Study On Shock Vulnerability Of Booster Explosive

The emergence of the low vulnerability ammunition puts forward the stringent requirements on the booster pellet of the detonation train in detonator, that is, the booster pellet must have the ability which accommodates the main charge to resist the unexpected energy stimulation. To solve this problem, in this paper, by using the experimental analysis, numerical simulation and quantum chemistry calculation, the physical and chemical factors and their rules which influence the vulnerability of booster explosive for shock wave in the practical application were studied, and the technical direction which could reduce the vulnerability of booster explosive for shock wave was put forward. This study can provide technical basis for the safe and reliable application of the booster, and enhance the survival ability and the reliability of the weapon system under the shock wave.(1) The experimental devices and methods were designed for the evaluation of the vulnerability of booster explosive for shock wave. Some factors, such as the shell materials, charge density, clearance between shell and charge, were analyzed by experiments, and the vulnerability of shock wave in the six present booster explosives were assessed by using these devices, and the order of the strength of response to shock wave was obtained. The results show that: with the decrease of material constrained wave impedance, the response strength of booster explosive to shock wave was decreased. When the material was identical, with the decrease of wall thickness, the response strength of booster explosive to shock wave was decreased. When the charge density was in the range of 82%TMD ~ 92%TMD, the response strength of booster explosive to shock wave was decreased with the decrease of the density. The gap between the shell and charge would decrease the response strength of booster explosive to shock wave. The response values of the six booster explosive to shock wave are in the order of JO9 C >JH17> JH14> JH6>insensitive RDX > insensitive PETN.(2) By using the finite element analysis software ANSYS/AUTODYN, the numerical simulation was carried out for the vulnerability of the booster pellet, and the initiation process and detailed image of axial propagation were found. The results show that: with the decrease of material constrained wave impedance, charge density or gap between the shell and charge, the response strength of booster explosive to shock wave was decreased. The numerical simulation is in agreement with the experimental result.(3) By using the molecular dynamics method, the different surface bonding energies and mechanical properties for several additives(fluoride rubber, calcium stearate and stearic acid) of booster explosive with different percentages in main charge RDX crystals were studied. By using the B3 LYP and MP2(full) methods with the 6-311G(d,p) and 6-311G(2df,2p) basis set, the molecular interaction energies of RDX???1,2-fluorine ethane, RDX???calcium acetate and RDX???acetic acid complexes are calculated, and the N–NO2 bond dissociation energies are also obtained. Based on the cooperative effect, AIM(atom in molecule) theory, reduced density matrix and the transition state theory, the nature of the sensitivity of explosives is expounded, and the source of the vulnerability is revealed. By using the theory of surface electrostatic potential, the impact sensitivity h50 of insensitive RDX, JH 14, JH 6 and JO9 C was predicted. The results show that,the adsorption explosive with the 1:1 ratio of the explosive and additive has the highest adsorption energy and the best mechanical properties, for which the explosive has the lowest sensitivity. The order of the adsorption energies is JH14 < JH6 < insensitive RDX. This shows that the sensitivity follows the order of JH14 > JH6 > insensitive RDX. The formation of co-crystal complex makes the N–NO2 bond of RDX strong, leading to a decreased sensitivity. The sensitivity of adsorbed explosives is not only originated from the formation of inter-molecular hydrogen bonding interaction, but also originated from the increased N–NO2 dissociation energy. The activation energy of N–NO2 bond cleavage in RDX???acetic acid is much larger than that of the RDX???1,2-fluorine ethane system. According to the relationship between the surface electrostatic potential and the impact sensitivity, the impact sensitivities of JO9 C, JH 14, JH 6 and insensitive RDX are28.15, 29.23, 29.75 and 32.03 cm, respectively.(4) According to the experiment, simulation and quantum chemical calculation results, the method by which the vulnerability is reduced puts forward as the following: the use of small shock impedance material as casing, reducing shell diameter thickness, reducing charge density, the radial clearance between shell and propellant, using the shaped structure and reducing the charge can reduce the response strength of booster explosive to shock wave from the point of view of physics. The introduction of additives which can form the strong bonding interaction on the crystal surfaces of the main charge or the strong inter-molecular interactions with the main charge, in particular using the co-crystal explosive for booster explosive, is expected to greatly reduce the vulnerability of booster explosive for shock wave.