Zhuo-Ping Duan

A Pore Collapse Model for Hot-spot Ignition in Shocked Multi-component Explosives

A new pore collapse model, in which the effect of the binder in Plastic Bonded Explosives (PBX) is taken into account, is developed and integrated into the so-called hot-spot ignition model of shocked explosives. A two-dimensional hydrocode DYNA2D is used to simulate the shock initiation of PBX, with a reaction rate model consisting of a hot-spot ignition term, a slow-burning term at low pressure and a high-pressure reaction term. The numerical results show that the model can successfully describe the effects of the strength and the content of the binder, particle size and porosity of explosives on the shock initiation.

Foil-like manganin gauges for dynamic high pressure measurements

Foil-like manganin gauges with a variety of shapes used in different ranges of pressure for the one-dimensional strain mode and axisymmetric strain mode were designed for measuring the detonation pressures of explosives and high shock pressure in materials. In the stress range of 0–53.5 GPa, the pressure–piezoresistance relationships of the manganin gauges were calibrated by the light gas gun and the planar lens of explosive. The piezoresistance coefficients were obtained in different ranges of pressure. To verify the coefficients, the detonation pressure (CJ pressure) of TNT explosive was measured by the manganin gauges, which give similar CJ pressure values to those reported by Zhang et al (2009 Detonation Physics (Beijing: Ordnance Industry Press)) with the maximum relative deviation being less than 3%.

Ignition and Growth Modeling of Shock Initiation of Different Particle Size Formulations of PBXC03 Explosive

The change in shock sensitivity of explosives having various explosive grain sizes is discussed. Along with other parameters, explosive grain size is one of the key parameters controlling the macroscopic behavior of shocked pressed explosives. Ignition and growth reactive flow modeling is performed for the shock initiation experiments carried out by using the in situ manganin piezoresistive pressure gauge technique to investigate the influences of the octahydro-1,3,5,7–tetranitro-1,3,5,7-tetrazocine (HMX) particle size on the shock initiation and the subsequent detonation growth process for the three explosive formulations of pressed PBXC03 (87% HMX, 7% 1,3,5-trichloro-2,4,6-trinitrobenzene (TATB), 6% Viton by weight). All of the formulation studied had the same density but different explosive grain sizes. A set of ignition and growth parameters was obtained for all three formulations. Only the coefficient G1 of the first growth term in the reaction rate equation was varied with the grain size; all other parameters were kept the same for all formulations. It was found that G1 decreases almost linearly with HMX particle size for PBXC03. However, the equation of state (EOS) for solid explosive had to be adjusted to fit the experimental data. Both experimental and numerical simulation results show that the shock sensitivity of PBXC03 decreases with increasing HMX particle size for the sustained pressure pulses (around 4 GPa) as obtained in the experiment. This result is in accordance with the results reported elsewhere in literature. For future work, a better approach may be to find standard solid Grüneisen EOS and product Jones-Wilkins-Lee (JWL) EOS for each formulation for the best fit to the experimental data.

Effects of HMX Particle Size on the Shock Initiation of PBXC03 Explosive

Abstract A series of shock initiation experiments are performed on the PBXC03 explosives in different formulations to understand the influence of the explosive particle size on the shock initiation, and the in-situ pressure gauge data are obtained which show that shock sensitivity decreases with the explosive particle size under the test condition used in this paper. Moreover, a mesoscopic reaction rate model which is calibrated by the experimental data on a medium formulation PBXC03 explosive is adopted and then applied to predict numerically the shock initiation of other PBXC03 explosives in different formulations. The numerical results are in good agreement with the experimental data.

Modeling and simulation of preshock desensitization in heterogeneous explosives using a mesoscopic reaction rate model

To understand and predict the response of explosive materials, numerical models are utilized to simulate various scenarios. Various hazard and vulnerability scenarios for explosives involve multiple shock compression. In the present study, a kind of mesoscopic model for shock ignition of solid heterogeneous explosives is examined in order to demonstrate its availability to account for the desensitization caused by multiple shocks in explosives. Since the mesoscopic model is based on the assumption of the elastic viscoplastic pore collapse mechanism, and on the other hand the desensitization mechanism is also usually described in connection with the closure of pores, the ability of the mesoscopic model to predict the desensitization effects must be analyzed. For this purpose, the mesoscopic model has been implemented in a hydrodynamic code (LS-DYNA) as a user-defined equation of state. For verification, the double shock, reflected shock and detonation-quenching experiments have been modeled and simulated. The data show that the model can reproduce various features of some of the previously reported experiments involving the preshock desensitization of solid explosives.

Prediction of Initial Temperature Effects on Shock Initiation of Solid Explosives by Using Mesoscopic Reaction Rate Model

Abstract A kind of mesoscopic reaction rate model is reexamined in this paper with the aim of getting rid of the temperature dependence of its experiential parameters and making it available to predict the shock initiation of solid explosives under different initial temperatures. It is found that the initial temperature effect is induced mainly by the temperature dependence of the local chemical reaction rate and the initial density of the explosives, and, via the introduction of such temperature dependence, the reaction rate model can predict well the shock initiation processes under different initial temperatures, in which just the experiential parameters under a certain temperature (e.g. the normal temperature) are needed. Moreover, for verification, the shock initiation processes of PBX-9501 under different initial temperatures were simulated numerically by using the DYNA2D software. The numerical results on the run distance to detonation are found to be in good agreement with previous experimental data.

Influence of Small Change of Porosity on Shock Initiation of an HMX/TATB/Viton Explosive and Ignition and Growth Modeling

All solid explosives in practical use are more or less porous. Although it is known that the change in porosity affects the shock sensitivity of solid explosives, the effect of small changes in porosity on the sensitivity needs to be determined for safe and efficient use of explosive materials. In this study, the influence of a small change in porosity on shock initiation and the subsequent detonation growth process of a plastic-bonded explosive PBXC03, composed of 87% cyclotetramethylene-tetranitramine (HMX), 7% triaminotrinitrobenzene (TATB), and 6% Viton by weight, are investigated by shock to detonation transition experiments. Two explosive formulations of PBXC03 having the same initial grain sizes pressed to 98 and 99% of theoretical mass density (1.873 g/cm3) respectively are tested using the in situ manganin piezoresistive pressure gauge technique. Numerical modeling of the experiments is performed using an ignition and growth reactive flow model. Reasonable agreement with the experimental results is obtained by increasing the growth term coefficient in the Lee-Tarver ignition and growth model with porosity. Combining the experimental and simulation results shows that the shock sensitivity increases with porosity for PBXC03 having the same explosive initial grain sizes for the pressures (about 3.1 GPa) applied in the experiments.

Theoretical Prediction of Expansion History of Metal Cylinder for Multicomponent Explosives

As a traditional experimental approach, the cylinder test has been widely applied to evaluate the ability to accelerate metal, acquire the specific dynamic energy, and calibrate the equation of state of the detonation product for an explosive. In this article, based on the constant metal-density Gurney formula, a theoretical approach to predicting the expansion history of a metal cylinder shell driven by the detonation product of a multicomponent explosive under any explosive mixture ratio is proposed, providing that the corresponding theoretical density and the initial internal energy and the Jones-Wilkins-Lee parameters of each explosive component in the multicomponent explosive are known. Based on this predicted expansion history, the ability to accelerate metal, the specific dynamic energy, and the equation of state of a multicomponent explosive under any explosive mixture can all be acquired without an extra cylinder test for the multicomponent explosive itself. For verification, numerical results for the expansion histories of a copper cylinder driven by the detonation products of a PBX-C03 and a Comp-B multicomponent explosive were calculated and found to be in reasonably good agreement with previous cylinder test data.

Mesoscopic effects on shock initiation of multi-component plastic bonded explosives

A series of one-dimensional Lagrangian tests have been performed to examine model parameters in the mesoscopic reaction rate model for shock initiation of multi-component plastic bonded explosives (PBXs) for two multi-component plastic bonded explosives PBXC03 (87% HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazoncine), 7% TATB (triaminotrinitrobenzene), and 6% binder by weight) and PBXC10 (25% HMX, 70% TATB, and 5% binder by weight). As the numerical results are in good agreement with experimental data, the model parameters have been used to predict the effects of variations in mesoscopic properties (the particle size, initial density, binder strength, and content) on the shock initiation characteristics of PBXC03 and PBXC10. It is found that the time to detonation for PBXC03 increases with all these mesoscopic properties, while the time to detonation for PBXC10 is basically independent of its mesoscopic properties. Thus, PBXC03 is sensitive to mesoscopic properties, but PBXC10 is not. Moreover, it is also found that the pressure-history curves behind the initial shock wave in PBXC03 have different trends from PBXC10, which implies different chemical reaction mechanisms. Further analysis reveals that it arises from the different hot spot ignition processes due to their different threshold initiation pressures. The hot spots are ignited gradually and almost simultaneously in PBXC03 and PBXC10, respectively.A series of one-dimensional Lagrangian tests have been performed to examine model parameters in the mesoscopic reaction rate model for shock initiation of multi-component plastic bonded explosives (PBXs) for two multi-component plastic bonded explosives PBXC03 (87% HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazoncine), 7% TATB (triaminotrinitrobenzene), and 6% binder by weight) and PBXC10 (25% HMX, 70% TATB, and 5% binder by weight). As the numerical results are in good agreement with experimental data, the model parameters have been used to predict the effects of variations in mesoscopic properties (the particle size, initial density, binder strength, and content) on the shock initiation characteristics of PBXC03 and PBXC10. It is found that the time to detonation for PBXC03 increases with all these mesoscopic properties, while the time to detonation for PBXC10 is basically independent of its mesoscopic properties. Thus, PBXC03 is sensitive to mesoscopic properties, but PBXC10 is not. Moreover, it is a...

Research on Equation of State For Detonation Products of Aluminized Explosive

ABSTRACT The secondary reaction of the aluminum powder contained in an aluminized explosive is investigated, from which the energy loss resulted from the quantity reduce of the gaseous products is demonstrated. Moreover, taking the energy loss into account, the existing improved Jones-Wilkins-Lee (JWL) equation of state for detonation products of aluminized explosive is modified. Furthermore, the new modified JWL equation of state is implemented into the dynamic analysis software (DYNA)-2D hydro-code to simulate numerically the metal plate acceleration tests of the Hexogen (RDX)-based aluminized explosives. It is found that the numerical results are in good agreement with previous experimental data. In addition, it is also demonstrated that the reaction rate of explosive before the Chapman-Jouget (CJ) state has little influence on the motion of the metal plate, based on which a simple approach is proposed to simulate numerically the products expansion process after the CJ state.