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Technical Discussions
Sunny
Sunny
02:20 Jan-17-2007
Ultrasonic Testing of Round Bars

Just want to make sure with experienced friends that only right way to look for defects inside the round bars volumetrically is to do longitudinal straight beam inspection. Shear wave is going to be good for certain depth only as it is refracted away from the center( depending on diameter). So only outer ring of certain depth( depending on diameter and refracted angle) can be inspected by shear wave.
Please comment.


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

Nigel

Engineering, - Specialist services
United Kingdom,
Joined Oct 2000
1096
06:58 Jan-18-2007
Re: Ultrasonic Testing of Round Bars
Hello Sunny

The most common defect in round bars are "stringers", elongated non-metallic inclusions. These may be detected using a compression wave probe from the O.D. and scanning around the circumference and along the bar's whole length. Make certain that you have good overlap between successive circumferential scans so that the complete volume is completely covered. You can also monitor for a relatively stable backwall response. Any areas where the backwall response changes significantly should be carefully examined.

I cannot see the value in shearwave inspection of a round bar unless you scan along the length looking for opposite-side surface-breaking defects.

Do you not have a procedure and acceptance criteria for this work?


----------- Start Original Message -----------
: Just want to make sure with experienced friends that only right way to look for defects inside the round bars volumetrically is to do longitudinal straight beam inspection. Shear wave is going to be good for certain depth only as it is refracted away from the center( depending on diameter). So only outer ring of certain depth( depending on diameter and refracted angle) can be inspected by shear wave.
: Please comment.
------------ End Original Message ------------




 
 Reply 
 
Rajesh Bose
Engineering, NDT Engineer
BP, USA, Joined Aug 2001, 3

Rajesh Bose

Engineering, NDT Engineer
BP,
USA,
Joined Aug 2001
3
06:24 Jan-18-2007
Re: Ultrasonic Testing of Round Bars
Navi,

The only way to find out volumetric flaws is using straight beam inspection. You can inspect along the circumference with proper overlapand also from the ends of the pipe. Make sure you use the right probe diameter and frequency ( to lessen the beam spread). There is no need for shear wave inspection.Be careful about the mode converted signals.



 
 Reply 
 
Navi
Navi
06:39 Jan-18-2007
Re: Ultrasonic Testing of Round Bars
----------- Start Original Message -----------
: Navi,
: The only way to find out volumetric flaws is using straight beam inspection. You can inspect along the circumference with proper overlapand also from the ends of the pipe. Make sure you use the right probe diameter and frequency ( to lessen the beam spread). There is no need for shear wave inspection.Be careful about the mode converted signals.
------------ End Original Message ------------

Thanks Raj



 
 Reply 
 
Sunny
Sunny
08:07 Jan-18-2007
Re: Ultrasonic Testing of Round Bars
----------- Start Original Message -----------
: Hello Sunny
: The most common defect in round bars are "stringers", elongated non-metallic inclusions. These may be detected using a compression wave probe from the O.D. and scanning around the circumference and along the bar's whole length. Make certain that you have good overlap between successive circumferential scans so that the complete volume is completely covered. You can also monitor for a relatively stable backwall response. Any areas where the backwall response changes significantly should be carefully examined.
: I cannot see the value in shearwave inspection of a round bar unless you scan along the length looking for opposite-side surface-breaking defects.
: Do you not have a procedure and acceptance criteria for this work?
:
: : Just want to make sure with experienced friends that only right way to look for defects inside the round bars volumetrically is to do longitudinal straight beam inspection. Shear wave is going to be good for certain depth only as it is refracted away from the center( depending on diameter). So only outer ring of certain depth( depending on diameter and refracted angle) can be inspected by shear wave.
: : Please comment.
------------ End Original Message ------------

Thanks for great advise Sir, yes we have procedure and acceptence criteria



 
 Reply 
 
Thomas F. Murphy
NDT Inspector
USA, Joined Jul 2000, 16

Thomas F. Murphy

NDT Inspector
USA,
Joined Jul 2000
16
03:00 Jan-18-2007
Re: Ultrasonic Testing of Round Bars
Hello all,

In my experience large solid steal cyldinders are generall inspected radially from the OD. Angles of small variance ~15 degrees may be used to aid detection on unlikely, but possible flaws not globular or solid in shape. Consideration must be given to sought flaw size, metal path, and material attenuation. Often high output pulser voltages as well as proper understanding of received frequency are necessary for repeated estimating a reflectors size. There is an ASTM procedural guide written my Mr George Wheeler of General Electric Company. I do not recall the number. Most end users of such large pieces of metal have highly defined procedures mich must be used for conformance to contracts.

T



 
 Reply 
 
Ingolf Hertlin
Ingolf Hertlin
09:30 Jan-19-2007
Re: Ultrasonic Testing of Round Bars
Hi,
there is another method to test for volumetrical defects: Acoustic Resonance Testing. You do not need in advance where the defects might be. The part is excited by an impulse, e. g. a hit. You can measure the induced langitudinal and transversal waves using a microphone in the sonic and ultrasonic range (up to 50 kHz) or on the surface with a laser vibrometer. With round bars we do two or three measurements under a certain angle to analyse certain effects on resonance frequencies.
This method is a comparative one and not useful for a single specimen, more used in mass production. The results are temperature and dimension dependent. Both dependencies can be compensated automatically. If you need more information you can download this from www.rte.de or www.rte-acoustics.com.
Best regards
Ingolf
----------- Start Original Message -----------
: Just want to make sure with experienced friends that only right way to look for defects inside the round bars volumetrically is to do longitudinal straight beam inspection. Shear wave is going to be good for certain depth only as it is refracted away from the center( depending on diameter). So only outer ring of certain depth( depending on diameter and refracted angle) can be inspected by shear wave.
: Please comment.
------------ End Original Message ------------




 
 Reply 
 

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