Ultrasonic Lamb wave tomography using scanned EMATs and wavelet processing

A continuous wavelet transform has been used to analyse multi-mode Lamb wave propagation. This was applied to experimental data from non-contact electromagnetic acoustic transducers (EMATs) in thin metal plates. The technique was able to identify the presence of s(0), a(0), a(1), s(1) and s(2) modes in an aluminium plate from a single waveform, and hence to separate the modes. The technique has been applied to tomographic reconstruction of artificial defects in plates from individual modes to illustrate the usefulness of the approach