|Ingolf Hertlin |
Classification of NDT methods
I would like to know if it is possible to classify NDT methods into VOLUME ORIENTED METHODS and SURFACE ORIENTED METHODS and whether the following assignment of commonly used NDT methods is correct:
1) VOLUME ORIENTED METHODS
- resonant analysis
- sound emission
2) SURFACE ORIENTED METHODS
- dye penetrant
- eddy current
- magnetic particle
- visual inspection
Are there other important methods that are not assigned?
Any comment welcome!
RTE Akustik + Prueftechnik GmbH
|Dave Utrata |
R & D,
Center for NDE, Iowa State University, USA, Joined Feb 2000, 37
Re: Classification of NDT methods I'm sure you will get many different responses to this question; I have to wonder why you would want to perform such a classification to begin with. The analysis seems to focus on surface or volumetirc FLAW detection, which is troublesome to my way of thinking.
Yes, eddy current will find surface flaws, but is also invaluable for material characterization. Ultrasonic velocity/attenuation measurement for this is likewise overlooked.
In my perspective (and I often teach the subject of NDE/T to non-NDE/T personnel) is that each tool has a different purpose, complete with its own advantages and limitations. Sometimes the overlap between methods is messy, but that's life, and we take a closer look at needs and cost constraints.
Interesting post, and as with many posts here, it opens a broader discussion.
|Jamie Gauthier |
Re: Classification of NDT methods This will be quite the "can of worms". There are many ways to determine surface and volumetric flaws. An inspection technique that would fall under UT would be TOFD (Time of Flight Diffraction). This is an excellent tool for volumetric and flaw sizing.
I apologize if this was already assumed under the heading UT.
Electronics Service/IT Support Manager
Advanced NDE Division
RTD Quality Services Inc.
|Peter Philipp |
PQS, United Kingdom, Joined Jan 2002, 7
Re: Classification of NDT methods Re Classification of NDT methods.
There is a new method of NDT that you have not included. It is Long Lange ultrasonics using guided waves.
More information can be found on the Guided Ultrasonics Ltd website.
This method is a Volume method as it screens 100% of the pipe material for the diagnostic length which can be up to 75m in each direction from the test location.
|D. Robert Hay |
TISEC Inc., Canada, Joined Apr 2002, 3
Re: Classification of NDT methods The classification you propose is a basic distinction that is or should be pointed out in NDT courses. The "surface-oriented" methods indeed limited to either surface-breaking flaws or those subsurface defects that can be detected by some physical manifestation at the surface. Finally, these methods are not useful for defects that are deeper into the material.
So what you are saying is correct. Perhaps if you can tweak the terminology somewhat it would be better. The term surface implies two dimensional whereas these surface-breaking flaws are not 2-dimensional. And voumentric implies 3-D. So this terminology may not be appropriate.
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