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Technical Discussions
Sunny
Sunny
00:26 Apr-02-2007
Dead Zone calculations

Could anyone explain how to calculate the dead zone on particular material for the Straight beam inspection. I understand it vary with transducer/instrument . What could be the general way how getting its extent.

Thanks


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

Nigel Armstrong

Engineering, - Specialist services
United Kingdom,
Joined Oct 2000
1096
04:50 Apr-03-2007
Re: Dead Zone calculations
Sunny

Dead zone is demonstrated by use of a block of the same material provided with near surface side-drilled holes. The depth at which you first obtain a discernible response from one of the holes will identify the extent of the dead zone for the instrument/probe/material combination.


----------- Start Original Message -----------
: Could anyone explain how to calculate the dead zone on particular material for the Straight beam inspection. I understand it vary with transducer/instrument . What could be the general way how getting its extent.
: Thanks
------------ End Original Message ------------




 
 Reply 
 
Sunny
Sunny
04:55 Apr-03-2007
Re: Dead Zone calculations
----------- Start Original Message -----------
: Sunny
: Dead zone is demonstrated by use of a block of the same material provided with near surface side-drilled holes. The depth at which you first obtain a discernible response from one of the holes will identify the extent of the dead zone for the instrument/probe/material combination.
:
: : Could anyone explain how to calculate the dead zone on particular material for the Straight beam inspection. I understand it vary with transducer/instrument . What could be the general way how getting its extent.
: : Thanks
------------ End Original Message ------------
Nigel,

What about using Flat Bottom Holes?




 
 Reply 
 
Roberto Falconio
Engineering, NDT/Metrology SUPERVISOR
El Salvador, Joined Feb 2000, 13

Roberto Falconio

Engineering, NDT/Metrology SUPERVISOR
El Salvador,
Joined Feb 2000
13
04:58 Apr-04-2007
Re: Dead Zone calculations
Hey guys,
Just my opinion, As far as I'm concern inmediately you plug the transducer you will appreciate that the initial pulse is some kind of wider making as a traingle shape (somtimes gets more irregular shapes), specially if your range is decreased. Under this conditions you can count the number of divisions between the flank of the initial pulse and where the "other traingle side" strikes the horizontal axis of the LCD. This is supposetly your dead zone area cause you may not display where an echo start in this zone (talking about the equipment). You may probably appreciate sometimes some echos peaks however you cannot discern where does its flanks are (always inside that zone). Nigel method might be more useful as you are testing with real discontinuities so you would expect to find a specific range. Just let me me know if its coincide with the area I'm talking about
Regards

----------- Start Original Message -----------
: : Sunny
: : Dead zone is demonstrated by use of a block of thesame material provided with near surface side-drilled holes. The depth at which you first obtain a discernible response from one of the holes will identify the extent of the dead zone for the instrument/probe/material combination.
: :
: : : Could anyone explain how to calculate the dead zone on particular material for the Straight beam inspection. I understand it vary with transducer/instrument . What could be the general way how getting its extent.
: : : Thanks
: Nigel,
: What about using Flat Bottom Holes?
------------ End Original Message ------------




 
 Reply 
 
A. Anev
Teacher, NDT instructor
Vector NDT Ltd., Bulgaria, Joined Nov 1998, 2

A. Anev

Teacher, NDT instructor
Vector NDT Ltd.,
Bulgaria,
Joined Nov 1998
2
03:40 Apr-05-2007
Re: Dead Zone calculations
The dead zone is measured for each system (transducer+cable+instrument) separately. And it would depend on the instrument gain and the required registration level (in terms of artificial flaw dimensions) for the given task. If you try to calculate it theoretically, the result may be very far away from the reality.
Is it possible that you need to calculate the near field length? excuse me for the question if this is not the case, but I saw many examples of these 2 terms misinterpreted.


----------- Start Original Message -----------
: Could anyone explain how to calculate the dead zone on particular material for the Straight beam inspection. I understand it vary with transducer/instrument . What could be the general way how getting its extent.
: Thanks
------------ End Original Message ------------




 
 Reply 
 
Afshin
Consultant, NDT/QC/WELD INSPECTION
Iran, Joined Nov 2005, 20

Afshin

Consultant, NDT/QC/WELD INSPECTION
Iran,
Joined Nov 2005
20
01:49 Apr-11-2007
Re: Dead Zone calculations
DEAR FRIEND,
FOR PRACTICAL DEAD ZONE CALCULATION,YOU CAN USE OF V1 BLOCK IN
AREA NEAR TO 50 mm DIA. PERSPEX .
---- Start Original Message -----------
: Could anyone explain how to calculate the dead zone on particular material for the Straight beam inspection. I understand it vary with transducer/instrument . What could be the general way how getting its extent.
: Thanks
------------ End Original Message ------------




 
 Reply 
 
P V SASTRY
P V SASTRY
09:52 Apr-11-2007
Re: Dead Zone calculations
Dear Sunny,

In pulse echo technique it varies with the gain setting too. So I advise not to bother too much about calculating the dead zone.

P V SASTRY

----------- Start Original Message -----------
: DEAR FRIEND,
: FOR PRACTICAL DEAD ZONE CALCULATION,YOU CAN USE OF V1 BLOCK IN
: AREA NEAR TO 50 mm DIA. PERSPEX .
: ---- Start Original Message -----------
: : Could anyone explain how to calculate the dead zone on particular material for the Straight beam inspection. I understand it vary with transducer/instrument . What could be the general way how getting its extent.
: : Thanks
------------ End Original Message ------------




 
 Reply 
 
Debdutta Mallik
Consultant,
Malaysia, Joined Jun 2005, 37

Debdutta Mallik

Consultant,
Malaysia,
Joined Jun 2005
37
04:11 Apr-18-2007
Re: Dead Zone calculations
Dear Friends,
Dead zone is a property of probe.So far I know it's not the property of instrument.Dead zone is the difference between electrical zero and real zero. Calculation may be very difficult unless having the step blocks.
Further informations are awaited related to the above.I'll be glad to know if there is any formulae for this.

Thanks,


Debdutta Mallik


 
 Reply 
 
TomNelligan
Engineering,
retired, USA, Joined Nov 1998, 390

TomNelligan

Engineering,
retired,
USA,
Joined Nov 1998
390
04:22 Apr-18-2007
Re: Dead Zone calculations
Dead zone -- the interval following the excitation pulse in which potential exchoes are obscured by ringdown -- is a property of BOTH the probe and the instrument. The response of any transducer is highly dependent on how it its pulsed. Changing pulse energy, type (spike, square wave, or tone burst), and damping, as well as receiver gain and filtering, will have a significant effect on the excitation pulse ringdown envelope and hence on dead zone length.

As others have suggested, your best approach is to simply measure it under your actual test conditions using appropriate reference blocks.

----------- Start Original Message -----------
: Dear Friends,
: Dead zone is a property of probe.So far I know it's not the property of instrument.Dead zone is the difference between electrical zero and real zero. Calculation may be very difficult unless having the step blocks.
: Further informations are awaited related to the above.I'll be glad to know if there is any formulae for this.
: Thanks,
:
: Debdutta Mallik
------------ End Original Message ------------




 
 Reply 
 
Joe Buckley
Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT, United Kingdom, Joined Oct 1999, 523

Joe Buckley

Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT,
United Kingdom,
Joined Oct 1999
523
05:36 Apr-18-2007
Re: Dead Zone calculations
I think there is a lot of confusion here, but Tom is absolutely correct.

The point which needs to be stressed is that Dead Zone is not something that could be calculated. It is the RESULT of a large number of factors, some of which will be difficult or impossible to measure/estimate. So the only valid approach is an empirical measurement, which will then apply only to the probe, instrument and test material combination.
Joe

----------- Start Original Message -----------
: Dead zone -- the interval following the excitation pulse in which potential exchoes are obscured by ringdown -- is a property of BOTH the probe and the instrument. The response of any transducer is highly dependent on how it its pulsed. Changing pulse energy, type (spike, square wave, or tone burst), and damping, as well as receiver gain and filtering, will have a significant effect on the excitation pulse ringdown envelope and hence on dead zone length.
: As others have suggested, your best approach is to simply measure it under your actual test conditions using appropriate reference blocks.
: : Dear Friends,
: : Dead zone is a property of probe.So far I know it's not the property of instrument.Dead zone is the difference between electrical zero and real zero. Calculation may be very difficult unless having the step blocks.
: : Further informations are awaited related to the above.I'll be glad to know if there is any formulae for this.
: : Thanks,
: :
: : Debdutta Mallik
------------ End Original Message ------------




 
 Reply 
 
Larry Mullins , E-mail:
Larry Mullins , E-mail:
06:27 Apr-18-2007
Re: Dead Zone calculations
Lest we forget, we need to throw in surface roughness, interface shape (e.g. concave/convex) and couplant thickness / variability. Crunch those numbers if you dare! I'm with Tom and Joe.

----------- Start Original Message -----------
: I think there is a lot of confusion here, but Tom is absolutely correct.
: The point which needs to be stressed is that Dead Zone is not something that could be calculated. It is the RESULT of a large number of factors, some of which will be difficult or impossible to measure/estimate. So the only valid approach is an empirical measurement, which will then apply only to the probe, instrument and test material combination.
: Joe
: : Dead zone -- the interval following the excitation pulse in which potential exchoes are obscured by ringdown -- is a property of BOTH the probe and the instrument. The response of any transducer is highly dependent on how it its pulsed. Changing pulse energy, type (spike, square wave, or tone burst), and damping, as well as receiver gain and filtering, will have a significant effect on the excitation pulse ringdown envelope and hence on dead zone length.
: : As others have suggested, your best approach is to simply measure it under your actual test conditions using appropriate reference blocks.
: : : Dear Friends,
: : : Dead zone is a property of probe.So far I know it's not the property of instrument.Dead zone is the difference between electrical zero and real zero. Calculation may be very difficult unless having the step blocks.
: : : Further informations are awaited related to the above.I'll be glad to know if there is any formulae for this.
: : : Thanks,
: : :
: : : Debdutta Mallik
------------ End Original Message ------------




 
 Reply 
 
Debdutta Mallik
Consultant,
Malaysia, Joined Jun 2005, 37

Debdutta Mallik

Consultant,
Malaysia,
Joined Jun 2005
37
00:44 Apr-20-2007
Re: Dead Zone calculations
Yes I agree with Tom and you also. Its a result of lot of factors related to instrment,probe etc and it cant be calculated on paper.

Regards,


Debdutta Mallik


 
 Reply 
 
Dhirender Singh , E-mail:
Dhirender Singh , E-mail:
01:30 Apr-20-2007
Re: Dead Zone calculations
It is determined by the characteristics of search unit, the ultrasonic instrumentation, and the test object.


---------- Start Original Message -----------
: DEAR FRIEND,
: FOR PRACTICAL DEAD ZONE CALCULATION,YOU CAN USE OF V1 BLOCK IN
: AREA NEAR TO 50 mm DIA. PERSPEX .
: ---- Start Original Message -----------
: : Could anyone explain how to calculate the dead zone on particular material for the Straight beam inspection. I understand it vary with transducer/instrument . What could be the general way how getting its extent.
: : Thanks
------------ End Original Message ------------




 
 Reply 
 
constant chuma , E-mail:
constant chuma , E-mail:
00:15 Apr-23-2007
Re: Dead Zone calculations
----------- Start Original Message -----------
: The dead zone is measured for each system (transducer+cable+instrument) separately. And it would depend on the instrument gain and the required registration level (in terms of artificial flaw dimensions) for the given task. If you try to calculate it theoretically, the result may be very far away from the reality.
: Is it possible that you need to calculate the near field length? excuse me for the question if this is not the case, but I saw many examples of these 2 terms misinterpreted.
:
: : Could anyone explain how to calculate the dead zone on particular material for the Straight beam inspection. I understand it vary with transducer/instrument . What could be the general way how getting its extent.
: : Thanks
------------ End Original Message ------------




 
 Reply 
 
Lucy McDuff
Lucy McDuff
06:39 Sep-14-2007
Re: Dead Zone calculations
----------- Start Original Message -----------
: Lest we forget, we need to throw in surface roughness, interface shape (e.g. concave/convex) and couplant thickness / variability. Crunch those numbers if you dare! I'm with Tom and Joe.
: : I think there is a lot of confusion here, but Tom is absolutely correct.
: : The point which needs to be stressed is that Dead Zone is not something that could be calculated. It is the RESULT of a large number of factors, some of which will be difficult or impossible to measure/estimate. So the only valid approach is an empirical measurement, which will then apply only to the probe, instrument and test material combination.
: : Joe
: : : Dead zone -- the interval following the excitation pulse in which potential exchoes are obscured by ringdown -- is a property of BOTH the probe and the instrument. The response of any transducer is highly dependent on how it its pulsed. Changing pulse energy, type (spike, square wave, or tone burst), and damping, as wellas receiver gain and filtering, will have a significant effect on the excitation pulse ringdown envelope and hence on dead zone length.
: : : As others have suggested, your best approach is to simply measure it under your actual test conditions using appropriate reference blocks.
: : : : Dear Friends,
: : : : Dead zone is a property of probe.So far I know it's not the property of instrument.Dead zone is the difference between electrical zero and real zero. Calculation may be very difficult unless having the step blocks.
: : : : Further informations are awaited related to the above.I'll be glad to know if there is any formulae for this.
: : : : Thanks,
: : : :
: : : : Debdutta Mallik
------------ End Original Message ------------

Ha ha, very clever Mr. Mullins, but you haven't contributed an answer.




 
 Reply 
 

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