Transient elastic wave propagation and scattering in plates : comparison between pulsed TV-holography measurements and finite element method predictions

Abstract

Pulsed TV-holography (PTVH) can be used for obtaining two-dimensional maps of instantaneous out-of-plane displacements in plates. In particular, our group has demonstrated that scattering patterns generated by the interaction of elastic waves with defects can be measured with PTVH and employed for the characterization of damage in nondestructive inspection of plate structures. Recently, we have succeeded in obtaining a quantitative description of experimental scattering patterns of quasi-Rayleigh (qR) waves produced by holes in harmonic regime using a finite element method (FEM) combined with a two-dimensional scalar wave equation, avoiding the standard and more complex vector approaches based on the rigorous linear elasticity theory. This scheme has been extended here for characterizing equivalent scattering phenomena in transient regime. Simulated scattering patterns, obtained with the scalar FEM, and the corresponding experimental patterns associated to the interaction of qR waves with holes, measured with our specifically developed PTVH system, have been compared. Results have shown that, except for the evaluation of the backscattering coefficient, a reasonable agreement between theory and experiment is obtained in both amplitude and phase, which confirms the feasibility and potential of the proposed scalar approximation for the characterization of experimental transient scattering patterns measured with our PTVH technique.