where expertise comes together - since 1996 -

The Largest Open Access Portal of Nondestructive Testing (NDT)

Conference Proceedings, Articles, News, Exhibition, Forum, Network and more

where expertise comes together
- since 1996 -
1267 views
Technical Discussions
Arianna Macchi
Consultant
Italy, Joined Apr 2005, 6

Arianna Macchi

Consultant
Italy,
Joined Apr 2005
6
09:01 Jun-06-2005
Couplant for porous stones

Dear colleagues

I'm trying to perform simple UT attenuation measurements on porous stones with a 500 KHz contact transducer in pulse-echo configuration. I'm using vaseline as couplant but I've noticed that when the couplant begins to melt (i.e. becomes more fluid) the sensitivity decrease significantly. By suppyling a new amount of fresh (more solid) substance, things get better, but this happens every 10-15 seconds.

Can you suggest me some possible alternative to vaseline??


 
 Reply 
 
John Brunk
Engineering, NDT Level III
Self employed, part-time, USA, Joined Oct 1999, 161

John Brunk

Engineering, NDT Level III
Self employed, part-time,
USA,
Joined Oct 1999
161
03:13 Jun-06-2005
Re: Couplant for porous stones
----------- Start Original Message -----------
: Dear colleagues
: I'm trying to perform simple UT attenuation measurements on porous stones with a 500 KHz contact transducer in pulse-echo configuration. I'm using vaseline as couplant but I've noticed that when the couplant begins to melt (i.e. becomes more fluid) the sensitivity decrease significantly. By suppyling a new amount of fresh (more solid) substance, things get better, but this happens every 10-15 seconds.
: Can you suggest me some possible alternative to vaseline??
------------ End Original Message ------------

Your data will be altered by couplant entering pores in the samples. You should use self-coupling (dry coupling)transducers. I have used these successfully to examine a variety of porous materials. One source for these is Ultran. If you can't obtain new transducers you might be able to use sheet dental adhesive as a coupling layer. Attenuation will then vary with pressure but maybe you could measure the difference between the first and second back reflections. You should try to get the vaseline out of your samples and re-test them.


 
 Reply 
 
Tom Nelligan
Engineering,
retired, USA, Joined Nov 1998, 390

Tom Nelligan

Engineering,
retired,
USA,
Joined Nov 1998
390
03:16 Jun-06-2005
Re: Couplant for porous stones
Several companies (including mine) offer very high viscosity ultrasonic couplants for use with normal incidence shear wave transducers. That sort of medium also works well for coupling longitudinal wave transducers on porous materials, because the very high viscosity limits absorption. I'd suggest that you try a commercial shear wave couplant.

Tom Nelligan
Senior Applications Engineer
Panametrics-NDT, a business of R/D Tech
www.panametrics-ndt.com


----------- Start Original Message -----------
: Dear colleagues
: I'm trying to perform simple UT attenuation measurements on porous stones with a 500 KHz contact transducer in pulse-echo configuration. I'm using vaseline as couplant but I've noticed that when the couplant begins to melt (i.e. becomes more fluid) the sensitivity decrease significantly. By suppyling a new amount of fresh (more solid) substance, things get better, but this happens every 10-15 seconds.
: Can you suggest me some possible alternative to vaseline??
------------ End Original Message ------------




 
 Reply 
 
Udo Schlengermann
Consultant, -
Standards Consulting, Germany, Joined Nov 1998, 177

Udo Schlengermann

Consultant, -
Standards Consulting,
Germany,
Joined Nov 1998
177
09:16 Jun-07-2005
Re: Couplant for porous stones
Reply

Hello,
coming back to the original task: Determination of sound attenuation:
On porous stones, I suppose, it can only be measured for longitudinal waves, and only using the through-transmission technique, with separate transmitter and receiver probes on opposite sides of the sample.
And this can only be a relative measurement compared to a reference sample, using always the same equipment and same set-up.
Losses by changing coupling conditions and by changing divergence losses of the sound beams from sample to sample are much bigger than the losses by attenuation (scattering) in the objects itself.
As mentioned in the replies from collegues before, the change of the elastic properties of couplant during measurement will change the sound transfer conditions (decreasing transmissivity at the boundaries. But filling the pores of your object with liquid will improve transmission in the object. So depending on the measurement conditions (time) the calculated attenuation coefficient will bea random figure.
On porous materials a valid relative attenuation coefficient can only be achieved by dry coupling conditions i.e. using dry coupling probes in a rig (probes aligned controlled pressure) or very thin foils between probes and sample to avoid pentration of a fluid couplant.

Kind regards
Udo Schlengermann
Applications Laboratory
GE Inspection Technologies GmbH
Huerth, Germany


----------- Start Original Message -----------
: Dear colleagues
: I'm trying to perform simple UT attenuation measurements on porous stones with a 500 KHz contact transducer in pulse-echo configuration. I'm using vaseline as couplant but I've noticed that when the couplant begins to melt (i.e. becomes more fluid) the sensitivity decrease significantly. By suppyling a new amount of fresh (more solid) substance, things get better, but this happens every 10-15 seconds.
: Can you suggest me some possible alternative to vaseline??
------------ End Original Message ------------




 
 Reply 
 

Product Spotlight

NovaScope 6000

The all-digital Novascope 6000 is a portable, ultra-high precision thickness gauge for high-speed
...
thickness measurement. Novascope 6000 has unmatched capabilities and unique features including: •Superior Resolution with high contrast, high-speed color RF display •High pulser voltage •Real-time video output •Increased internal/external data storage •Programmable SetUp features •Battery & AC Powered
>

Teletest Focus+

Teletest Focus+ electronics have superior capabilities than rivals on the market. Beyond the usual
...
test features, Focus+ has 24 transmit channels and 24 receive channels, with an additional on-board switching capabilities. The instrument's frequency range is 10–300 kHz.
>

SITEX CPSERIES

Teledyne ICM’s CPSERIES has been designed with a view to revolutionizing the handling and perfor
...
mances of portable X-Ray sets. Despite having managed to halve the weight of similar portable X-Ray generators available on the market (while continuing to provide the same power output), the SITEX CPSERIES generators feature a shutter, a laser pointer, a beryllium window, an aluminum filter and two integrated diaphragms (customized sizes are available upon request). Without compromising the robustness and reliability for which ICM products are renowned, the small size and light weight of the SITEX CPSERIES will radically change the way that you perform your RT inspections. And you will see a positive impact in terms of both quality and return on investment (ROI).
>

Research and Applications Development For NDT

The Research and Applications Development (RAD) group is a newly formed team within Acuren dedicat
...
ed to tackling challenging inspection problems. Our focus is the development of novel, field deployable, advanced inspection techniques for use in cases where standard NDT methods are ineffective. We don't wait for new innovations, we engineer them. From concept to commissioning.
>

Share...
We use technical and analytics cookies to ensure that we will give you the best experience of our website - More Info
Accept
top
this is debug window