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langtuteng2
Armenia, Joined Nov 2014, 196

langtuteng2

Armenia,
Joined Nov 2014
196
16:42 Jun-05-2019
strange phenomenon for TCG curve construction using SX and PA PROBE

Hi, today I construct a TCG curve for S scan, angle from 40 degree to 75 degree, angle resolution is 1 degree, and use Olympus OmniScan SX PAUT equipment, 5L64A32 probe and SA32-N55S wedge, and the reflectors are side drilled holes whose depth are 10mm, 20mm, 30mm and 40mm, the material of block is mild steel. After I set the essential parameters and calibrate velocity, delay and sensitivity, I found the echo comes from 20mm depth SDH was much lower than 10mm SDH. also, the echo comes from 20mm depth SDH was much lower than 30mm SDH. it is so strange.
could anyone know the reason. thanks in advance

 
 Reply 
 
Ali
NDT Inspector,
Iran, Joined Mar 2013, 109

Ali

NDT Inspector,
Iran,
Joined Mar 2013
109
20:21 Jun-05-2019
Re: strange phenomenon for TCG curve construction using SX and PA PROBE
In Reply to langtuteng2 at 16:42 Jun-05-2019 (Opening).

What was the focal depth? Which reflectors you have selected for sensitivity calibration? Can you upload some photos of S-Scan before and after calibrations?

 
 Reply 
 
rarseneau
rarseneau
21:02 Jun-05-2019
Re: strange phenomenon for TCG curve construction using SX and PA PROBE
In Reply to langtuteng2 at 16:42 Jun-05-2019 (Opening).

It likely has to do with your focal depth as Ali stated. You are going to get your best response where you are focusing.

 
 Reply 
 
R
,
Inspections X-ray And testing, Australia, Joined Mar 2019, 2

R

,
Inspections X-ray And testing,
Australia,
Joined Mar 2019
2
00:34 Jun-06-2019
Re: strange phenomenon for TCG curve construction using SX and PA PROBE
In Reply to langtuteng2 at 16:42 Jun-05-2019 (Opening).

I would have left the focal depth at the default 50 mm. Have you verified your velocity is somewhere around 3200M/S. Langtuteng did you have trouble calibrating the initial velocity?
The 100 and 200 reflectors should have been near perfect when setting the velocity, your calibration error can be caused by selecting depth rather than radius in the Velocity cal step of the wizard.

 
 Reply 
 
langtuteng2
Armenia, Joined Nov 2014, 196

langtuteng2

Armenia,
Joined Nov 2014
196
01:51 Jun-06-2019
Re: strange phenomenon for TCG curve construction using SX and PA PROBE
In Reply to R at 00:34 Jun-06-2019 .

thanks Ali, i used the IIW block to calibrate the velocity, and the velocity is 3226m/s. I think velocity, delay, and sensitivity calibration in wizard are all right. So I don't know why the echo envelope height comes from SDH in depth of 20mm is much lower than SDH in depth of 10mm and 30mm.

 
 Reply 
 
Ali
NDT Inspector,
Iran, Joined Mar 2013, 109

Ali

NDT Inspector,
Iran,
Joined Mar 2013
109
04:38 Jun-06-2019
Re: strange phenomenon for TCG curve construction using SX and PA PROBE
In Reply to langtuteng2 at 01:51 Jun-06-2019 .

Did you adjust dB during TCG calibration for each reflectors? Do you have same problem for other setups?

 
 Reply 
 
langtuteng2
Armenia, Joined Nov 2014, 196

langtuteng2

Armenia,
Joined Nov 2014
196
10:43 Jun-06-2019
Re: strange phenomenon for TCG curve construction using SX and PA PROBE
In Reply to Ali at 04:38 Jun-06-2019 .

I carried out the following steps:
1.adjust the gain, move the probe back and forth smoothly across the SDH whose depth is 10mm, and the highest point on echo envelop is almost 80%FSH, then I chose 'add'. then I move the probe back and forth smoothly across the SDH whose depth is 10mm, the echo envelop was almost 80%FSH;
2. then I chose the 'next point' and 'next' until I move the probe back and forth smoothly across the SDH whose depth is 20mm, and the highest point on echo envelop is almost 15%FSH. (I think this is abnormal. ) then I chose 'add'. then I move the probe back and forth smoothly across the SDH whose depth is 20mm, the echo envelop was almost 80%FSH;
3. then I chose the 'next point' and 'next' until I move the probe back and forth smoothly across the SDH whose depth is 30mm, and the highest point on echo envelop is almost 70%FSH. then I chose 'add'. then I move the probe back and forth smoothly across the SDH whose depth is 30mm, the echo envelop was almost 80%FSH;
So, I think for the depth 20mm, there is some abnormal during constructing TCG

 
 Reply 
 
Andrej
ApplusRtd, Lithuania, Joined May 2019, 9

Andrej

ApplusRtd,
Lithuania,
Joined May 2019
9
12:20 Jun-06-2019
Re: strange phenomenon for TCG curve construction using SX and PA PROBE
In Reply to langtuteng2 at 10:43 Jun-06-2019 .

Did you check dead elements and be sure the paste is good enough.

 
 Reply 
 
Ali
NDT Inspector,
Iran, Joined Mar 2013, 109

Ali

NDT Inspector,
Iran,
Joined Mar 2013
109
14:27 Jun-06-2019
Re: strange phenomenon for TCG curve construction using SX and PA PROBE
In Reply to langtuteng2 at 10:43 Jun-06-2019 .

Maybe there is some wrong with reflector that located on 20mm depth.Try with another TCG block.

 
 Reply 
 
langtuteng
Armenia, Joined Nov 2014, 196

langtuteng

Armenia,
Joined Nov 2014
196
15:41 Jun-06-2019
Re: strange phenomenon for TCG curve construction using SX and PA PROBE
In Reply to Andrej at 12:20 Jun-06-2019 .

thanks.before TCG construction, I have checked the dead element and all elements are working. paste is also good enough.

 
 Reply 
 
langtuteng
Armenia, Joined Nov 2014, 196

langtuteng

Armenia,
Joined Nov 2014
196
15:43 Jun-06-2019
Re: strange phenomenon for TCG curve construction using SX and PA PROBE
In Reply to Ali at 14:27 Jun-06-2019 .

thanks, I will try again with other block

 
 Reply 
 
Andrej
ApplusRtd, Lithuania, Joined May 2019, 9

Andrej

ApplusRtd,
Lithuania,
Joined May 2019
9
15:53 Jun-06-2019
Re: strange phenomenon for TCG curve construction using SX and PA PROBE
In Reply to langtuteng at 15:43 Jun-06-2019 .

If you tried to change from skew90 to skew270, checked the probe and wedge, then probably TCG block is the reason.

 
 Reply 
 
Wellsy
,
Inspections X-ray And testing, Australia, Joined Mar 2019, 2

Wellsy

,
Inspections X-ray And testing,
Australia,
Joined Mar 2019
2
22:39 Jun-06-2019
Re: strange phenomenon for TCG curve construction using SX and PA PROBE
In Reply to langtuteng at 15:43 Jun-06-2019 .

You've answered your own question. When creating a TCG your aiming to get the amplitude to 80% for each SDH, this requires adding a little gain at each point until the reflector is at 80% screen height.

 
 Reply 
 

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