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Re: acoustic speed of liquid metal
Posted by: Linas Svilainis , E-mail: svilnis@rf.ktu.lt, on May 13, 1997 at 19:18:58:In Reply to: Re: acoustic speed of liquid metal posted by : Steffen Bonss on May 13, 1997 at 08:45:12:
: : :
: : : : I would like to measure the acoustic speed in liquid titanium
: : : : during laser gas alloying. The enclosed figure shows the intended
: : : : arrangement. Can you give useful hints about suitable transducers
: : : : and frequencies?
: The cooled coupling plate is planned to make of an AlMg-alloy.
: The maximum temperature at the point of transducer contact shall
: be about 373 K...
373K=100C? It should not be a problem-we could offer longitudinal wave foccused
transducers in a 5-10MHz range, which have wide bandwidth (90%BW@-6dB).
Of course, the transducer design should be adjusted bearing in mind the temperature and
material of investigation.
: ... measuring the melting depth should be possible, if the
: echos are measurable....
I am not familiar with titanium properties(attenuation,
aproximate speed of melted media, how nasty this material is).
Therefore I am not suggesting going higher frequencies.
The 10MHz transducer will give you about 0.6mm wavelength.
In such case the echoes from top and bottom of the bath
will "stick" to each other(I assume your bath depth is
of such order).Using first reflection "stripping" procedure
and resonant investigation techniques this could be handled.
(http://www.ultrasonic.de/article/wsho0597/linas/linas.htm#4)
Nice results for multiple reflections case are in R.Freemantle paper
(http://www.ultrasonic.de/article/wsho0597/freem/freem.htm)
Paper of W. Hillger describe the technical aspects os similar problem:
(http://www.ultrasonic.de/article/wsho0597/hillger/hillger.htm)
The methods mentioned deal with thin composite plates,
but the results obtained should be aplicable to your case too.
Might be I am going too far and simple deconvolution
procedures (for instance L1 norm or ASE) could handle this easily.
Basing the experience with other materials, ultrasound speed
should go down substantially,which should ensure relevant
reflection from solid/liquid interface.
The other question,which I raise again is the influence of
temperature of solid titanium. The TOF change due to temperature
should be about 0.05% for 1C(I use steel data). If temperature
is raised from 20 to 500C, then one has 25% 'float' in
measurements. This should be compensated somehow.
Linas Svilainis
http://vingis.ktu.lt/ultrasound/transduc.htm