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ASTM Selected Technical Papers
M3D III: Mechanics and Mechanisms of Material Damping
By
A Wolfenden
A Wolfenden
1Mechanical Engineering Department,
Texas A&M University
,
College Station, TX 77843
;
symposium chairman and editor
.
Search for other works by this author on:
VK Kinra
VK Kinra
2Aerospace Engineering Department,
Texas A&M University
,
College Station, TX 77843
;
symposium chairman and editor
.
Search for other works by this author on:
ISBN-10:
0-8031-2417-1
ISBN:
978-0-8031-2417-2
No. of Pages:
417
Publisher:
ASTM International
Publication date:
1997

Amplitude-dependent damping, being nonlinear, has associated with it an acoustic harmonic spectrum. Sufficient data have now accumulated to make desirable an effort to understand the complicated results. We have recently suggested that a sharp dip as a function of amplitude of the third harmonic in iron can be explained as a phase cancellation effect. A simple model, a discontinuous jump in amplitude of a sine wave, indicated that the phase of the emitted acoustic radiation depended on the phase of the jump. Supposing a distribution of breakaway stresses for dislocation segments, one expects that some segments will be emitting with a phase sufficiently different from others to give significant cancellation effects. In this paper, using a more physical representation of the breakaway event, we confirm the results on the tendency of the phases and observe qualitatively that they may be adequate to explain the data for brass as well as iron. Detailed modeling now seems worthwhile.

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,
M. C.
,
Mason
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, and
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, “
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,”
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,
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2.
Coronel
,
V. F.
and
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,
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, “
Internal Friction and Harmonic Generation in Iron
,”
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, Vol.
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,
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Rozenberg
,
L. D.
,
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,
Plenum Press
,
New York
,
1971
, pp. 239–257.
4.
Lauterborn
,
W.
and
Holzfuss
,
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, “
Acoustic Chaos
,”
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, Vol.
1
, No.
1
,
01
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, pp. 13–26.
5.
Beshers
,
D. N.
,
Jon
,
M. C.
,
Beshers
,
G. M.
, and
Seth
,
V.
, “
Non-linear Mechanical Phenomena at High Amplitudes and Dislocation Dynamics
,”
Internal Friction and Ultrasonic Attenuation in Solids
,
Hasiguti
R. R.
and
Mikoshiba
N.
, Eds.,
University of Tokyo Press
,
1977
, pp. 623–626.
6.
Beshers
,
D. N.
and
Oppenheim
,
A.
, “
The Generation of Acoustic Harmonics by Dislocation Dipoles and Loops
,”
Journal of Applied Physics
, Vol.
52
, No.
11
,
11
1981
, pp. 6509–6521.
7.
Beshers
,
D. N.
and
Coronel
,
V. F.
, “
Fourier Analysis of Hysteretic Damping Mechanisms
,”
Journal de Physique
, Vol.
46
, Colloque C10, Supplement to No.
12
,
12
1985
, pp. C10-171–C10-173.
8.
Beshers
,
D. N.
and
Coronel
,
V. F.
,
Journal of Alloys and Compounds
, Vol.
211/212
, pp. 104–106.
9.
Nabarro
,
F. R. N.
,
Theory of Crystal Dislocations
,
Oxford
,
London
,
1967
, p. 709.
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