The potential of scattered or diffracted ultrasound in the determination of crack depth

Silk, M.G.; Lidington, B.H.

doi:10.1016/0029-1021(75)90024-9

Cited by 40 publications

(13 citation statements)

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“…Bulk waves or surface waves can be used. An example is timeof-flight diffraction (TOFD) [4,5] where an ultrasonic probe is placed on either side of the location being inspected. If an embedded crack is present its size is determined using the time-of-flight of the ultrasonic signals scattered from its two tips.…”

Section: Overview Of Ultrasonic Methodsmentioning

confidence: 99%

Accurate depth measurement of small surface-breaking cracks using an ultrasonic array post-processing technique

Felice

Velichko

Wilcox

2014

NDT & E International

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a b s t r a c tIn this paper, the half-skip configuration of the Total Focusing Method (TFM) is used to image and size surface-breaking cracks. The TFM is an ultrasonic array post-processing technique which is used to synthetically focus at every image point in a target region. This paper considers the case of inspecting for cracks which have initiated from the far surface of a parallel-sided sample using an array on the near surface. Typically, only direct ray paths between the array and image points are included in the TFM algorithm and therefore the image obtained for this case consists only of root and tip indications; no specular reflection from the crack faces is captured. The tip indication often has such a poor signal-to-noise ratio that reliable crack depth measurement is challenging. With the Half-Skip TFM, instead of using directly-scattered signals, the image is formed using ultrasonic ray paths corresponding to the ultrasound that has reflected off the back surface and has then undergone specular reflection from the crack face back to the array. The technique is applied to experimental and simulated array data and is shown to measure the depth of small cracks (depth o1 mm) with greater reliability than methods which rely on tip diffraction.

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Section: Overview Of Ultrasonic Methodsmentioning

confidence: 99%

Accurate depth measurement of small surface-breaking cracks using an ultrasonic array post-processing technique

Felice

Velichko

Wilcox

2014

NDT & E International

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“…Time of flight diffraction (TOFD) is an ultrasound technique developed for the NDT of nuclear power plants [5][6][7], and it has been used for general weld inspection [4]. Standard inspections may use a normal incidence compression wave transducer to check the HAZ for laminar defects, followed by an angle incidence transducer for defects in the weld itself (requiring a reflection, or skip, off the back-wall, before reaching the weld region).…”

Section: Weld Defectsmentioning

confidence: 99%

Weld defect detection using PPM EMAT generated shear horizontal ultrasound

Petcher

Dixon

2015

NDT & E International

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a b s t r a c tAustenitic welds are inspected using PPM EMAT generated shear horizontal (SH) waves. Results are compared to measurements taken using a 1D piezoelectric phased array using the total focusing method (TFM). For the first time there is clear experimental evidence of the SH wave method demonstrating higher sensitivity to defect detection. SH waves suffer less beam steering in a weld than either compression or SV waves, which can miss defects due to weld microstructure anisotropy and attenuation. All defects were identified from every side of the weld/plate using the SH waves, but this was not possible using the piezoelectric transducer.

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“…TOFD was developed to help in the NDT of nuclear power plants [2], [3], [4], [5] , used to locate (using the intersection of elliptical loci [6] ) and size defects either within the bulk of a sample or surface breaking cracks [7], [8] . TOFD uses a separate emitter and receiver that are held in a fixed geometry as they are scanned along a surface of a test sample, Figure 1a.…”

Section: Time Of Flight Diffraction (Tofd)mentioning

confidence: 99%

Obtaining more information from time-of-flight-diffraction measurements

2012

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Time of flight diffraction and imaging (TOFDI) is based on time of flight diffraction (TOFD); it adds cross-sectional imaging to examine the bulk of a sample. Multiple wave modes are generated by a pulsed laser beam, ablative source and are received by a sparse array of non-contact electromagnetic acoustic transducers (EMATs). A B-scan is formed from multiple data captures (A-scans), with time and scan axes, and colour representing amplitude. B-scans may contain horizontal lines from surface waves propagating directly from emitter to receiver, or via a back-wall reflection, and angled lines after reflection off a surface edge. A Hough transform (HT), modified to deal with the constraints of a Bscan, can remove such lines. A parabola matched filter has been developed to identify features in the B-scan caused by scattering from point-like features, reducing them to peaks. The processed B-scan is processed further to form a crosssectional image, enabling detection and positioning of multiple defects. Phase correlation of camera images is used to track the relative position between transducer and sample to sub-pixel precision.

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The potential of scattered or diffracted ultrasound in the determination of crack depth

Cited by 40 publications

References 0 publications

Accurate depth measurement of small surface-breaking cracks using an ultrasonic array post-processing technique

Accurate depth measurement of small surface-breaking cracks using an ultrasonic array post-processing technique

Weld defect detection using PPM EMAT generated shear horizontal ultrasound

Obtaining more information from time-of-flight-diffraction measurements

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