Nonlinear Acoustic Imaging: Fundamentals, Methodology, and NDE-Applications

Krohn, N.; Pfleiderer, K.; Stoessel, R.; Solodov, Igor; Busse, G.

doi:10.1007/978-1-4020-2402-3_12

Cited by 14 publications

(8 citation statements)

References 6 publications

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“…Ultrasonic oscillations at the delamination location can be observed long after the incident waves had passed the delaminated area (figure 5(c)). A similar phenomenon was observed by Krohn et al [26] and Willemann et al [27], and a possible explanation for this phenomenon is given below. Figure 6 shows a schematic through-the-thickness side view of a delamination.…”

Section: Standing Waves Produced By Delaminationsupporting

confidence: 84%

Automated detection of delamination and disbond from wavefield images obtained using a scanning laser vibrometer

Sohn

Dutta

et al. 2011

Smart Mater. Struct.

161

118

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The paper presents signal and image processing algorithms to automatically detect delamination and disbond in composite plates from wavefield images obtained using a scanning laser Doppler vibrometer (LDV). Lamb waves are excited by a lead zirconate titanate transducer (PZT) mounted on the surface of a composite plate, and the out-of-plane velocity field is measured using an LDV. From the scanned time signals, wavefield images are constructed and processed to study the interaction of Lamb waves with hidden delaminations and disbonds. In particular, the frequency-wavenumber (f-k) domain filter and the Laplacian image filter are used to enhance the visibility of defects in the scanned images. Thereafter, a statistical cluster detection algorithm is used to identify the defect location and distinguish damaged specimens from undamaged ones.

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Section: Standing Waves Produced By Delaminationsupporting

confidence: 84%

Automated detection of delamination and disbond from wavefield images obtained using a scanning laser vibrometer

Sohn

Dutta

et al. 2011

Smart Mater. Struct.

161

118

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“…7 to 9. In the experiments, the methodology of NLV [6] that includes an intense CW acoustic excitation (flexural waves) in the kHz-frequency range combined with a laser probing of the spectra ε 0 increases, τ grows from 0 to T/2. This affects dynamic characteristics of the higher harmonics ( Fig.…”

Section: Experiments On Higher Harmonic Generation By Defectsmentioning

confidence: 99%

“…The NLV [6] uses a sensitive scanning laser interferometer for detecting nonlinear vibrations of defects. The excitation system includes piezo-stack transducers operating at 20 and 40 kHz.…”

Section: Can Applications In Ndt: Nlv For Defect-selective Imagingmentioning

confidence: 99%

New Opportunities for NDT Using Non-Linear Interaction of Elastic Waves with Defects

Solodov¹,

Döring²

2011

SV-JME

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When material is subjected to an intense load, its stiffness changes due to elastic nonlinearity. This effect is especially pronounced in damaged materials, so that nonlinearity can be used as an indication of incipient damage. Under dynamic load, mechanical constraint between the fragments of planar defects provides gigantic nonlinearity in finite-amplitude contact vibrations. The local vibration spectra acquire a number of new frequency components which are used as signatures of damage. The experimental implementation of nonlinear NDT relies on the use of laser interferometers (Nonlinear Laser Vibrometry, NLV) to detect the nonlinear waves that are generated selectively by defects. In addition, the planar defects as localized sources of nonlinear vibrations efficiently radiate nonlinear airborne ultrasound (Nonlinear Air-Coupled Emission, NACE). The frequency conversion mechanism concerned with contact nonlinearity of the defect vibrations provides an efficient generation of air-coupled higher-order ultra-harmonics, ultrasubharmonics, and combination frequencies. Both the NLV and NACE are proposed for remote scanning and high contrast defect-selective imaging in nonlinear NDT.

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“…In the past years, nonlinear imaging techniques such as b-scan, c-scan or tomography [30] [31] and applies it to a defect acting as a source of nonlinear elastic waves [32][33][34][35]. The scattered signal is recorded, the frequency generated by the primary source is filtered out using a band pass filter, and the resulting signal is time reversed and re-injected by the receiver: due to the (t → −t) symmetry, the wavefield back-propagates to its original (nonlinear) source, focusing energy at the defect location at a specific time.…”

mentioning

confidence: 99%

Proof of Concept for an Ultrasensitive Technique to Detect and Localize Sources of Elastic Nonlinearity Using Phononic Crystals

et al. 2017

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The appearance of nonlinear effects in elastic wave propagation is one of the most reliable and sensitive indicators of the onset of material damage. However, these effects are usually very small and can be detected only using cumbersome digital signal processing techniques. Here, we propose and experimentally validate an alternative approach, using the filtering and focusing properties of phononic crystals to naturally select and reflect the higher harmonics generated by nonlinear effects, enabling the realization of time-reversal procedures for nonlinear elastic source detection. The proposed device demonstrates its potential as an efficient, compact, portable, passive apparatus for nonlinear elastic wave sensing and damage detection. DOI: 10.1103/PhysRevLett.118.214301 In recent years, phononic crystals (PCs) have attracted great attention due to their unconventional dynamic behavior, with effects such as negative refraction [1], frequency band gaps [2,3], wave filtering or focusing [4][5][6], acoustic cloaking [7][8][9], subwavelength sensing [10,11], etc. Their periodic structure, rather than single material constituents, is responsible for their behavior, which exploits Bragg scattering [12,13]. Their attractive properties to act as stopband filters [12] or to concentrate energy in selected frequency ranges [14] makes them potentially interesting for nonlinear elastic source detection and to reveal the presence of defects, e.g. cracks, in a sample. This is because, in general, a nonlinear response is generated at the defect location and several possible features may appear, including the generation of higher order harmonics [15][16][17] or subharmonics [18,19], the nonlinear dependence of the elastic modulus and of attenuation coefficients on strain [20][21][22], and, as a consequence, the shift of the resonance frequency with increasing excitation amplitude [23,24] and the failure of the superposition principle [25,26]. All of these possible signatures can be used to detect and monitor the presence and evolution of damage, exploiting the greater sensitivity of nonlinear detection techniques compared to conventional linear ones [27].In the past years, nonlinear imaging techniques such as b scan, c scan, and tomography [28] have attracted much interest. A particularly robust and efficient approach is the combination of time reversal (TR) and nonlinear elastic wave spectroscopy (NEWS). This technique (TR-NEWS) exploits space-time focusing of the wave field achieved in TR [29] and applies it to a defect acting as a source of nonlinear elastic waves [30][31][32][33]. The scattered signal is recorded, the frequency generated by the primary source is filtered out using a bandpass filter, and the resulting signal is time reversed and reinjected by the receiver: due to the (t → −t) symmetry, the wave field back propagates to its original (nonlinear) source, focusing energy at the defect location at a specific time. Many studies have proved the efficiency and robustness of TR-NEWS in various configurations, for ...

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Nonlinear Acoustic Imaging: Fundamentals, Methodology, and NDE-Applications

Cited by 14 publications

References 6 publications

Automated detection of delamination and disbond from wavefield images obtained using a scanning laser vibrometer

Automated detection of delamination and disbond from wavefield images obtained using a scanning laser vibrometer

New Opportunities for NDT Using Non-Linear Interaction of Elastic Waves with Defects

Proof of Concept for an Ultrasensitive Technique to Detect and Localize Sources of Elastic Nonlinearity Using Phononic Crystals

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