Under extreme compression, hydrogen goes through a series of phase transitions, and may transform to an exotic metal predicted by theoretical calculations. The pursuit of metallic hydrogen by the high pressure community is intense due to the predicted room temperature superconductivity and super-fluidity. Unfortunately, significant technical obstacles present for such studies. On one hand, achieving the pressure of metallic hydrogen is daunting, as a result, there has been no consensus on the success synthesis of cold compressed metallic hydrogen yet. On the other hand, accurate characterizations of ultra-dense hydrogen remain very difficult, especially for measuring crystal structure. The lack of crystal structural information (the most fundamental information of a material) of hydrogen prevents understanding how does hydrogen evolves structurally to achieve the predicted metal from an insulating solid. In order to measure the crystal structure of hydrogen at ultrahigh pressures, we developed a series of advanced synchrotron X-ray diffraction techniques, and extended the crystal structural data of hydrogen to 254 GPa, which doubled the previous pressure record. In this paper, we will introduce our technical developments and discuss the related issues, in order to provide guidance for measuring crystallographic data of solid hydrogen at higher pressures.

Magnesiosiderite [(Mg,Fe)CO₃] is one of the main carriers for carbon to enter the deep Earth, and the presence of iron will cause great change of mineral physical properties. The effects of ferrous iron’s spin transition on the thermodynamic properties of magnesiosiderite have been studied by first principle calculations. The volume of (Mg,Fe)CO₃ low spin state (LS) decreases, while the volume of (Mg,Fe)CO₃ high spin state (HS) decreases slightly at lower temperature and increases at higher temperature, as compared with that of MgCO₃. In the whole range of temperature and pressure studied in this work, the volume of LS state is smaller than that of HS state. The thermal expansions of HS and LS magnesiosiderite reduce with respect to that of MgCO₃, respectively. The effects of coexistence of HS and LS have been considered, in which the calculations show that the thermal expansion and velocity present abnormal increase and decrease, respectively. Meanwhile, the abnormal change peaks could move to high pressure as the increasing of temperature.

The sensitivity of Rayleigh-Taylor instability of tin driven by explosion to the initial parameters of sample (initial amplitude, wavelength and thickness of sample) and the initial parameters of SG constitutive model are numerical investigated by using an in-house Eulerian detonation and shock wave code. It concludes that the initial parameters of sample have a significant effect on the RT instability of Sn. The Sn RT instability grows more slowly with the initial amplitude decreasing, and a cutoff initial amplitude exists. A most unstable mode (wavelength) exists, when the initial wavelength is larger than this value, the RT instability grows faster as the initial wavelength diminishes; on the contrary, the RT instability grows slower as the initial wavelength decreases. The larger thickness of sample can restrain the growth of RT instability greatly, and a cutoff thickness of sample also exists. The Sn RT instability growth is not sensitive to the strain hardening coefficient and exponent, and it is greatly sensitive to the pressure hardening coefficient and thermal softening coefficient. But it should be a practical path to estimate the material strength of Sn through modifying the pressure hardening coefficient of SG model.

This paper presents a numerical model of the square dispersing device for simulating the process of shell failure and fuel dispersion by LS-DYNA software. Combined with the results of the field experiments, this model reveals in detail the influence of the fillet angle and groove depth on the shell rupture process and fuel dispersion speed. The results show that the shell edge would no longer rupture when the fillet radius increases to 10 mm or the groove depth increases to 1.2 mm, since different groove depth would effectively reduce the nonuniform shell rupture. And when the depth of edge and middle groove is 1.2 mm and 1.6 mm respectively, the shell is uniformly ruptured. In addition, a special dispersing device with 10 mm fillet angle, 0.8 mm edge groove depth and 1.2 mm middle groove depth, could not only make the shell uniformly ruptured, but also increase the strength of the shell. Meanwhile, it would reduce the average velocity difference of fuel dispersion by 22%, which effectively improve the fuel dispersing efficiency.

This paper introduces key design techniques for PVDF sensitive element used in dynamic compression experiments. Based on the sensitive element design, electrode design, sensitive element polarization and sealing, PVDF dynamic pressure sensors are well design and produced. We also made dynamic experiments in order to calibrate the PVDF sensor. The results show that A-type uncertainty is less than 10%, which can be used in the dynamic pressure range of 0.3–10.0 GPa. We will extend the application to higher pressure range and consider the temperature effects.

The shock initiation reaction of A-type insensitive explosive has been investigated by means of the one-dimensional planar impact experiment and photon Doppler velocimetry technique (PDV). In this experiment, a sapphire flyer was launched by the powder gun and then impacted the stepped insensitive explosive A. Meanwhile, the wedge-shaped lithium fluoride (LiF) windows coated with aluminum films were stuck to the different rear interfaces of stepped explosive. Therefore, the particle velocities among these interfaces could be measured. By employing the impedance matching method, the particle velocities in the explosive A were eventually obtained. The experimental results show that the PDV has a higher precision than the multiple electromagnetic particle velocity gauge. The effects of the speed probe’s angle, the probe’s aperture, and the refractive index of the window are briefly analyzed. The relative uncertainty of the measured speed is within 1%.

To investigate the impulsive resistance property of the carbon fiber reinforced polymer and epoxy (CFRP/Epoxy) laminate, the dynamic response and failure behaviors of the CFRP/Epoxy laminate beam subjected to varying impulsive intensities were experimental studied. The impulsive loading was generated by the impact of aluminum foam projectile which was fired by a one-stage light gas gun system. To capture the dynamic process of the impacts, a high-speed camera was employed. The impulsive resistance property in terms of dynamic failures, deformation profiles, midpoint deflections, failure modes and specific energy absorption was analyzed by considering the intensity effects of the impulsive loading. The results indicate that the rate of midpoint deflection response increases with the increasing impulses. The deformation regime of the composite beam changes from structural deformation to local deformation with the increasing impulses, accompanying with server matrix and fiber damages. With the impulse increasing, the specific energy absorption (SEA) undergoes three stages which are directly related to the failure modes of the laminates.

Metals are widely used in the defense industry and civil engineering and an understanding of the mechanical properties of metals under intense dynamic loadings is of great significance for the design and assessment of weapons and protective structures. In this paper, the dynamic yield strengths (HELs) of 93 tungsten alloy and 921A steel at very high strain rates are determined by plate impact tests using a two-stage light gas gun system. The paper consists of three parts: firstly, the basic principle of the plate impact experiment is briefly introduced; secondly, the experimental data is analyzed in some details; finally, the dynamic yield strengths of 93 tungsten alloy and 921A steel at very high strain rates are determined. The experimental results show that the dynamic yield strengths of 93 tungsten alloy at strain rates of 1.7 × 10⁵ s⁻¹ and 3.1 × 10⁵ s⁻¹ are 2.10 GPa and 2.78 GPa respectively and the dynamic yield strengths of 921A steel at strain rates of 3.6 × 10⁵ s⁻¹, 4.7 × 10⁵ s⁻¹ and 6.2 × 10⁵ s⁻¹ are 2.08 GPa, 2.67 GPa and 3.15 GPa, respectively. The experimental results also show that the dynamic increase factors for 93 tungsten alloy and 921A steel at very high strain rates are between 2 and 3.

The finite element model of a ceramic beam impacted by a blunt-nosed projectile was established, and the impact damage evolution process of the beam was simulated. The simulation results are in good agreement with experimental results, which confirms the validity of the model. On this basis, the finite element model of a nacre-like ceramic/polyurea composite beam impact by the same projectile was established. Its damage evolution process was compared with that of the ceramic beam. Effects of impact velocity of projectile on damage process are studies for the two beams. The obtained results show that the damage of the ceramic beam expands conically, and the beam undergoes global damage. The damage of the nacre-like composite beam expands in a cylindrical shape in the longitudinal direction (i.e., impact direction), and the beam undergoes local damage, which gives a good ability to maintain structural integrity. Moreover, as the impact velocity of the projectile increases, the range and extent of damage of the ceramic beam increases significantly. Differently, when the impact velocity exceeds a certain value, the damage range of the nacre-like composite beam changes insignificantly, while its damage extent grows with the increase of impact velocity.

Exploring the stress and failure characteristics of rock is the key to study the safety of rock underground engineering, thus many scholars expect to make breakthrough in the study of rock constitutive model. In this paper, a constitutive model is proposed to describe the rock under cyclic loading and unloading. Firstly, it is assumed that the micro-unit strength of rock obeys Octahedral shear stress theory and the micro-unit failure of rock obeys Weibull probability formula, and the damage variables in rock constitution and the damage factors contained in micro-unit strength of rock expression are transformed into the constitutive equation. Then the parameters such as stress, strain and others representing the damage constitutive model of rock under loading and unloading can be obtained and are used to express the micro-unit strength and damage variables. Substituting the micro-unit strength and damage variables into the proposed rock constitutive model, a function expression can be carried out by an equation transformation. Through the comparison and analysis of the fitting data with the experimental results, the modified fitting parameters are acquired, and can be substituted into the function to revise the damage constitutive model. Finally, the necessary sensitivity analysis of the fitting parameters is implemented to obtain the practical physical significance of each fitting parameter.

The effect of crystal texture on the numerical results was studied based on the theory of crystal plasticity, and the polycrystalline compression shear sample (SCS) model with texture was established. The influence of micro-grain on the macroscopic mechanical properties in the process of finite deformation under static loading condition was studied in terms of material and sample structure. Because of the particularity of model geometry, the stress, strain and deformation characteristics of skewed slot were computed. Considering the effect of friction on the specimen during compression, the influence of friction coefficients on the deformation process was analyzed numerically. The influences of grain number, element number and element type on the mechanical properties of polycrystalline compression shear model under the same friction coefficient were calculated. The stress states of grain with different orientations in key parts of the specimen were also studied.

A supersonic earth-penetrating projectile is designed where two different metal materials are used for the projectile’s body. Experiments of projectiles with mass of 25 kg and impact velocity ranging from 1 100 m/s to 1 300 m/s are implemented by a cannon with caliber of 203 mm. The process of projectile penetrating into the reinforced concrete target is simulated based on a numerical method. Based on the experimental and simulation results, the projectile’s structural response and mass loss in supersonic condition were investigated. The results show that the two damage modes of projectile with different metal materials in supersonic penetration condition are head eroding and wall friction corrosion. The degree of damage and the head erosion amount are related to the metal materials of projectiles. The G50 metal with high-strength is appropriate to be used for the projectile body in supersonic penetration with impact velocity of 1 200 m/s. The phenomenon of diameter shrinkage is analyzed, and some suggestions are put forward for the design of projectile body structure in future engineering application.

In this work we carried out research on the anti-explosion effect of heptafluoropropane in the process of methane-air premixed gas explosion propagation in equivalent ratio, in order to solve the explosion accidents in the process of gas transportation. This experiment used a horizontal pipeline explosion characteristic test system with an aspect ratio of L/D=108, studied the effects of different volume fractions of heptafluoropropane on the maximum explosion pressure, maximum pressure rise rate and flame propagation velocity of 9.5% methane-air premixed gas under strong ignition. The experimental results show that when the 2.5 m long pipe section is used as the heptafluoropropane explosion suppression zone, the minimum volume fraction of heptafluoropropane which can suppress the 9.5% methane-air premixed gas explosion flame propagation is 5%; when the concentration of heptafluoropropane is 1% to 4%, the propagation of the explosion flame cannot be suppressed, and the flame propagation speed is accelerated compared with the control group; when the concentration of heptafluoropropane is 1% to 6%, the peak value of the explosion pressure at the source of explosion and end of pipe gradually decreases with the increase of the concentration of heptafluoropropane; when the concentration of heptafluoropropane is 3%, the peak value of the explosion pressure at the explosion suppression zone increase by 10.9% compared with the control group.

Based on the similar model test, the stress wave propagation rule, crack formation mechanism and displacement distribution characteristics of rock mass in the underground anchorage chamber under the simultaneous explosion of concentrated explosive source at top and side of arch are studied by explicit nonlinear dynamic analysis program LS-DYNA3D. By comparing and analyzing the compressive stress time-history curves of the experimental and calculation model, it is found that the simulation results are consistent with the experimental results and conform to the stress wave propagation law, which indicates that the numerical simulation results are reliable. Under explosion of the source, the stress wave propagates to the surrounding rock mass in a circular way. When the stress wave is transmitted to the free surface, it will be reflected and form the stretching wave, which forms the phenomenon of “spalling crack” under the ground and above the tunnel. There are cracks extending along the radial direction of the chamber at the middle point of the explosion source on the top and side of arch. The bolt can play a role in strengthening the rock mass. The distribution of cracks in the anchorage chamber is less than that in the unanchored chamber. The displacement peak value of the surrounding rock at the radial axes of the two blasting sources is the largest and most easily destroyed.

In order to improve the quality of explosive welding and to solve the problem of high noise and low efficiency, Cu is selected as the flyer plate and Q235 steel is used as the base plate. The LS-DYNA software and the smoothed particle hydrodynamics (SPH) method are used to design the uniform distribution and the ladder distribution scheme, and the effect of the nitrate explosive on the explosive welding interface wave is studied. The results of the uniform distribution show that the collision pressure gradually increases along the detonation direction; the more amount of explosive, the greater the collision pressure and the higher the interface wave shape . In the ladder distribution scheme, four schemes are designed by changing the height of the initiation and the end of the explosive. The results show that the ladder distribution can eliminate the uneven phenomenon of the interface wave in the explosion welding, and keep the size of interface waveform consistent, and the amount of explosives will be saved. The waveform is best when the height of the initiation and the end of detonation is 67.2 mm and 42.0 mm, respectively. By studying the formation process of interface wave, the SPH results of formation process of interface wave simulated is in good agreement with the jet indentation mechanism, which shows the effectiveness of the jet indentation mechanism to explaining the formation process of interface wave.