The dynamic release behavior of OFHC copper under 10~20 GPa shock pressure was simulated by using the Johnson-Cook (JC) constitutive model and Steinberg-Cochran-Guinan (SCG) constitutive model, respectively. Comparisons between the simulations and the experimental results show that the strain rate effect during the release process of copper under such shock pressure ranges is still obvious. And the simulation of JC model gives better agreement with experimental results than the simulation of SCG model in which the strain rate effect is ignored.

Melting temperatures of OFHC (Oxygen-Free High Conductivity) copper at pressures ranging from 110 GPa to 140 GPa were measured on a two-stage light-gas gun by optical radiometry techniques and using LiF single crystal as window, based on such a conclusion that the melting temperatures at the sample/window interface pressure is equal to the release temperature, and close to the interfacial temperature if the OFHC copper sample is initially shocked or released into the region adjacent to the liquidus. The obtained data are consistent with the experimental results of high-pressure sound velocity measurements and theoretical predictions, and the melting behavior of OFHC copper at high pressure can be approximately described with Lindemann melting law. The method for melting temperature measurements we proposed in this paper avoided derivation of Hugoniot temperature, which simplified the determination of melting temperature, and provided a potential approach for melting temperature measurements of metals.

Raman scattering spectroscopy was used to investigate stability of n-pentane in Moissanite anvil cell from 0.07 GPa up to 4.77 GPa at ambient temperature. The result shows that CH₃ symmetric and asymmetric stretching vibration, CH₂ symmetric and asymmetric stretching vibration and -(CH₂)_n - in-phase twist mode at 2 877 cm^-1, 2 964 cm^-1, 2 856 cm^-1, 2 935 cm^-1 and 1 303 cm^-1, respectively, shifted to higher frequency according to quasi-linearity with pressure increase, and an abrupt visible change was taken place, indicating that it is a sort of phenomenon of freezing at overpressurization. In addition, a high-pressure transition phase may appear in crystallized n-pentane in the range of 2.84~4.77 GPa. The equilibrium freezing pressure of n-pentane is (1.90±0.05) GPa at 27 ℃ by measuring with the method of crystal-liquid coexistence.

In the framework of density functional theory, the static structure properties and phase transition of aluminium are calculated using the augmented plane wave plus local orbitals (APW+lo) method with generalized gradient approximation (GGA) for the exchang-correlation energy. The critical values for the phase transitions (fcc-hcp, fcc-bcc, hcp-bcc) are 220 GPa, 300 GPa and 380 GPa, respectively. Our results are in consistent with existing data obtained from different methods and also in good agreement with experiments.

The spectra of energy dispersive X-ray diffraction with synchrotron radiation of double perovskite compound Sr₂CrWO₆ have been studied in situ high pressure pressure up to 34.5 GPa using a diamond anvil cell at room temperature. The experimental results indicate that the sample undergoes a crystal structural change at about 9 GPa. The resistance-pressure and capacitance-pressure relationships in the pressure range of 0~20 GPa show that there is an electronic structural change in Sr₂CrWO₆ in the pressure range of 2~5 GPa.

Compared to the traditional numerical methods, meshless SPH method is more suitable to simulate the hypervelocity impact in that it can simulate the material interface clearly and overcome the numerical instability due to the large mesh deformation in the Lagrange method. In SPH, in order to get the physical value of one nodal at time t, it is firstly required to find the neighboring nodes interacting with it, so the calculation speed is slower and the calculation time is longer than that of the FEM. This paper adopts the coupling method of SPH and Lagrange to simulate the 3D hypervelocity impact problem. The results show that the coupling method can save largely time while keep the accuracy approximately to that of SPH.

The 4th International Symposium on Supercritical Fluid Technology for Energy, Environment and Electronics Applications was introduced in this report. Progresses on supercritical fluid technology for energy, environment and electronics applications in recent years was described, respectively.

It is indicated that the constitutive equations at high strain rates proposed by Johnson-Cook (J-C), Zerilli-Armstrong (Z-A) and Bodner-Parton (B-P) collapse the data of flow stress in compression, tension, torsion, and shear into simple curve with the scalar quatities ‘effective’ stress and ‘effective’ strain, however, the collapsed data of flow stress did not include the data in the planar shock wave tests. The SCG constitutive equation proposed by Steinberg et al for the planar shock wave tests is discussed, which describes the coupled high pressure and high strain rate effects on the plastic deformation of materials. Basing on the recent experiments at elevated temperatures and high strain rates and the shear strength measurements during shock loading, the flow stress for tungsten at high pressure and high strain rates is estimated with J-C and SCG constitutive equations, respectively. It is concluded that the J-C, Z-A and B-P constitutive equations may not be appropriate to describe the plastic behavior of materials at high pressure and high strain rates, comparing with SCG constitutive equation. It is emphasized that the physical background of the constitutive equation at high pressure and high strain rates is different from that at low pressure and high strain rates.

A new damage evolution equation for ductile materials is presented based on the statistical meso-scopic damage mechanism, which consistent well with the results of analysing the mechanical responses for the spherical cell containing a single central spherical void. The model presented is incorporated in a hydrodynamic one-dimensional finite-difference computer code, to simulate the process of spallation of OFHC copper. The calculation is in good agreement with the experimental data.

Symmetrical impact experiments for single crystal LiF were conduced at two-stage light-gas gun with a VISAR diagnostic. Longitudinal and bulk sound velocities, and unloading path of LiF were obtained up to 79.1 GPa shock pressure. Experimental results indicate a good linearity between the Lagrangian longitudinal sound velocity and the particle velocity. There is no evidence of shock-induced melting or phase transition for LiF in the present pressure range. The LiF unloading path and velocity profiles show a clear transformation from the elastic release to the plastic unloading.