Surface reconstruction accuracy using ultrasonic arrays: Application to non-destructive testing

Malkin, Robert; Franklin, Amanda C.; Bevan, Rhodri L. T.; Kikura, Hiroshige; Drinkwater, Bruce W.

doi:10.1016/j.ndteint.2018.03.004

Cited by 35 publications

(11 citation statements)

References 15 publications

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“…As different methods have been used to generate volumetric images in the past, it is worth clarifying that the method described and implemented here involves capturing a single FMC dataset from each array position and stitching all resulting 3D TFM images together. A similar stitching method was used in [14] in the context of 2D imaging using a 1D array, whereby multiple small TFM images with overlapping regions were stitched to produce an image that was larger in size than the individual images.…”

Section: Image Processing Methodsmentioning

confidence: 99%

“…The liquid acts as an acoustic couplant between the array and the component. The surface profile can be extracted from the ultrasonic data using an imaging algorithm [14,15], so previous knowledge of the surface is not required. In a previous study [16], a 2D array was used to generate 3D images in immersion; however, in this case the test specimen had a planar surface and determining the surface position from the data is straightforward.…”

Section: Introductionmentioning

confidence: 99%

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Volumetric imaging through a doubly-curved surface using a 2D phased array

McKee

Bevan

Wilcox

et al. 2020

NDT & E International

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Ultrasonic phased arrays have become widely used in recent years in non-destructive testing (NDT). However, most NDT arrays are 1-dimensional (1D), which generate 2dimensional (2D) images from a single position and lack the ability to focus accurately through surfaces that are curved in multiple directions. In this paper, a 2D phased array is used to experimentally image artificial defects (represented by bottom-drilled holes and electrical discharge machined notches) within a test specimen with a doubly-curved surface profile in an immersion configuration. The array is mechanically scanned above the entire surface of the specimen and the 3-dimensional (3D), or volumetric, images generated at each position are combined to produce a single image of the specimen's entire surface. The surface profile is then extracted and discretised for interior volumetric imaging. The results show that the root mean square (RMS) error between the ultrasonically extracted surface and the true surface is 0.04 mm and 95% of absolute errors are less than 0.07 mm. Finally, the positions of visible defects are measured, using (i) the depth above the back wall and (ii) the lateral distance from a notch on the specimen's surface, and compared to their true values. The study shows that the standard deviation of depth and lateral position measurements is 0.68 mm and 0.89 mm respectively. Defects that are located beneath regions of sufficiently steep surface curvature were unable to be imaged.

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Section: Image Processing Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Volumetric imaging through a doubly-curved surface using a 2D phased array

McKee

Bevan

Wilcox

et al. 2020

NDT & E International

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“…Nevertheless, the reliability of such inspections still demands further investigation. Strong artifacts were observed in the images of some cases, probably caused by the influence of the surface profile [ 5 , 12 , 21 , 22 ]. Even when using the surface-adapted total focusing method (TFM), limitations were observed when imaging under sharp curvatures [ 21 ].…”

Section: Introductionmentioning

confidence: 99%

Probe Standoff Optimization Method for Phased Array Ultrasonic TFM Imaging of Curved Parts

Filho

Bélanger

2021

Sensors

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The reliability of the ultrasonic phased array total focusing method (TFM) imaging of parts with curved geometries depends on many factors, one being the probe standoff. Strong artifacts and resolution loss are introduced by some surface profile and standoff combinations, making it impossible to identify defects. This paper, therefore, introduces a probe standoff optimization method (PSOM) to mitigate such effects. Based on a point spread function analysis, the PSOM algorithm finds the standoff with the lowest main lobe width and side lobe level values. Validation experiments were conducted and the TFM imaging performance compared with the PSOM predictions. The experiments consisted of the inspection of concave and convex parts with amplitudes of 0, 5 and 15 λAl, at 12 standoffs varying from 20 to 130 mm. Three internal side-drilled holes at different depths were used as targets. To investigate how the optimal probe standoff improves the TFM, two metrics were used: the signal-to-artifact ratio (SAR) and the array performance indicator (API). The PSF characteristics predicted by the PSOM agreed with the quality of TFM images. A considerable TFM improvement was demonstrated at the optimal standoff calculated by the PSOM. The API of a convex specimen’s TFM was minimized, and the SAR gained up to 13 dB, while the image of a concave specimen gained up to 33 dB in SAR.

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“…The benefit of the immersion approach is that it allows inspection of complex profile components without requiring prior knowledge of their geometries [17], [18]. Instead, those geometries are measured directly from the acquired ultrasonic data through post-processing with a surface reconstruction technique [19], [20].…”

Section: Introductionmentioning

confidence: 99%

Plane Wave Imaging Techniques for Immersion Testing of Components With Nonplanar Surfaces

Rachev

Wilcox

Velichko

et al. 2020

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

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Plane Wave Imaging (PWI) is an ultrasonic array imaging technique used in non-destructive testing, that has been shown to yield high resolution with few transmissions. Only a few published examples are available of PWI of components with nonplanar surfaces in immersion. In these cases, inspections were performed by adapting the transmission delays in order to produce a plane wave inside the component. This adaptation requires prior knowledge of the component geometry and position relative to the array. The current paper proposes a new implementation, termed PWI Adapted in Post-Processing (PWAPP), which has no such requirement. In PWAPP the array emits a plane wave as in conventional PWI. The captured data is input into two post-processing stages. The first reconstructs the surface of the component, the latter images inside of it by adapting the delays to the distortion of the plane waves upon refraction at the reconstructed surface. Simulation and experimental data are produced from an immersed sample with a concave front surface and artificial defects. These are processed with conventional and surface corrected PWI. Both algorithms involving surface adaptation produced nearly equivalent results from the simulated data, and both outperform the non-adapted one. Experimentally, all defects are imaged with Signal-to-Noise Ratio (SNR) of at least 31.8 and 33.5 dB for respectively PWAPP and PWI adapted in transmission, but only 20.5 dB for conventional PWI. In the cases considered, reducing the number of transmissions below the number of array elements shows PWAPP maintains its high SNR performance down to number of firings equivalent to a quarter of the array elements. Finally, experimental data from a more complex surface specimen is processed with PWAPP resulting in detection of all scatterers and producing SNR comparable to that of the Total Focusing Method. Index Terms-ultrasound, non-destructive evaluation, plane wave imaging, immersion testing, signal processing, complex geometry.Rosen K. Rachev was born in Burgas, Bulgaria, in 1993. He received the M.Eng. degree in Mechanical Engineering from the University of Bristol, Bristol, U.K., in 2016. He is currently pursuing the D.Eng. degree in Nondestructive Evaluation in the Ultrasonics and Nondestructive Testing Research Group, University of Bristol. He is working on advanced ultrasonic data processing algorithms for pipeline in-line inspections, and his project is sponsored by Baker Hughes. His research interests include nondestructive evaluation for the oil and gas industry, ultrasonic phased array surface reconstruction, adaptive imaging, and defect characterisation.

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Surface reconstruction accuracy using ultrasonic arrays: Application to non-destructive testing

Cited by 35 publications

References 15 publications

Volumetric imaging through a doubly-curved surface using a 2D phased array

Volumetric imaging through a doubly-curved surface using a 2D phased array

Probe Standoff Optimization Method for Phased Array Ultrasonic TFM Imaging of Curved Parts

Plane Wave Imaging Techniques for Immersion Testing of Components With Nonplanar Surfaces

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