Evaluation of crack parameters by a nonlinear frequency-mixing laser ultrasonics method

Mézil, Sylvain; Chigarev, Nikolay; Tournat, Vincent; Gusev, Vitalyi

doi:10.1016/j.ultras.2016.04.005

Cited by 29 publications

(9 citation statements)

References 30 publications

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“…when submitted to an input wave of frequency F c , the output signal exhibits peaks at frequencies ±F c + n c m a where n is a signed integer, c m the modulation speed and a the distance between two grounded electrodes. This generalized non-linear phenomenon occurs in any structure that is modulated in time 6, [25][26][27] and is analogous to the classical acousto-optical Brillouin scattering 28 . Additionally, our piezoelectric STMS becomes strongly non-reciprocal, and for specific modulation characteristics, one-way wave propagation can be achieved.…”

Section: Introductionmentioning

confidence: 97%

Non-reciprocal behavior of one-dimensional piezoelectric structures with space-time modulated electrical boundary conditions

Croënne

Vasseur

Matar

et al. 2019

Journal of Applied Physics

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Propagation of longitudinal acoustic waves in a one-dimensional piezoelectric structure with space-time modulated electrical boundary conditions is investigated. An analytical model allowing the calculation of eigenmodes for spatially continuous shifts of electrical boundary conditions is compared with finite difference time domain (FDTD) simulation results for a discrete set of time-varying spatially fixed conditions. Both models predict that such a structure behaves as a non-reciprocal device exhibiting unidirectional propagation properties in some frequency ranges. The modulus and direction of the modulation speed vector strongly affect this non-reciprocal behavior. Moreover other nonlinear phenomena such as frequency up and down conversions, wave packet distortion and parasitic echoes occurring in such systems are investigated in detail. Importance of these phenomena is discussed in the context of nonlinear acoustic wave-based components for radio-communication systems.

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Section: Introductionmentioning

confidence: 97%

Non-reciprocal behavior of one-dimensional piezoelectric structures with space-time modulated electrical boundary conditions

Croënne

Vasseur

Matar

et al. 2019

Journal of Applied Physics

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“…Ultrasonic Testing (UT) including conventional piezo-electric methods [1] , [2] and Laser Ultrasonic (LU) techniques [3] , [4] , [5] , [6] , is widely used in defect detection, location and evaluations. The Synthetic Aperture Focusing Technique (SAFT) is one of the imaging algorithms [1] for generating 2D and 3D imaging of defects by synthesizing ultrasonic signals from small aperture transducer(s) to improve the lateral resolution using point-by-point scanning.…”

Section: Introductionmentioning

confidence: 99%

“…The LU techniques have characteristics such as non-contact and non-destructive testing [3] , [4] , [5] , and can be conducted in wide frequency bands, on curved complex surfaces, or in hostile environments [6] , [8] . Successful demonstrations have been produced for detecting cracks in stainless steel plates [16] and imaging the layering of curved interfaces [9] , [10] using the LU-SAFT.…”

Section: Introductionmentioning

confidence: 99%

Non-destructive laser-ultrasonic Synthetic Aperture Focusing Technique (SAFT) for 3D visualization of defects

Chen

Ying

et al. 2021

Photoacoustics

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The Laser Ultrasonic (LU) technique has been widely studied. Detected ultrasonic signals can be further processed using Synthetic Aperture Focusing Techniques (SAFTs), to detect and image internal defects. LU-based SAFT in frequency-domain (F-SAFT) is developed to visualize horizontal hole-type defects in aluminum. Bulk acoustic waves are non-destructively generated by irradiating a laser line-source, and detected using a laser Doppler vibrometer at a point away from the generation. The influence of this non-coincident generation-detection on the equivalent acoustic velocity used in the algorithm is studied via velocity mappings. Because the wide-band generation characteristic of the LU technique, frequency range selections in acoustic wave signals are implemented to increase Signal-to-Noise Ratio (SNR) and reconstruction speed. Results indicate that by using the LU F-SAFT algorithm, and incorporating optimizations such as velocity mapping and frequency range selection, small defects can be visualized in 3D with corrected locations and improved image quality.

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“…This approach was later advanced by applying the laser radiation not only for crack modulation but also for generation of ultrasound. The frequency-mixed components of the spectrum are detected by in-contact accelerometers [60][61][62][63][64] and contactless optical techniques, such as interferometry and beam deflection. 61 Furthermore, the contrast of photoacoustic imaging of cracks is improved because of the strong dependence of optoacoustic conversion efficiency on the state of the crack.…”

Section: Introductionmentioning

confidence: 99%

Laser ultrasonic monitoring of reversible/irreversible modification of a real crack under photothermal loading

Zhang

et al. 2020

Structural Health Monitoring

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We study the responses of laser-generated acoustic waves to localized reversible/irreversible modifications of microscopic asperities on crack surfaces during crack closure, which is an essential process in nonlinear photoacoustic/photothermal crack detection techniques. Our laser ultrasonics technique involves optical measurement of the transmission and mode conversion of the laser-generated surface acoustic waves caused by the crack. Reversible/irreversible modifications of asperities can be achieved via non-contact photothermal loading of the crack. Three photothermal loading cycles were realized in individual succession and were monitored using the laser ultrasonics technique at various experimental locations along the crack. In our experiments, each photothermal loading cycle includes multiple successive subcycles, in which the material is first heated and then cooled to its equilibrium temperature, thereby initiating local closing, followed by opening of the crack. Each subcycle is monitored twice using the laser ultrasonics technique, once each at the end of heating and cooling. Furthermore, each successive subcycle is accomplished at a higher power of heating laser than that of the previous subcycle. Significant differences in the peak-to-peak amplitude of the surface skimming longitudinal acoustic wave, which is excited by mode conversion of the Rayleigh wave by the crack, are revealed during the first cycle of photothermal loading. These differences clearly indicate a partial irreversibility of the mechanical processes occurring in the crack surfaces during subcycles of the first cycle. In a larger temporal scale, irreversible modification of crack surfaces is observed from the significant difference between the experimental results of the first photothermal loading cycle and the subsequent two cycles, whereas a reversible response of the crack surface to thermoelastic loading is observed from the similarity of the measurements accumulated during the two subsequent cycles.

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Evaluation of crack parameters by a nonlinear frequency-mixing laser ultrasonics method

Cited by 29 publications

References 30 publications

Non-reciprocal behavior of one-dimensional piezoelectric structures with space-time modulated electrical boundary conditions

Non-reciprocal behavior of one-dimensional piezoelectric structures with space-time modulated electrical boundary conditions

Non-destructive laser-ultrasonic Synthetic Aperture Focusing Technique (SAFT) for 3D visualization of defects

Laser ultrasonic monitoring of reversible/irreversible modification of a real crack under photothermal loading

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