Gurney Energy Research Articles

Numerical Simulations of 122 mm M-21OF Missile Fragments Propulsion

This paper presents numerical simulations of 122 mm M-21OF rocket fragments propulsion. A simplified geometry of the rocket was constructed and analysed with two main numerical FE approaches: a mesh-based lagrangian-eulerian FSI method and a coupled meshless SPH–lagrangian approach. The resulting fragment velocities were compared with those obtained from an analytical approach (Gurney formula). The shell fragmentation process was also successfully depicted. Both numerical approaches differed from the analytical velocity results to a comparable degree. Considering that the Gurney energy of a high-explosive is obtained from cylinder expansion tests, results obtained with the Gurney method can be treated as a reference point and validation method for natural fragmentation warhead models.

Research on the quasi-isentropic driving model of aluminized explosives in the detonation wave propagation direction

Taking CL-20 (Hexanitrohexaazaisowurtzitane)-based aluminized explosives with high gurney energy as the research object, this research experimentally investigates the work capability of different aluminized explosive formulations when driving metal flyer plates in the denotation wave propagation direction. The research results showed that the formulations with 43 μm aluminum (Al) powder particles (The particle sizes of Al powder were in the range of 2∼43 μm) exhibited the optimal performance in driving flyer plates along the denotation wave propagation direction. Compared to the formulations with Al powder 13 μm, the formulations with Al powder 2 μm delivered better performance in accelerating metal flyer plates in the early stage, which, however, turned to be poor in the later stage. The CL-20-based explosives containing 25% Al far under-performed those containing 15% Al. Based on the proposed quasi-isentropic hypothesis, relevant isentropy theories, and the functional relationship between detonation parameters and entropy as well as Al reaction degree, the characteristic lines of aluminized explosives in accelerating flyer plates were theoretically studied, a quasi-isentropic theoretical model for the aluminized explosive driving the flyer plate was built and the calculation methods for the variations of flyer plate velocity, Al reaction degree, and detonation product parameters with time and axial positions were developed. The theoretical model built is verified by the experimental results of the CL-20-based aluminized explosive driving flyer plate. It was found that the model built could accurately calculate the variations of flyer plate velocity and Al reaction degree over time. In addition, how physical parameters including detonation product pressure and temperature varied with time and axial positions was identified. The action time of the positive pressure after the detonation of aluminized explosives was found prolonged and the downtrend of the temperature was slowed down and even reversed to a slight rise due to the aftereffect reaction between the Al powder and the detonation products.

Detonation of high explosives containing phosphorus(V) nitride, P3N5

AbstractComposition A4 (RDX/wax, 94/6 wt %) modified with additional phosphorus(V) nitride, P3N5 (CAS‐No.: [12136‐91‐3]) and aluminum does not show increased detonation velocity, Gurney energy or blast pressure when compared with the baseline formulation. The general failure of P3N5 to contribute to the detonation performance is understood to result from the low negative enthalpy of formation of P3N5 that makes this compound a “heat sink” in the detonation and post detonation zone. A formulation containing both P3N5 and Al (RDX/P3N5/Al/wax: 50.76/36/10/3.24 wt %) shows superior luminosity and temperature of the post detonation fireball when compared with both Comp A4 and even aluminized Comp A4 (Hexal=RDX/Al/wax: 65.8/30/4.2 wt %). The superior luminosity is understood to be due to formation of aluminum phosphate, AlPO4 a material with high optical emissivity which however, decomposes above T=1600 °C.

Switchable Explosives: Performance Tuning of Fluid-Activated High Explosive Architectures.

We present our discovery of switchable high explosives (HEs) as a new class of energetic material that cannot detonate unless filled with a fluid. The performance of fluid-filled additive-manufactured HE lattices is herein evaluated by analysis of detonation velocity and Gurney energy. The Gurney energy of the unfilled lattice was 98% lower than that of the equivalent water-filled lattice and changing the fluid mechanical properties allowed tuning of the Gurney energy and detonation velocity by 8.5% and 13.4%, respectively. These results provide, for the first time since the development of HEs, a method to completely remove the hazard of unplanned detonations during storage and transport.

Detonation Characteristics of an Aluminized DNAN‐Based Melt‐Cast Explosive

AbstractInvestigations of the detonation characteristics of a new aluminized DNAN‐based melt‐cast explosive RMA‐2X (containing 30 wt.% DNAN (2,4‐dinitroanisole), 30 wt.% NTO (3‐nitro‐1,2,4‐triazol‐5‐one), 10 wt.% HMX (1,3,5,7‐tetranitro‐1,3,5,7‐tetraazacyclooctane) and 30 wt.% aluminum) were undertaken, as well as a lithium fluoride (LiF) substituted explosive RMF‐2X (containing 30 wt.% DNAN, 30 wt.% NTO, 10 wt.% HMX and 30 wt.% LiF). The interfacial velocity experiment was carried out to measure the reaction zone parameters (including the CJ pressure, the pressure at the Von Neumann spike, and the reaction zone length) of RMA‐2X. The cylinder test was also performed, and employing the test data, the detonation velocity, the Gurney energy, and the detonation energy of RMA‐2X were calculated. Investigation results are analyzed and some conclusions are drawn. The role of aluminum in the detonation characteristics are also discussed. Finally, parameters of the Jones‐Wilkins‐Lee equation of state of the detonation products were confirmed.

Study on the Effect of NTO on the Performance of HMX-Based Aluminized Cast-PBX.

3-Nitro−1,2,4-triazol−5-one (NTO) is an explosive with broad application prospects. To study the effect of NTO content on the properties of HMX-based cast-PBX (polymer bonded explosive), five different HMX/NTO-based cast-PBXs were prepared and characterized by experiments and simulations. The results show that the addition of NTO is beneficial to reduce the mechanical sensitivity of cast-PBX, but will reduce the energy level of cast-PBX. We then found that with the increase in NTO content, cast-PBX showed a trend of first increasing and then decreasing in terms of mechanical properties, specific heat capacity (Cp) and thermal conductivity (λ). In addition, we found that the Gurney energy (Eg) of N30 is 2.31 kJ/g. Finally, the increase in NTO content greatly improves the thermal safety performance of the cast-PBXs, and numerical simulation of slow cook-off can be used as one reliable method to obtain the ignition location, ignition temperature and the transient temperature distribution.

Gurney model for non-standard cylinder with increased wall thickness and its application in aluminized explosives

To meet the requirements of an aluminized explosive cylinder test with a longer energy release time, a non-standard cylinder structure with a larger wall thickness was designed, which can not only extend the effective expansion time of detonation products but also avoid a great increase in the test charge mass. The non-standard cylinder was filled with TNT explosives for its relatively stable Gurney energy, and the experimentally generated parameters were compared with those of Φ50 and Φ100 mm standard cylinders. Based on this, a more accurate Gurney Model for Non-Standard Cylinder (GM-NSC) was proposed taking into account the influence of shell deformation and axial movement of detonation products compared with the traditional Gurney model. The analysis results show that the proposed GM-NSC model curve is suitable for both non-standard and standard cylinders. Finally, the method was applied to DNAN-based aluminized explosives, and the experimental results show that the method can characterize more thoroughly the effect of the detonation product expansion enhanced by the rapid reaction of aluminum powders.

Energy Performance of HMX‐Based Aluminized Explosives Containing Polytetrafluoroethylene (PTFE)

AbstractInvestigation of the energy performance of HMX‐based aluminized explosives added with polytetrafluoroethylene (PTFE) oxidizer was undertaken and compared with the PTFE‐free aluminized explosive of similar formulation. Firstly, the heat of explosion was measured in a calorimetric bomb, next the underwater explosion was conducted, then the cylinder expansion test was performed, and finally, the detonation reaction zone parameters were determined by the interface particle velocity experiment. Compared with the PTFE‐free aluminized explosive, the addition of PTFE into aluminized explosives increases the heat of explosion significantly from the calorimetric data. The PTFE‐containing aluminized explosive also yields the longer first bubble oscillation time in the underwater explosion than the PTFE‐free and ammonium perchlorate‐containing counterparts. From the cylinder test data, the wall velocity and Gurney energy were determined. The aluminized HMX containing PTFE shows an inferior acceleration ability to PTFE‐free aluminized HMX, but exhibits a stronger afterburning potential. The addition of PTFE to aluminized HMX decreases detonation velocity and CJ pressure and increases the detonation reaction zone time and length. It has reasons to believe that the PTFE partially decomposes in detonation reaction zone. Conclusions on the potential use and suggestion for future research of PTFE as an oxidizer in aluminized explosives are drawn.

Evaluation of the Detonation Characteristics of Aluminized DNAN‐Based Melt‐Cast Explosive by the Detonation Cylinder Test

AbstractTo investigate the detonation characteristics of a new aluminized DNAN‐based melt‐cast explosive RDA‐2 (containing DNAN (2,4‐dinitroanisole), HMX (cyclotetramethylene tetranitramine) and aluminum), a series of cylinder tests were conducted. The LiF (lithium fluoride) explosive of a similar formulation was also tested to study the influence of aluminum on the detonation characteristics of RDA‐2. The cylinder wall expansion velocities were recorded by Photonic Doppler Velocimetry (PDV). From the experimental data, the detonation velocity, the Gurney energy, the detonation energy, and the CJ pressure of the explosives were calculated. Both the detonation velocity and CJ pressure results indicate that the aluminum seems to have no significant influence on the chemical reaction zone of RDA‐2. The experimental data shows that a large amount of aluminum reacts behind the CJ point. Finally, the parameters of the Jones‐Wilkins‐Lee (JWL) equation of the state of the detonation products were determined.

Gurney Equation Change for the Symmetric Sandwich

AbstractSixteen symmetric sandwiches of explosive/copper have been fired. The traditional Gurney equation for energy density is found to be 3–8 % low compared to Cylinder test results. The suggestion is made to divide the Gurney energy by the square of the cosine of the edge angle caused by the fanning out of the metal. This introduces a fundamental correction to the Gurney equation for the unidirectional nature of detonation.

Thermally Stable and Low‐Sensitive Aluminized Explosives with Improved Detonation Performance

AbstractTwo new types of aluminized explosives TATB/HMX/Al and LLM‐105/Al were formulated and compared with the formerly reported TATB/Al explosives in terms of thermal stability, mechanical sensitivity, and detonation performance. Firstly, the heat of the explosion was measured and two formulations were selected as the investigated samples. Next the thermal stability was studied by simultaneous thermogravimetric analysis/differential scanning calorimetry (TGA/DSC) and thermal cook‐off tests. Then the impact and friction sensitivity were measured, and finally the detonation performance was characterized by cylinder tests and particle velocity measurements of the detonation reaction zone. From the calorimetric data, the new types of explosives increase the heat of the explosion significantly. In terms of thermal stability, LLM‐105/Al=65/30 is more stable than TATB/HMX/Al=50/15/30, but both of them are inferior to TATB/Al=70/25. The impact sensitivity of the two new explosives is higher than that of TATB/Al=70/25, and all of the samples are insensitive to friction. For detonation performance, both of the two new samples are superior to TATB/Al=70/25, and LLM‐105/Al=65/30 exhibits the best performance that it has the highest Gurney energy, detonation velocity, and detonation pressure. Conclusions about how to use those aluminized explosives to generate optimal effects are drawn.

Influences of FOX-7 and NTO on the metal driven ability and underwater explosion power of HMX-based aluminized explosives

In order to investigate the metal driven abilities of two newly HMX-based aluminized explosives (XL: 31% HMX, 31% FOX7, 30% Al, 8% binder; EL: 31% HMX, 31% NTO, 30% Al, 8% binder), multiple cylinder tests were conducted to gain the cylinder wall expansion process and evaluate Gurney energy. Then the parameters of JWL-Miller equation of state were determined based on experimental expansion data. For evaluating the underwater explosion power of XL and EL, we numerically simulated the propagation of shock wave and bubble pulsation under water. The experimental and modeling results showed that the metal driven ability and underwater explosion overpressures of XL were obvious better than EL, but the specific bubble energy of XL was only about 3% higher than EL. Compared with NTO, FOX-7 better improve metal driven capacity, underwater explosion power and secondary combustion rate of aluminized explosives. Those conclusions may provide useful suggestions for designing HMX-based insensitive aluminized explosives.

Prediction of Cylinder Wall Velocity Profiles for ANFO Explosives Combining Thermochemical Calculation, Gurney Model, and Hydro‐Code

AbstractTheoretical prediction of performance indicators of explosives plays an important role in the development of new explosives and explosive formulations. Of particular interest is the possibility to estimate the velocity of metal liner driven by an explosive charge. We present a theoretical model for estimation of metal cylinder wall velocity profiles of non‐ideal ANFO explosives. The model is based on thermochemical calculations using EXPLO5 code, expressing the Gurney energy in terms of JWL equation of state, and using hydro‐code simulation. The Wood‐Kirkwood detonation theory, incorporated in EXPLO5, is applied for calculation of detonation parameters of non‐ideal ANFO explosives. It was found that this approach enables prediction of cylinder wall velocity for ANFO explosives, with the error at V/V0=7 expansion ratio not exceeding 100 m/s.

Research on the High Safety Velocity of Detonator Flyer

Flyer is the key part of the non-primary detonator, which determines whether the detonator could explode. In the present paper, the flyer plate model driven by explosive is applied to the flyer calculation of the excitation device. The velocity range of the detonation velocity and the flyer is determined by experiments, and compared with the numerical results.. Comparing the results, the conclusion is made that the unstable detonation happened in the excitation power, and Gurney energy is only 10%~30% of explosion heat, and some factors which could affect the flyer velocity are also given.

Estimation of Explosive Energy Output by EXPLO5 Thermochemical Code

Detonation velocity, detonation pressure, and detonation heat are usually used as a measure of explosive's performance. However, they do not answer the question how fast an explosive can accelerate the surrounding metal liner. A semi‐empirical solution to this problem was proposed byR. W. Gurneyin 1943. In this paper we used thermochemical calculations to calculate energy of detonation products along the expansion isentrope and to estimate the Gurney energy and cylinder wall velocity from it. It was found that for the same degree of the products expansion, experimentally determined Gurney energy is systematically less than calculated detonation energy due to the energy losses. At about threefold expansion of the products, the detonation energy matches very well with an experimental Gurney energy.

Detonation Characteristics of an Aluminized Explosive Added with Boron and Magnesium Hydride

AbstractInvestigation of the detonation characteristics of an aluminized explosive added with boron (B) and magnesium hydride (MgH2) were undertaken and compared with the aluminized explosive of similar formulation. Firstly, the explosion heat was measured in a vacuumed calorimetric bomb, then the detonation pressure was determined by the interface velocity experiment, and finally the cylinder expansion test was performed. From the calorimetric data, the addition of B and MgH2 into an aluminized explosive increases the heat of explosion slightly. From the detonation pressure data, the addition of B and MgH2 appears to have no significant influence to the detonation pressure. From the cylinder test data, the detonation velocity, wall velocity, Gurney energy and detonation energy were determined. The aluminized explosive added with B and MgH2 shows weak acceleration ability, but exhibits a stronger afterburning potential. Finally the equation of state of the detonation products was determined for different casing conditions. Conclusions about how to use B and MgH2 in aluminized explosives to generate optimal effects are drawn.

A mesoscale study on explosively dispersed granular material using direct simulation

Explosively dispersed granular materials frequently exhibit coherent particle clustering and jetting structures. Influencing the mass concentration and related particle reaction and energy release, this phenomenon is of significant interest to the study of flow instability and mixing in heterogeneous detonation and explosion. Largely inhibited by the complex mesoscale multiphase interactions involved in the dispersal process, the underlying mechanism remains unclear. In this study, mesoscale direct simulations that capture coupled multiphase interactions and deterministic granular dynamics are conducted to investigate particle clustering and jetting formation in explosively dispersed granular payloads consisting of inert particles. Employing a mesoscale simulation framework that models particles as discrete entities and resolves the interfaces and collisions of individual particles in stochastically generated payloads with randomly distributed particle positions and sizes, numerical cases that cover a set of stochastic payloads, burster states, and coefficients of restitution are solved and analyzed. A valid statistical dissipative property of the mesoscale discrete modeling with respect to Gurney velocity is demonstrated. The predicted surface expansion velocities can extend the time range of the velocity scaling law with regard to Gurney energy in the Gurney theory from the steady-state termination phase to the unsteady evolution phase. Dissipation analysis based on the mesoscale discrete modeling of granular payloads suggests that incorporating the effects of porosity can enhance the prediction of Gurney velocity for explosively dispersed granular payloads. On the basis of direct simulations, an explanation for particle clustering and jetting formation is proposed to increase the understanding of established experimental observations in the literature.

Insensitive high explosives: IV. Nitroguanidine – Initiation & detonation

This paper reviews the detonative properties of low bulk density (LBD), high bulk density (HBD) Nitroguanidine (NGu)(1), CAS-No: [556-88-7] and 82 explosive formulations based on NGu reported in the public domain. To rank the performance of those formulations they are compared with 15 reference compositions containing both standard high explosives such as octogen (HMX)(2), hexogen (RDX)(3), pentaerythritol tetranitrate (PETN)(4), 2,4,6-trinitrotoluene (TNT)(5) as well as insensitive high explosives such as 3-nitro-1,2,4-triazolone (NTO)(6), 1,3,5-triamino-2,4,6-trinitrobenzene (TATB)(7), 1,1-diamino-2,2-dinitroethylene (FOX-7)(8) and N-Guanylurea dinitramide (FOX 12)(9). NGu based formulations are superior to those based on FOX-12 or TATB and are a close match with FOX-7 based explosives, the latter just having higher Gurney Energies (∼10%) and slightly higher detonation pressure (+2%). NGu based explosives even reach up to 78% of the detonation pressure, 82% Gurney energy and up to 95% of detonation velocity of HMX. LBD-NGu dissolves in many melt cast eutectics forming dense charges thereby eliminating the need for costly High Bulk Density NGu. Nitroguanidine based formulations are at the rock bottom of sensitiveness among all the above-mentioned explosives which contributes to the safety of these formulations. The review gives 132 references to the public domain. For a review on the synthesis spectroscopy and sensitiveness of Nitroguanidine see Ref. [1].

Sensitivity of Energetic Materials: Theoretical Relationships to Detonation Performance and Molecular Structure

It has been known for decades that high performances for explosives (as characterized by detonation velocity D, detonation pressure P, or Gurney energy EG) are connected with high impact sensitivities, i.e., low values of the drop weight impact height h50. This trade-off is theoretically substantiated for the first time. It stems from the primary role of the amount of chemical energy evolved per atom for both performance and sensitivity. Under realistic assumptions, log(h50) increases linearly with D–4 or equivalently with P–2 or EG–1. This prediction proves consistent with experimental data for nonaromatic nitro compounds. The occurrence of different explosophores on the same molecule is suggested as a factor influencing the performance-sensitivity trade-off. Finally, it is shown that a large body of data may be explained by the present approach, which naturally integrates thermodynamic (energy content) as well as kinetic (activation energies) aspects. This model should help in designing powerful high en...

NTO-based Melt-cast Insensitive Compositions

This paper presents research on insensitive melt-cast explosive compositions based on 3-nitro-1,2,4-triazol-5-one (NTO) and containing TNT, wax, Al and RDX. The viscosity of the compositions in the operating temperature range was measured. Thermal analysis was performed as well as thermal stability and sensitivity to mechanical and thermal stimuli were tested. The detonation parameters were also determined. Finally, the acceleration ability (Gurney energy) and the JWL coefficients for the detonation products were established.