STN Easy INSPEC: Search Results: TOFD

INSPEC Answer Number 1 - © 1997 IEE
Title
	An evaluation of the performance of the TOFD technique as a means of sizing flaws, with particular reference to flaws with curved profiles.
Author
	Silk, M.G.
Publication Source
	Insight-Non-Destructive Testing and Condition Monitoring (April 1996) vol.38, no.4, p.280-7. 4 refs. Published by: British Inst. Non-Destructive Testing CODEN: ITMOEN ISSN: 1354-2575 SICI: 1354-2575(199604)38:4L.280:EPTT;1-A
Document Type
	Journal
Treatment Code
	Experimental
Country of Publication
	United Kingdom
Language
	English
Abstract
	Simulated TOFD data have been employed as a means of evaluating the ability of the ultrasonic TOFD technique to size flaws in both the through-thickness and length dimensions. The interest in the evaluation arose as a result of an earlier study which suggested that the fundamental precision of the technique may be greater than is currently assumed. The current assumptions are based on the results of blind trials and it may be that the difference between the expected and achieved precisions is simply a reflection of the wide natural variability of flaws. On the other hand it may be that the procedures currently employed to estimate the flaw size are insufficient or that the trials themselves incorporate other sources of error: These possibilities were of sufficient interest to warrant a preliminary study of the sizing potential of the technique. The results of the study indicate that the potential of the technique for determining the through-thickness extent of flaws is greater than has been assumed. The results from this trial are consistent with a precision of 0.25% of the specimen thickness, whereas the current assumption is a precision in the region of 2% of specimen thickness. An allowance must be made for the use of simulations rather than real data, but it is difficult to envisage this bridging the gap between these figures. An alternative explanation that should be considered is whether the confirmatory (destructive or other NDT) examinations associated with blind trials are contributing to the apparent errors. Ideally, these should not be producing errors greater than 0.25% of specimen thickness but it is difficult to believe that this could be achieved in practice. As regards flaw length, the results from this study highlight a distinction between flaws with a substantially flat profile (broadly parallel to the surface) and flaws with a continuously curving profile. The former group would include many common flaws such as slag lines and most lack of fusion defects. The latter would include most surface-breaking cracks.
Accession Number
	96:5276358

INSPEC Answer Number 2 - © 1997 IEE
Title
	Estimates of the probability of detection of flaws in TOFD data with varying levels of noise.
Author
	Silk, M.G. (Nat. NDT Centrer, Harwell, UK)
Publication Source
	Insight-Non-Destructive Testing and Condition Monitoring (Jan. 1996) vol.38, no.1, p.31-6. 0 refs. Published by: British Inst. Non-Destructive Testing CODEN: ITMOEN ISSN: 1354-2575 SICI: 1354-2575(199601)38:1L.31:EPDF;1-P
Document Type
	Journal
Treatment Code
	Theoretical; Experimental
Country of Publication
	United Kingdom
Language
	English
Abstract
	Artificially generated B-scan data have been produced which has allowed useful trials of flaw detection by the TOFD technique to be carried out. The results obtained give an indication of the limits of operation of the technique under various circumstances and the cost of these trials is probably less than 5% of that of carrying out equivalent practical investigations. At typical and moderate levels of background noise, the PoD achieved was 100%, while the PFI was zero at typical noise levels and less than 3% at moderate noise levels. The PoD fell and the PFI rose as the noise levels increased further. The precisions achieved in flaw location and flaw sizing well exceeded those normally quoted for TOFD. The results from the trials have been compared with the predictions of a model that is used to predict the probability of detection (PoD) associated with TOFD. This comparison shows that the model predictions are quite pessimistic in some important areas and may be used to justify some changes in the model. At the present level of development the use of artificial B-scans should not be considered as a replacement for practical trials, but they provide a useful test-bed to establish general levels of detectability and to compare operators and procedures.
Accession Number
	96:5208072

INSPEC Answer Number 3 - © 1997 IEE
Title
	SG nozzle inspection-AEA's ultrasonic system cuts its teeth.
Author
	Daniels, W.L. (AEA Technol., Risley, UK); Hawker, B.M.; Loy, D.F.
Publication Source
	Nuclear Engineering International (Jan. 1996) vol.41, no.498, p.23-5. 0 refs. Published by: Reed Business Publishing CODEN: NEINBF ISSN: 0029-5507 SICI: 0029-5507(199601)41:498L.23:NIUS;1-X
Document Type
	Journal
Treatment Code
	Practical
Country of Publication
	United Kingdom
Language
	English
Abstract
	AEA Technology has developed an ultrasonic in-service inspection system and procedures to detect and size service-induced defects in complex-geometry nozzles. Particularly applicable to PWR steam generator feedwater nozzles, the procedure combines optimised pulse-echo defect detection with time-of-flight diffraction (TOFD) sizing and computerised data reconstruction System, procedure and personnel performance were tested in blind trials at the EPRI NDE Center, Charlotte, NC, and the first "live" use of the system was successfully completed recently at a nuclear power plant in the USA.
Accession Number
	96:5167438

INSPEC Answer Number 4 - © 1997 IEE
Title
	High-accuracy defect sizing for CRDM penetration adapters using the ultrasonic TOFD technique (PWR inspection).
Author
	Atkinson, I. (NDE Services, AEA Technol., Risley, UK)
Publication Source
	Insight-Non-Destructive Testing and Condition Monitoring (March 1995) vol.37, no.3, p.175-8. 0 refs. CODEN: ITMOEN ISSN: 1354-2575
Document Type
	Journal
Treatment Code
	Practical; Experimental
Country of Publication
	United Kingdom
Language
	English
Abstract
	Ultrasonic time-of-flight diffraction (TOFD) is the preferred technique for critical sizing of throughwall orientated defects in a wide range of components, primarily because it is intrinsically more accurate than amplitude-based techniques. For the same reason, TOFD is the preferred technique for sizing the cracks in control rod drive mechanism (CRDM) penetration adapters, which have been the subject of much recent attention. Once the considerable problem of restricted access for the UT probes has been overcome, this inspection lends itself to very high accuracy defect sizing using TOFD. In qualification trials under industrial conditions, depth sizing to an accuracy of <or=0.5 mm has been routinely achieved throughout the full wall thickness (16 mm) of the penetration adapters, using only a single probe pair and without recourse to signal processing.
Accession Number
	95:4982070

INSPEC Answer Number 5 - © 1997 IEE
Title
	TOFD comes of age (nuclear engineering).
Author
	Wedgwood, F.A. (National NDT Centre, AEA Technol., Didcot, UK)
Publication Source
	Nuclear Engineering International (Jan. 1995) vol.40, no.486, p.35-7. 0 refs. CODEN: NEINBF ISSN: 0029-5507
Document Type
	Journal
Treatment Code
	Practical
Country of Publication
	United Kingdom
Language
	English
Abstract
	For detecting cracks, particularly in thick section pressure vessels where the crack is growing from an inaccessible surface, ultrasonics techniques are the most appropriate available. In the most widely used "pulse echo" method, ultrasound is reflected from the face of the crack, whereas the diffraction method relies on the much weaker reflections from crack extremities. The latter, which has come to be known as Time of Flight Diffraction or TOFD, has certain advantages, particularly in speed and reliability, and is increasingly being exploited.
Accession Number
	95:4855973

INSPEC Answer Number 6 - © 1997 IEE
Title
	Ultrasonic C-SCAN imaging system for inspection of fabricated mechanical parts.
Author
	Patankar, V.H.; More, S.R.; Joshi, V.M.; Bairi, B.R. (Electron. Div., BARC, Bombay, India)
Publication Source
	1992.
	Proceedings of National Symposium on Computer Applications in Power Plants Bombay, India: Bhabha Atomic Res. Centre, 1992. p.425-8 of xii+549 pp. 3 refs. Conference: Bombay, India, 8-10 Dec 1992 Sponsor(s): Board Res. Nuclear Sci.; Dept. Atomic Energy
Document Type
	Conference Article
Treatment Code
	Practical
Country of Publication
	India
Language
	English
Abstract
	Ultrasonic C-SCAN imaging system for NDT/NDE of fabricated mechanical parts such as plates, rods, blocks etc. is under development at Electronics Division, BARC. It provides flaw visualisation in the form of 2D images. The system is based around an IBM PC/AT compatible computer and dedicated hardware/software has been developed to create an advanced ultrasonic inspection environment. Development of sophisticated techniques and data analysis software have been undertaken to make the system suitable for a wide range of critical in-service inspection tasks at nuclear power stations. Real time colour graphics has been planned for comprehensive data presentation. Features such as Time Of Flight Diffraction (TOFD) technique, RF Digitization and Synthetic Aperture Focusing Technique (SAFT) enable reliable and accurate means of defect sizing and analysis. A powerful and convenient menu driven operator interface system has been designed to increase its versatility for a wide range of inspection jobs.
Accession Number
	93:4553920

INSPEC Answer Number 7 - © 1997 IEE
Title
	Depth measurement of short cracks with an acoustic microscope.
Author
	Knauss, D.; Bennink, D.D.; Zhai, T.; Briggs, G.A.D.; Martin, J.W. (Dept. of Metall. & Sci. of Mater., Oxford Univ., UK)
Publication Source
	Journal of Materials Science (15 Sept. 1993) vol.28, no.18, p.4910-17. 18 refs. CODEN: JMTSAS ISSN: 0022-2461
Document Type
	Journal
Treatment Code
	Experimental
Country of Publication
	United Kingdom
Language
	English
Abstract
	The depth of short cracks (70-200 mu m surface length) has been measured with an acoustic microscope by utilizing the nondestructive time-of-flight diffraction technique (TOFD). The depth measurements were first carried out in the transparent polymer polystyrene, thus allowing a comparison between the acoustical values and direct optical measurements: the agreement in the results was better than 95%. The depth of a 70 mu m long crack in an aluminium alloy was then measured, demonstrating the application of the technique to metals.
Accession Number
	93:4501204

INSPEC Answer Number 8 - © 1997 IEE
Title
	In-line inspection using time-of-flight diffraction.
Author
	Lilley, J.; Osborne, P. (Sonomatic Ltd., Woolston, UK)
Publication Source
	Welding and Metal Fabrication (Oct. 1991) vol.59, no.8, p.457-8, 460. 0 refs. CODEN: WLMFAM ISSN: 0043-2245
Document Type
	Journal
Treatment Code
	Practical
Country of Publication
	United Kingdom
Language
	English
Abstract
	The authors look at the potential of an alternative NDT technique, time-of-flight diffraction (TOFD), to replace the traditional methods of inspecting fabricated tubular components. The disadvantages of conventional ultrasonic and radiographic inspection are outlined and the processes compared with TOFD. TOFD has the capability to resolve the upper and lower edges of a buried planar flaw where the main axis of the flaw is perpendicular to the main axis of the incident ultrasonic beam. The interaction of the beam with various major flaws is described.
Accession Number
	92:4090891

INSPEC Answer Number 9 - © 1997 IEE
Title
	Flaw growth monitoring as an aid to lifetime prediction.
Author
	Silk, M.G.; Whapham, A.D.; Hobbs, C.P. (Nat. Nondestructive Testing Centre, Harwell Lab., UK)
Publication Source
	International Journal of Materials & Product Technology (1989) vol.4, no.3, p.215-31. 13 refs. CODEN: IJMTE2 ISSN: 0268-1900
Document Type
	Journal
Treatment Code
	General Review; Theoretical
Country of Publication
	Switzerland
Language
	English
Abstract
	The error in the determination of flaw size using accurate non-destructive testing (NDT) techniques is no longer likely to be the limiting factor in the classification of flaws. Now, however, both the time of flight diffraction (TOFD) technique and the alternating current potential drop (ACPD) technique might achieve precisions of 0.25 mm or better in estimating flaw growth. The monitoring approach can then be shown to have economic benefits without affecting the essential structural safety argument for the plant. The justification for monitoring is reviewed and experimental flaw-monitoring data is presented.
Accession Number
	90:3540026

INSPEC Answer Number 10 - © 1997 IEE
Title
	Zipscan 3 and TOFD offer improved sizing accuracy.
Author
	Browne, B.
Publication Source
	Nuclear Engineering International (Oct. 1989) vol.34, no.423, p.24-6. 0 refs. CODEN: NEINBF ISSN: 0029-5507
Document Type
	Journal
Treatment Code
	Practical
Country of Publication
	United Kingdom
Language
	English
Abstract
	Work carried out at EPRI and elsewhere has confirmed that time-of-flight diffraction (TOFD) techniques using Zipscan equipment provide very accurate defect sizing. Further improvements are embodied in the latest generation of equipment, Zipscan 3.
Accession Number
	89:3502956

INSPEC Answer Number 11 - © 1997 IEE
Title
	Accuracy in locating a point scatterer in ultrasonic testing, using the TOFD technique.
Author
	Mak, D.K.
Publication Source
	British Journal of Non-Destructive Testing (Sept. 1989) vol.31, no.9, p.481-4. 7 refs. CODEN: BJNTAS ISSN: 0007-1137
Document Type
	Journal
Treatment Code
	Experimental
Country of Publication
	United Kingdom
Language
	English
Abstract
	The equations for calculating the errors in locating a point defect in ultrasonic testing have been derived for two-dimensional as well as three-dimensional space. Experimental data have been collected. They illustrate what kind of error estimate is expected in positioning a point defect. This will yield a quantitative error estimate of flaw sizing.
Accession Number
	89:3497750

INSPEC Answer Number 12 - © 1997 IEE
Title
	The interpretation of TOFD data in the light of ASME XI and similar rules.
Author
	Silk, M.G. (The Nat. NDT Centre, Harwell, UK)
Publication Source
	British Journal of Non-Destructive Testing (May 1989) vol.31, no.5, p.242-51. 8 refs. CODEN: BJNTAS ISSN: 0007-1137
Document Type
	Journal
Treatment Code
	Experimental
Country of Publication
	United Kingdom
Language
	English
Abstract
	Considers implications of the ASME XI and other rules for the (TOFD) and defines its current limitations. It is implicitly assumed that the TOFD technique is used both to locate and size flaws and is applied in the manner currently possible on site using the ZIPSCAN equipment.
Accession Number
	89:3407658

INSPEC Answer Number 13 - © 1997 IEE
Title
	Nuclear NDT development at Harwell.
Author
	Collingwood, J.C. (Div. of Mater. Phys. & Metall., UKAEA, Harwell, UK)
Publication Source
	NDT International (Feb. 1987) vol.20, no.1, p.33-41. 34 refs. Price: CCCC 0308-9126/87/010033-09$3.00 CODEN: NDITDS ISSN: 0308-9126
Document Type
	Journal
Treatment Code
	General Review; Experimental
Country of Publication
	United Kingdom
Language
	English
Abstract
	A review is presented of nuclear-oriented NDT development work at Harwell, illustrating the synergy between this and the National NDT Centre's non-nuclear programme. Most of the work in recent years has been concerned with automated ultrasonic inspection techniques for the proposed Sizewell 'B' PWR pressure vessel, and Harwell's part has been to develop the time-of-flight diffraction method (TOFD) as a stand-alone technique for defect detection and sizing. The value of this technique, which originated in the Centre's non-nuclear work, has been amply demonstrated in trials involving thick plate weld and nozzle specimens. Currently the main item in the nuclear programme is the improvement of ultrasonic inspection capability for austenitic castings and welds, for both PWR and fast reactor applications, by means of advanced scanning and signal processing techniques. In examining this and other current interests, the strong influence of theoretical modelling is noted.
Accession Number
	87:2883259

INSPEC Answer Number 14 - © 1997 IEE
Title
	Calculation of the effects of electronic threshold and pulse height walk on observed neutron time-of-flight distributions.
Author
	Ajitanand, N.N. (Nuclear Phys. Div., Bhabha Atomic Res. Centre, Bombay, India)
Publication Source
	Nuclear Instruments and Methods (15 Oct. 1980) vol.176, no.3, p.545-7. 3 refs. CODEN: NUIMAL ISSN: 0029-554X
Document Type
	Journal
Treatment Code
	Theoretical
Country of Publication
	Netherlands
Language
	English
Abstract
	Using a simple formulation of the pulse height walk a computer program has been written to calculate the expected neutron time-of-flight distribution (TOFD) corresponding to a given neutron spectrum for a certain neutron threshold. The effect of varying each instrumental parameter is studied. A fitting procedure is used to obtain the values of these parameters from the TOFD corresponding to a known neutron spectrum. The same values can then be used in the analysis of the TOFD corresponding to an unknown spectrum measured with the same instrumental settings.
Accession Number
	81:1634770

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