The method of preparing metastable materials (e.g.amorphous materials) by rapid compression-induced solidification and related research progress are reviewed in this paper.The authors prepared successfully bulk amorphous polymer PET (ethylene terephthalate), amorphous polymer PEEK (polyetheretherketone), mesomorphic phase of polymer iPP (isotactic polypropylene), amorphous sulfur, nanophase selenium, and two metallic glass La₆₈Al₁₀Cu₂₀Co₂ and Nd₆₀Cu₂₀Ni₁₀Al₁₀ using a rapid compression apparatus.These results indicate that the rapid compression is an effective method to prepare bulk metastable materials of many substances.It has been clearly demonstrated by recent experimental results that the size of metastable materials prepared by this method is not restricted by thermal conductivity, and furthermore it has been found that there exist a critical pressure and a critical compression rate of obtaining metastable phase during the rapid compression-induced solidification.

With the elemental boron powder and chromium powder as raw materials, CrB₂ compound was prepared successfully at 6 GPa and 1 200 ℃ by using high temperature and high pressure method.X-ray diffraction (XRD), X-ray energy dispersive spectroscopy (EDS), hardness tester and scanning electron microscopy (SEM) were used to characterize the physical properties of the sample.The results show that the synthetic CrB₂ is hexagonal structure with space group of P6/mmm, and the lattice constants a and b are 0.297 and 0.307 nm, respectively.From the SEM micrographs, it can be seen that the grain diameter ranges from 5 to 40 μm, and the crystalline quality is good.Moreover, the synthetic sample exhibits high hardness value.By comparing the experimental results obtained under different synthetic conditions, it is found that both the temperature and ratio of raw materials affect the synthesis of CrB₂, and an increase in the proportion of boron in raw materials contributes to the formation of the desired product CrB₂.

Bound charges of poled PZT 95/5 ferroelectric ceramics will be released under shock wave loading to form a high-power electrical energy output.For a shock loading perpendicular to the polarization direction, a model describing the depolarization and discharge process of PZT 95/5 ceramic by normal shock-wave is proposed in this paper.The effects of shock-wave pressure on the wave velocity and depolarization phase transition process were considered systematically.The depoling process of PZT 95/5 ferroelectric ceramics was analyzed by a parallel circuit with a current source, a capacitance and a conductance.The changes in the dielectric constant and conductivity during shock loading were taken into account.The output current characteristics of ferroelectric ceramics discharging process under short circuit and resistive load conditions, and the effects of changes in the dielectric constant and conductivity were analyzed and compared with the experimental results.The results show that the present theoretical model predicts well the discharge process of PZT95/5 ferroelectric ceramics under shock compression.

Air/He and air/R22 cylindrical interface instabilities were calculated by gas kinetic scheme (GKS) under the assumption that the components have the same temperature and velocity in the cell.The density distributions at different time, the displacement histories and the average velocity of characteristic points at the interface were obtained.The displacements of characteristic points increased with time gradually when the shock wave passed through the interface.The average velocities of characteristic points agreed with the results of previous experiments and numerical simulations very well.The comparisons between the simulation results and literature data suggest that the GKS which is based on the particles movement has a good simulation performance for the cylindrical interface instability.

In order to test the impact mechanical properties of geopolymer concrete (GC) effectively, the slag and fly ash were used to fabricate the highly fluidized C30 GC.Based on the prepared GC, the parameter control of split Hopkinson pressure bar (SHPB) system was investigated, and the law between striker velocity, pulse shaper diameter and the optimum constant strain rate was obtained.The results indicate that the pulse shaping technique eliminates the phenomenon of wave oscillation and reduces the dispersion effect effectively; the rise time of the stress wave after shaping is higher than that of rectangular wave, which guarantees the dynamic stress equilibrium; a nearly constant strain-rate loading can be achieved through the integrated control of striker velocity and pulse shaper diameter.

There is an increasing attention in determining the dynamic mechanical properties of low-impedance and brittle materials, but it is difficult to acquire exact experimental results by a conventional Hopkinson pressure bar test because of their small failure strain and weak transmission strain signal.A new method applied to Hopkinson bar dynamic mechanics test was presented in this paper.The velocities of input and output bar ends were measured by the laser micro-displacement interferometer technology, and the stress-strain relation of sample was achieved by this method.The proposed method is validated through numerical simulation and experiment.

If the bandwidth of measurement system can not cover completely the effective bandwidth of a blast wave signal, a dynamic error is inevitably introduced.By using the shock-tube based dynamic calibrated data, a dynamic mathematical model of measurement system is established, and a dynamic compensated digital filter is designed, which shortens the dynamic response time of test system and widens the work bandwidth significantly.The experimental data processing by the correction filter improves the reliability of the uncertainty.The simulation results show that this method can effectively eliminate the dynamic error and increase the accuracy of test data.

In order to provide basic data for quickly predicting JWL (Jones-Wilkins-Lee) parameters of multi-component explosive with any component ratio, this paper presents a theoretical approach for quickly determining the expansion characteristics of cylinder driven by detonation products of multi-component explosive in a cylinder test.Namely, based on the JWL parameters of each component in multi-component explosive, according to energy conservation principle and using Gurney model, the expansion displacement-time curve of cylinder under the detonation driving of multi-component explosive can be obtained.Meanwhile, utilizing energy conservation principle and the relationship between detonation velocity, detonation pressure and detonation heat from constant γ equation of state in classical detonation theory, this paper also presents a theoretical approach for determining the detonation velocity and detonation pressure of multi-component explosive with any component ratio.Using this method, the cylinder expansion characteristics, detonation velocity and detonation pressure of a PBXC03 and a PBXC10 multi-component explosive were calculated, respectively.It is found that the calculated results are in good agreement with previous experimental results, which verifies the feasibility of the theoretical approach.

To explore the afterburning reaction of TNT explosive, the underwater explosion method and an experimental device designed to enhance the afterburning reaction of explosives were used to investigate the energy output structure, and the afterburning reaction energy in different ambient atmosphere was calculated.The experimental data of afterburning reaction was simulated by using Miller energy release model.The results show that the experimental device filled with oxygen or air can increase the afterburning reaction energy output of TNT explosive significantly.The measured afterburning reaction energy increases with the increase of the content of oxygen, and in the studied range, the afterburning reaction energy reaches the maximum value of 4.90 kJ/g, but does not reach the theoretically maximum value.The computed shock wave pressure histories agree with the measured ones well, which indicates that the Miller energy release model is practicable.

Fire extinguishing by explosive water mists is a new method with high efficiency and rapid fire-extinguishing performance.In order to study the process of explosive water mists acting on oil fire, a CCD camera, a fine thermocouple and an infrared thermometer were used to capture the images of fire extinguishing by explosive water mists and the temperature variation during extinguishing process.The experimental results show that the temperature drops sharply while the explosive water mists impact on the oil-fire surface, and the fall time is in accord with the fire extinguishing duration from CCD images.Also, when the water bag is placed 1.0 m above the oil pan with 3 kg water and 2.02 g explosive, the extinguishing duration time is about 200 ms.A fine thermocouple can be used as an accurate measuring device to represent the temperature variation of the extinguishing process, while an infrared thermometer is a good auxiliary means to qualitatively investigate the temperature change of extinguishing process.

In order to investigate the influence of particle size of powder material and its distribution on the properties of powder liner, W and Cu powders were chosen as the main material of shaped charge liner, and a bit of bismuth powder was added to increase the liquidity of the mixed powders.The particle properties of the W and Cu powders were studied by means of scanning electron microscopy.It showed that the W powder was regular, while the Cu powder was irregular.In the condition of material mixture ratio being certain, three sets of liners were developed through changing the particle size of each component, and their microstructure, density, Vickers hardness and penetration power were studied.The results show that reducing the particle size can effectively improve the compactness, density and penetration power of powder liner when the powder material properties and proportion are unchanged, but it has no significant effect on the Vickers hardness of powder liner.

At present, there is a lack of systematic research on the shaped charge jet penetration under large normal angle condition, especially the special phenomenon of jet ricochet.Three ricochet models, including Tate model, Rosenberg model and compressible fluid-mechanics model, were comparatively analyzed, and the experiments of jet penetration into steel and aluminum targets were also conducted.Theoretical analysis shows that the compressible fluid-mechanics model is the best one to predict the rebounding angle.The experiment results indicate that under large normal angle condition, the penetration depth decreases with the increase of normal angle, and the vertical penetration depth is just about ten percents of that of normal penetration.When the velocity of shaped charge jet head is 6 800 m/s, the ricochet angle is between 6° and 7° for 603 armor steel and between 5° and 6° for aluminum.

Numerical simulation and analysis of jet penetration in ceramic/rubber/steel composite armor with different rubber interlayer thicknesses at the impact angles of 30° and 60° were conducted by applying LS-DYNA dynamic analysis software.The jet velocity, target deformation and remaining penetration depth were obtained through the standard shaped charge experiment, and the effects of inclination angle and rubber interlayer thickness on the anti-jet penetration property of composite armor were analyzed.The results show that the inclination angle has a great influence on the defense property of ceramic/rubber/steel composite armor against shaped charge jet, especially large inclination angle; the rubber interlayer has a certain impact on the penetration performance of jet, however the effect of its thickness is quite small.

An extension of the Wen-Jones model for the perforation of fully-clamped circular thin metal plates struck transversely by flat-faced projectiles at the center was made.Based on previous studies, an effective strain failure criterion was suggested to predict the perforation of the thin metal plates.It is shown that the present model predictions are in good agreement with available experimental data for mild steel plates as well as aluminum alloy targets.The present model and the Wen-Jones model produced similar results although they are constructed using different failure criteria, which indicates that the Wen-Jones model can be seen as a special case of the present model when the ductility of plate is large enough.

The techniques of magnetically driven quasi-isentropic compression and magnetically driven hyper-velocity flyer plates are new experimental method and tool, which are developed in the last decade and widely applied in the fields of shock dynamics and high energy density physics.The physical process of magnetically driven flyer plates was simulated by three-dimensional magneto-hydrodynamics software.The calculated free surface velocities agreed well with the experimental results.The magnetic diffusion velocity and effective thickness of flyer plate were obtained by results of temperature, density and magnetic field profiles.The simulation results show that the side edge deformation of flyer plate is mainly caused by the non-uniformity of Lorentz force associated with the inhomogeneous distribution of current along the width direction of the electrode panel.Thus, the edge deformation can be improved by optimizing the current distribution on the loading surface of electrode panel along the width direction.

A calculation model of laser-driven multi-layer flyer velocity was established based on Gurney theory.By modifying laser energy absorption coefficient, the velocity of the multi-layer flyer driven by laser pulse beam was calculated.The effects of layer materials and layer configuration on the flyer velocity were analyzed.The multi-layer film configuration which was capable of forming high velocity flyer was decided.An intense laser driven multi-layer flyer experiment was conducted, in which piezoelectric film sensors were employed to measure the flight time of flyer traveling different distances.The velocity and acceleration of flyer were obtained.The results show that the acceleration characteristics of multi-layer flyer driven by different laser energies are similar.Laser energy has little influence on acceleration time.The flyer velocity increases at first and then decreases with the increase of ablation depth.Ablation layer has an optimal depth for energy absorption at different energies.

This review introduces the effects of high hydrostatic pressure on the molecular volume, non-covalent bond and conformation of protein.The molecular volume is decreased, and the hydrogen bond, electrovalent bond, and hydrophobic interaction are influenced by compression.The secondary, tertiary and quaternary structures of protein are influenced by pressure below 800 MPa.Tertiary and quaternary structures are more pressure-sensitive than secondary structure.Pressure below 8 GPa does not influence the primary structure of proteins.

The influence of shock compression on the germination rate of plant seeds was investigated experimentally by a light gas gun and numerically by finite element method.The deformation of cover-plate and the shock wave propagation in groove were simulated by ANSYS AUTODYN.The germination rates of two kinds of plant seeds (alfalfa and turnip) were assayed after experiments, and the experimental results indicated the different sensitivity of these two seeds and the relationship between germination rate and peak pressure.At the peak pressure of 385 MPa, the relative germination rates of alfalfa and turnip seeds were decreased to 65.4% and 6.1%, respectively.Different type of damage seeds were observed by a scanning electron microscope.It is believed that the damage is only a minor factor for germination rate of plant seeds.