A physical criterion of dynamic tensile fracture has been introduced, based on the knowledge of the micro-mechanism and the measurement of the damage evolution. The physical criterion has suggested two critical damage parameters, named as the critical void coalescence damage D_l and the critical fracturing damage D_f. These two parameters are associated with a damage function model and a percolation-softening function, by which the fracture process is characterized as that the damage slowly increases in a linear manner from the initial state (D=D₀) to the void linkage state (D=D_l), then changes to a nonlinear growth and rapidly approaches to the critical fracturing state (D=D_f), while a final step catastrophically leads to the complete fracture state (D=1.0). Experimental measurements and numerical simulations for both of the plate impact and the cylindrical tube have verified that these two parameters (D_l and D_f) physically constrain the dynamic tensile fracture and may be considered as the intrinsic material constant. Application of this physical criterion for the prediction of dynamic tensile fracture under intricate loading and for complex geometrical system has been discussed.

For investigating kinetic behavior of pressure induced phase transitions, it is the most expected to combine high time-resolved diagnostic probes with the precise compression techniques. In fact, an indirect way in large volume press is compare characterization results of recovered samples with their experienced conditions including pressure, temperature and time. As a typical example, relationship between p-T conditions and time for diamond nucleation in C-H-O system is discussed by previous experimental data, demonstrated that extending loading time under HP/HT is propitious to form high pressure stable phase. In contrast, some meta-stable phases, such as bulk amorphous sulfur, metallic glasses and amorphous polymers etc., were obtained by rapid compression process. The results indicated that many substances can show the kinetic features of phase transition in the scale of compression rate from 1 GPa to 1 TPa/s. The kinetic phase diagrams with three dimensions (pressure, temperature and time) could be established through both of the static or rapid compression experiments.

Academician JING Fu-Qian pioneered two new fields of shock wave physics research in China at the end of the 1980s, that are shock wave physics applied to the Earth science and to the Space science and technology, called go up to the sky and go into the Earth. Academician JING Fu-Qian led us to carry out the only one Major scientific project of high pressure Geosciences-Study on the physical properties under high temperature and high pressure for materials in the important boundaries of the Earth's interior, he also directed the research of hypervelocity impact and protection against space debris impact in China. The recent research advances of shock wave physics applied to the frontier and hot spots of the Earth sciences in China were introduced in great detail and reviewed, including (1) the phase stability, equation of state, sound velocities, and thermo-elasticity of the Earth's lower mantle dominant minerals (Mg, Fe)SiO₃ perovskite and MgO-FeO system;(2) the possible mineralogical composition of the lower mantle;(3) the high pressure melting curve of Fe and Fe-O-S system;(4) constrained the light element in the Earth's outer core from the equation of state, sound velocities of Fe-O-S system;(5) the possible mineralogical interpretations of the seismic velocity anomaly in the lower mantle and core-mantle boundary;(6) Near Earth Object impact hazard and defense response. The current problems were emphasized and the new research trends were prospected. The authors dedicated this paper to commemorate the 1st anniversary of Academician JING Fu-Qian passed away.

High pressure can cause rearrangement of atoms in microstructure, and arouses reconfigurations of electronic states, which often brings new materials and new properties. The rich and colorful new phenomena and properties in the typical molecule system have been observed under high pressure. Studies of these new phases and behaviors in typical molecular system under high pressure are very important and significative. Two types of substance, i.e.elementary crystals and small-molecule compounds, are investigated thoroughly on structures and properties under high pressure, and demonstrate various features. In the elementary crystals, such as pressure-induced phase transition and metallization in I₂ (solid iodine) and N₂ (polymeric nitrogen), and in the small-molecule compounds, such as the hydrogen-bond and halogen-bond interactions in crystalline iodoform and bromoform under high pressure, the effects from dihydrogen bonds in ammonia borane which determining the complex dynamics behavior of rotations of the NH₃ and BH₃ groups under high pressure, etc.are discussed deeply. The distinct behaviors of molecular dissociation, reconstruction of crystal structures, and pressure-induced metallization in the typical small-molecule system under high pressure are very different from the ones at ambient conditions. Exploration of the typical small-molecule crystals under high pressure provides an important way to discover the new structures, new materials and new physical phenomena and properties.

The theoretical calculation on thermal conductivity of explosive is still one problem. We presented our developed two calculation methods for thermal conductivity of explosive. The first one is based on atomic motion equation. We derived the formulations of thermal flux in system and thermal conductivity of system. It is suitable to calculate the thermal conductivity in different directions. The second one is based on the phonon-phonon dispersion model and Debye model. This method can effectively calculate the thermal conductivity under pressure. Using these two methods, we have calculated the thermal conductivity of HMX under pressure, and deeply analyzed the factors which affect the thermal conductivity of HMX.

Using diamond anvil cell (DAC) combined with synchrotron axial X-ray diffraction (AXRD) techniques, the stress transmission behavior among materials with different strengths was investigated under non-hydrostatic compression. In our experiments, powder mixtures of platinum (Pt) and cubic silicon carbide (β-SiC), Pt and tungsten carbide (WC), as well as WC and β-SiC, were compressed up to 56, 61, and 25 GPa, respectively. We found that the stress transmission among the grain boundary of two different materials is discontinuous due to their strength difference, and the observed stress difference increases with the strength difference. The stronger material has a smaller observed stress near the minimum stress direction under non-hydrostatic compression in DAC at the same loading.

The tungsten alloy melting behaviors under high-velocity shock loading is investigated by Molecular Dynamic (MD) method combined with Embedded Atom Method (EAM) potential of tungsten alloy. First, the shock model of tungsten alloy is set up and the numerical simulations of lattice planes (100), (110), (111) under the shock loadings with the same velocity are conducted respectively. The Hugoniot curve and the relative data of pressure, temperature, volume and particle velocity behind the shock wave are obtained. Based on the analyses of the data and the curve, it is found that the shock pressure is in proportion to the shock temperature and inversely proportional to the shock volume. The above conclusions fit to experimental data well when the loading velocity is low, which are extended to the high-velocity impact field. The calculations show the plasticity of tungsten under high-velocity impact in qualitative description.

The basic principle and the parallel design strategy of the PMMIC-3D parallel program which using Euler method based on the message passing interface (MPI) mode were stated. After numerically stimulating the fortification mode, it can be seen that the results of numerical stimulation basically match with the reality and the physical laws. The shock waves of explosive detonation in fortifications not only had a higher peak overpressure, but also had a longer duration of action. When the shock wave met the wall, it would reflect and produce the reflected high pressure. Because of the diffraction convergence, the local high pressure would be brought about in a certain region behind the wall, in which the destructive effect was much larger compared with the shock waves of air explosion. The propagation process and the interaction of shock waves can be seen clearly by the numerical stimulation, which can determine the arrival time of the shock waves at various positions. The optimal explosive charge can be ensured by comparing the overpressure value of shock waves at different places.

High-pressure and high-temperature (HPHT) synthesis has play growing importance in exploring new materials. It has the merits of producing many new compounds that otherwise could not be synthesized at ambient conditions. The conventional HPHT facilities are based on so called one stage model reaching pressures up to 10 GPa. It is well understood that the higher synthesis pressure is, the more new compounds will be obtained. Here we introduce a state of the art new type high pressure synthesis facility based on double stage model of the six over eight multi anvils large volume high pressure machine that can reach unprecedented 20 GPa and 2 000 ℃. With the six over eight double stage facilities, much more new high pressure compounds are expected.

We report here the additive Runge-Kutta methods for computing reactive Euler equations with a stiff source term, and in particular, their applications in gaseous detonation simulations. The source term in gaseous detonation is stiff due to the presence of wide range of time scales during thermal-chemical non-equilibrium reactive processes and some of these time scales are much smaller than that of hydrodynamic flow. The high order, L-stable, additive Runge-Kutta methods proposed in this paper resolved the stiff source term into the stiff part and non-stiff part, in which the stiff part was solved implicitly while the non-stiff part was handled explicitly. The proposed method was successfully applied to simulate the gaseous detonation in a stoichiometric H₂-O₂-Ar mixture based on a detailed elementary chemical reaction model comprised of 9 species and 19 elementary reactions. The results showed that the stiffly-accurate additive Runge-Kutta methods can well capture the discontinuity, and accurately describe the detonation complex wave configurations such as the triple wave structure and cellular pattern.

The measurement of sound velocity of materials under high temperature and high pressure (HTHP) is an important research content in high pressure science. As a fundamental physical property of liquids, velocity of sound wave in liquids is very important and useful, for many thermodynamic parameters may be derived from sound velocity. However to date, there is little direct experimental information on macroscopic thermodynamic properties of liquids or melts under high pressure, especially the experimental technique to measure sound velocity of liquid has not been well established. The purpose of this paper is to give a brief review on various sound speed measurement techniques of liquid materials under high pressure and a detailed introduction on some new breakthroughs nearly, and finally to point out some expectations in this research field.

The inversion of visco-elastic constitutive relation from the measured data of a spherical wave experiment is a challenging research. Starting from the governing equations for linear visco-elastic spherical waves which are based on the ZWT visco-elastic constitutive relation, the analytical expression for the attenuation of strong-discontinuous visco-elastic spherical wave front is derived, and consequently a new method is proposed, by which the high-strain-rate visco-elastic parameters could be inversed from a series of particle velocity profiles measured in a spherical wave experiment. The first step is to determine the high-strain-rate elastic module from wave velocity measurements when the quasi-static material parameters are known. Then the high-strain-rate relaxation time can be determined from the attenuation factor. Thus the required visco-elastic constitutive relation can be obtained. Using those material parameters obtained by such a new inversion method, the visco-elastic spherical wave profiles are calculated by the characteristics method. The good agreement between the numerical predictions and the experimental results well supports this proposed new inversion method.

In-situ pressure-induced phase transition of ionic liquids [Emim][PF₆] and [Bmim][PF₆] have been studied under high pressure and room temperature by using Raman spectroscopy and high-pressure diamond anvil cell (DAC) apparatus. With the increase of pressure, [Emim][PF₆] experiences the solid-solid phase transition at about 0.86 GPa, and [Bmim][PF₆] experiences the liquid-solid phase transition at about 0.62 GPa and the solid-solid phase transition at about 1.45 GPa. Furthermore, the decrease of pressure of [Bmim][PF₆] has also been discussed in details. Pressure-released Raman spectra shows that the phase transition of [Bmim][PF₆] is reversible under pressure up to 2 GPa.

We used high resolution 5th-order WENO (Weighted Essentially Non-Oscillatory) scheme, Level Set method and interface treatment method-RGFM (Real Ghost Fluid Method) in simulating compressible multi-medium flow with high density and high pressure ratio. Simulation of one-dimensional gas-water interaction problem was performed, and the accuracy and reliability of the method was verified. This method is applied to two-dimensional deep water and near free surface explosion simulation. From the simulation results of underwater explosion, it indicates that this method can simulate the shock wave generation, propagation, reflection and transmission after interation with the interface in underwater explosion. This method is strongly advantageous in simulating compressible multi-medium flow with high density ratio, high pressure ratio and strong discontinuity.

The pressure chamber of “600 ℃ and 20 MN servo-controlled triaxial rock testing system with high temperature and high pressure” has adopted the piston- thick-walled cylinder structure. Compared with normal pressure chamber, the inner diameter rises to 300 mm, the outside diameter becomes 1 060 mm and the height grows to 1 100 mm. The size of test specimen also amounts to Ø200 mm×400 mm. The calibration test applies internal heating type and electronic heating approach with low voltage and high current. Before the system is put into use, the reference temperature point should be calibrated. Thus, nine thermocouples were placed in and outside the specimen to observe the temperature variation at these observation points, and to study temperature field characteristics inside of specimen, as well as its relationship with reference point temperature. The calibration experiment results indicate that, the temperature data collected from the middle of the junction of NaCl and micanite paper are stable and reliable, and are in a favorable linear relationship with the inner temperature. Therefore, the place is qualified to be the reference temperature point in the heating process. The test results show that the inner temperatures of the specimen are higher than the temperatures of the junction of NaCl and micanite paper in the same cross section, the middle temperatures of whom are higher than those on both ends. In the inner axial direction, the upper end and the bottom temperature are symmetric to the middle of the specimen whose temperature is higher than either of those of the both ends. The disparity from middle to end grows bigger as the heating temperature increases, the maximum gradient is 0.85 ℃/mm. In the radial direction, the larger distance from the central point, the greater trend of linear temperature distribution. While the central temperature is the lowest, the surface temperature is the highest. The biggest temperature gradient is about 0.5 ℃/mm. The temperature at the central point, 40 mm from the central point, 80 mm from the central point and on the surface of the specimen are respectively larger than the reference temperature by 21%, 27%, 28% and 29%. Whereas, in the inner axial direction, the upper end temperature and the bottom temperature are close, only 1.5% lower than the reference temperature. It is testified that the heating approach is reasonable, and the accuracy of temperature control is high and the temperature of test specimen is well-distributed.

A high precision numerical algorithm MVPPM (multi-viscous-fluid piecewise parabolic method) is proposed and applied to the multi-viscous-fluid dynamics problems. Several two and three dimensional single-mode Richtmyer-Meshkov instability models with different amplitude and wavelength are numerically simulated by this method. Comparisons show that the evolving of interface is highly sensitive to the initial conditions of perturbation. Both two and three dimensional calculated amplitudes and growth rates of perturbed interface are consistent with the predictions of theoretical models, while the strength of initial perturbation is small. The three dimensional numerical results are identical with the two dimensional ones at the linear stage and larger than the two dimensional ones at the nonlinear stage for the perturbation with the same wavelength and amplitude. Therefore the effects of nonlinearity and three dimensions play a dominant role in the development of Richtmyer-Meshkov instability.

The critical initiation energy and critical tube diameter of C₂H₂-O₂-Ar mixtures were measured in the experiment. The relationship between explosion length, which is theoretical calculated from critical energy, and detonation cell size as well as critical tube diameter was analyzed. The relationship between critical initiation energy and induction zone length was also investigated for each mixture. The results show that, for C₂H₂-O₂ mixtures, a parametric relationship between explosion length and cell size is R₀=26λ, however, this function is changed to R₀=37.3λ and R₀=54.8λ when 50% and 70% argon diluted, respectively. The relationship between critical tube diameter and explosion length is R₀=2D_C. The results indicate that detonation has stable one-dimension ZND structure when argon dilution up to 70%, and a linear relationship is found between critical energy and the cube of induction zone length.

Recently, an explosive method developed in our group shows promise to prepare He@C₆₀ at high yield. However, the explosive process is rather complex, and much remains unknown about the interaction between fullerenens under this extreme condition. In order to unveil the physical origin of such a process, ab initio molecular dynamics (AIMD) method was used to study the collision of C₆₀O or C₆₀ at high temperature and high pressure by explosivion-based method. Many species such as CO@C₆₀ and C₅₉O were generated when the initial speed of collision is 3.28 km/s. By the process of destruction and restoring process of fullerene cage, the endrohendral fullerence can be formed. Such results will be helpful to understand the formation mechanism of endohedral fullerences and to control the formation of fullerene cages by experimental conditions.

In order to gain the rule between them, the mathematic model of single stage pulse induction coilguns is built, and the launch process is simulated and analyzed. The electrical-to-kinetic energy conversion efficiency of system is regarded as a target function, and the initial position of the armature, the discharge voltage and the capacitance of capacitor banks are regarded as variables. Results of analysis indicate that the time of projectile to be accelerated in the drive-coil should match the time of current rising in the drive-coil. As a rule, the high energy conversion efficiency can be gained in the system with capacitor banks of high voltage and low capacitance.

The temporal and spatial distribution of explosion cloud in diffused experiment is analyzed and studied. Cloud diffusion in the atmosphere is simulated by fluid dynamics software. Initial conditions of the cloud are optimized by calculation and experimental program. Cloud movement process rising in vortex flow and flow parameters such as density, velocity, temperature and pressure are obtained from the simulation. The formation mechanism of the explosive “mushrooms” cloud and the vortex movement in gravity caused by different buoyancy force are discussed and analyzed.