Quantitative analysis of the agreement between scalar finite element simulation and pulsed TV-holography detection of the scattering of Rayleigh-Lamb waves in plates

Abstract

The instantaneous out-of-plane displacement two-dimensional (2-D) maps associated to the scattering generated by the interaction of Rayleigh-Lamb waves with defects in plate structures can be measured using pulsed TV-holography (PTVH) and employed to characterize damage in non-destructive inspection applications. On the basis of visual comparisons we have shown previously that, except for the amplitude in the backscattering zone, a reasonable description of the measured experimental scattering patterns produced by holes both in harmonic and transient regimes can be obtained using the finite element method (FEM) combined with a 2-D model based on the scalar wave equation. In this work a systematic quantitative analysis of the agreement between FEM simulated maps and filtered experimental PTVH maps is developed considering both the spatial distribution of the local (pixel-wise) error in amplitude and phase and the corresponding global (averaged) errors over different areas in the 2-D image of the acoustic field. Changes produced in the experimental values by the speckle noise and variations introduced in the numerical values by the uncertainty in the characterization of the incident acoustic wave and the shape and position of the hole are characterized in order to obtain the net value of the error between theory and experiment.