Automatic recording of the flash delay time of explosives
Abstract Generated abstract
The paper describes an apparatus for automatically recording the flash delay time of explosives under thermal initiation, a parameter relevant to explosive sensitivity and ignition mechanisms. The proposed design places a weighed explosive charge in a thin metal foil piston attached to a falling rod, which closes an electrical timing circuit on contact with a heated metal block and opens it at the moment of explosion, stopping the recorder. The authors report that, with controlled charge mass, density, piston dimensions, and geometry, the setup provides reproducible heating conditions and can be used with electronic or electromechanical timing systems over a wide accuracy range. An example temperature dependence for lead azide demonstrates the apparatus, including its suitability for measuring short delay times in the high-temperature region.
Full Text
AUTOMATIC RECORDING OF THE DELAY TIME OF EXPLOSIVE FLASHES
Yu. N. SUKHUSHIN, Yu. A. ZAKHAROV
(Presented by the scientific seminar of the Department of Radiation Chemistry, Chemical Engineering Faculty)
The sensitivity of explosives to various initial impulses (thermal, mechanical, explosive, etc.) is an important characteristic both for practical work with explosives and in considering the mechanism of the process of excitation and development of an explosion.
The sensitivity of explosives to a thermal impulse is characterized by the flash temperature of the explosive. The development of chemical self-
Fig. 1. Apparatus for determining the temperature dependence of the flash delay
the acceleration of the reaction in determining the flash temperature accounts for the phenomenon of flash delay. In testing explosives, the flash delay is usually recorded with a stopwatch [1—3]. The literature [4] contains a description of an apparatus for determining the ignition time; however, the use of automatic dropping of pellets and synchronization of the latter with a photographic recording system makes the described apparatus complex and unsafe.
We constructed an apparatus in which automatic recording of the flash delay was achieved according to the following principle: a weighed portion of explosive was placed in a piston (1) made of thin metal foil (Fig. 1), fastened to a metal rod (2). The rod falls into the furnace (3); at the same time the piston with the weighed portion, upon reaching the heated surface of a metal block placed in the furnace, closes the electrical circuit of the time-recording system. At the moment of explosion the contact is broken and the time recording stops; since the rod has a limiter (4), reclosing does not occur. Any electronic or electromechanical stopwatch may be used as the time-recording system. We used a time-recording system that made it possible to vary the recording accuracy from 0.05 to 0.0001 sec. For this purpose the counting part of a circuit for recording pulses of a VSP (4) was used. A GZ-33 generator (5) was used as the pulse sensor. Since such a circuit operates in the open state, a relay (6) was used to convert the operation of the circuit to the closed state. By maintaining constant the weighed portion and density of the explosive, as well as the dimensions of the piston and the position of the piston relative to the supporting rod-contact (2), it is possible to achieve sufficiently constant heating conditions for the weighed portion of the initiating explosive and thereby obtain results with good reproducibility.
Fig. 2. Temperature dependence of the flash delay for two charge diameters.
Figure 2 shows the temperature dependence of the flash delay for pure $\mathrm{PbN_6}$ at a density of $3\ \mathrm{g/cm^3}$ for two charge diameters. Thus, the installation described makes it possible automatically to record the flash-delay time of explosive substances, and the registration circuit employed makes it possible to determine the delay in the high-temperature region, i.e., short flash-delay times.
REFERENCES
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K. K. Andreev, A. F. Belyaev. Theory of Explosives. Moscow, Oborongiz, 1960.
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D. S. Avanesov. Laboratory Manual on Physicochemical Testing of Explosives. Moscow, Oborongiz, 1959.
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F. A. Baum, K. P. Stanyukovich, B. I. Shekhter. Physics of Explosion. Moscow, Fizmatgiz, 1959.
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J. E. Abel, B. Reitzner, Device for determining ignition time in RSI, 34, No. 6, 681–690 (1963).
Noted Misprints
| Page | Line | Printed | Should read |
|---|---|---|---|
| 4 | Table 4 | Splitting | Splitting, gauss |
| 8 | Fig. 2 | 1000 Å | 10000 Å |
| 19 | 1st from bottom | V. M. Likhin DAN SSSR |
V. M. Lykhin DAN SSSR |
| 22 | 24 from top | $\mathrm{O}^{=} = \square + 2e + 1/2\mathrm{O}_2$ | $\mathrm{O}^{=} = \square^{-} + e + 1/2\mathrm{O}_2$ |
| 23 | 13 from top | Due to electrons | Due to the capture of electrons |
| 23 | 16 from top | crystals of constants | crystals of constant |
| 28 | 7 from bottom | $\mathrm{A}^{-}\mathrm{A} \rightleftarrows {}^{0}_{\tau} + \bar e$ | $\mathrm{A}^{-} \rightleftarrows \mathrm{A}^{0}_{\tau} + \bar e$ |
| 36 | 12 from bottom | Zoumeine | Roumeine |
| 40 | 3 from top | at the exit | at the entrance |
| 44 | 5 from bottom | (II) | (I) |
| 47 | 3 from top | and surrounding | in surrounding |
| 51 | Table 1 | $\mathrm{NH}^{3+}$ | $\mathrm{NH}_3^{+}$ |
| 51 | Table 1 | $\mathrm{HCl}_{37}^{+}$ | $\mathrm{HCl}^{37+}$ |
| 54 | Fig. 2 | $t$ (sec) | $\lg t$ (sec) |
| 64 | 5 from top | in crystals makes it possible to obtain with a controlled magnitude of the surface |
in crystals with a controlled surface magnitude makes it possible to obtain |
| 69 | 8 from top and 13 from bottom |
PP–III | PP–III |
| 70 | Table 1 | $0.99 + 1.06 \cdot 10^{13}$ | $0.99 + 1.06 \cdot 10^{13}$ |
| 70 | 3 and 6 from bottom | A. D. Uobbe D. A. Zakharov |
A. D. Yoffe Yu. A. Zakharov |
| 71 | authors | 0.5% | 0.05% |
| 71 | 7 from bottom | $\lg \delta$ | $\lg \sigma_{\gamma}$ |
| 74 | caption under Fig. 4 |
$\mathrm{N}_3^{--} \sim\!\!\to \mathrm{N}_3^{0} + 1$ | $\mathrm{N}_3^{-} \sim\!\!\to \mathrm{N}_3^{0} + e$ |
| 77 | 10 from bottom | HO | $\mathrm{H}_0$ |
| 77 | caption under Figs. 1 and 2 |
ClO | $\mathrm{ClO}_3^{-}$ |
| 79 | 5 and 6 from top | $\mathrm{Cl}_4^{--} \sim\!\!\to \mathrm{Cl}_{4,1},[\mathrm{ClO}_4^{-}]^{*}$ | $\mathrm{ClO}_4^{-} \sim\!\!\to \mathrm{ClO}_4,e,[\mathrm{ClO}_4^{-}]^{*}$ |
| 81 | 17 from bottom | % 1168 | No. 1168 |
| 88 | 8 from top | $\mathrm{NH}_3$ | ${}^{15}\mathrm{NH}_3$ |
| 91 | 2 from bottom | $\mathrm{I}_{18}$ | $\mathrm{I}_{18}$ |
| 91 | 11 from bottom | ${}_{14}\mathrm{N}_{15}\mathrm{N}^{+},{}_{12}\mathrm{C}_{16}\mathrm{O}^{+}$ | ${}_{12}\mathrm{C}_{16}\mathrm{O}^{+},{}_{14}\mathrm{N}_{15}\mathrm{N}^{+}$ |
| 111 | 1 from bottom | Kadelats | Kadelatsi |
| 126 | 7 from top | Kj | Kl |
| 128 | 1 from bottom | $\mathrm{G} = g + J$ | $\mathrm{G} = g + \gamma$ |
| 132 | 11 from top | V | $V_k$ |
| 146 | 5 from bottom | spectrometry | spectroscopy |