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Technical Discussions
Kristine
Kristine
00:53 May-27-2003
under water shear wave couplant needed!


We are looking for an ultrasonic shear wave viscous couplant for use under water, Does anybody have an idea what could be used for this? Thank you,

Kristine




    
 
 Reply 
 
Rich Roberts
Engineering, Executive Managment
Quest Integrity Group, USA, Joined Nov 1998, 78

Rich Roberts

Engineering, Executive Managment
Quest Integrity Group,
USA,
Joined Nov 1998
78
01:57 May-27-2003
Re: under water shear wave couplant needed!
Dear Kristine,
I am a little confused. Why are you not using the water as your couplant?

Regards, Rich


:
: We are looking for an ultrasonic shear wave viscous couplant for use under water, Does anybody have an idea what could be used for this? Thank you,
.
: Kristine
.



    
 
 Reply 
 
Neil Burleigh
Sales
Krautkramer Australia Pty Ltd, Australia, Joined Dec 2002, 158

Neil Burleigh

Sales
Krautkramer Australia Pty Ltd,
Australia,
Joined Dec 2002
158
00:39 May-28-2003
Re: under water shear wave couplant needed!
:
: We are looking for an ultrasonic shear wave viscous couplant for use under water, Does anybody have an idea what could be used for this? Thank you,
.
: Kristine
.
Hi Kristine,
Before I can give you some insight I need to ask a couple of questions.
Do you have to use shear waves under water?
Are you generating the sound waves such that they are perpendicular to the contact surface?
Finally do you need to move the transducer along the surface of the test piece?

Regards

Neil


    
 
 Reply 
 
happybird
happybird
02:04 May-28-2003
Re: under water shear wave couplant needed!
Hi!Neil:
Thanks a lot for your reply,the answer is as following:

yes,i have to use shear wave under water to keep a constant temperature for the small cubic sample(ceramics)
yes,the waves are perpendicular to the contact surface.
no,i don't need to move the transducer along the surface of the test piece,but i have to depart the transducer and the sample after experiment.
hope to hear from you again!


: :
: : We are looking for an ultrasonic shear wave viscous couplant for use under water, Does anybody have an idea what could be used for this? Thank you,
: .
: : Kristine
: .
: Hi Kristine,
: Before I can give you some insight I need to ask a couple of questions.
: Do you have to use shear waves under water?
: Are you generating the sound waves such that they are perpendicular to the contact surface?
: Finally do you need to move the transducer along the surface of the test piece?
.
: Regards
.
: Neil
.



    
 
 Reply 
 
happybird
happybird
02:07 May-28-2003
Re: under water shear wave couplant needed!
Dear Rich:
Thanks a lot for your reply,actully,the singal is not good when i use water as the couplant.


: Dear Kristine,
: I am a little confused. Why are you not using the water as your couplant?
.
: Regards, Rich
.
:
: :
: : We are looking for an ultrasonic shear wave viscous couplant for use under water, Does anybody have an idea what could be used for this? Thank you,
: .
: : Kristine
: .
.



    
 
 Reply 
 
Russ
Russ
04:54 May-28-2003
Re: under water shear wave couplant needed!
This may be simplistic, but why not use immersion transducers; i.e., those matched to water?
-r

: Dear Rich:
: Thanks a lot for your reply,actully,the singal is not good when i use water as the couplant.




    
 
 Reply 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1268

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1268
06:33 May-28-2003
Re: under water shear wave couplant needed!

It sounds like you might be using an SH shear wave probe to monitor dV/dT. A nonNewtonian viscous fluid is required to support these shear waves and the easiest to get is honey. There are commercially available SH shear coplants but this is the easiest to start with.

But honey is water soluble so you will need to make a fixture that clamps the probe to the ceramic block. This will need to be fairly tight to entrap the honey (perhaps make a small seal around the probe so prevent water moving in to disolve the honey away.
Ed

: This may be simplistic, but why not use immersion transducers; i.e., those matched to water?
: -r
.
: : Dear Rich:
: : Thanks a lot for your reply,actully,the singal is not good when i use water as the couplant.
.



    
 
 Reply 
 
Philippe Rubbers
Engineering
SCM, South Africa, Joined Nov 1998, 21

Philippe Rubbers

Engineering
SCM,
South Africa,
Joined Nov 1998
21
06:46 May-28-2003
Re: under water shear wave couplant needed!
OK so shear waves don't propagate in water...
We have used honey for some of our applications; this may be worth a try assuming you can do the test faster than it dissolves into the water. This is both in-expensive and easy to obtain. There are some brittle epoxies out there, which may do the trick if you do not mind polishing/re-shoeing the probes after the test.


    
 
 Reply 
 
Uli Mletzko
R & D, Retired
Germany, Joined Nov 1998, 89

Uli Mletzko

R & D, Retired
Germany,
Joined Nov 1998
89
08:34 May-28-2003
Re: under water shear wave couplant needed!
: This may be simplistic, but why not use immersion transducers; i.e., those matched to water?
: -r

I'm watching this confusing discussion and think, that there is a lot of mutual misunderstanding, maybee also some lack of knowledge.

So I will ty to explain my personal point of view.

(i) In liquids no shear forces and therefore no shear waves can be transmitted, only compression waves. So in immersion technique each and every transducer can output only compression waves.

(ii) If a transducer is in direct contact with the specimens surface (using water as couplant, e.g.), emmiting inclined compression waves, then inclined shear waves are generated, going into the specimen. The inclination is due to Snell's law.

(iii) If you need to generate shear waves perpendicular to the surface of the specimen, then you really have a problem. You need a special straight beam shear wave transducer. But there is no way to bring the waves into a liquid couplant (see above (i) ). You have to
(a) either press the transducer with high force to the specimens surface, so that the molecules of the transducer surface are in friction contact with the molecules of the specimen,
(b) or you glue the transducer to the specimen's surface, but the glue after hardening should be not floppy or squashy, but rigid or stiff (I hope that these English terms are correct),
(c) or you use a couplant, which is not 'liquid' like water, but tough. Some people report that they have used crystallized honey. You may also use old, almost dry ketchup or grease or similar. The problem is always, that the couplant has to transduce shear forces in parallel to the surface. And if you have to do the tests under water, you have one more problem, that the couplant might be solved by the water.

If your specimen has magnetic properties, it might be possible to use EMAT probes, but of course this will not work with ceramics.

I hope that this will answer some questions.

Regards
Uli Mletzko
NDT Group, MPA,
University of Stuttgart, Germany


    
 
 Reply 
 
Henry Herrera
R & D,
UT Quality, Canada, Joined Jun 2000, 16

Henry Herrera

R & D,
UT Quality,
Canada,
Joined Jun 2000
16
09:53 May-28-2003
Re: under water shear wave couplant needed!
...because in water the shear modulus G is aprox. = 0, you will not found shear wave in water.
But, why not use longitudinal waves using water as couplant?

Regards

Henry


: Dear Rich:
: Thanks a lot for your reply,actully,the singal is not good when i use water as the couplant.
.
:
: : Dear Kristine,
: : I am a little confused. Why are you not using the water as your couplant?
: .
: : Regards, Rich
: .
: :
: : :
: : : We are looking for an ultrasonic shear wave viscous couplant for use under water, Does anybody have an idea what could be used for this? Thank you,
: : .
: : : Kristine
: : .
: .
.



    
 
 Reply 
 
John Brunk
Engineering, NDT Level III
Self employed, part-time, USA, Joined Oct 1999, 160

John Brunk

Engineering, NDT Level III
Self employed, part-time,
USA,
Joined Oct 1999
160
03:13 May-28-2003
Re: under water shear wave couplant needed!
:I have used self-coupling (or dry-coupling) straight beam transverse wave transducers made by Ultran Laboratories to measure shear wave velocities. They were a little lower in sensitivity than similar trasducers that required a couplant, but easier to use and they worked very well for me. Call Mahesh Bhardwaj at (814) 466-6200 or mcb@ultranlabs.com
.
: We are looking for an ultrasonic shear wave viscous couplant for use under water, Does anybody have an idea what could be used for this? Thank you,
.
: Kristine
.



    
 
 Reply 
 
Grant Reig
Grant Reig
02:37 May-30-2003
Re: under water shear wave couplant needed!
Kristine / Hai Faeng

Water will actually serve as a filter for the shear waves rather than a couplant, which I assume is not your intent.

Aside form the Dow Resin 276-V9 which seems to be hard to come by there are a few things you could try.

Believe it or not, I have found Starburt Fruit Candy to work quite well as a shear wave couplant. It is water soluble and after a few hours it will dissolve, however, hopefully you can take the necessary readings in that time window. It works best if you chew it slightly and use a thin layer between the transducer face and test piece. Too thick of a layer will give you echos similar to that of a delay line probe.

I have also tried hot candle wax with little to no success, but other things you might want to try may include tree sap, Chap Stick, or possibly Vaseline.

Hope this is of help & best of luck!

Grant Reig
Tranducer Sales Engineer
GE Panametrics
800.225.8330 x1383

: Dear Rich:
: Thanks a lot for your reply,actully,the singal is not good when i use water as the couplant.
.
:
: : Dear Kristine,
: : I am a little confused. Why are you not using the water as your couplant?
: .
: : Regards, Rich
: .
: :
: : :
: : : We are looking for an ultrasonic shear wave viscous couplant for use under water, Does anybody have an idea what could be used for this? Thank you,
: : .
: : : Kristine
: : .
: .
.



    
 
 Reply 
 

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