The strength expression of material under shock loading has been reviewed. The effects of the hydrostatic pressure and the high strain rate on the strength, has been discussed. A modified form for the Hugoniot elastic limits was given associated with the Drucker-Prager yield criterion. Free surface velocity histories were measured by VISAR in plate impact experiments on alumina with a light gas gun. The experimental determination of the dynamic strength of alumina was discussed and open problems were clarified. By comparing the strength expressions of ceramic materials with the experimental results, the differences were mentioned. Analysis and discussion were made for the experiment phenomenon.

In explosive consolidation of nano-powders, the duration in which the loading changed markedly on nano-particles by shock wave is far longer than the time of stress wave propagating through the character length of the particles; and the ceramic powders behave brittleness during explosive shock consolidation. The elastic hypothesis is put forward based on the two facts mentioned above, and the hypothesis is used to deduce the stress status in particles during the process of consolidation. The three criteria of brittleness fracture of damage (Hugonoit elastic limit, dynamic yield strength and theoretical shear strength) are reviewed. The probability of fracture of ceramic particles is estimated by the intersection value of the three criteria. Based on the calculation, it is concluded that there are two maximal shear positions: one is located in the depth of 0.5 nm in particle from the contact surface, where the shear stress is maximum; the other is located further from the surface. This result offers a reference for interpreting the plasticity and fracture during the process of explosive consolidation.

Based on the dynamic process of helium bubble growth under high strain-rate, the dynamic equation of helium bubble growth has been presented. The effects of internal pressure of helium bubble, inertia, viscosity, surface tension of base material and environment temperature on helium bubble with 1 nm radius have been considered respectively. Results indicate that: (1) At high strain-rate loading, the original internal pressure may help to accelerate the growth of the helium bubble. When the radius of helium bubble is larger than 1 μm, the internal pressure is too small and it may be omitted. (2) The effect of surface tension is very weak in the whole process of helium bubble growth. (3) The growth of helium bubble may be restrained by the inertia. And this effect will be more obvious with the growth of diameter. (4) While all the above effects are important, the effect of temperature needs to be particularly emphasized. With the temperature rising, the viscosity will decrease and the internal pressure will increase, the growth of helium bubble will be accelerated.

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.