Advanced Reflector Characterization with Ultrasonic Phased Arrays in NDE Applications

Wilcox, Paul D.; Holmes, C.; Drinkwater, Bruce W.

doi:10.1109/tuffc.2007.424

Cited by 99 publications

(40 citation statements)

References 12 publications

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“…Thus, it is important to examine other ways in which the underlying array data may be used. The work of Wilcox and his colleagues [5][6][7], for example, are excellent examples of advanced flaw characterization methods that attempt to find other patterns and features that can be extracted from phased array inspections. The equivalent flaw sizing approach of Engle et al [8] is also a case where an array is used not to form crack images but to act instead as a steerable single element transducer that can effectively collect crack scattering data in multiple directions that can then be used to obtain crack size and orientation information.…”

Section: Discussionmentioning

confidence: 99%

Imaging Measurement Models

Schmerr

2014

Fundamentals of Ultrasonic Phased Arrays

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In Chap. 12, we described the ways in which images can be formed with phased arrays, including a two-dimensional (2-D) far field imaging measurement model. More general imaging measurement models will be developed in this chapter for forming images in 3-D with 2-D arrays and for forming images of 2-D scatterers with linear arrays. As found in Chap. 12 for the 2-D case, these imaging measurement models can be directly related to SAFT imaging and the total focusing method (TFM).

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Section: Discussionmentioning

confidence: 99%

Imaging Measurement Models

Schmerr

2014

Fundamentals of Ultrasonic Phased Arrays

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“…In what follows the focus will be on the case where N is even (the analysis is virtually identical for the case where N is odd) and so we will take this row of A (and hence A T ) to form our Toeplitz approximation. Substitutingŷ m = − y/2 into Equation (12) gives the first N/2 entries in the first row of the Toeplitz matrixĀ T as…”

Section: Crack Sizing Using the Maximum Eigenvaluementioning

confidence: 99%

“…The remaining terms in the first row ofĀ T are set equal to zero (that is Figure 2(c)). Note that the absolute value present in Equation (12) has been removed sinceŷ p − y/2 < 0 and −3.8317 < 2πâ 2 (ŷ p − y/2) < 0 in our regime of interest and so it follows that J 1 (2πâ 2 (ŷ p − y/2)) < 0.…”

Section: Crack Sizing Using the Maximum Eigenvaluementioning

confidence: 99%

“…Once the FMC data has been collected, post processing algorithms are applied to extract information associated with a flaw, presenting a difficult inverse scattering problem. Considerable effort has been expended in developing imaging techniques to characterize internal defects via the exploitation of these FMC data-sets (or their equivalent in other fields) [12][13][14]. However, even for the simplest of planar crack defects, an element of subjectivity is introduced using such imaging techniques to size objects (particularly those which measure less than two wavelengths), due to their reliance on the choice of imaging threshold at which the defect measurements are taken.…”

Section: Introductionmentioning

confidence: 99%

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A spectral method for sizing cracks using ultrasonic arrays

Cunningham¹,

Mulholland²,

Tant³

et al. 2017

Inverse Problems in Science and Engineering

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Ultrasonic phased array systems are becoming increasingly popular as tools for the inspection of safety-critical structures within the non-destructive evaluation industry. The data-sets captured by these arrays can be used to image the internal structure of individual components, allowing the location and nature of any defects to be deduced. Although there exist strict procedures for measuring defects via these imaging algorithms, sizing flaws which are smaller than two wavelengths in diameter can prove problematic and the choice of threshold at which the defect measurements are made can introduce an aspect of subjectivity. This paper puts forward a completely objective approach specific to cracks based on the Kirchhoff scattering model and the approximation of the resulting scattering matrices by Toeplitz matrices. A mathematical expression relating the crack size to the maximum eigenvalue of the associated scattering matrix is derived. Analysis of this approximation shows that the method will provide a unique crack size for a given maximum eigenvalue whilst providing a quick calculation method which avoids the need to numerically generate model scattering matrices (the computation time is up to 10 3 times faster). A sensitivity analysis demonstrates that the method is most effective for sizing defects that are commensurate with or smaller than the wavelength of the ultrasonic wave. The method is applied to simulated FMC data arising from finite element calculations where the crack length to wavelength ratios range between 0.6 and 1.9. The recovered objective crack size exhibits an error of 12%. ARTICLE HISTORY

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“…One popular beamforming technique in SA is the dynamic focusing to compensate emission and reception delays simultaneously known as Total Focussing Method (TFM). Futhermore, SA post-processing allows to combine the TFM image with other information contained in the data to improve image quality [5].…”

Section: Introductionmentioning

confidence: 99%

Improving Synthetic Aperture Image by Image Compounding in Beamforming Process

Martínez-Graullera¹,

Higuti²,

Martín³

et al. 2011

AIP Conference Proceedings

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ABSTRACT. In this work, signal processing techniques are used to improve the quality of image based on multi-element synthetic aperture techniques. Using several apodization functions to obtain different side lobes distribution, a polarity function and a threshold criterium are used to develop an image compounding technique. The spatial diversity is increased using an additional array, which generates complementary information about the defects, improving the results of the proposed algorithm and producing high resolution and contrast images. The inspection of isotropic plate-like structures using linear arrays and Lamb waves is presented. Experimental results are shown for a 1-mm-thick isotropic aluminum plate with artificial defects using linear arrays formed by 30 piezoelectric elements, with the low dispersion symmetric mode S0 at the frequency of 330 kHz.

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Advanced Reflector Characterization with Ultrasonic Phased Arrays in NDE Applications

Cited by 99 publications

References 12 publications

Imaging Measurement Models

Imaging Measurement Models

A spectral method for sizing cracks using ultrasonic arrays

Improving Synthetic Aperture Image by Image Compounding in Beamforming Process

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