Re: TOFD Probes

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Re: TOFD Probes
Posted by: Rathgeb/Meier , E-mail: meierrai@erls19.kwu.siemens.de, on September 20, 1996 at 19:17:40:
In Reply to: TOFD Probes posted by : Ed Ginzel on September 19, 1996 at 19:26:55:
: Most probes used for TOFD are circular or nearly square.
: Would it be feasible or practical to use a rectangular
: shaped element to effectively increase the energy input
: to a thick test piece? e.g. a 6mm x 18mm element. The
: small vertical dimension (6mm) would be intended to
: preserve the increased divergence angle needed for TOFD.
: If so, would the receiver probe need to be of the same
: dimension?
Many thanks for your question.
Siemens does not have so much experience in TOFD-technique,but
we asked experts from AEA in England. AEA did some investigations
to this problem and have bad experience with squared ore rectangular
shaped probes: The parallel edges of squared or rectangular probes
cause interferencies due to diffraction at the crystal edges.
This will reduce your signal to noise ratio and should therefore
be avoided. AEA experience is, that in case of steel material the
diameter of the probe is not so much limited.
If you do need an increase of energy and want to get a smaler
beam width in the horizontal direction, you should better use
elliptical transducers.
To cover a maximal area of inspection, the beam width of the
transmitter and the receiver should correspond.

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Comments:
: : Most probes used for TOFD are circular or nearly square. : : Would it be feasible or practical to use a rectangular : : shaped element to effectively increase the energy input : : to a thick test piece? e.g. a 6mm x 18mm element. The : : small vertical dimension (6mm) would be intended to : : preserve the increased divergence angle needed for TOFD. : : If so, would the receiver probe need to be of the same : : dimension? : Many thanks for your question. : Siemens does not have so much experience in TOFD-technique,but : we asked experts from AEA in England. AEA did some investigations : to this problem and have bad experience with squared ore rectangular : shaped probes: The parallel edges of squared or rectangular probes : cause interferencies due to diffraction at the crystal edges. : This will reduce your signal to noise ratio and should therefore : be avoided. AEA experience is, that in case of steel material the : diameter of the probe is not so much limited. : If you do need an increase of energy and want to get a smaler : beam width in the horizontal direction, you should better use : elliptical transducers. : To cover a maximal area of inspection, the beam width of the : transmitter and the receiver should correspond.

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