noisy signals