Nonlinear acoustic time reversal imaging using the scaling subtraction method

Abstract

Lab experiments have shown that the imaging of nonlinear scatterers using time reversal acoustics can be a very promising tool for early stage damage detection. The potential applications are however limited by the need for an extremely accurate acquisition system. In order to let nonlinear features emerge from the background noise it is necessary to enhance the signal-to-noise ratio as much as possible. A comprehensive analysis to determine the nonlinear components in a recorded time signal, an alternative to those usually adopted (e.g. fast Fourier), is proposed here. The method is based on the nonlinear physical properties of the solution of the wave equation and takes advantage of the deficient system response scalability with the excitation amplitude. In this contribution, we outline the adopted procedure and apply it to a nonlinear time reversal imaging simulation to highlight the advantages with respect to traditional imaging based on a fast Fourier analysis of the recorded signals.

The Ultrasonic Polar Scan for Composite Characterization and Damage Assessment: Past, Present and Future

“…However, it is well-known from literature that nonlinear wave phenomena show an increased sensitivity to early stage damage features as well as to certain classes of contact defects [42][43][44][45]. For this reason, the present authors are currently upgrading the U(B)PS methodology towards the nonlinear regime.…”

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

“…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.…”

“…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]. The idea behind SSM is that a high amplitude excitation will activate nonlinear defects within the sample, whereas a low amplitude excitation does not provide enough power to trigger the nonlinearity in the defects and, therefore, the low amplitude response will serve as reference signal as if the medium were fully linear.…”

Evolution of damage-induced nonlinearity in proximity of discontinuities in concrete

“…As an alternative, we have recently proposed a scaling subtraction method (SSM) (Scalerandi et al, 2008a; et al, 2009) which allows to detect the influence of the nonlinearity of the sample on the portion of the signal at the fundamental frequency, with benefits in terms of signal-to-noise ratio. We have shown elsewhere the sensitivity of the method both to the presence of nonlinearity (Scalerandi et al, 2008b) and to its evolution (Bruno et al, 2009).…”