A two-dimensional pseudospectral model for time reversal and nonlinear elastic wave spectroscopy

Abstract

One way to characterize metallic materials in the presence of defects like dislocation networks is to measure their large dynamic nonlinear elastic response. In this numerical study, a new method combining the nonlinear elastic wave spectroscopy (NEWS) method with a time reversal (TR) process is proposed. This method, called NEWS-TR, uses nonlinear analysis as a pretreatment of time reversal and then consists of retrofocusing only nonlinear components on the defect position. A two-dimensional pseudospectral time domain algorithm is developed here to validate the NEWS-TR method as a potential technique for damage location. Hysteretic nonlinear behavior of the materials being studied is introduced using the Preisach-Mayergoyz model. Moreover, in order to extend this solver in two dimensions, the Kelvin notation is used to modify the elastic coefficient tensor. Simulations performed on a metallic sample show the feasibility and value of the NEWS-TR methodology for microdamage imaging. Retrofocusing quality depends on different parameters such as the filtering method used to keep only nonlinear components and the nonlinear effect measured. In harmonic generation, pulse inversion filtering seems to be a more appropriate filtering method than classical harmonic filtering for most defect positions, mainly because of its ability to filter all fundamental components.

Dual energy time reversed elastic wave propagation and nonlinear signal processing for localisation and depth-profiling of near-surface defects: A simulation study

“…The most widely applied NEWS filtering techniques that are used either in pre-or post-processing are pulse inversion (also called Phase Coded Pulse Sequence PCPS filtering) or harmonic filtering [10,[14][15][16][17][18]. Although pulse inversion and harmonic filtering have proven to be effective, even for localisation techniques that are not using TR [1,2,10,11], another interesting NEWS filtering method, called Scaling Subtraction Method (SSM), has been recently suggested by Scalerandi et al [20].…”

“…Fundamentally, two approaches can be distinguished, depending on the order in which TR and NEWS are applied [12][13][14][15][16][17][18][19][20][21]. If the signals recorded at the surface of an object are first filtered in such a manner that only the nonlinear components of the signals remain, a subsequent traditional TR procedure using these NEWS filtered signals will automatically converge the energy in space to the defected zone that created the nonlinear components in the signals.…”

Imaging of human tooth using ultrasound based chirp-coded nonlinear time reversal acoustics

“…These methods, already adopted as a powerful tool for several applications (NDT and medicine), are efficient approaches for focusing acoustic energy in a complex propagation medium: noisy, scattering and complex shape medium [12,16,[27][28][29].…”

Excitation symmetry analysis method (ESAM) for calculation of higher order non-linearities

“…ESAM has been tested with real data coming from experiments in ultrasound imaging using TR-NEWS and NEWS-TR methods [9,10] which are based on Nonlinear Elastic Wave Spectroscopy (NEWS) combined with Time Reversal Acoustics (TR). The main objective of this kind of experiments [11] is to combine TR-NEWS and PI in order to evaluate nonlinear properties of damaged steel samples with cracks.…”