Based on the two-dimensional axisymmetric Euler equations coupling with chemical reactions, the phenomena of implosion combustion for hydrogen-air mixture were numerically studied by using wave propagation algorithm with Superbee limiter in resonator cavity. The effects of resonator shapes on initiation and detonation were discussed. Results show that the shock wave induced by combustion firstly reflected back and forth from walls and the axis of the resonator cavity, which led to multiple the shock-flame interactions and enhanced the flame combustion. Then the reflected shock wave produced by the parabolic reflector in resonator cavity frequently penetrated the flame, which led to continuous flame excitation. Finally, DDT occurred. Simultaneously, the repeated shock-flame interactions caused the instability and distortion of the flame, and then formed asymmetrical collapsing of the flame front. The different shapes of reflector caused the change of focus, which could influence the shock-flame interaction and made detonation onset change, even not occurred.

This paper examines the failure modes of ductile metal plates subjected to impact by rigid flat-ended projectiles at normal incidence. General speaking, there are two failure modes which can occur in a ductile metal plate: simple shear failure with global deformation, and localized adiabatic shear plugging. Based on the thermoplastic constitutive relationship of Bai and Johnson, an adiabatic shear plugging model is first proposed. When combined with the Wen-Jones model which describes simple shear failure with global response, a critical condition for the change in these two failure modes is obtained. It transpires that the present theoretical predictions are in good agreement with available experimental observations in terms of failure modes and ballistic limits.

The software of LS-DYNA was applied to simulate the formation process of a high velocity rod-shaped projectile from the modified hemispherical liner. Its formation mechanism was analyzed. It was demonstrated that the initiation methods such as center point initiation, four-point initiation and peripheral initiation had an effect on the formation and the performance parameters of the high velocity rod-shaped projectile. The results of numerical computation indicate that the shaped charge with the modified hemispherical liner can form the rod-shaped penetrator with high velocity, large slenderness and rational mass distribution. Its formation mechanism combines that of the shaped jet and the over-turned explosively formed projectile, i.e. the upper half of liner directly collapses along the axial line and the lower half of liner is gradually overturned when closing the axial line. There are some differences of the shape and performance parameters of the rod-shaped penetrators formed under the different initiation methods. The peripheral initiation is the best excellent initiation method. The experimental result shows a good agreement with results of numerical simulations.

Nanometer-sized MnFe₂O₄ powders were synthesized by detonation of two kinds of emulsion explosives with different oxygen balance (OB) values. The phase structure and the different components of the two samples obtained from the emulsion explosives were characterized and compared by X-ray diffraction (XRD). According to the results of DSC and XRD, the samples were heated at 200 ℃, 260 ℃, 280 ℃, 500 ℃ for 1 h and 360 ℃ for 40 min respectively. And at 280 ℃, pure nanometer-sized MnFe₂O₄ powders were obtained, their morphology was observed by transmission electron microscopy (TEM). The results of the experiments indicate that detonation powders of the EE with negative OB value are relatively purer than those of the EE with zero OB value, and 280 ℃ is a suitable temperature for thermal treatment. Detonation method has the advantages of convenience and rapidness for nano-particles synthesis and simplity for post-thermal treatment.

From theoretical and experimental aspects, the shear modulus of material at the solid-liquid phase region was discussed when the material has attained its phase transition equilibrium and concluded that the shear modulus did not equal to zero as soon as the material began to melt. Using percolation theory, the connectivity of solid phase in solid-liquid phase region was calculated and the critical melting mass fraction is 0.687 when the shear modulus of material equal to zero. The melting unstable factor of material, presented by us, can represent qualitatively the change of correlative physical parameters in melting process.

A numerical model which is based on the hyperbolic two-step model is developed to investigate the microscopic energy transport in silicon thin films during ultra-fast laser heating. It is observed that, electrons dominate energy transport within a few picoseconds. The coupling processes between electrons and phonons are non-local due to the ballistic transport of electrons, and the coupling coefficient is found to be much more strongly dependent on electron temperature than lattice temperature. The speed of heat wave propagation is the same magnitude as that of the electron energy transport. Predictions from the numerical model agree with available experimental data during ultra-fast laser heating.

The stress-strain curves of the α-zirconium which strain rate ranges from 3.3×10^-4 s^-1 to 1.5×10³ s^-1 under room temperature were obtained, and the parameters of Johnson-Cook model were determined through these experiments. The computed free-surface velocity profiles using dynamic damage and fracture model consist with the experimental measurements at 4.3 GPa and 5.1 GPa peak pressure. The comparison indicates that the determined dynamic parameters of α-zirconium are valid.

Based on two phase flow model of interior ballistics, considered that the weight of ignition charge is comparable with the secondery charge and many of its products are solid, the so called four phase flow model of interior ballistics adaptive to the combustion process in the electric squib has been established. In the model, gas products, solid products, ignition charge and secondery chare, all be taken as a phase, each of them is described by mass, momentum and energy equation, and they are related by mutual actions, which are the source terms in the before-mentioned equations. Caculated result by the model is in agreement with the test of the electric squib. This shows that the model describes reasonably the combustion process in the electric squib, and can be as an assistant tool for evaluating of the performance of electric squib.

Explosive welding is a solid state fusion welding process in which the joining of two metals is accomplished by the application of the pressure released by the detonation of an explosive layer. It is widely used to manufacture material sandwich components. But when explosive was set on a thin fly plate, the deflection would take place because of the weight of explosive and the fly plate itself. In this paper, based on the analysis of the deflection of the big and thin plate which is supported by smooth cylindrical pin at four boundaries, the slope of the fly plate which endured uniform pressure of weight was developed. Combined with the explosive welding subsonic speed limit and fluid limit, the minimal thickness was calculated to make sure explosive welding can be successful. At last, the formula of the minimal thickness was gained in the conditions that the material, length, width of fly plate were all confirmed.

A theoretical Hugoniot curve of iron has been calculated based on Grüneisen equation of state and internal energy conservation consideration, using a set of optimized or thermophysical parameters and both ε- and liquid-iron models. This determined Hugoniot curve is well in accord with the revised Hugoniot data [J Appl Phys, 2000, 88: 5496] on the whole, and could be further divided into two parts. The first one can well describe the revised data below ~200 GPa with ε-phase model, while the second can approximately replicate the revised data above ~260 GPa with liquid-phase model. It is thus convinced that the range between ~200 GPa and ~260 GPa should be in solid/liquid mixed state, i.e, a small kink appearing on the revised Hugoniot at ~200 GPa is due to a solid-liquid transition, rather than a solid-solid transition at ~200 GPa that was inferred from Brown's analysis [Geophys Res Lett, 2001, 28: 4339].