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- since 1996 -
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Technical Discussions
Rajiv
Director,
CALTECH ENGINEERING SERVICES, India, Joined Mar 2003, 13

Rajiv

Director,
CALTECH ENGINEERING SERVICES,
India,
Joined Mar 2003
13
13:42 Dec-05-2012
Freqency of Probe & Velosity

I would like to use Ultarsonic Thickness Gauge for testing Plastic / Epoxy material thickness on concrete.
Please advice probe and velosity applicable for the gage.
Thanks in advance.

Rajiv

 
 Reply 
 
Sudheer Jai Krishnan
Sudheer Jai Krishnan
16:53 Dec-05-2012
Re: Freqency of Probe & Velosity
In Reply to Rajiv at 13:42 Dec-05-2012 (Opening).

Hello Rajiv,

Greetings.Can you kindly let us know the thickness of the plastic/epoxy that you would be interested in finding the thickness?

Regards

Sudheer Jai Krishnan

 
 Reply 
 
Rajiv
Director,
CALTECH ENGINEERING SERVICES, India, Joined Mar 2003, 13

Rajiv

Director,
CALTECH ENGINEERING SERVICES,
India,
Joined Mar 2003
13
13:46 Dec-06-2012
Re: Freqency of Probe & Velosity
In Reply to Sudheer Jai Krishnan at 16:53 Dec-05-2012 .

Dear Sudheer Jai Kishan,
Thickness of plastic/ epoxy is maximum 3mm.
I hope you have solution for above.

Regards,

RAJIV

 
 Reply 
 
Sudheer Jai Krishnan
Sudheer Jai Krishnan
20:32 Dec-06-2012
Re: Freqency of Probe & Velosity
In Reply to Rajiv at 13:46 Dec-06-2012 .

Hi Rajiv,

It is possible. I do not know what gage you use, but i have tested (may be few days back) the thickness of fiber glass, GFRP etc with 45MG and 38DLP thickness gages. The thickness of the fiber glass was around 1.3mm and the GFRP was about 5mm that i used.

You will definitely get a backwall from the interface of the epoxy/plastic on concrete. I will recommend to try with M112 or M110 (if you have a 45MG or 35Series or a 38DL) which will be 5Mhz and 10Mhz transducer for which you must be able to get a good reading.

Please do the test and let us know your result

Regards

Sudheer Jai Krishnan

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

Tom Nelligan

Engineering,
retired,
USA,
Joined Nov 1998
390
21:12 Dec-06-2012
Re: Freqency of Probe & Velosity
In Reply to Sudheer Jai Krishnan at 20:32 Dec-06-2012 .

Keep in mind that for this to work, the coating/concrete boundary must be relatively smooth. If the coating was applied over rough concrete, sound waves will be largely scattered rather than reflected and it may be difficult to find a clean echo.

As for sound velocity, you should calibrate that on a coating sample of know thickness since it could vary widely, anywhere from less than 1800 m/s for some urethane coatings to greater than 2500 m/s for some hard epoxies.

 
 Reply 
 
Andrew Hurrell
Consultant, Ultrasonic Transducer Production
Precision Acoustics Ltd, United Kingdom, Joined Apr 2000, 25

Andrew Hurrell

Consultant, Ultrasonic Transducer Production
Precision Acoustics Ltd,
United Kingdom,
Joined Apr 2000
25
13:22 Dec-11-2012
Re: Freqency of Probe & Velosity
In Reply to Tom Nelligan at 21:12 Dec-06-2012 .

To add to Tom's point

If the underlying substrate is rough then a slightly lower frequency probe would result in a longer wavelength and would therefore be less sucesptible to scattering problems

If you need a custom designed probe for this type of application, do get in contact

Best wishes

Andrew

 
 Reply 
 
Jeff Leak
R & D, Ultrasonic Phased Array, Physical Science, NAS-410 LIII
NASA, USA, Joined Dec 1999, 37

Jeff Leak

R & D, Ultrasonic Phased Array, Physical Science, NAS-410 LIII
NASA,
USA,
Joined Dec 1999
37
18:17 Dec-11-2012
Re: Freqency of Probe & Velosity
In Reply to Rajiv at 13:42 Dec-05-2012 (Opening).

I am going to jump in and see if I can make it simple for you:

* You likely have an Ultrasonic Thick Guage
* You want to measure thickness of Plastic that is bonded to Concrete
* You want to know what frequency to use and what material velocity to use

I would use the 5Mhz dual-element transducer that likely came with the unit. The material velocity for Platic will be low ... maybe around 0.0931m/s? Just lift the transducer off and look for a signal ... couple it back to the Platic surface and look for a signal. If you find one it would be the bond-interface of the Platic-to-Concrete, essentially the thickness of the Platic. Set the Gate on that signal and adjust the velocity manually or just do an auto-cal and make it read 3mm in a section that you know is 3mm thick.

Hope I got that right! Good luck ...

 
 Reply 
 

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