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Technical Discussions
Frits Dijkstra, RTD bv Rotterdam, NL
R & D
Applus RTD Technological Center, Netherlands, Joined Jan 2004, 6

Frits Dijkstra, RTD bv Rotterdam, NL

R & D
Applus RTD Technological Center,
Netherlands,
Joined Jan 2004
6
04:45 Jan-23-2004
Ultrasonic backscatter flaw sizing

In the November 2003 issue of Insight, Jacques, Moreau and Ginzel claim to have developed a new sizing technique in their article "Ultrasonic backscatter sizing using phased array – developments in tip diffraction flaw sizing". I would like to react to this article, and my statement is that the method is approx. 30 years old.

In the years 1972 to 1975, my company RTD participated in a Dutch Joint Industry project, "Ultrasonic Flaw Sizing". The outcome of this project was presented around 1975 by my late boss Arie de Sterke and myself at various occasions. During a Colloquium of the International Institute of Welding (IIW) on "Nondestructive Determination of Type, Position, Orientation and Size of Weld Defects", I had the privilege of giving a presentation there, entitled "Flaw Evaluation with Particular Reference to Flaw Size Estimation". One of the sizing methods presented was the so called Flaw Tip Reflection Method, capable of sizing defects by using waves scattered by their tips. This method had, apart from machined notches, also been extensively tested on natural defects (lack of side wall fusion, cracks). The method was even commercially used, both in a petrochemical and in a nuclear environment using focused probes. Ironically, all this happened in the same period that Maurice Silk first published about Time of Flight Diffraction.

In the meantime, a lot of technical improvements have opened the door to a much better use of such ideas. Computers have become extremely powerful, transducer technology has improved and phased arrays have been developed. Therefore I sincerely hope that Flaw Tip Reflection / Diffraction / Backscatter (what's in a name?) will be granted a second life.

Regards,

Frits Dijkstra



    
 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1261

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1261
00:57 Jan-26-2004
Re: Ultrasonic backscatter flaw sizing
Frits:
Thank you for your further background on this technique.

But we are not taking credit for the "original idea" of backscatter tip sizing. You will note that the title extention is "-developments in tip diffraction flaw sizing". It was never represented in this paper that the backscatter sizing technique was a "new sizing technique" as you have stated.

If anxious to credit the "original" principles perhaps Huygens (1629-1695) is appropriate. Or more pertinent to the principles of ultrasonics would be Filipczynski in the early 1960s relating to his descriptions of the mode conversion and boundary effects at flaws.

You mentioned that it was a work of RTD in the mid to late 1970s that you participated in for flaw sizing. This parallels activities in other venues on backscatter as well. One of the references we used was a paper by Gruber. He notes in his 1980 paper that Sachse, Beissner & Burkhardt, and Bifulco & Sachse all published papers explaining separation in time of arrival signals off flaw tips in the early to mid 1970s. Excellent work by the Japanese "Tip Diffraction Working Group" of the Japanese soicety for NDI was assembled during the 1980s and was drawn on extensively in our background work.

The purpose of our paper was not to suggest a "new" technique but to show how the old ideas could provide even better results with the new technology of phased array.

The technique described in the Japanese references did not provide a tolerance range but it was indicated that the smallest flaw that could be practically sized then was 4mm. The ability to control the conditions using a phased array probe that requires no physical motion allowed the tolerance to be reduced to less than 1mm and provided reasonable estimates of orientation. Some time ago I posted a topic to the forum that pointed out the ridiculous claims being made by some concerning flaw sizing to 0.3mm "accuracy" using proprietary amplitude sizing techniques. The improvements made to the backscatter technique have not achieved 0.3mm tolerances claimed by some. But the technique is not some dark secret and it is founded on good physics that has been under development for many years.

I too hope that the work done in the past by diligent researchers can continue to add to a broad and sturdy foundation to our developing NDT capabilities.
Ed Ginzel

----------- Start Original Message -----------
: In the November 2003 issue of Insight, Jacques, Moreau and Ginzel claim to have developed a new sizing technique in their article "Ultrasonic backscatter sizing using phased array – developments in tip diffraction flaw sizing". I would like to react to this article, and my statement is that the method is approx. 30 years old.
: In the years 1972 to 1975, my company RTD participated in a Dutch Joint Industry project, "Ultrasonic Flaw Sizing". The outcome of this project was presented around 1975 by my late boss Arie de Sterke and myself at various occasions. During a Colloquium of the International Instituteof Welding (IIW) on "Nondestructive Determination of Type, Position, Orientation and Size of Weld Defects", I had the privilege of giving a presentation there, entitled "Flaw Evaluation with Particular Reference to Flaw Size Estimation". One of the sizing methods presented was the so called Flaw Tip Reflection Method, capable of sizing defects by using waves scattered by their tips. This method had, apart from machined notches, also been extensively tested on natural defects (lack of side wall fusion, cracks). The method was even commercially used, both in a petrochemical and in a nuclear environment using focused probes. Ironically, all this happened in the same period that Maurice Silk first published about Time of Flight Diffraction.
: In the meantime, a lot of technical improvements have opened the door to a much better use of such ideas. Computers have become extremely powerful, transducer technology has improved and phased arrays have been developed. Therefore I sincerely hope that Flaw Tip Reflection / Diffraction / Backscatter (what's in a name?) will be granted a second life.
: Regards,
: Frits Dijkstra
------------ End Original Message ------------




    
 
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