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- since 1996 -
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Technical Discussions
Simon
Simon
10:33 Jan-17-2019
Purpose of using 30 degree probe in Ultrasonic Testing

Hi everybody,
Please help me to understand the purpose of using 30 degree probe in Ultrasonic Testing
Thanks !

 
 Reply 
 
Anmol Birring
Consultant,
Birring NDE Center, Inc., USA, Joined Aug 2011, 755

Anmol Birring

Consultant,
Birring NDE Center, Inc.,
USA,
Joined Aug 2011
755
12:10 Jan-19-2019
Re: Purpose of using 30 degree probe in Ultrasonic Testing
In Reply to Simon at 10:33 Jan-17-2019 (Opening).

Bad Choice.
This is close to the 1st critical angle of 32.6 degrees. shear wave drops at angles below 40 degrees

 
 Reply 
 
Neil Burleigh
Sales
Krautkramer Australia Pty Ltd, Australia, Joined Dec 2002, 158

Neil Burleigh

Sales
Krautkramer Australia Pty Ltd,
Australia,
Joined Dec 2002
158
23:44 Jan-20-2019
Re: Purpose of using 30 degree probe in Ultrasonic Testing
In Reply to Simon at 10:33 Jan-17-2019 (Opening).

If my memory serves me this wedge designation was mainly used in the USA and the sound wave produced was a 30 degree shear wave in carbon steel, not much use for most people.
But it also produced a high angle 'L' wave in stainless steel and it also produced 'creeping' waves

regards

Neil Burleigh

 
 Reply 
 
Bruce McPherson
Consultant
MFL Services, United Kingdom, Joined Mar 2009, 26

Bruce McPherson

Consultant
MFL Services,
United Kingdom,
Joined Mar 2009
26
09:03 Jan-21-2019
Re: Purpose of using 30 degree probe in Ultrasonic Testing
In Reply to Simon at 10:33 Jan-17-2019 (Opening).

We used them successfully to detect longitudinal cracks on the bore of thick walled steel pipe.
The beam from a typical shear wave probe, when placed on the outer surface of the pipe would simply not intersect the internal surface of the pipe and was therefore unable to detect the cracks.
We used several probes in the 20-30 degree range depending on the actual thickness of the pipe.
We called them "angled compression probes", but I'm not sure if this is the correct technical term for them

 
 Reply 
 
Edward Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1282

Edward Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1282
13:58 Jan-21-2019
Re: Purpose of using 30 degree probe in Ultrasonic Testing
In Reply to Neil Burleigh at 23:44 Jan-20-2019 .

Neil, your recollection of the old days reminded me that the probe and the technique used to be called the 30-70-70. Some people today like to call this a creeping wave probe. The 30° shear is subcritical so has a bulk compression mode associated with it that has an angle of refraction of approximately 70°.
There is a good description of the various options for dissimilar metal weld inspections provided in a paper in a 1996 edition of NDT.net https://www.ndt.net/article/pow1297/schmid/schmid1.htm#4213

 
 Reply 
 

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