The author gives examples on known problems when TOFD is used and recommends not discarding proven test
methods in favor of the cost-saving factor of TOFD, however, TOFD can be a
valuable
add-on for other test methods.
By A. Hecht, BASF, Ludwigshafen (D)
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The Time-of-Flight-Diffraction-Technique
The article describes the main TOFD principles and applications. With use of TOFD the Probability of Detection (POD) increases greatly. Advantages and drawbacks of the method are listed. It is mentioned that AEA Sonomatic succeeded in reducing the dead zone to 2 mm.
By N. Trimborn, SONOMATIC, Oosterhout (NL). English by Rolf Diederichs.
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Time of Flight Diffraction Technique -
Its Limitations - Actual & Perceived
The article is an comprehensive - 46 kbyte text - review of the TOFD technique.
The author discusses many aspects, e.g., accuracy, repeatability, coverage, resolution, defect types, and last not least costs, where the real value of TOFD lies - despite its few inherent limitations. He concluded - yes, TOFD does have its limitations - but so do all other techniques when used isolation.
By Bill Browne, CATS International (ZA)
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The rapid analysis of TOFD data incorporating the provisions of standards
This paper describes some of the developments that have been carried out to ease decision making processes, to aid conformity with
TOFD standards, to improve the speed of data analysis and to allow flaw growth monitoring.
By M.G.Silk AEA Technology, Harwell Laboratory, United Kingdom
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Recent developments for automatic on-line TOFD inspection
The BRITE-EURAM "NDT Methods for Flaw Detection During Welding" has been investigating the possibilities of performing NDT between weld runs as an on-line operation.
The two methods which have shown the most promise for this application are radioscopy (or real time radiography, RTR) and Time of Flight Diffraction (TOFD) ultrasonic testing.
This article describes recent TOFD developments within the project.
Finally a brief outline of the final TOFD trials for the project will be given.
By Shaun Lawson, University of Surrey (UK)
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Ultrasonic crack depth measurement of surface bracking cracks in piping [D]
The article introduces results of a program for validation different ultrasonic test techniques for crack depth determination of surface bracking cracks. Two techniques, the TOFD technique and the angle beam testing with mirror effect, both using time of flight measurement of the diffracted signal from the crack tip, are employed.
Since it is not certain that all crack edges generate diffracted waves, the optimized ultrasonic pulse echo technique should be used. Applying TOFD as an additional analytic method for
verification of Impulse Echo Technique or Radiography results seems to be more applicable.
By T. Just, G. Csapo, TÜV Nord, Hamburg, D |
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The draft European TOFD Standard ENV 583-6 : 1997
Time of Flight diffraction technique as a method for defect detection and sizing
Summarize of the draft European standard ENV 583-6. The draft was submitted to CEN members and will undergo a practicle test for three Years. After two Years are statements requested from all members, especially the question if CEN should supersedes the draft by a final EN standard.
By Rolf Diederichs
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The British TOFD standard BS 7706
Guide to Caliabration and setting-up of the Ultrasonic Time of Flight diffraction (TOFD) technique for defect detection, location and sizing of flaws.
This is a guide standard and thus contains a lot of detail about the technique in addition to the application requirements. The annex D presents informative examples of typical scans (image on right side - 90 KByte zoomed =>).
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TOFD Lecture and Podium discussion at the DGZfP meeting in Dortmund
Mr. Udo Schlengermann of Krautkraemer introduced the TOFD technique.
In the podium discussion, the majority of participants warned of disadvantages of the TOFD method. The panel's major statements are summarized.
By Rolf Diederichs
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Can TOFD replace conventional Ultrasonic Testing on welding?
That question was posted by Rolf Diederichs on the UTonline Workshop in May '97. Answers were given by Hermann Wuestenberg, Udo Schlengermann and Ed Ginzel.
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75 TOFD Abstracts were delivered by Literature Services
We searched STNEasy on the FIZ Karlsruhe Database Host and found abstracts
from the COMPENDEX and INSPEC
Database. Thanks for their copyright permission for UTonline. Also thanks to
the NDT Literature Service of the BAM for their
32 German abstracts of international literature.
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UT
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Internet Search Engines turned out many results for TOFD, however most of them were advertisements without much information. The only 'real' links pointed to UTonline and to the TOFD on the Surrey University Homepage by Dr. Shaun Lawson, which had been listed for some time in the NDT Library. One reply to our Newsgroup question contained the Homepage of CATS International (ZA), an excellent resource which led us to the article by
Bill Browne shown here.
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