Fabry-Perot measurements and analysis of TOW-2A liner collapse and jet formation Page: 4 of 10
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16TH INTERNATIONAL SYMPOSIUM ON BALLISTICS
SAN FRANCISCO, CA, 23-28 SEPTEMBER, 1996
FABRY-PEROT MEASUREMENTS AND ANALYSIS OF TOW-2A-
LINER COLLAPSE AND JET FORMATION
S. Christian Simonson, Kris A. Winer, R. Don Breithaupt,
G. Rex Avara, and Dennis W. Baum
Lawrence Livermore National Laboratory, P.O. Box 808 L-170
Livermore, CA 94551-0808 USA
A TOW-2A 146-mm shaped charge was fired and observed with five-beam Fabry-Perot
laser velocimetry. The liner collapse velocities were measured at five lines of sight
covering the outer half of the liner. A record of 8-10 gs in length was obtained for each
sight line. The velocity records at late time differ for each location, reflecting the varying
charge-to-mass ratio as the end of the liner is approached. The results were analyzed
with the CALE 2-D hydrodynamic simulation code. The calculations reproduce the
jump-off times, the shapes of the velocity jumps, and the late-time velocity asymptotes,
but they underestimate the jump-off velocities by 6-7%. The calculations show that there
exist no features in the Velocity records that require spallation to account for them.
Rather, the standard Steinberg-Guinan material model adequately accounts for the
response of this copper liner to LX-14.
INTRODUCTION
As part of an effort to obtain better information on the behavior of liner materials in shaped
charges, an experiment was conducted to observe the liner collapse process by means of multi-
beam Fabry-Perot velocimetry [1]. The time resolution of the Fabry-Perot velocimeter is high
enough to see the important features of the liner acceleration after the passage of the detonation
wave in the high explosive (HE). By employing multiple beams, the effect of varying charge-
to-mass (C/M) ratio along the liner can be studied.
An additional reason for studying the liner acceleration is to observe or infer the pattern of
density waves in the liner as it collapses. When these density waves arrive in the convergence
zone, they cause oscillations in the pressure that drives the jet (see, for example, [2]).
Depending on the magnitude and frequency of these pressure oscillations in the convergence
region, it is conceivable that they could influence the eventual breakup of the jet. If the wave
pattern were the result of a simple process of shock propagation and reverberation in a
homogeneous liner, then the amplitude of the density waves may remain fairly large during the
collapse process, and one might expect a series of regular pressure oscillations in the
convergence region. If, on the other hand, an internal spall surface were to develop, with wave
reflections off interior and exterior boundaries, plus the generation of additional waves when
the spall layer closes, then these multiple waves reverberating in the liner would lead to a
complicated pattern of pressure oscillations in the jet formation region. For these reasons, the
Fabry-Perot measurements may have implications for eventual jet particulation as well as for
liner collapse.
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Simonson, S. C.; Winer, K. A.; Breithaupt, R. D.; Avara, G. R. & Baum, D. W. Fabry-Perot measurements and analysis of TOW-2A liner collapse and jet formation, article, July 1, 1996; California. (https://digital.library.unt.edu/ark:/67531/metadc672219/m1/4/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.