Carbon resistor gauges for measuring shock and detonation pressures. I. Principles of functioning and calibration

The state of the art relative to the measurement of shock and detonation pressures of the magnitude generaled by condensed high explosives is reviewed. Carbon resistors have been shown to provide a relatively inexpensive and direct method for such measurements, provided adequate calibration data are available. The gauge is fabricated by heat-sealing the carbon resistor (470 Ω, 0.125 W) into a suitable plastic material such as polystyrene; when subjected to a strong shock wave, the gauge undergoes compression and the conductivity increases in proprtion to the magnitude of the pressure. The present investigation was concerned with the experimental derivation of calibration equations relating the pressure (in gigapascal) as a function of the conductivity change ΔG (in siemens). The point of inflaction occurring at approximately 2.36 GPa, corresponding to 0.02082 S, is in agreement with previous observations in the literature. Additional experiments are being planned to resolve a problem concerning oscillatory ringing in the gauge voltage records.     

Carbon resistor gauges for measuring shock and detonation pressures. III. Revised calibration data and relationships

For many years, carbon resistors have formed the basis for measurement of shock and detonation pressures associated with condensed explosives. The gauge is fabricated by heat-sealing the resistor into a plastic material such as polystyrene. When subjected to a strong shock wave, the resistance decreases, and the resulting increase in conductance is a function of the magnitude of the pressure. The present investigation was concerned with the experimental derivation of revised calibration equations, which was necessitated by the need to incorporate a terminating resistor into the gauge circuitry. The use of this resistor decreased the effect of standing waves and eliminated oscillatory ringing in the recorded signal. Typical records over a wide range of pressures are presented. An error analysis of the recorded data showed that the uncertainty in the measured pressure was of the same order of magnitude as the uncertainty in the interpretation of the recorded voltage from which the conductance was computed. An extensive discussion of the relevancy of the experimental data is presented, and the need for additional calibration experiments is stressed.     

Modeling the shock initiation of detonation of heterogeneous explosives

Conclusions The present review shows that accurate experiments on determining the evolution of predetonation-wave parameters and the high time resolution achieved in recording the interaction of steady DW with barriers form the basis of modern numerical modeling. The Zel'dovich-Neumann-Dering physical model used in most calculations has received sufficient experimental confirmation in modern investigations. One basic reason for the formation of hot spots as centers of chemical reaction is heating of the material as a result of SW interaction with the pores.The review has illustrated the diversity of existing approaches to modeling and forms of macrokinetic equations obtained and shown that they now allow the initiation to be described in a one-dimensional formulation and, in a number of cases, in two-dimensional geometry, including the action of rarefaction waves, as well as permitting the estimation of critical conditions of excitation and propagation of detonation. The use of numerical models offers the possibility of obtaining new qualitative information on the processes accompanying the initiation of detonation and correctly interpreting the experimental results.Novosibirsk. Translated from Fizika Goreniya i Vzryva, Vol. 23, No. 5, pp. 132–147, September–October, 1987.     

MgH2型复合敏化储氢乳化炸药的制备及其爆轰性能

为了提高乳化炸药的爆炸威力,研制出了一种MgH₂型复合敏化储氢乳化炸药。该乳化炸药采用包覆后的MgH₂与玻璃微球复合敏化,两种材料分别起到含能添加剂和敏化剂的作用。通过研究“热点”数量和包覆材料对炸药爆轰性能的影响,确定了MgH₂型复合敏化储氢乳化炸药的配方。利用水下爆炸实验和猛度实验,研究了MgH₂型复合敏化储氢乳化炸药的爆轰特征参数和水下爆炸特性。实验结果表明,MgH₂型复合敏化储氢乳化炸药的铅柱压缩量为24.3 mm,达到军用炸药的猛度;与传统玻璃微球型乳化炸药相比,其水下爆炸峰值压力虽然下降了4.90%,但比冲击波能、比气泡能和总能量分别提高了7.83%、22.94%和18.32%。MgH₂型复合敏化储氢乳化炸药的猛度和做功能力得到了显著提高。     

Density dependence of detonation velocity for some explosives

The nonmonotonic dependence of the detonation velocity of a cylindrical charge on density for explosives of the 2nd type is due to the effect of the finite charge diameter and is related to an increase in the width of the reaction zone with a reduction in the porosity of the explosive. __________ Translated from Fizika Goreniya i Vzryva, Vol. 42, No. 4, pp. 116–124, July–August, 2006.     

On mixing of the products of detonation of composite explosives in the chemical reaction region

The problem of mixing of the products of detonation of composite explosives is of principal importance for the synthesis of ultrafine diamond from composite mixtures and also for chemistry of detonation processes as a whole. An analysis of mixing in the chemical reaction region due to molecular diffusion shows that this mechanism may be important only for grain sizes of several micrometers. If the grain sizes reach tens or hundreds of micrometers, only partial mixing on the grain boundaries is possible. Investigations of the hydrodynamic mechanism of mixing shows that it may occur owing to a nonuniform velocity field behind the detonation wave front in the mixture and to the development of turbulence and cumulative processes during pore implosion. In mixtures with grain sizes of the order of 30 μm, these processes can lead to appreciable mixing during the time of ≈0.5 μs and longer. Theoretical estimates are compared with the results of experiments performed at the Lavrentyev Institute of Hydrodynamics of the Siberian Branch of the Russian Academy of Sciences and at the Altai Scientific and Industrial Enterprise (Biisk) for studying the synthesis of ultrafine diamond with the use of the isotope method.     

Initiation and development of detonation as a result of the action of weak shock waves on liquid explosives

Summary Clearly, in handling liquid explosives safely it is important to take into account, among other things, their actual physical state. Whereas for most liquid explosives the initiating pressures for simple homogeneous compression are high (60–120 kbar); in the presence of cavitation the same liquids exploded at relatively low pressures (about 0.1–10 kbar) and, in their sensitivity to waves shock, resemble (or may even be inferior to) powdered explosives (according to [16] the initiating pressure for PETN at a density of 1.0 g/cm³ is 2.5 kbar). Under favorable conditions, especially if the vessel is capable of conducting elastic disturbances, the development of explosion in liquids leads to a low-velocity detonation which may subsequently resolve into normal detonation. In this respect, the propagation of low-velocity regimes in liquids is very similar to the propagation of low-velocity detonation in powdered explosives. Our present lack of definite ideas, about the specific reaction initiation mechanism associated with the collapse of cavities in liquids places considerable diffculties in the way of any quantitative analysis of the experimental data on the excitation and propagation of explosions. Fizika Goreniya i Vzryva, Vol. 5, No. 3, pp. 354–361, 1969     

Analysis of the response of piezopolymer pressure gauges to a plane shock wave

We consider a phenomenological model for piezopolymer pressure gauges designed for registration of plane shock-wave pulses. We analyze the response of the gauges taking into account the physical phenomena observed in polarized polymer films upon action of high-intensity shock waves, the thermodynamic state of the material comprising the sensitive element, and the measurement circuit parameters. We compare the numerical calculations with experimental data for gauges made from polyvinylidene fluoride in the dynamic pressure range up to 16 GPa. We show that at such pressures, the electrical response is mainly determined by the change in the residual polarization of the piezofilm as a result of its compression.Institute of Chemical Physics at Chernogolovka. 142432 Chernogolovka. Translated from Fizika Goreniya i Vzryva, Vol. 30, No. 3, pp. 130–135, May–June 1994.     

Measurement of pressure and temperature with shock loading for porous composite materials

Novosibirsk. Translated from Fizika Goreniya i Vzryva, Vol. 25, No. 2, pp. 129–133, March–April, 1989.     

Detonation velocity deficit and curvature radius of flexible detonation fuses

The detonation velocity deficit in bending flexible detonating fuses is studied, based on the detonation wave’s corner effects and delay time phenomenon. A physical model and a theoretical mathematical equation of the detonation velocity deficit are established by using the dimensional analysis. Based on experimental data, a semi-empirical formula of the detonation velocity deficit for bending fuses in the same charge size is derived. It is shown that the detonation velocity deficit and the reciprocal of the curvature radius are in an exponential relationship.