Adiabatic shear band (ASB) may cause damages and failures of many metal materials under impact loading, which is a key issue in the research of damage mechanism. The theoretical study is mainly focused on the relationship among the strain, stress, speed of shear and the initial flaw size in one-dimension shear conditions, which is used to determine the possibility of the generation of ASB. By experimental investigations, the features of ASB of titanium alloy, tungsten alloy and high-strength structural steel, including deformation fields, local temperature and the threshold value for ASB generating, can be detected. However, since there is little study on the real-time and in-situ measurements on the evolution process of ASB, the failure details according to the shear-localization are still unknown. In this paper, the real-time observations and visualizations on the evaluation of ASB in 45 steel under different impact conditions in SHPB are presented. The generating and evaluating processes in a single sample are detected and analyzed by a self-design optical system and the self-designed software, which is based on Digital Correlation method with high resolution. At the same time, the numerical simulations and micro-observations by SEM are obtained by LS-DYNA and the simulation results are in good agreement with the experimental ones.

To obtain dynamic behavior of materials at very high temperature, a new experimental system of high temperature split Hopkinson pressure bar (SHPB) is investigated. The steel bars in the inside section of the furnace are replaced with relatively close acoustic impedance matched short ceramic bars. Compared to the traditional high temperature SHPB system, this system can be used under higher loading and higher experimental temperatures, and it is more convenient than the auto-assembling high temperature SHPB system. In addition, the effect of impedance mismatch is investigated by numerical simulation, which proves veracity of the results. The dynamic compressive properties of anti-hydrogen steel at high temperature up to 800 ℃ are tested by this system. Results show that the flow stress of material decreases with the increase of the temperature.

In order to improve the present aviation ejection lifesaving system and enhance success possibility of safe escape, the application of Miniature Detonating Cord (MDC) on the aviation ejection-escape-system is proposed. The explosion cutting process of plexiglass (PMMA) plate and Canopy by MDC are simulated employing nonlinear dynamic explicit program LS-DYNA3D. The variation of cutting depth with charge quantities is obtained, which agrees well with the experimental result. Simulation result shows that the geometry of PMMA has slight influence on the cutting effect. This study may provide the powerful foundation for the design of the aviation ejection lifesaving system.

Quasi-static and dynamic compression experiments of unannealed Ta-10W alloy specimen are implemented by MTS and split Hopkinson pressure bar equipments. Quasi-static compression yield strength is gained. In addition, the stress-strain history and dynamic compression yield strength are obtained when strain rate ranges from 700 s^-1 to 3 100 s^-1. The experiment results indicate that unannealed Ta-10W is preferably flexile. There is no crack on the surfaces of specimen after experiments. The quasi-static and dynamic compression strength of unannealed Ta-10W alloy is quite large. Quasi-static compression yield strength is about 930 MPa, and the dynamic compression yield strength is over 1 GPa. Dynamic compression yield strength of Ta-10W is dependent on strain rate, and it grows from 1.0 GPa to 1.3 GPa when strain rate increases from 700 s^-1 to 3 100 s^-1.

The JWL equation of state of detonation product for insensitive high explosive JB-9014 was further studied. The particle velocity, displacement, and acceleration of the cylinder wall were obtained from the modified standard cylinder test. The parameters of JWL equation of state were derived from analytical analysis and non-linear curve fit. The cylinder expanding process was numerical simulated using the ANSYS/LS-DYNA3D. The simulation results are consistent with the experimental results, which indicate that the parameters of JWL equation of state derived in this work are suitable and reliable.

The characteristics of fragments, which are numerical studied with Smoothed Particle Hydrodynamic (SPH) algorithms, come from the steel cylinder subjected to the detonation of internal short cylinderical explosive charge. Grady spall model is employed to describe the spall failure of the steel cylinder. Stochastic failure is used to define the failure models, in which Mott distribution is used to depict the failure strain. Mass distribution and velocity of fragments are mainly discussed. The results show that the part near the head of explosive begins to fracture after the steel cylinder expands to a certain extent, and then the part around the explosive disaggregates to fragments. For the closed cylinder, the ends are the other weakness position. The fragments around the explosion centre are smaller with high velocity, while the fragments around cylinder ends are larger with low velocity. The fragments near the explosion centre are relatively concentrated in the space.

Graphitic carbon nitride (g-C₃N₄) is prepared by pyrolysis of melamine. At room temperature, the structure change of the g-C₃N₄ is investigdted by in situ high pressure angle-dispersive X-ray diffraction with a synchrotron radiation source, which is in a diamond-anvil cell. The results show that structural phase transition occurred in g-C₃N₄ within 16.57 GPa pressure range. The crystal structure changes from graphitic to triclinic structure at 6.6 GPa. The isothermal equation of the state of C₃N₄ is fitted using the Birch-Murnagha equation of state.

Thermal stability of Ti₂AlN-Al at high pressure is studied. Based on X-ray diffraction (XRD) and scanning electron microscopy (SEM), it was found that the thermal stability was mainly dependent on the temperature, but less on the pressure. When the pressure is 3, 4 and 5 GPa, the lowest reaction temperature of Ti₂AlN-Al was between 500 and 600 ℃, and the decomposition products depended on temperature. When the temperature was up to 900 ℃, Ti₂AlN-Al had completely decomposed and most of the final products were Al₃Ti and TiN.

Over-driven detonation is achieved by high speed flyer impacting, which is driven by explosive. The time when the shock wave passes through the samples is detected. Using “the impedance matching method”, the Hugoniot of the product of the JB-9014 explosive can be obtained. It is shown that the simple D-u equation can not fit the Hugoniot data well. With relation to the explosive, it is better to use quadratic in D-u equation. Using conservation relations of physical variable before and after the shock wave, the D-u data can be translated to p-V data. Then the p-v equation can be obtained by fitting the p-V data.

By using a diamond anvil cell the trans, trans-Dibenzylideneacetone molecular crystal was studied with high pressure Raman, fluorescence spectroscopy and EDXRD at room temperature. A crystalline to crystalline phase transition is found at 1.0~1.3 GPa; meanwhile, a pressure induced chemical reaction is observed and the reaction is completed around 6.5 GPa. The EDXRD spectra show that a new covalent bond produces in this chemcial reaction process. The possible chemical reaction paths are suggested as the openning of C=C bond of the molecule and then combination between adjacent molecules. Another crystalline to crystalline phase transition forms around 11 GPa. After the pressure is released, the newly formed phase of material can remain stable at ambient conditions.