Numerical simulation of impact breakage of gun propellant charge

Fragmentation of gun charge bed is the basic reason of bore burst. Fragmentation dynamics of charge bed is the kernel content of launch safety. In order to simulate fragmentation of propellant bed, there is a need to obtain the packing structure of propellant bed at first. In this paper, the packing process of propellant bed under gravity is simulated, and the close-grained structure of propellant bed is achieved. Then, the 3D discrete element model of propellant bed is presented and the numerical analysis code, which can simulate impact fragmentation behavior of propellant grains, is developed. The fragmentation process of propellant bed under an impact load is calculated by the code, and the entire failure process of propellant grains is presented. Furthermore, the results obtained from simulations are in acceptable agreements with experiment observations, which indicates the accuracy of the computational model.     

Tetramethylammonium Neptunium(IV) Isothiocyanate [N(CH3)4]4[Np(NCS)8]

A new Np(IV) complex, [N(CH₃)₄]₄[Np(NCS)₈], was prepared. Its crystal structure was determined, and the absorption spectra in the IR and near IR ranges were measured. Crystal data: a = 27.280(6), b = 12.288(3), c = 13.493(3) Å, space group Pna2₁, Z = 4, V = 4523(2) A³, R = 0.044, wR(F ²) = 0.091. The crystal structure of the compound consists of [Np(NCS)₈]^{4 -} anions and N(CH₃)₄ ⁺ cations. The coordination polyhedron of the Np atom is a distorted tetragonal antiprism formed by the nitrogen atoms of eight NCS^- ions.     

Shocked materials at the intersection of experiment and simulation

Understanding the dynamic lattice response of solids under the extreme conditions of pressure, temperature and strain rate is a scientific quest that spans nearly a century. Critical to developing this understanding is the ability to probe and model the spatial and temporal evolution of the material microstructure and properties at the scale of the relevant physical phenomena—nanometers to micrometers and picoseconds to nanoseconds. While experimental investigations over this range of spatial and temporal scales were unimaginable just a decade ago, new technologies and facilities currently under development and on the horizon have brought these goals within reach for the first time. The equivalent advancements in simulation capabilities now mean that we can conduct simulations and experiments at overlapping temporal and spatial scales. In this article, we describe some of our studies which exploit existing and new generation ultrabright, ultrafast x-ray sources and large scale molecular dynamics simulations to investigate the real-time physical phenomena that control the dynamic response of shocked materials.     

Phase diagrams of the ternary liquid systems [Ce(NO3)3(TBP)3]-C10H22-[UO2(NO3)2(TBP)2] and [Ce(NO3)3(TBP)3]-C10H22-[Th(NO3)4(TBP)2] and of the quaternary liquid system [Ce(NO3)3(TBP)3]-C10H22-[UO2(NO3)2(TBP)2]-[Th(NO3)4(TBP)2]

The phase diagrams of the ternary liquid systems [Ce(NO₃)₃(TBP)₃]-C₁₀H₂₂-[UO₂(NO₃)₂(TBP)₂] and [Ce(NO₃)₃(TBP)₃]-C₁₀H₂₂-[Th(NO₃)₄(TBP)₂] and of the quaternary liquid system [Ce(NO₃)₃(TBP)₃]-C₁₀H₂₂-[UO₂(NO₃)₂(TBP)₂]-[Th(NO₃)₄(TBP)₂] at T = 298.15 K are constructed. The phase diagrams are characterized by areas of homogeneous solutions and of two-phase liquid systems (systems with phase separation), with one phase (I) enriched in [Ce(NO₃)₃(TBP)₃], [Th(NO₃)₄(TBP)₂], and [UO₂(NO₃)₂(TBP)₂], and the other phase (II), in C₁₀H₂₂. Using the data on the mutual solubility of the components in the systems under consideration and equations of the NRTL model, the parameters of intermolecular interactions and the excess Gibbs energies (G ^ex) were calculated for the binary, ternary, and quaternary systems. Passing from the ternary system [Ce(NO₃)₃(TBP)₃]-C₁₀H₂₂-[Th(NO₃)₄(TBP)₂] to the quaternary system [Ce(NO₃)₃(TBP)₃]-C₁₀H₂₂-[UO₂(NO₃)₂ (TBP)₂]-[Th(NO₃)₄(TBP)₂] does not appreciably affect the distribution of C₁₀H₂₂ between phases I and II, but leads to the redistribution of [Ce(NO₃)₃(TBP)₃] into phase II and of [Th(NO₃)₄(TBP)₂] into phase I.     

Review of impact fusion concepts [EM launchers]

The authors review the main features of the impact fusion concept in which gram-sized metallic projectiles from electromagnetic launchers collide around heavy-hydrogen fusile gas to produce thermonuclear plasma whose pressure brings the projectiles to rest, providing a pulse of fusion power during the `turnaround' of the projectiles. They discuss the concepts of nonmagnetic as well as magnetically insulated, impact fusion, showing how its potential advantages as an inertial confinement system could be realized. Of particular interest is magnetically insulated impact fusion, where the decreased plasma heat loss may allow lower impact velocities, consistent with the nearer-term state of the art of electromagnetic launchers. Also considered is the concept of mechanical helicity injection that allows both convenience and flexibility in producing the final magnetic configuration     

Micrometeorite impact simulation at EMI — a review

Activities at EMI in the field of hypervelocity impact techniques are reported. Optimization experiments have been carried out with a light gas gun in order to achieve projectile velocities up to 10 km/s. Different methods for measuring the projectile velocities have been developed and adapted according to respective velocity and mass ranges of projectiles. Experimental efforts have been undertaken to accelerate also microgram particles in light gas guns. Masses as small as 37 μg can be accelerated as individual particles. As examples, several contributions to recent space projects are described.     

Charge injection into poly[methyl(phenyl)silylene]

Space-charge-limited currents have been measured in thin films of poly[methyl(phenyl)silylene] provided with Al and hole-injecting ITO electrodes. Electroluminescence observed at high voltages was interpreted as being due to a double injection. The thermo-modulated space-charge-limited current technique has been employed to determine the structure of traps in the low-voltage (single-injection) regime.     

飞机驾驶舱后观察窗抗鸟撞试验及数值模拟研究

为了对飞机驾驶舱后观察窗玻璃进行抗鸟撞设计,进行了后观察窗玻璃抗鸟撞试验,试验中测量了观察窗玻璃上两个点的应变时间历程。利用大型商用碰撞分析软件PAM-CRASH建立了全尺寸鸟撞后观察窗玻璃有限元计算模型,对鸟撞后观察窗试验过程进行了数值模拟,比较了应变及位移时间历程曲线的计算结果和试验结果,二者良好的一致性表明计算模型的合理性。在此基础上分析了内外层玻璃厚度及中间空气层厚度对后观察窗结构抗鸟撞动响应的影响规律,为飞机驾驶舱后观察窗玻璃的抗鸟撞设计提供技术指导。     

Physicochemcial analysis of the phase diagram of the ternary liquid system [Y(NO3)3(TBP)3]-tetradecane-[UO2(NO3)2(TBP)2]

The phase diagram of the ternary liquid system (TLS) [Y(NO₃)₃(TBP)₃]-tetradecane-[UO₂ · (NO₃)₂(TBP)₂] (TBP is tri-n-butyl phosphate) at 298.15 K is constructed. The TLS is characterized by an area of homogeneous solutions and an area of two-phase liquid systems with one of the phases (I) enriched in [Y(NO₃)₃(TBP)₃] and [UO₂(NO₃)₂(TBP)₂] and the other phase (II), in tetradecane. The inter-molecular interaction parameters and excess Gibbs energies (g ^E ) for the binary systems and TLS along the binodal curve were calculated from data on the mutual solubility in the binary system [Y(NO₃)₃(TBP)₃]-tetradecane and the ternary liquid system, using equations of the NRTL theory. For the binary system [Y(NO₃)₃(TBP)₃]-[UO₂(NO₃)₂(TBP)₂], g ^E < 0, and for the other binary systems, g ^E > 0. An algorithm is given for computer calculation of the binodal curve and nodes for the TLS within the framework of NRTL equations using the intermolecular interaction parameters.     

Reaction of [60]Fullerene with Terbium(IV) Fluoride

Abstract

A reaction between [60]fullerene and terbium(IV) fluoride is shown to be a new example of the thermally induced disruption of the fullerene skeleton. “Hyperfluorination” occurs at the elevated temperature (350° C) thereby producing species C₆₀ Fx (x > 60). The fluorination products were characterized by mass spectrometry and IR spectroscopy methods.     

粉状阳离子聚丙烯酰胺的研制

用聚丙烯酰胺胶体,在≥20％浓度的硫酸盐溶液中,进行Mannich反应,经真空干燥后,制取水溶性阳离子型高分子。初步探讨了盐浓度、温度、时间、配比对产物的阳离子度、溶解性的影响。     

Fracture surface morphology of poly[bis(trifluoroethoxy)phosphazene]

Poly[bis(trifluoroethoxy)phosphazene] (PBFP) films were prepared from tetrahydrofuran solution. Fracture surface morphology was studied by scanning electron microscopy. Two morphologies associated with heat treatment have been established: (a) cospherically grown aggregates are obtained in solution-cast films and films heated through the T(1) transition; (b) aggregates of irregular shaped crystalline platelets obtained after melting and crystallization. Ion etching was also applied to the fracture surface in order to clarify the morphological and structural features. The striations originally associated with the [c] axis direction of PBFP crystals can be accentuated on the fracture surface of original as-cast spherulitic films by employing this technique. The texture of the fracture surface after etching is compared with that obtained for an oriented fibre made from this polymer. From this comparison it can be concluded that the [c] axis direction is perpendicular to the spherulite radius. Furthermore the morphology is analogous in many respects to that of Kevlar.     

Crystal structure of poly[bis(3,4-dimethylphenoxy)phosphazene]

The crystal structure and chain conformation of poly[bis(3,4-dimethylphenoxy)phosphazene] — PB (dMe) PP — have been studied by X-ray diffraction techniques. The unit cell of this polymer shows an orthorhombic form with the crystallographic parameters a=2.05, b=1.49, c (chain axis)=0.998 nm. Its space group is determined as Pbcn-D _2h ¹⁴ where the molecular chains are located at the centre and each corner of the unit cell, which contains eight monomeric units; these molecular chains possibly have a — (trans ₃ cis)₂-conformation. The R factor calculated from the final crystal structure was estimated as 16.9%. As with other types of polyorganophosphazenes, the thermotropic transformation in PB (dMe) PP takes place from the three-dimensionally ordered state to its two-dimensional psuedohexagonal form (a _h = 1.49 nm), accompanied by a latent heat change at 96 °C.