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Technical Discussions
Derek Stewart
Derek Stewart
09:50 Sep-27-1996
Acoustic Attenuation

Hi!

My name is Derek Stewart and I am a graduate student
at the University of Virginia. I am working on a problem
where I am modeling acoustic waves in tungsten. However,
so far, I have been unable to find any information about
the acoustic attenuation in tungsten. I know this panel
is specializing in transducers, but since you are also
experts in ultrasonics, I was wondering if any of you
would possibly know the value or possible references
to explore.

Thanks ahead of time,

Derek


Derek Stewart
das4k@virginia.edu



    
 
 Reply 
 
Yoseph Bar-Cohen
R & D,
Jet Propulsion Lab (JPL), USA, Joined Nov 1998, 26

Yoseph Bar-Cohen

R & D,
Jet Propulsion Lab (JPL),
USA,
Joined Nov 1998
26
09:29 Sep-30-1996
Re: Acoustic Attenuation
Tungsten is a highly attenuative, highly reflective material. The
degree of attenuation depends on the grain structure. Because of the
high density, the impedance of tungsten is one of the highest of all
materials and it is about 100 g/cc^2 sec.

Yosi


: Hi!

: My name is Derek Stewart and I am a graduate student
: at the University of Virginia. I am working on a problem
: where I am modeling acoustic waves in tungsten. However,
: so far, I have been unable to find any information about
: the acoustic attenuation in tungsten. I know this panel
: is specializing in transducers, but since you are also
: experts in ultrasonics, I was wondering if any of you
: would possibly know the value or possible references
: to explore.

: Thanks ahead of time,

: Derek

:
: Derek Stewart
: das4k@virginia.edu




    
 
 Reply 
 
W. Grandia
W. Grandia
00:41 Oct-01-1996
Re: Acoustic Attenuation
I looked up the information for the acoustic parameters in Tungsten and found something in the book from Prof Gordon Kino: Acoustic Waves with subtitle: Devices, Imaging & Analog Processing; Prentice Hall ISBN 0-13-003047-3. Page 551.
This is a table generated by Dr. Allen Selfridge.
It states:
Vl = 5.2 (km/s)
Vs = 2.9 (km/s)
Densitymo = 19.4 (kg/m3 x 10 6)
Zl = 101.0 (density x long. velocity)
Zs = 56.3 (density x shear velocity)
s = 0.27 (dB/cm)
The attenuation A = a/f2 dB. s 2/m x 10 -15)
(No value of A at any frequency was given)

Further more there are some Tungsten parameters given in "Ultrasonics, fundamentals , applications by Dale Ensminger., page 210, book ISBN: 0-8247-7659-3
No attenuation information is given, however it states the following useful information:
1) Tungsten: Bar (c0) = 4.60, Bulk (cB) =5.18, Shear (cs ) = 2.87, Dens=19.25,
Characteristic impedance (rcB) = 9.98, Poisson's ratio 0.28,
2) Tungsten annealed: Bar (c0) = 4.62, Bulk (cB) =5.22, cs=2.89, Dens=19.30,
Characteristic impedance (rcB) = 10.07
3) Tungsten: Bar (c0) = 4.31, Bulk (cB) =5.46, cs=2.62, Dens=19.10, Characteristic
impedance =10.42
4) Tungsten, drawn: Bulk (cB) =5.41, cs=2.62, Dens =19.30, Characteristic
impedance =10.44
5) Tungsten: (cB) =5.17, cs=2.62, Dens =19.30, Characteristic
impedance =10.00, reference 24
The above information is probably not sufficient. Attenuation is influenced by absorption, grain structure, beam spreading, hysteresis and temperature. It is probably the best to make some simple measurements to derive the numbers for the specific application.
In regards to attenuation of guided plate wave modes in Tungsten, the problem becomes very complex to calculate and again, it is probably best to measure it.




    
 
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