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Technical Discussions
Mike Leger
Mike Leger
07:40 Aug-22-2003
Bolt Stress Measurement

I am interested in using one of the new portable digital UT instruments such as the Panametrics Epoch 4 to perform bolt elongation measurements in order to verify proper bolt stretch instead of one of the bolting specific measurement instruments. The new digital instruments have very accurate clocks and gating systems that should be adequate for this purpose.
I have the ability to mock up the intended application and perform accurate physical measurements to empirically qualify the technique. I understand the need for consistency in transducer mounting and that there is a change in velocity as load increases. The studs are grade 630, 1.625” diameter and 16” long. My questions are:

· Is there any major fault in this reasoning?
· Where can I find more data on the change in velocity vs. load (acoustoelasticity) for steels?

Thanks,
Mike Leger



 
 Reply 
 
Jacek Szelazek
Jacek Szelazek
02:58 Aug-26-2003
Re: Bolt Stress Measurement
Hello Mike,

I think your idea is fine and it should work.
If you can recognize "back face" echo, what, depending on bolt shape and bolt faces configutation, can be difficult, you can monitore time of flight changes versus load.
Time changes will be due to elastoacoustic effect and bolt elongation.
To calculate stress or load value you should know how stress is distributed along the bolt. The wave propagating between faces will average stress and elongation along all 16".

Assuming that 8" of the bolt are stresses, you can expect time of flight changes about 4 ns/MPa of tensile load (according to my rough calculations).

One more practical problem in ultrasonic stress measurement is the influence of temperature on ultrasonic pulse velocity. All readings should be taken in the same temperature.

Jacek

----------- Start Original Message -----------
: I am interested in using one of the new portable digital UT instruments such as the Panametrics Epoch 4 to perform bolt elongation measurements in order to verify proper bolt stretch instead of one of the bolting specific measurement instruments. The new digital instruments have very accurate clocks and gating systems that should be adequate for this purpose.
: I have the ability to mock up the intended application and perform accurate physical measurements to empirically qualify the technique. I understand the need for consistency in transducer mounting and that there is a change in velocity as load increases. The studs are grade 630, 1.625” diameter and 16” long. My questions are:
: · Is there any major fault in this reasoning?
: · Where can I find more data on the change in velocity vs. load (acoustoelasticity) for steels?
: Thanks,
: Mike Leger
------------ End Original Message ------------




 
 Reply 
 
seyyed mohammad atifeh
seyyed mohammad atifeh
02:52 Dec-29-2005
Re: Bolt Stress Measurement
I am student of mechanical engineering in polytechnic ( tehran iran) in MSc level.iam interested and it is my thesis to evaluate bolt stress measuring with ultrasonic waves and know the effect of some parameter on precision of this method , for example : temp, stress level, bolt size , bolt geometry , transducer, ultrasonic method , bolt material , and ... .
if you can help me, i like to have relation with you by email and you answer my questions during doing this project.
firstly if it is possible , give me some information about:
1:acoustoelastic
2:how acoustoelastic constants can be determined.
3: specially bolt stress measurement
4: set up for bolt stress measurement.
5: & how can i start the project.
: Thanks
best regards
seyyed mohammad atifeh




 
 Reply 
 

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