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Technical Discussions
x.chen
x.chen
03:37 Jul-06-2000
how can the shear wave transducers excite SH Wave?

As we know, the sh wave is usually excited by EMATs. But limited by the experiment equiments, I recently want to excite SH wave using shear wave transducers in a plate. Can I excite it? How can I do? where can i find some articles about shear wave transducers?


    
 
 
Uli Mletzko
R & D, Retired
Germany, Joined Nov 1998, 89

Uli Mletzko

R & D, Retired
Germany,
Joined Nov 1998
89
00:32 Jul-06-2000
Re: how can the shear wave transducers excite SH Wave?
: As we know, the sh wave is usually excited by EMATs. But limited by the experiment equiments, I recently want to excite SH wave using shear wave transducers in a plate. Can I excite it? How can I do? where can i find some articles about shear wave transducers?

It might be possible to use standard SV probes, coupled to the side of a plate. This could be equivalent to SH waves, excited at the surface of a plate by EMAT. But this is depending on your measuring or research task.

Regards
Uli Mletzko
NDT group, MPA
University of Stuttgart, Germany



    
 
 
Ed Ginzel
R & D, -
Materials Research Institute, Canada, Joined Nov 1998, 1252

Ed Ginzel

R & D, -
Materials Research Institute,
Canada,
Joined Nov 1998
1252
03:11 Jul-06-2000
Re: how can the shear wave transducers excite SH Wave?
Excitation of SH shear waves has been more popular
since the introduction of EMATs but prior to EMATs
SH Shear waves were also generated using piezo-electric
materials. A piezo ceramic can be polarised in several
ways, depending on the distortion you require when the
electric field is applied (dilational, extentional,
radial).

Most industrial applications use dilational mode and
shear waves are produced by mode conversion (these are
SV shear waves).

If the element is polarised to distort in the
extentional mode so dispacement is parallel to the test
surface, a direct shear action may occur in the test
piece (SH shear). The problem with using piezo elements
for this type of wave mode is the coupling efficiency.

Most liquids will not support a shear mode. To couple
(acoustically) the probe to the the test piece for SH
shear modes you require a non-Newtonian viscous fluid.
There are several commercially available such couplants
but I have found honey to be about as good as any.

The advantage of EMATs over piezo elements is their
ability to be moved over the test piece. Sliding a
probe through honey and maintaining constant quality
of coupling is impossible.
EMATs, however, produce an undamped signal so
resolution suffers. Piezo elements with 1 or 2 cycles
are ideal for signal analysis. This has been useful
for determining birefringence in anisotropic materials.

Ed

: As we know, the sh wave is usually excited by EMATs. But limited by the experiment equiments, I recently want to excite SH wave using shear wave transducers in a plate. Can I excite it? How can I do? where can i find some articles about shear wave transducers?




    
 
 
Harold Dunegan
Harold Dunegan
03:48 Aug-10-2000
Re: how can the shear wave transducers excite SH Wave?
You can excite Sh shear waves in a plate by using a
commercial shear transducer, placing it on the edge of
the plate with particle motion parallel to the plate.





    
 
 

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