CP620, Shock Compression of Condensed Matter - 2001
edited by M. D. Furnish, N. N. Thadhani, and Y. Horie
© 2002 American Institute of Physics 0-7354-0068-7/02/$ 19.00
INVESTIGATION OF ISENTROPE FOR DETONATION PRODUCTS OF
TATB-BASED COMPOSITION
Yu.A. Aminov, M.M. Gorshkov, V.T. Zaikin, G.V. Kovalenko, Yu.R. Nikitenko,
G.N. Rykovanov
Russian Federal Nuclear Center - VNIITF, Snezhinsk 456770
Abstract. The modified impedance matching method was used for investigation of isentropic expansion of
the detonation products of plasticized TATB-based composition. Experimental installation consists of flat
aluminum flyer plate, aluminum "shield", the sample of explosive and inert barrier. The thickness of
explosive sample is 15 mm. It was used 14 substances with various densities. Measured values of the shock
wave velocity in the barrier were used for determination of particle velocity and pressure. Obtained results
are in agreement with simulation and with experimental data for similar composition T2.
INTRODUCTION
HE sample
For build-up of empirical equations of state
(EOS) for detonation products (DP) the information
on DP shock compression and isentropic expansion
is necessary in addition to usually determined
explosive parameters (initial density, stationary
detonation velocity, DP parameters in ChapmanJouguet point, etc.). The impedance matching
method is usually used for such experiments. In this
method a shock wave velocity D is measured in
inert barrier bordering to explosive charge. In this
case, pressure P and particle velocity U in
contacting substances are equal and can be found if
the equation of state for barrier substance is known.
Selecting different materials for barrier, it is
possible to receive experimental data in, for
example, P(U) form for investigated explosive. In
our experiments, the modified impedance matching
method was used for investigation of the plasticized
TATB-based composition (PCT) with initial density
po^l.91 g/cc.
Gauges
Flyer plate "Shield"
Barrier
FIGURE 1. The installation for impedance matching method
experiments.
A 15 mm thick explosive sample was shocked by
an 8 mm aluminum flyer plate through a 4 mm
aluminum "shield". The flyer velocity was
W=3.6 km/s, that corresponds to the values of
pressure in PCT at the leading shock front «28 GPa
according (1). The time to detonation for similar
explosive PBX-9502 at such pressure does not
exceed 0.1 us (2).
The choice of barrier materials (Table 1) was
made to investigate DP in pressure range P=0.150 GPa. The mean shock velocity D in a barrier was
measured apart from L}=5 mm up to L2=10 mm by
EXPERIMENTAL INSTALLATION
Figure 1 shows the scheme of experimental
installation used in our experiments.
875
pressure is more than Chapman-Jouguet pressure
(Pa),
electrocontact gauges to exclude the influence of
chemical reaction zone.
In each measuring planes 8 gauges apart from
7 mm up to 21 mm from axis of symmetry placed,
the obtained data averaged. In experiments with
non-metallic substances, the gauges were covered
with an aluminum foil of 10 um width. In
experiences with liquids, the gauges were positioned
in handsets with brass bottom of 50 urn width.
For preliminary calculations of experimental
system we used one-dimensional hydrodynamic
code VOLNA (3), permitting calculations with
precise fronts of shock and detonation waves. The
equations of state from (4) were used for unreacted
explosive and its detonation products. The reaction
rate parameters were selected from the plane-wave
experiments results (4). At these parameters run to
detonation is near 7 mm that is in agreement with
data (2) for PBX-9502 and allows us to use in
experiment a 15 mm explosive charge. The
calculated reaction zone length is near 1 mm. Its
influence has an effect in a barrier apart less than 6
mm. According to calculation, the rarefaction wave
does not perturb a constant pressure profile during
measuring.
ou-
I
0
T, (5)
T 2 ( 6)
•
PCT
50- }————
*
40-
0
T
0
A
ou
<
o'
200
10-
A""
-»-i
O «•
*S...A...-4
0-
1
2
3
4
5
6
7
Particle velocity (mm/us)
FIGURE 2. Experimental data for PCT and T2 explosives
60
experiment
calculation with EOS (4)
main isentrope for EOS (4)
50-
DISCUSSION OF RESULTS
OH
Table 1 shows the measured in a barrier shock
wave velocities and substances used for the barrier.
For determination of the particle velocity U and the
pressures P were used the law of momentum
conservation on shock front and linear D(U)
dependence for barrier:
1
2
3
4
5
6
7
Particle velocity (mm/^is)
FIGURE 3. Comparison of experimental and calculated with
EOS (4) curves.
we obtain an overdriven detonation. For similar
compositions (with TATB/inert ratio approximately
90/10) the experimental and theoretical ChapmanJouguet pressure spread is 26-31 GPa. To
investigate influence of C-J pressure value on
experimental results the VOLNA calculations were
carried out with DP equations of state from (4)
(Po=30.6 GPa) and (7) (PCj=26 GPa). As it is seen
from figures 3 and 4 the calculations is in the good
agreement with experiments for both EOS, therefore
at the used scheme of initiation it is possible the DP
supracompression. Thus, the obtained experimental
data can be used for EOS verification only if in the
calculations the experimental set-up is accurately
reproduced.
P=p0DU, D=
The experimental points in P(U) form are shown
in Fig. 2, where they are compared to the
experimental data for similar composition T2
(p0=1.855 g/cc). Impedance matching method (5)
and laser interferometry (6) were used to receive the
data for T2.
The good agreement with the laser interferometry
data (6) is observed, while the lower pressures are
measured in experiments (5).
In our experiments the constant pressure profile
in DP was created by a thick flyer plate. If this
876
TABLE 1. Experimental Data Obtained in Impedance Matching Method Experiments
D
U
Po
Substance
g/cc
mm/us
mm/jis
copper
8.92
5.528±0.068
1.07±0.05
P
GPa
52.813.3
aluminium
2.73
7.772±0.079
1.7310.06
36.811.7
magnesium
1.74
7.345±0.034
2.27±0.04
29.010.7
PMMA
1.18
6.785±0.135
2.76±0.11
22.111.4
water
1.00
6.460±0.067
3.00±0.09
19.310.7
polyethylene
0.92
7.296±0.028
2.92±0.07
19.610.6
ethyl alcohol
0.80
6.634±0.155
3.16±0.12
16.811.1
n-hexane
0.65
6.688±0.063
3.34±0.10
14.510.6
0.77
5.881±0.031
3.30±0.12
15.010.7
0.72
5.895±0.066
3.45±0.11
14.610.6
0.51
5.647±0.109
3.72±0.11
10.710.5
0.31
5.498±0.124
4.1610.15
7.110.4
0.16
5.583±0.068
4.5510.13
4.110.2
0.00115
7.675±0.079
7.0210.10
0.0610.003
polystyrene
air
REFERENCES
1.
60
50-
2.
t
• experiment
o calculation with EOS (7)
—— main isentrope for EOS (7)
3.
4030-
4.
2010-
5.
01
2
3
4
5
6
7
Particle velocity (mm/us)
6.
FIGURE 4. Comparison of experimental and calculated with
EOS (7) curves.
7.
877
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