Estimation of the Lamb wave phase velocity dispersion curves using only two adjacent signals

Abstract

Lamb waves are used in various non-destructive testing (NDT) and structural health monitoring (SHM) applications due to their velocity sensitivity to the properties of the material and their propagation over the entire thickness of the object over a long distance with low attenuation. However, the interpretation of the received signals is complex due to the Lamb waves dispersion nature, multiple mode generation, reflections and other. This work presents a novel method for the Lamb waves fundamental modes phase velocity dispersion evaluation and reconstruction of these curves segments using only two signals measured at two close points. The carried out investigation using simulated signals has shown that the proposed method works with an extremely high accuracy - the mean relative error from the true values is less than 0.01%. The proposed method has been experimentally verified in two different mediums: isotropic – aluminium plate and anisotropic GFRP plate. The obtained results have indicated have that the mean relative error from the true values is less than 1% in the aluminium case. The comparison of the results obtained in the GFRP plate case has indicated that the proposed method allows to reconstruct the phase velocity dispersion curves segments in the object of complex structure.