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Technical Discussions
mohsen
NDT Inspector,
arta industry testing, Iran, Joined Jan 2013, 19

mohsen

NDT Inspector,
arta industry testing,
Iran,
Joined Jan 2013
19
16:38 Jan-23-2013
the problem with probe 60

hi
when i calibrate my ut set with various angle probs i check them with ledge of calibration block until i be sure that my calibration is true. this work will respond for probe 45 & 70 and UT set illustrate true depth and distance front of the probe but when i do this work with prob 60 i'm having trouble! why is this and UT set can't illustrate true values? This does not cause any problem in work? What can be done to fix the problem? thanks for your responds..

    
 
 Reply 
 
James Scalf
NDT Inspector,
Global Integrity, Canada, Joined Oct 2012, 273

James Scalf

NDT Inspector,
Global Integrity,
Canada,
Joined Oct 2012
273
20:55 Jan-23-2013
Re: the problem with probe 60
In Reply to mohsen at 16:38 Jan-23-2013 (Opening).

Mohsen,

Have you checked the true angle of the sound path for your 60 degree probe on a calibration block? If it is out by even +/-2 degrees (which is why there is an acceptable varience for most probes of +/- 2 Degrees) then your distance measurements could be out. If you are inputting 60 degrees into your machine and it is calculating the trigonometry with that value but your actual probe sound path angle is say 56 degrees, your machine will give you a measurement based on wrong data as measured.

Another possibility is if you are using a shearwave transducer with a shearwave angulation based on the wrong material type (Snell's Law) if the angulation was manufactured into it to be used on 1018 steel and now you are trying to use it on 7075 Aluminium again you will haev erronious measurements.

    
 
 Reply 
 
Fernando
NDT Inspector,
Brazil, Joined Jan 2011, 4

Fernando

NDT Inspector,
Brazil,
Joined Jan 2011
4
21:28 Jan-23-2013
Re: the problem with probe 60
In Reply to mohsen at 16:38 Jan-23-2013 (Opening).

Mr. James,

The 60 degrees probe can also provide some trouble because the ultrasonic wave is more likely to strikes a medium boundary at an angle near to the critical angle.

Have you ever had some troubles due to what I mentioned above?




    
 
 Reply 
 
mohsen
NDT Inspector,
arta industry testing, Iran, Joined Jan 2013, 19

mohsen

NDT Inspector,
arta industry testing,
Iran,
Joined Jan 2013
19
22:15 Jan-23-2013
Re: the problem with probe 60
In Reply to James Scalf at 20:55 Jan-23-2013 .

Mr James
all my probe sets (45,60,70 degrees) are sona test. my machine is sona test ( model 350) too. my calibration block is steel. but I'm having problem with calibration of probes 60 degrees 2&4 Mhz. I always must give 52 degree angle! in machine until I recieve true values. you can check this issue with your sets..

    
 
 Reply 
 
bobtwodogs
bobtwodogs
23:28 Jan-23-2013
Re: the problem with probe 60
In Reply to mohsen at 22:15 Jan-23-2013 .

Have you tried a different 60 probe and made a comparision ?

    
 
 Reply 
 
john
john
23:31 Jan-23-2013
Re: the problem with probe 60
In Reply to mohsen at 16:38 Jan-23-2013 (Opening).

my understanding of your question:
you have calibrated your 60 deg probe on cal block and are trying to confirm the cal on the edge of cal block using corner trap?

Do not use corner trap to verify. use instead the sdh in the cal block, as a "corner trap" signal is not the actual corner being reflected.

    
 
 Reply 
 
mohsen
NDT Inspector,
arta industry testing, Iran, Joined Jan 2013, 19

mohsen

NDT Inspector,
arta industry testing,
Iran,
Joined Jan 2013
19
00:02 Jan-24-2013
Re: the problem with probe 60
In Reply to john at 23:31 Jan-23-2013 .

dear john
then what when I want to test the thick specimen that I know it has LOP?what can I recognise true depth of LOP? I faced very much to this issue and before start of test I forced calibrated my machine with ledge of specimen! otherwise my results is false

    
 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1268

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1268
00:26 Jan-24-2013
Re: the problem with probe 60
In Reply to mohsen at 16:38 Jan-23-2013 (Opening).

zoom image
Moshen, I suspect Fernando's reply may hold the clue to your problem. Echo-transmittance losses due to the reflection of the 60° beam from the vertical face of the block will result in a non-symmetrical response relative to the beampath to the corner. Attached is a Civa simulation plot. It shows that the peak response of the 60 does not occur with a soundpath that travels to the corner (bottom) of the plate. Instead, the peak will occur at a point closer to the corner and with a soundpath less than the calculated hypotenuse.
If your range amd exit point are correct as confirmed on the 100mm radius of the IIW block and the angle confirmed using the hole in the IIW block, that is the best check. a corner reflector will not be a reliable tool for the depth with 60°
    
 
 Reply 
 
Carlos Correia
R & D, - -
UCV & EGROUP, Venezuela, Joined Oct 2008, 120

Carlos Correia

R & D, - -
UCV & EGROUP,
Venezuela,
Joined Oct 2008
120
01:36 Jan-24-2013
Re: the problem with probe 60
In Reply to Ed Ginzel at 00:26 Jan-24-2013 .

"...; an angle wedge produces an asymmetric sound beam along the axis of refraction. Asymmetry causes variation in signal amplitude and beam width as a function of angular position. As the refracted angle increases, signal amplitude decreases and greather beam widths are observed." Moles, Sjerve,. PHASED ARRAY IIW HANDBOOK,PAG 7.

    
 
 Reply 
 
Nigel Armstrong
Engineering, - Specialist services
United Kingdom, Joined Oct 2000, 1096

Nigel Armstrong

Engineering, - Specialist services
United Kingdom,
Joined Oct 2000
1096
09:59 Jan-24-2013
Re: the problem with probe 60
In Reply to Carlos Correia at 01:36 Jan-24-2013 .

Thanks to Ed for his sterling work to shed light on the mysteries of UT and to Carlos for pointing the way to the Moles / Sjerve IIW book.

    
 
 Reply 
 
mohsen
NDT Inspector,
arta industry testing, Iran, Joined Jan 2013, 19

mohsen

NDT Inspector,
arta industry testing,
Iran,
Joined Jan 2013
19
10:46 Jan-24-2013
Re: the problem with probe 60
In Reply to Ed Ginzel at 00:26 Jan-24-2013 .

Thanks for your excellent answer. and now what is your solution to my problem? The actual angle probe down to 52 degrees to receive the right depth of LOP?

    
 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1268

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1268
13:40 Jan-24-2013
Re: the problem with probe 60
In Reply to mohsen at 10:46 Jan-24-2013 .

Moshen, I think a way forward is to look at your specific flaw location and use this understanding to select the best option. For lack of side-wall fusion, the 60° beam will be OK. For incomplete penetration it will produce the error illustrated. The error in depth position will increase with a increasing vertical extent of the incomplete penetration. If you suspect the flaw to be incomplete penetration in a single V weld, the flaw is surface connected. You should know that its depth is the plate thickness. Confirm the characterisation and correct depth with a 45° beam.

    
 
 Reply 
 
mohsen
NDT Inspector,
arta industry testing, Iran, Joined Jan 2013, 19

mohsen

NDT Inspector,
arta industry testing,
Iran,
Joined Jan 2013
19
15:27 Jan-24-2013
Re: the problem with probe 60
In Reply to Ed Ginzel at 13:40 Jan-24-2013 .

Ed thanks for your guide, now I can explain this issue to my employer.. can I ask another question? I'm working on a project that relate to CNG cylinders of cars. we can only inspect them with VT equipment now and we want progress our tests with another method, do you have any information in this matter? for example AE or UT we think is suitable. what's your opinion? thanks a lot..

    
 
 Reply 
 

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