The numerical simulations of hypervelocity impact of Al-spheres on bumper at normal are carried out using the smoothed particle hydrodynamics (SPH) technique. The simulation results are compared with experimental results, and the simulated hole diameters of bumper and debris cloud are well consistent with experimental results. The effect of impact velocity, bumper thickness, projectile diameter, materials, shape of projectile, interval on produced debris cloud are further analyzed. Regarding the length and diameter as index, orthogonal design method is applied to analyze the primary and secondary relations on the debris cloud's index of the three factors, that is impact velocity, bumper thickness and projectile diameter. The results indicate that bumper thickness is the main influence factor of debris cloud's length while projectile diameter is the main influence factor of debris cloud's diameter.

Shock-induced phase transformation (body-centered cubic α phase to hexagonal close-packed ε phase) in single crystal iron has been investigated by means of molecular dynamics (MD) simulations using an embedded atom method (EAM) potential. The simulated dimension is 28.7 nm×22.9 nm×22.9 nm in size with 1.28×10⁶ atoms. The shock wave is generated by using a piston impact on the sample along the [100] direction. By analyzing the motion history of atoms under shock compression, the phase transformation mechanism has been outlined. The simulation results show that the phase transformation mechanism contains two steps: the atoms on the {011} planes are compressed along the 〈100〉 direction to form a hexagon in the first step, and then the atoms on {011} planes in the 〈0-11〉 direction are slipped to create the hcp structure in the second step. The results also show that the slip planes are only the (011) and (0-11) planes which are parallel with the shock wave propagation.

A theoretical method was proposed to evaluate the Hugoniot parameters of the preheated metals based on Grüneisen equation of state. This method offsets some disadvantages of BACT and can be used to estimate Hugoniot parameters of all kinds of solids with preheating in principle. This method was applied to calculate the Hugoniot parameters for Al and TC4 at different initial temperatures up to 1 200 K and compared the obtained results with the available data reported in literature. It is shown that the moderate preheating of metal does not result in an obvious deviation from its principal Hugoniot. Thus the rough treatment in hypervelocity impact experiments that the Hugoniot of preheated flyer is approximated to be the principal Hugoniot is reasonable.

Four internal heating modes in Bridgman anvil were designed in this work. Heater was made of tantalum and graphite flakes. Two thermocouples were used to measure the temperature change of the central and upside section in sample cavity with input voltage. Temperature gradients were roughly discussed. Under 0.1 GPa, highest temperature reached in sample cavity was higher than 1 300 ℃. In addition, sample temperature change with input voltage was also measured up to 1 000 ℃ under 5.0 GPa.

The structural behavior and the electronic properties of AgCl under pressure are extensively studied by using the pseudopotenial plane-wave method and generalized gradient approximation within density functional theory. The theoretical transition pressure corresponding to the phase transition from rocksalt to monoclinic structure is obtained from the enthalpy calculations. The location of the valence band maximum and the conduction band minimum in the entire Brillouin zone are predicted for both structures. The rocksalt and monoclinic phase of AgCl are both semiconductors with indirect gap and the variations of the band gaps with pressure indicate that they do not become metallization before structural instability. Furthermore, the bonding between Ag and Cl atoms becomes less ionic or more covalent under compression.

The air drag coefficients of spherical tungsten fragments are studied. The fragment includes ideal sphere and real fragment formed by a warhead. The experimental results show that: (1) for ideal spheres, the attenuation coefficient of velocity is constant, the air drag coefficient is slightly affected by the initial velocity and is a linear function of initial velocity, and (2) for real fragments formed by a warhead, the flight performances are different from ideal spheres, the air drag coefficient is affected by the flight velocity and is a linear function of flight velocity.

h-BCN compounds were synthesized with C₃H₆N₆ and B₂O₃ as raw materials, combined with heat treatment, high pressure and high temperature. An amorphous BCN precursor was prepared at 1 100 K under vacuum. Annealed for 30 min, at 1 500 K under 5.0 GPa, the amorphous BCN precursor crystallizes into hexagonal BCN compound with lattice constants of a=0.250 5 nm, c=0.665 9 nm determined by using the reflex module combined in the Materials Studio program analysis. The shape and SAD of sample also approved that the sample was h-BCN crystal by TEM analysis. The grain size about was 200 nm. XPS analysis was applied for the sample. The results confirmed bending energy of C—C, C—N, C—B, N—B. It indicated atom level chemical combination of BCN. The composition and content of the sample were analyzed by EDX.

We conducted acceleration-time measurement of penetration experiments in targets with 100 mm diameter, 4.0 caliber-radius-head, 25 kg projectiles. The 3 m×3 m×3m and 2 m×2 m×2m concrete targets had an nominal unconfined compressive strength of 35 MPa and density 2 450 kg/m³. Projectiles were designed to contain a single-channel acceleration data recorder, so we recorded accelerations in the bore of the gun and accelerations during the penetration event. A 100 mm diameter powder gun launched the 25 kg projectiles to striking velocities between 310 and 632 m/s. We compared the measured penetration depths and acceleration-time data with the calculated results using Forrestal formula. The calculated results are in good agreement with rigid-body acceleration measurements for the rise times and peak plateau responses. The acceleration-time data of projectiles can be helpful for devising armour-piercing projectile and defense engineering.

Dense nanocrystalline BaTiO₃ ceramics with a grain size of 50 nm were prepared under 6 GPa at 1 000 ℃ using a high pressure sintering method. The sintered bulk is uniform and the relative density is above 97%. We annealed the ceramic samples in oxygen to eliminate the oxygen vacancies caused by high pressure. After anneal, several broadened peaks were observed through dielectric measurements. However, these peaks are very different from those of coarser-grained ceramics. The observation of polarization hysteresis loop provides the solid evidence of ferroelectricity in these nano-sized BaTiO₃ ceramics. It is believed that the absence of 90° domains and the existence of depolarization field caused by nonferroelectric grain boundaries contribute to the slim loop.

A numerical simulation method for calculation of the three-stage light-gas gun impacts on launch flier to hypervelocity is presented. Based on multi-fluid volume of fraction (VOF) and parabolic piecewise method (PPM), a multi-fluid parabolic piecewise method (MFPPM) shock wave physics code is developed to calculate the experimental hypervelocity launchers. To verify and validate our code of MFPPM, some experimental hypervelocity launchers from Sandia National Laboratories are simulated, and the numerical results of flier velocity are excellent in agreement with that experiment (the maximal relative error is 1.07%). Experiment and simulation results of our experiment on the three-stage light-gas gun are given (the maximal relative error is 1.04%). To satisfy well of the high-pressure equation of state (EOS) data measurement, an improved design model from the computation is presented.