Resolution enhancement of ultrasonic defect signals for crack sizing

Shakibi, Babak; Honarvar, Farhang; Moles, Michael; Caldwell, James T.; Sinclair, A. N.

doi:10.1016/j.ndteint.2012.08.003

Cited by 41 publications

(16 citation statements)

References 14 publications

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“…AR deconvolution based on Burg method (AR/BM) has attracted interest due to its superresolution capability [24], [34]. However, due to the high tendency of line-splitting (reconstructions including artifacts that suggest additional layers that are not present) when a larger order is applied as well as the additional constraint from Levinson-Durbin recursion [24], the AR/BM result may not provide reliable reconstruction of multilayered coatings, especially when the absence of prior knowledge of the various layers since in practice the choice of parameters to provide reliable reconstruction may require one to know the layer thicknesses beforehand, which, needless to say, defeats the entire purpose.…”

Section: Principlementioning

confidence: 99%

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Thickness characterization of multi-layer coated steel by terahertz time-of-flight tomography

Zhai

Locquet

Roquelet

et al. 2020

NDT & E International

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Terahertz time-of-flight tomography is employed to characterize the individual layers in a multilayer coating on steel substrates. The multilayers, containing up to three layers, consist first of a cataphoretic layer, sealer, and varnish progressing upward from the steel substrate. The individual layer thicknesses were reconstructed from the experimental data using autoregressive spectral extrapolation based on the modified covariance method (AR/MCM), which extrapolates the frequency components of the transfer function into the low signal-tonoise-ratio (SNR) regions from the high SNR regions. Due to the high sensitivity of AR/MCM to the presence of noises, wavelet denoising, in some cases, was needed to precondition the data prior to application of AR/MCM. The method is verified numerically and experimentally, showing that it can reconstruct individual layers in the 10-m range, and good agreement is found between the thicknesses of individual layers extracted by AR/MCM and characterized by eddy-current measurements.

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Section: Principlementioning

confidence: 99%

“…AR based on the modified covariance method (AR/MCM) to minimize the sum of squares of the forward and backward prediction errors, is employed [34]. Compared with AR/BM, the most remarkable advantage of AR/MCM is the reduced occurrence of line-splitting due to the restriction in the AR order selection.…”

Section: Principlementioning

confidence: 99%

Thickness characterization of multi-layer coated steel by terahertz time-of-flight tomography

Zhai

Locquet

Roquelet

et al. 2020

NDT & E International

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“…Ultrasonic inspection is an important technique in non-destructive testing (NDT) [1] and its use can be found in a range of safety critical applications, including nuclear [2], railway [3], petroleum [4,5], and aerospace industries [6].…”

Section: Introductionmentioning

confidence: 99%

The effect of distortion models on characterisation of real defects using ultrasonic arrays

Bai

Velichko

Clare

et al. 2020

NDT & E International

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Characterisation of real defects is one of the main challenges in ultrasonic nondestructive testing (NDT), especially for small defects having irregular shapes.Traditional methods such as ultrasonic array imaging are limited by the image resolution, and in this paper, we consider using the scattering matrix which is extractable from the full matrix of transmit-receive array data. We describe a procedure in which the experimental measurements are used to perform characterisation and reveal the associated uncertainties. Moreover, we explore performance of this characterisation procedure and propose a robust defect characterisation approach. The performance of the proposed approach is studied experimentally, and the sizing errors are small (within 0.09λ or 0.23mm for fatigue cracks at 2.5 MHz, and within 0.38λ or 0.24mm for volumetric defects in an additive manufactured specimen at 10 MHz). In addition, reliable estimation of defect angle/width is achieved.

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“…Although the use of higher frequencies and shear waves (e.g. combined with a deconvolution approach [8]) can help to improve the time resolution of ultrasonic A-scans, the achievable imaging resolution, and hence the sizing performance, is well known to be limited by diffraction. In practice this means that only defects larger than about two wavelengths can be reliably sized [9].…”

Section: Introductionmentioning

confidence: 99%

Grain Scattering Noise Modeling and Its Use in the Detection and Characterization of Defects Using Ultrasonic Arrays

Bai

Velichko

Drinkwater

2019

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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In the field of ultrasonic array imaging for nondestructive testing (NDT), material structural noise caused by grain scattering is one of the main sources of error when characterising defects that are found in polycrystalline materials. The existence of grains can also severely affect the detection performance of ultrasonic testing, making small defects indistinguishable from the grain indications due to ultrasonic attenuation and backscatter. This paper proposes a model in which the statistical distribution of the defect data is obtained from different realisations of the grain structure. This statistical distribution, termed the defect+grains model in this paper, is shown to contain information that is needed for detection and characterisation of defects. Hence, given a specific measurement configuration, the characterisation result can be obtained by constructing a defect+grains model based on multiple realisations of each possible defect and calculating their probability. The detection, classification, and sizing accuracy are shown to be predictable by quantifying the probabilities that an experimentally measured defect matches the different defect+grains models. This defect+grains modelling approach gives insight into the detection/characterisation problem, leading to an evaluation of the fundamental limits of the achievable inspection performance.

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Resolution enhancement of ultrasonic defect signals for crack sizing

Cited by 41 publications

References 14 publications

Thickness characterization of multi-layer coated steel by terahertz time-of-flight tomography

Thickness characterization of multi-layer coated steel by terahertz time-of-flight tomography

The effect of distortion models on characterisation of real defects using ultrasonic arrays

Grain Scattering Noise Modeling and Its Use in the Detection and Characterization of Defects Using Ultrasonic Arrays

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