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Volume Graphics GmbH
Leading industrial companies around the world look for defects in their products using Volume Graphics software.

6369 views
00:26 Apr-02-2007
Sunny
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


 
04:50 Apr-03-2007

Nigel Armstrong

Engineering, - Specialist services
United Kingdom,
Joined Oct 2000
1094
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 ------------




 
04:55 Apr-03-2007
Sunny
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?




 
04:58 Apr-04-2007

Roberto Falconio

Engineering, NDT/Metrology SUPERVISOR
El Salvador,
Joined Feb 2000
13
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 ------------




 
03:40 Apr-05-2007

A. Anev

Teacher, NDT instructor
Vector NDT Ltd.,
Bulgaria,
Joined Nov 1998
2
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 ------------




 
01:49 Apr-11-2007

Afshin

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




 
09:52 Apr-11-2007
P V SASTRY
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 ------------




 
04:11 Apr-18-2007

Debdutta Mallik

Consultant,
Malaysia,
Joined Jun 2005
37
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


 
04:22 Apr-18-2007

TomNelligan

Engineering,
retired,
USA,
Joined Nov 1998
390
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 ------------




 
05:36 Apr-18-2007

Joe Buckley

Consultant, ASNT L-III, Honorary Secretary of BINDT
Level X NDT, BINDT,
United Kingdom,
Joined Oct 1999
515
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 ------------




 
06:27 Apr-18-2007
Larry Mullins , E-mail:
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 ------------




 
00:44 Apr-20-2007

Debdutta Mallik

Consultant,
Malaysia,
Joined Jun 2005
37
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


 
01:30 Apr-20-2007
Dhirender Singh , E-mail:
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 ------------




 
00:15 Apr-23-2007
constant chuma , E-mail:
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 ------------




 
06:39 Sep-14-2007
Lucy McDuff
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.




 


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