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- since 1996 -

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Technical Discussions
vikar
NDT Inspector
India, Joined Jan 2004, 1

vikar

NDT Inspector
India,
Joined Jan 2004
1
08:35 Jan-13-2004
flaw sizeing

how to size a flaw .need information ,books,notes help me.
for both normal beam &angle beam .
this is very basic.iam new in this field


 
 Reply 
 
J. Mark Davis
Teacher, And Consultant
University of Ultrasonics, Birmingham, Alabama, USA, Joined Mar 2000, 85

J. Mark Davis

Teacher, And Consultant
University of Ultrasonics, Birmingham, Alabama,
USA,
Joined Mar 2000
85
01:54 Jan-13-2004
Re: flaw sizing
Go the the www.ndt.net web site. Go to the publications section to review the Advanced UT Flaw Sizing Handbook.

This will outline some advanced UT Sizing Methods such as ID Creeping Waves, Tip Diffraction, Bi-Modal and High Angle Focused L Wave (HALT Probe), and Focused Shear Wave (HAST Probe) Techniques.

Sincerely,

J. Mark Davis

----------- Start Original Message -----------
: how to size a flaw .need information ,books,notes help me.
: for both normal beam &angle beam .
: this is very basic.iam new in this field
------------ End Original Message ------------




 
 Reply 
 
Mike
Mike
00:07 Jan-14-2004
Re: flaw sizeing
----------- Start Original Message -----------
: how to size a flaw .need information ,books,notes help me.
: for both normal beam &angle beam .
: this is very basic.iam new in this field
------------ End Original Message ------------

First, book a training course...


 
 Reply 
 
N. Kuppusamy
Consultant, NDT Level-III Engineer
Advanced Inspection & Testing (S) Pte Ltd, Singapore, Joined Dec 2003, 34

N. Kuppusamy

Consultant, NDT Level-III Engineer
Advanced Inspection & Testing (S) Pte Ltd,
Singapore,
Joined Dec 2003
34
03:33 Jan-14-2004
Re: flaw sizeing
Mr.Vikar,

You can get the information regarding Defect sizing in any standard book on Ultrasonic Testing. API RP 2X also gives guidelines for flaw sizing. The advanced Ultrasonic Flaw sizing Handbook by J.Mark Davis also very useful ( available from www.astn.org ).

Basically there are 3 methods of flaw sizing:

1. Beam Boundary Intercept Technique
a. 6dB drop method.
b. 20 dB drop method

2. Maximum Amplitude Drop method

3. Amplitude comparison Technique
a. constructing DAC and comparing defect with it.
b. Employing DGS (Distance, Gain & Sizeing)scale.

The 6db drop & 20dB method are good for the determination of defect size greater than beam width, espicially length. The 6dB and 20dB beam profile should be used to minimize the error.

The maximum Amplitude drop method should be used with care to avoid sizing in the near zone. Probes with high diameter-to-wavelength ratio are prefered to use this technique.

The most important aspect of ultrasonic testing is the experience. You must practice a lot with test pieces and blocks with artificial defects using various probes ( frequency, size, angle ). Practicing under the supervision of experienced technician is highly valuable. Over the period you will master in defect evaluation and sizing.

Regards,

N.Kuppusamy

----------- Start Original Message -----------
: how to size a flaw .need information ,books,notes help me.
: for both normal beam &angle beam .
: this is very basic.iam new in this field
------------ End Original Message ------------




 
 Reply 
 
Nitin
Nitin
06:39 Oct-04-2012
Re: flaw sizeing
In Reply to N. Kuppusamy at 03:33 Jan-14-2004 .

N. Kuppusamy Sir,
My query is in the regarding of 6 dB drop method.
Is there any posibility of finding the oversize or under size of a defect using 6dB drop method even if the method is ideally used???

 
 Reply 
 
Andrew Cunningham
NDT Inspector
Canada, Joined Jun 2008, 239

Andrew Cunningham

NDT Inspector
Canada,
Joined Jun 2008
239
00:12 Oct-05-2012
Re: flaw sizeing
In Reply to Nitin at 06:39 Oct-04-2012 .

My query is in the regarding of 6 dB drop method.
Is there any possibility of finding the oversize or under size of a defect using 6dB drop method even if the method is ideally used???

6dB drop does not work on any natural defects, unless it has square ends. (To prove a point, try and size the 50mm SDH in the IIW V1.) 6dB drop can undersize, lack of root fusion, lack of side wall fusion, lack of inter pass fusion and cracks if the ends taper or twist. It is OK for porosity and laminations. Each type of defect should be sized with a technique that suits the defect. It is all too easy to say one method suits all. But in the real world there is no such method.
I would strongly recommend that you learn “defect characterization” first, and then you can learn the sizing methods to suit each type of defect. Also be aware of books with pseudo-science and their false claims.
There is a lot written in this forum about sizing methods, that you have access to free of charge.

 
 Reply 
 

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