Detection of subsurface defects using laser based technique

Kromine, Alexei K.; Fomitchov, Pavel A.; Krishnaswamy, Sridhar; Achenbach, Jan Drewes

doi:10.1063/1.1373946

Cited by 19 publications

(4 citation statements)

References 4 publications

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“…PZT ceramics showed a high scattering behavior at optical wavelength [4], resulting in noisy measurements. Scanning laser Doppler vibrometer has been employed for 3-dimensional visualization of acoustic wave interference with inclusions and damages in metallic plates, piezo-ceramics and piezo-crystals [5,6]. The scanning laser Doppler vibrometer experiments are expensive and require a thin reflective coating on the sample surface.…”

Section: Related Workmentioning

confidence: 99%

Classification of Micro-Damage in Piezoelectric Ceramics Using Machine Learning of Ultrasound Signals

Tripathi

Habib

Agarwal

et al. 2019

Sensors

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Ultrasound based structural health monitoring of piezoelectric material is challenging if a damage changes at a microscale over time. Classifying geometrically similar damages with a difference in diameter as small as 100 μm is difficult using conventional sensing and signal analysis approaches. Here, we use an unconventional ultrasound sensing approach that collects information of the entire bulk of the material and investigate the applicability of machine learning approaches for classifying such similar defects. Our results show that appropriate feature design combined with simple k-nearest neighbor classifier can provide up to 98% classification accuracy even though conventional features for time-series data and a variety of classifiers cannot achieve close to 70% accuracy. The newly proposed hybrid feature, which combines frequency domain information in the form of power spectral density and time domain information in the form of sign of slope change, is a suitable feature for achieving the best classification accuracy on this challenging problem.

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Section: Related Workmentioning

confidence: 99%

Classification of Micro-Damage in Piezoelectric Ceramics Using Machine Learning of Ultrasound Signals

Tripathi

Habib

Agarwal

et al. 2019

Sensors

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“…Considerable attentions have been focused on detection, elimination of subsurface defects in substrates and on exploration of the mechanism that subsurface defects decrease laser-induced damage threshold of optical components [1][2][3][4] . However, the influence of subsurface defects on optical properties of dielectric thin films has not been studied yet.…”

Section: Introductionmentioning

confidence: 99%

Theoretical analysis of optical properties of dielectric coatings dependence on substrate subsurface defects

et al. 2006

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A model for refractive index of stratified dielectric substrate was put forward according to theories of inhomogeneous coatings. The substrate was divided into surface layer, subsurface layer and bulk layer along the normal direction of its surface. Both the surface layer (separated into N 1 sublayers of uniform thickness) and subsurface layer (separated into N 2 sublayers of uniform thickness), whose refractive indices have different statistical distributions, are equivalent to inhomogeneous coatings respectively. And theoretical deduction was carried out by employing characteristic matrix method of optical coatings. An example of mathematical calculation for optical properties of dielectric coatings had been presented. The computing results indicate that substrate subsurface defects bring about additional bulk scattering and change propagation characteristic in thin film and substrate. Therefore, reflectance, reflective phase shift and phase difference of an assembly of coatings and substrate deviate from ideal conditions. The model will provide some beneficial theory directions for improving optical properties of dielectric coatings via substrate surface modification.

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“…The Scanning Laser Source (SLS) technique employs a line-focused high-power laser source which is swept across the test specimen and passes over surface-breaking anomalies [2][3][4]. The generated ultrasonic waves are detected with an ultrasonic detector located either at a fixed distance from the laser source or at a fixed position on the test specimen.…”

Section: Introductionmentioning

confidence: 99%

<title>A model for the ultrasonic detection of surface-breaking cracks by the scanning laser-source technique</title>

Arias

Achenbach²

2004

SPIE Proceedings

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A model for the Scanning Laser Source (SLS) technique is presented. The SLS is a novel laser based inspection method for the ultrasonic detection of small surfacebreaking cracks. The generated ultrasonic signal is monitored as a line-focused laser is scanned over the defect. Characteristic changes in the amplitude and the frequency content are observed. The modeling approach is based on the decomposition of the field generated by the laser in a cracked two-dimensional half-space, by virtue of linear superposition, into the incident and the scattered fields. The incident field is that generated by laser illumination of a defect-free half-space. A thermoelastic model has been used which takes account of the effect of thermal diffusion, as well as the finite width and duration of the laser source. The scattered field incorporates the interactions of the incident field with the surface-breaking crack. It has been analyzed numerically by a direct frequency domain boundary element method. A comparison with an experiment for a large defect shows that the model captures the observed phenomena. A simulation for a small crack illustrates the ability of the SLS technique to detect defects smaller than the wavelength of the generated Rayleigh wave.

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Detection of subsurface defects using laser based technique

Cited by 19 publications

References 4 publications

Classification of Micro-Damage in Piezoelectric Ceramics Using Machine Learning of Ultrasound Signals

Classification of Micro-Damage in Piezoelectric Ceramics Using Machine Learning of Ultrasound Signals

Theoretical analysis of optical properties of dielectric coatings dependence on substrate subsurface defects

<title>A model for the ultrasonic detection of surface-breaking cracks by the scanning laser-source technique</title>

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