On application of the plate dent test for the performance evaluation of emulsion explosives

The use of plate dent technique to evaluate w/o emulsion explosives is discussed in this paper. Experiments carried out with aluminium and mildsteel blocks show that the dent test results could give an idea about explosive performance. Attempts have been made to correlate the plate dent data with various detonation properties. Estimated detonation pressure did not yield a satisfactory correlation with either dent depth or dent volume. The role of detonation energy in governing the test result is highlighted. It is suggested that the plate dent test could be employed to assess the performance characteristics of large diameter, booster sensitive explosives.     

Analytic Model of Reactive Flow

A simple analytic model allows prediction of rate constants and size effect behavior before a hydrocode run, if size effect data exist. It utilizes detonation velocity, average detonation rate, pressure and energy at infinite radius. This allows the derivation of a generalized radius, which becomes larger as the explosive becomes more non‐ideal. The model is applied to near‐ideal PBX 9404, in‐between ANFO and most non‐ideal AN. The power of the pressure declines from 2.3, and 1.5 to 0.8 across this set. The power of the burn fraction, F, is 0.8, 0 and 0, so that an F‐term is important only for the ideal explosives. The size effect shapes change from concave‐down to nearly straight to concave‐up. Failure is associated with ideal explosives when the calculated detonation velocity turns in a double‐valued way. The effect of the power of the pressure may be simulated by including a pressure cut‐off in the detonation rate. The model allows comparison of a wide spectrum of explosives providing that a single detonation rate is feasible.     

Explosives Performance Potential - A New Definition

A new method for predicting explosive performance potential is suggested. This parameter, which has the dimension of power density, can be theoretically evaluated from three readily available quantities, as the product of the cube root of the volume ratio of detonation products to reactant, heat of detonation, and detonation velocity of the explosive. The calculated performance potential has been found to correlate well with the strength and brisance data for a number of explosives. Experimental detonation pressure gives equally satisfactory correlation; since its measurement is difficult, the approach advocated here is preferable.     

The State of the Detonation Products of Solid Explosives

The polytropic equation, together with the detonation relations, provides practicable values for all the quantities characterizing the detonation products of solid, high explosives apart from the temperature. Its application, however, is restricted to material at absolute zero, that is to solids possessing purely potential energy. Thus polytropic detonation products have the characteristics of solids although their state of aggregation is gaseous. In fact the polytropic equation can be derived by assuming a solid under an internal, expansive pressure sufficient to break all atomic bonds. In terms of the Debye theory this represents an approximation which is valid in the absence of the thermal energy contribution from atomic vibrations. This requirement is satisfied by the detonation products of solid explosives of sufficiently high density since their heat of detonation is completely absorbed by the breakage of atomic bonds or the sublimation of the atomic lattice. The sublimation process in the course of the reaction also allows the Chapman-Jouguet temperature of the detonation products to be determined from the equilibrium between the phases. In addition the fracture theory provides material data which assign a metallic character to the polytropic detonation products and indicate that they form a conducting plasma.     

Calculation of the Energy of Explosives with a Partial Reaction Model. Comparison with Cylinder Test Data

The energy delivered by explosives is described by means of the useful expansion work along the isentrope of the detonation products. A thermodynamic code (W‐DETCOM) is used, in which a partial reaction model has been implemented. In this model, the reacted fraction of the explosive in the detonation state is used as a fitting factor so that the calculated detonation velocity meets the experimental value. Calculations based on such a model have been carried out for a number of commercial explosives of ANFO and emulsion types. The BKW (Becker‐Kistiakowsky‐Wilson) equation of state is used for the detonation gases with the Sandia parameter set (BKWS). The energy delivered in the expansion (useful work) is calculated, and the values obtained are compared with the Gurney energies from cylinder test data at various expansion ratios. The expansion work values obtained are much more realistic than those from an ideal detonation calculation and, in most cases, the values predicted by the calculation are in good agreement with the experimental ones.     

A Simple and Rapid Evaluation of Explosive Performance – The Disc Acceleration Experiment

It is crucial in the development of a new explosive to obtain an evaluation of performance early in the process when the availability of material is limited. Evaluation requires dynamic measurements of detonation velocity, pressure, and expansion energy – typically in separate experiments that require large amounts of material, time, and expense. There is also a need for evaluation of the total available thermodynamic energy. The dynamic evaluations, in particular, have been a major hindrance to development of new explosives. The new experimental testing method to be described here requires small charges and obtains accurate measurement of all three of the detonation performance characteristics in a single test. The design, a Disc Acceleration eXperiment (DAX), provides an initial condition of steady detonation and a charge‐geometry amenable to 2D hydrodynamic simulations. The velocity history of a metal disk attached to the end of the explosive charge is measured with Photonic Doppler Velocimetry (PDV). This disc velocity data is analyzed to give both CJ pressure and expansion energy. The detonation velocity is obtained with probes along the charge length. The experiments and subsequent analyses are concentrated on LX‐16, a known PETN based explosive, for the purpose of establishing the accuracy of the method and to provide a standard for comparison with other explosives. We present details of the experimental design and also detonation velocity and PDV results from a number of experiments. The total available internal energy for the explosive was obtained from published detonation calorimetry measurements by Ornellas [1], and from thermodynamic equilibrium calculations. An equation‐of‐state (EOS) for LX‐16 was derived from hydrodynamic simulations of thin plate‐push velocity‐time data. We will show a successful comparison with a previously published Jones‐Wilkins‐Lee (JWL) EOS for PETN by Green and Lee [2–4].     

Calculation of Detonation Properties of Gaseous Explosives Using Generalized Reduced Gradient Nonlinear Optimization

In this paper, a study on the development of a numerical modeling of the detonation of C H N O‐based gaseous explosives is presented. In accordance with the numerical model, a FORTRAN computer code named GasPX has been developed to compute both the detonation point and the detonation properties on the basis of Chapman–Jouguet (C‐J) theory. The determination of the detonation properties in GasPX is performed in chemical equilibrium and steady‐state conditions. GasPX has two improvements over other thermodynamic equilibrium codes, which predict steady‐state detonation properties of gaseous explosives. First, GasPX employs a nonlinear optimization code based on Generalized Reduced Gradient (GRG) algorithm to compute the equilibrium composition of the detonation products. This optimization code provides a higher level of robustness of the solutions and global optimum determination efficiency. Second, GasPX can calculate the solid carbon formation in the products for gaseous explosives with high carbon content. Detonation properties such as detonation pressure, detonation temperature, detonation energy, mole fractions of species at the detonation point, etc. have been calculated by GasPX for many gaseous explosives. The comparison between the results from this study and those of CEA code by NASA and the experimental studies in the literature are in good agreement.     

Experimental study on the effect of titanium hydride content on the detonation performance of emulsion explosives

In order to improve the explosion characteristics of emulsion explosives, titanium hydride was added to emulsion explosives to produce a new type of hydrogen storage emulsion explosives. Charges with different contents of titanium hydride were evaluated through underwater explosion experiments and detonation velocity tests. The tests on underwater explosion and detonation velocity reveal that compared to pure emulsion explosives, the detonation parameters of emulsion explosives containing titanium hydride showed a trend of first increasing and then decreasing. When the mass ratio of titanium hydride in the emulsion explosive is 1 % to 3 %, all detonation parameters have been improved to a certain extent. When the mass ratio of titanium hydride in the emulsion explosive is 3 % to 10 %, only part of the detonation parameters (specific impulse, specific shock energy, specific total energy and volume energy density) has been improved. The maximum increase of specific impulse, specific shock energy, specific total energy and volume energy density of emulsion explosive containing titanium hydride is 7.06 %, 8.95 %, 3.97 % and 8.22 %, respectively. Based on the analysis, it is evident that though powdered TiH₂ participates in the detonation reaction process of the emulsion explosive, the majority of TiH₂′s energy is released during the secondary reaction occurring after the detonation wave front. Therefore, the detonation performance of emulsion explosives can be effectively improved by adding a certain mass ratio of titanium hydride.     

Critical detonation diameter of industrial explosive charges: Effect of the casing

The critical detonation diameter of industrial explosive charges is analyzed as a function of their state characteristics (composition, density, and structure) and the presence of a casing. The main reason for the increase in the critical diameter with increasing density of ammonium nitrate explosive charges is the reduction in the energy release rate in the chemical reaction zone of the detonation wave. The effect of the particle size of the components and the amount of the sensitizing component on the critical diameter of powdered and granular explosives fits into the concept of explosive combustion. An analytical formula for the critical detonation diameter of emulsion explosives is obtained which correctly describes experimental data. A possible mechanism of the effect of metal casings on the critical detonation diameter is considered for porous explosives whose detonation velocity is lower than the sound velocity in the casing.     

Predicting High Explosive Detonation Velocities from their composition and structure (II)

An earlier paper⁽¹⁾ described a simple linear relationship between detonation velocity of 64 ideal C,H,N,O type explosives at their theoretical maximum densities (TMD's) and a factor. F, that is dependent solely upon chemical composition and structure. Based upon available experimental data for nine fluorine-containing explosives, the equation for calculating the factor has been expanded to include compositional terms for fluorinated compounds. In addition, the reliability of the linear relationship has been further tested against seven more recently published C,H,N,O type explosive experimental detonation velocity data points. The calculated detonation velocity values for all 16 explosives lie within 6.0% of experimental with an absolute error of ± 3.0%.     

含铝典型炸药爆轰参数计算研究

用途不同,对炸药的爆速、爆压、爆热要求不一样。准确、快速计算炸药的爆轰参数对于设计指定性能新型炸药和炸药的应用研究具有十分重要的意义。本文用不同的方法对含铝炸药的爆轰参数进行了计算,采用含铝炸药经验公式计算含铝炸药的爆速、ω-Г公式方法计算的爆压、盖斯定律计算爆热,较其他计算方法计算结果相对误差小。     

铝粉含量对梯铝炸药爆压和冲击波参数的影响

测试了以TNT为基不同含量含铝炸药的爆压和空中爆炸冲击波参数,通过分析铝粉对炸药爆压、空中爆炸参数和爆炸冲击波超压的影响,建立了爆压与铝氧比的关系曲线、5种TNT基含铝炸药的冲击波相似律方程和TNT/Al炸药的爆压与空中爆炸冲击波超压的关系式.结果表明,随着铝粉含量的增加,炸药的爆压呈指数衰减,近距离的冲击波超压也快速减小,但爆炸场温度和爆炸火球的直径及持续时间会增大.     

金属柱壳约束对非理想炸药驱动效率的影响

通过分析金属柱壳在内部炸药滑移爆轰作用下的动力学响应,建立了爆轰产物压力与壳体径向膨胀位移、材料动态屈服强度之间的关系式。基于Taylor假定确定了壳体完全破裂时爆轰产物压力的阈值。以两种具有相近格尼系数的RDX基含铝炸药为例,对该模型的适用性进行了验证。结果表明,相同壳体下,与无硝酸酯的RDX基含铝炸药相比,含硝酸酯的RDX基含铝炸药的驱动能量利用率具有明显优势。当壳体材料动态屈服强度从0.2GPa增至0.8GPa时,其有效作功能的相对增量约从7.5%迅速增大至15.2%,符合战斗部实际应用中的趋势,表明该分析模型可用于非理想炸药驱动作功性能的综合评价。     

VLW爆轰产物状态方程的发展及应用

以国际公认理论完美的维里(VIRIAL)状态方程为基础,建立了VLW炸药爆轰产物状态方程,简述了VLW炸药爆轰产物状态方程的形成背景,呈现了VLW方程的推导过程;应用VLW方程计算了军用高能炸药、民用工业炸药、凝聚相炸药、气相燃料空气炸药的爆轰性能参数,以及火箭推进燃烧性能参数,推导了爆轰产物的热力学函数(内能、熵、化学位等)。结果表明,应用VLW方程计算的参数结果准确合理;成功解决了高温下(T*>20)高级维里系数计算难题,准确表达了爆轰条件下的维里方程属性。     

Numerical Modeling of Underwater Explosion Properties for an aluminized explosive

Underwater explosion properties of an aluminized explosive, DXD-03, were numerically modeled by two burn techniques; a programmed-burn technique and a rate equation calibrated from two-dimensional steady-state detonation experiments based on the detonation shock dynamics. The modeling by using the programmed-burn technique did not reproduce experimental data well; 12% to 34% error in peak pressure and 20% error in bubble period. The modeling by using the rate equation reproduced the experimental observations very well. Although there was some difference in peak pressure, the shock profile agreed very well with experimental observation. The calculated bubble period agreed with the experimental data within 1%. This result demonstrates that the underwater explosion properties for aluminized explosives can be calculated only when the slow energy release of aluminium is modeled properly.     

Detonation characteristics of emulsion explosives sensitized by MgH2

Preliminarily results on the reaction mechanism of detonation of composite emulsion explosives sensitized by MgH₂, which simultaneously plays the role of an energetic material, are presented. Compared to emulsion explosives sensitized by glass microspheres, emulsion explosives sensitized by magnesium hydride have a different reaction mechanism of detonation. The shock wave overpressure, specific impulse, shock wave energy, and bubble energy are all greatly increased with the use of MgH₂, and it is noticeable that the shock wave overpressure and shock wave energy increase by 17% and 24%, respectively. In addition, emulsion explosives sensitized by MgH₂ improve significantly in terms of detonation velocity and brisance. These emulsion explosives also meet safety requirements.     

Relationship between brisance of explosives and their molecular-atomic structures

The explosives with various molecular-atomic structures substantially differ by their detonation velocities and brisance but often are similar by the expansion of their detonation products (DP's) which mainly consist of the same molecules. Such explosives referred to as “usual” show the relationship between ϱD and brisance determined by different methods. There are linear correlation relations between the results obtained. This relationship is not observed with the “unusual” explosives which differ from the “usual” ones by the chemistry of detonation processes. These explosives include liquid explosives, explosive-oxidants. CNO- and HNO-explosives and also CHNOF-explosives. Their calculation of thc detonation parameters and brisance from the same criterions which characterize the chemical composition of the explosives and the detonation products, results in some errors. Taking these differences into account it is possible in some cases markedly to increase the accuracy of the detonation parameters. As an example is the calculation of the detonation pressure to within 3% based on the linear correlation relation between the pressure (P_J) and the relative detonation impulse (I_rel) which characterizes the charge ability to do work at the initial stages of thc expansion of the detonation products: The relative impulse, in its turn, may be calculated both for “usual” and “unusual” explosives from the atomic composition of an explosive, its density and the enthalpy of the formation with the error that does not exceed the experimental (2%).     

炸药破甲威力与爆轰参数之间定量关系的探讨

探讨了炸药的破甲威力与爆轰参数之间的关系,发现在一定计算精度范围内,炸药的破甲威力与爆速Ｄ的关系比较复杂,而与爆压Ｐ的关系相对比较简单且具有较高的计算准确度,据此提出,爆压Ｐ与破甲深度ｈ、与破孔体积Ｖ之间的定量关系式。对单质炸药和混合炸药的计算结果表明,计算值与实验值的一致性令人满意。根据这一定量关系,可以确定提高炸药破甲威力的两条件途径,一是提高炸药的爆压,即提高炸药的能量,二是通过设计新型装药结构,提高炸药能量的利用率,应用本文定量关系,不仅能够预测炸药的破甲威力,而且对于寻求具有优良破甲威力的炸药及设计新型装药结构具有一定的参考价值。     

Carbon resistor gauges for measuring shock and detonation pressures. II. Detonation pressure of carbohydrate-metal composite explosives

An estimate of the detonation pressure of carbohydrate-metal composite explosives has been obtained experimentally by use of carbon resistor pressure gauges mounted in the wall of the confining tubes. The composite explosives were formulated from a pharmaceutical mixture of 10/90 nitroglyccrin/ß-lactose by weight, and was rendered detonable by inclusion of flaked aluminum and both flaked aluminum and ammonium perchlorate. The detonation pressure of the nitroglyccrin/ß-lactose mixture with 10 percent aluminum by weight was approximatcly 1.1 GPa. The incorporation of 30 percent ball-milled ammonium perchlorate to this formnlation increased the detonation pressure to 12.2 GPa. These pressures must be considered as estimates of the true detonation pressure, because of (a) the suspected non-ideality of the detonation state of these explosives, (b) the statistical nature of the response of the gauges, and (c) possible inconsistencies in the interpreatation of the gauge records. It is recommended that a number of gauges be used in a given experiment, and the results be averaged as one means of cireumventing the above difficulties.     

Predicting High Explosive Detonation Velocities from their composition and structure

A simple, empirical linear relationship between detonation velocity at theoretical maximum density and a factor, F, that is dependent solely upon chemical composition and structure is postulated for a gamut of ideal explosives. The explosives ranged from nitroaromatics, cyclic and linear nitramines, nitrate esters and nitro-nitrato aliphatics to zero hydrogen explosives, carbonless explosives and hydrogen rich explosives. Of the 64 explosives evaluated, 95% had calculated detonation velocity values within 5% of experimental and 98% within 7%. Only nitromethan varied grossly (−; 13%) from calculated velocity and the absolute error for all explosives is ±2.3%.