Modelling for characterizing defects in plates using two-dimensional maps of instantaneous ultrasonic out-of-plane displacement obtained by pulsed TV-holography

Abstract

It has been demonstrated that non-destructive inspection of plates can be performed by using two-dimensional maps of instantaneous out-of-plane displacements obtained with a self-developed pulsed TV-holography system. Specifically, the interaction of guided elastic waves with defects produces scattering patterns that contain information about the defects (position, dimensions, orientation, etc.). For quantitative characterization on this basis, modeling of the wave propagation and interaction with the defects is necessary. In fact, the development of models for scattering of waves in plates is yet an active research field in which the most reliable approach is usually based on the rigorous formulation of elasticity theory. By contrast, in this work the capability of a simple two-dimensional scalar model for obtaining a quantitative description of the output two-dimensional maps associated to artificial defects in plates is studied. Some experiments recording the interaction of narrowband Rayleigh waves with artificial defects in aluminum plates are presented, in which the acoustic field is obtained from the TV-holography optical phase-change maps by means of a specially developed two-step spatio-temporal Fourier transform method. For the modeling, harmonic regime and free-stress boundary conditions are assumed. Comparisons between experimental and simulated maps are included for defects with different shapes.

Characterization of defects in plates by two-dimensional ultrasonic displacement maps: comparison between pulsed TV-holography measurements and finite element method predictions

“…Also, we restrict the scope of the model to scattering phenomena produced by through-thickness holes with residual depth e = 0 (see figure 1b) for which plate geometry depends only on (x 1 , x 2 ) coordinates. In these conditions, 15 the scattering for the out-of-plane component of displacement u 3 over plane (x 1 , x 2 , h) (top surface of the plate) can be modeled by means of the partial differential equation…”

“…15 In this work a state-of-the art numerical method 16 was employed for obtaining simulated scattering data and includes, to the best of our knowledge for the first time, a direct comparison between simulated and experimental ultrasonic 2D scattering patterns of guided waves by defects in plates (a hole and a slot) both in near-field and far-field simultaneously.…”

Numerical modeling and measurement by pulsed television holography of ultrasonic displacement maps in plates with through-thickness defects

“…Comparison between experimental and simulated scattering patterns of narrowband guided waves with holes and slots in aluminum plates shows a fair match, both in near-and far-field zones, which allows a subsequent quantitative characterization of the defects on this basis. To the best of our knowledge, apart from our corresponding recent presentation in a congress, 19 this is the first time that such a comparison is reported.…”

FFT based approaches in micromechanics: fundamentals, methods and applications

“…Recently, an FC-based solver for linear elastic 3D domains introduced in (Amlani and Bruno 2016) has been utilized in Amlani et al (2019b) to simulate ultrasonic NDT experiments on thin aluminum plates: a pulsed TV-holography (PTVH) system records the 2D acoustic field of the instantaneous out-of-plane displacement over the surface (López-Vázquez et al 2009. This enables measurements of both the spatial and temporal evolution of incident vibrations that subsequently scatter upon interaction with drilled holes of varying shapes and sizes.…”