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- since 1996 -
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Technical Discussions
Alex G
Alex G
03:26 Sep-04-2007
4Mhz vs 2Mhz UT Probe
Is anybody can explain to me what is the difference of using a 4Mhz ultrasonic probe and 2Mhz probe in UT scanning/testing of steel in Shear wave or compression wave technique.



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

Tom Nelligan

Engineering,
retired,
USA,
Joined Nov 1998
390
05:19 Sep-04-2007
Re: 4Mhz vs 2Mhz UT Probe
Higher frequency provides better resolution -- you can see smaller flaws and measure thinner materials.

Lower frequency provides better penetration -- you can test thicker materials, and get cleaner response from scattering or attenuating materials like castings or fiberglass.

Selecting the optimum transducer for a given test often involves a compromise between these two factors. Choose whatever works best based on experimentation with appropriate reference standards.

----------- Start Original Message -----------
: Is anybody can explain to me what is the difference of using a 4Mhz ultrasonic probe and 2Mhz probe in UT scanning/testing of steel in Shear wave or compression wave technique.
------------ End Original Message ------------




    
 
 Reply 
 
Nigel Armstrong
Engineering, - Specialist services
United Kingdom, Joined Oct 2000, 1096

Nigel Armstrong

Engineering, - Specialist services
United Kingdom,
Joined Oct 2000
1096
04:25 Dec-17-2007
Re: 4Mhz vs 2Mhz UT Probe
First assume the probes are of identical design apart from PE crystal thickness.

Look at the effect of changing frequency in the major equations for UT.

Frequency and wavelength are inversely proportional so increaing frequency means decreasing wavelength (for fixed sound velocity), therefore smaller defects can be detected with higher frequency.

If your test item has a rough surface or coarse grain structure then you will use a lower frequency probe to minimise losses from scattering of sound at the test surface

Increasing frequency/decreasing wavelength means increasing Near Field so need to be more careful about relative gain settings in the near field

Decreasing frequency/increasing wavelength means more beam spread. So greater probability of picking up misoriented defects with low frequency probes or conversely missing such defects with higher frequencies.

Hope this helps.

equations----------- Start Original Message -----------
: hello,
: i think ,when u will use 4Mhz probe u will get more resolution & sensitivity.but it will effect ur transducer design.
: : Is anybody can explain to me what is the difference of using a 4Mhz ultrasonic probe and 2Mhz probe in UT scanning/testing of steel in Shear wave or compression wave technique.
: hello,
: i think ,when u will use 4Mhz probe u will get more resolution & sensitivity.but it will effect ur transducer design.
------------ End Original Message ------------




    
 
 Reply 
 
Maniraj
Maniraj
10:09 Oct-13-2016
Re: 4Mhz vs 2Mhz UT Probe
In Reply to Nigel Armstrong at 04:25 Dec-17-2007 .

how do i know crystal thickness?

    
 
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Mario Talarico
NDT Inspector,
Italy, Joined May 2010, 411

Mario Talarico

NDT Inspector,
Italy,
Joined May 2010
411
23:06 Oct-13-2016
Re: 4Mhz vs 2Mhz UT Probe
In Reply to Tom Nelligan at 05:19 Sep-04-2007 .

zoom image


2-4-mhz inclusions

Practical consequences: a 4 MHz probe can 'collect' and totalize contribution of a series of small indications generated by small inclusions lying in the same plane and form a single important signal; where a 2 Mhz probe reduces or even lose the signal.

They know something the old foxes of steel mills!

greetings
mario
    
 
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