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Technical Discussions
David Harvey
Engineering
ATI - Wah Chang, USA, Joined Nov 2002, 42

David Harvey

Engineering
ATI - Wah Chang,
USA,
Joined Nov 2002
42
06:18 Apr-06-2005
Side lobes

I am looking for a good, rather basic (read: clear) discussion of the effect of the sound beam side lobes on performance of both contact and immersion tests. Is anyone aware of literature that addresses the subject, or that has wisdom to share?

Please respond to the message board, and not to my email address, since my company's spam filtering often filters messages from unfamiliar addresses.


 
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Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1300

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1300
05:51 Apr-07-2005
Re: Side lobes
David:
As for an easy read I suggest the new book by RD Tech on Introduction to Phased Array ULtrasonic Technology. There are a few related topics. But it makes little difference if the lobe is a grating lobe from a phased array probe or it is a lobe from a poorly backed single element unit or even a result of working in the near zone, the result is all about the same, i.e. an increase in pressure off-axis from the main beam (where you were expecting a continuous drop).

In line focused immersion probes we often see "horns" on either end of the beam when doing a plot of amplitude versus displacement across a calibration target like a small stainless steel ball.

When vertically sizing using the dB drop method we might see the effect in the vertical plane as a series of peaks as we move forward and back in a weld inspection. A small point reflector might be mistaken to be a multi-faceted flaw as a result.

It is all nicely covered in the book I referenced with images for illustration.
Ed

----------- Start Original Message -----------
: I am looking for a good, rather basic (read: clear) discussion of the effect of the sound beam side lobes on performance of both contact and immersion tests. Is anyone aware of literature that addresses the subject, or that has wisdom to share?
: Please respond to the message board, and not to my email address, since my company's spam filtering often filters messages from unfamiliar addresses.
------------ End Original Message ------------




 
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