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- since 1996 -
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Technical Discussions
Arianna Macchi
Consultant
Italy, Joined Apr 2005, 6

Arianna Macchi

Consultant
Italy,
Joined Apr 2005
6
07:34 Apr-01-2005
Low frequency Transducers

Dear Colleagues

I'm planning to test very attenuative samples of plastic materials (both for flaw detection and thickness measurements), for which I should need very low frequency transducers (let's say in the range 100-250 KHz) of good performances to be used in pulse-echo mode because I have no access to both surfaces.

I would like to have some suggestions on what brand and model of transducers use. I saw some Krautkramer probe in their catalog but it seems that they only can be used in through-transmission mode

Best regards to all

Arianna Macchi




    
 
 Reply 
 
Ed T.
Ed T.
08:26 Apr-01-2005
Re: Low frequency Transducers
----------- Start Original Message -----------
: Dear Colleagues
: I'm planning to test very attenuative samples of plastic materials (both for flaw detection and thickness measurements), for which I should need very low frequency transducers (let's say in the range 100-250 KHz) of good performances to be used in pulse-echo mode because I have no access to both surfaces.
: I would like to have some suggestions on what brand and model of transducers use. I saw some Krautkramer probe in their catalog but it seems that they only can be used in through-transmission mode
: Best regards to all
: Arianna Macchi
------------ End Original Message ------------

What size and type of defects are you looking for?



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

Tom Nelligan

Engineering,
retired,
USA,
Joined Nov 1998
390
00:19 Apr-01-2005
Re: Low frequency Transducers
Panametrics-NDT can supply 100 KHz and 250 KHz broadband contact transducers for pulse/echo testing of highly attenuating plastics or similar materials. They're not in our standard catalog, but we can quote them on a custom basis. If you can provide us with samples of your material, we can recommend a specific test approach based on a sample evaluation.

Also, if you haven't already done so, you should consider the use of a square wave pulser in this sort of application. That's something we can also offer.

Tom Nelligan
Senior Applications Engineer
Panametrics-NDT, a busines of R/D Tech


    
 
 Reply 
 
Arianna Macchi
Consultant
Italy, Joined Apr 2005, 6

Arianna Macchi

Consultant
Italy,
Joined Apr 2005
6
09:34 Apr-02-2005
Re: Low frequency Transducers
----------- Start Original Message -----------
: What size and type of defects are you looking for?
------------ End Original Message ------------

Cracks and voids not smaller than 4-5 mm



    
 
 Reply 
 
Miroslav Omelic
NDT Inspector, EN 474 - RT3; UT3; MT3; PT2; VT2; ET1
Croatia, Joined Oct 1999, 14

Miroslav Omelic

NDT Inspector, EN 474 - RT3; UT3; MT3; PT2; VT2; ET1
Croatia,
Joined Oct 1999
14
07:51 Apr-04-2005
Re: Low frequency Transducers
Dear Arianna,
I am affraid that with chosen frequencies you should not see defects sizes smaller than 4,6 mm if is velocity (in required plastic material) 2300 m/s and with nominal testing frequency 0,25 MHz.
You must take in your account that fact - depending wave length and testing frequency with velocity.

Best regards
Miroslav Omelic

----------- Start Original Message -----------
: : What size and type of defects are you looking for?
: Cracks and voids not smaller than 4-5 mm
------------ End Original Message ------------




    
 
 Reply 
 
Arianna Macchi
Consultant
Italy, Joined Apr 2005, 6

Arianna Macchi

Consultant
Italy,
Joined Apr 2005
6
03:49 Apr-04-2005
Re: Low frequency Transducers
----------- Start Original Message -----------
: Dear Arianna,
: I am affraid that with chosen frequencies you should not see defects sizes smaller than 4,6 mm if is velocity (in required plastic material) 2300 m/s and with nominal testing frequency 0,25 MHz.
: You must take in your account that fact - depending wave length and testing frequency with velocity.
: Best regards
: Miroslav Omelic
------------ End Original Message ------------

It would be enough for me....the only problem is to find the proper transducers to work in pulse-echo mode. It seems that if you are finding 250 or 100 KHz transducers you can only work in trasmission mode.




    
 
 Reply 
 
Martin Schickert
Martin Schickert
08:27 Apr-05-2005
Re: Low frequency Transducers
----------- Start Original Message -----------
: : Dear Arianna,
: : I am affraid that with chosen frequencies you should not see defects sizes smaller than 4,6 mm if is velocity (in required plastic material) 2300 m/s and with nominal testing frequency 0,25 MHz.
: : You must take in your account that fact - depending wave length and testing frequency with velocity.
: : Best regards
: : Miroslav Omelic
: It would be enough for me....the only problem is to find the proper transducers to work in pulse-echo mode. It seems that if you are finding 250 or 100 KHz transducers you can only work in trasmission mode.
------------ End Original Message ------------

There are some low-frequency transducers designed for pulse-echo testing of concrete which you probably could use. We employ special made Krautkrämer devices from the series G 0,2 R. They have higher nominal frequencies but are very broad-band. Another choice are Karl Deutsch S 40 HB 0,1-0,3. While these conventional transducers transmit pressure (longitudinal) waves, T 1802 transducers made by Acoustic Control Systems, Moscow, feature dry point contact and shear (transversal) wave excitation. All these devices have their own issues; you may contact me directly in case of questions.


    
 
 Reply 
 
Simon Amallraja
Director
PET Aviation Systems P Ltd, India, Joined Jul 2003, 20

Simon Amallraja

Director
PET Aviation Systems P Ltd,
India,
Joined Jul 2003
20
07:40 Apr-06-2005
Re: Low frequency Transducers
----------- Start Original Message -----------
: : : Dear Arianna,
: : : I am affraid that with chosen frequencies you should not see defects sizes smaller than 4,6 mm if is velocity (in required plastic material) 2300 m/s and with nominal testing frequency 0,25 MHz.
: : : You must take in your account that fact - depending wave length and testing frequency with velocity.
: : : Best regards
: : : Miroslav Omelic
: : It would be enough for me....the only problem is to find the proper transducers to work in pulse-echo mode. It seems that if you are finding 250 or 100 KHz transducers you can only work in trasmission mode.
: There are some low-frequency transducers designed for pulse-echo testing of concrete which you probably could use. We employ special made Krautkrämer devices from the series G 0,2 R. They have higher nominal frequencies but are very broad-band. Another choice are Karl Deutsch S 40 HB 0,1-0,3. While these conventional transducers transmit pressure (longitudinal) waves, T1802 transducers made by Acoustic Control Systems, Moscow, feature dry point contact and shear (transversal) wave excitation. All these devices have their own issues; you may contact me directly in case of questions.
------------ End Original Message ------------

You can also contact Mr. Robert Drawnaw of Valpeyfisher, who are making special UT Transducers for various applications. They also have Low Freq probes and Acoustic Microscopy probes.

www.vfultrasound.com


    
 
 Reply 
 

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