The research on hydrogen under high pressure has always been a hot topic both in experimental and theoretical physics, the enthusiasm is rooted from the pursuit of its pressure-induced metallic state – metallic hydrogen. The pressure induced metallization of hydrogen is an electric phase transition from a wide gap insulator to a small gap semiconductor, and finally to a closed gap metal. However, due to the limitation of high pressure experiment conditions, the bandgap and electronic structure of the wide-gap hydrogen has never been directly observed. In this paper we will discuss the technical challenge and the development of experiment research on hydrogen metallization, meanwhile we will present our experiment results and the technical advance on the direct measurement of the wide-gap hydrogen by using inelastic X-ray scattering technique, and finally the outlook.

Barium germanate (BaGeO₃) was studied using double-sided laser-heating diamond anvil cell (LHDAC). At ambient conditions, BaGeO₃ has a pseudowollastonite structure. At about 12 GPa, BaGeO₃ crystal begin to translate into an amorphous phase. The amorphous BaGeO₃ was further pressurized to about 22 GPa and then heated at (1800 ± 200) K conditions. Raman spectra shows the amorphous BaGeO₃ transforms into a new high pressure phase, which has not been reported so far. The new high pressure phase of BaGeO₃ was further measured with the synchrotron radiation X-ray diffraction in the pressure ranges of 0−17.4 GPa. The diffraction patterns can be indexed with a 6H-type hexagonal perovskite structure and this structure remained stable as the pressure unloading to ambient pressure. In order to obtain the structural parameters of the new high pressure phase of BaGeO₃, the X-ray diffraction patterns of 17.4 GPa and ambient pressure were refined with a model structure of 6H-type perovskite using the Rietveld method. The experimental pressure-volume data was fitted with the second-order Birch-Murnaghan equation of state, and obtained the volume bulk modulus and zero-pressure unit-cell volume are K₀ = 150(2) GPa and V₀ = 373.0(3) A³ respectively. On the basis of the experimental results in this study, we also carried out the first-principle theoretical calculation on the 6H-type perovskite BaGeO₃. The calculated lattice constants and volume with the corresponding pressures are good agreement with the experimental results. Furthermore, the calculated volume bulk modulus and zero-pressure unit-cell volume are K₀ = 153(1) GPa, V₀ = 374.2(1) A³ respectively. The calculated Raman spectra at 20.0 GPa is also well consistent with the experimental results. This study not only complements the structural phase transition of pseudowallastonite BaGeO₃ at high temperature and high pressure, but also builds a solid foundation for further characterizing the physical and chemical properties of pseudowallastonite BaGeO₃, and gives a chance to develop the perovskite structured germanate functional materials. In addition, this study has an important indicative significance for us to understand the phase transition rule and stability of silicate perovskite, the physical and chemical properties and changes of Earth's lower mantle.

The fabrication process of the high-entropy alloys (HEAs) at the atomic scale was investigated numerically through molecular dynamics (MD) approach, with which the micro-structures of Al_xCoCrFeNi were analyzed. The mechanical properties of the fabricated specimens with different Al contents subjected to axial loads were explored at different temperatures. Numerical results show that the high-entropy alloys Al_xCoCrFeNi undergoes the elastic, yielding and plastic stages in order when subjected to tensile. After yielding, dislocation lines emerge in the material, followed by the stacking faults and twins. The material produces inhomogeneous plastic deformation with the continuous generation and disappearance of dislocations. This analysis suggest that the lattice distortion effect is induced by the radius difference between Al atoms and other atoms, additionally, the binding force between them affects the Young's modulus and yield stress of high-entropy alloys. Moreover, the increase of temperature leads to more severe thermal vibration between metal atoms, larger atomic dynamic energy, increasing distance between atoms, while decreasing binding force between atoms, thereby resulting in a decrease of alloy elastic modality and yield stress. The effect of temperature is similar to that of the lattice distortion.

The motion relationship between shock wave and fragment directly determines the coupled damage effect on the target. In the present study, the finite volume method and mesh adaptive technique are used to study the motion of the circular rigid body, the attenuation of the shock wave and the motion law of both under the high temperature and high pressure gas loads. The results show that the shock wave formed by high temperature and high pressure air masses reflects and diffracts from the cylindrical fragments, and the pressure difference formed before and after the fragments is the main reason for its acceleration. In cases with a fixed number of fragments, the larger the spaces between the fragments and the center, the lower the initial velocities. When the space is fixed, the greater the number of fragments, the larger the initial velocities. In addition, it is also found that there is a complicated chase relationship between the leading shock wave and the fragment. When the initial velocity is large, the fragment and the shock wave is found to meet twice. With the initial velocity decreasing they meet one time. With the initial velocity decreasing further they cannot meet. The front-to-back relationship between the shock wave and the fragments is expected to affect whether there is a coupled damage to the target.

During the preparation of nano TiO₂ particles via the gaseous detonation method, a portable nano-powder collection platform was located inside the gaseous detonation tube where the nano-TiO₂ powders were collected based on the detonation reaction. The growth mechanism of gaseous detonation preparing nanoparticles was investigated experimentally for the first time. The results demonstrated that the TiO₂ powders collected from platform and detonation tube wall consisted of rutile and anatase phases, and the particle size of TiO₂ from platform is much smaller than that of tube wall. The particle size was significantly affected by the distance from platform to the end of detonation tube, and the closer the distance, the smaller the TiO₂ particle size. The growth mechanism of nanoparticles prepared via gaseous detonation method was revealed based on the theory of detonation/shock wave propagation and experimental observation in detonation tube.

Damage localization was performed for the typical carbon fiber (CF) and glass fiber (GF) reinforced epoxy composite laminates through in-situ measurement technology. The electrode array was developed by utilizing the conductivity of CF reinforced epoxy composite laminates. The influence of plate thickness on the damage localization was investigated. For non-conductive GF reinforced epoxy composite laminates, multi-walled carbon nanotubes coated GF bundles sensors (MWCNT@GF) were fabricated, and the sensors were embedded into the laminates to form the sensor network. The influence of different incident angles on the localization was investigated. For the above two methods, an impact damage localization algorithm was developed and compiled. The results show that the damage position of CF/epoxy and GF/epoxy composite laminates can be located with high accuracy by using the self-resistance of CF and embedding MWCNT@GF sensors.

The dynamic fracture behavior of material containing helium bubbles is the focus of many research fields. In this work, the spall damage of pure aluminum containing boron inclusions or helium bubbles is studied by plane impact experiments. The experiments were done for three types of targets: pure aluminum, Al-¹⁰B and neutron irradiated Al-¹⁰B to obtain helium bubbles. The targets response to the dynamic loading was obtained from the free surface velocity profiles which were measured by dual laser heterodyne velocimetry. The results show that, the spall strength and Hugoniot elastic limit of these targets were calculated. It is found that the spall strength of pure aluminum is 1.28 GPa, and the addition of ¹⁰B in pure aluminum reduces the spall strength of material by about 50%. However, Al-¹⁰B with helium bubbles is not found to have higher spall strength compared to samples without bubbles, which means that the influence of helium bubble on the dynamic fracture properties of the material is not significant. In addition, the effects of boron and helium bubbles on the Hugoniot elastic pole of aluminum are discussed.

Ceramics is commonly used as ballistic resistant material due to lightweight and high strength properties. However, due to its brittleness, the use efficiency of ceramics is low, and local breakdown often leads to the breakage of the whole ceramic. In order to improve the use efficiency of ceramics, a composite structure of layered gradient ceramic ball and aluminum was presented in this study, and the influences of ceramic ball size and hitting position were studied with numerical simulation method. The anti-ballistic mechanism of ceramic ball-metal composite structures was analyzed from the deformation of bullet and target plate, the change of bullet velocity and the plastic wave propagation, and then the optimization design of anti-ballistic structure was proposed. The results show that the ceramic ball with a diameter of 7.2 mm has an excellent property of anti-ballistic capability. The layered gradient ceramic ball structure designed can further improve the anti-ballistic capability. The ceramic ball-metal composite target plate is damaged locally, and the other parts of the target still have the anti-ballistic capability.

In order to resolve the problem of martyred detonation of insensitive munitions or fuzes during combat readiness and logistical storage, numerical simulation of detonation sequence of the fuze under shock wave was carried out by using nonlinear finite element method. The growth course, propagation law and critical detonation distance of the fuze explosive train were obtained. And the criterion of shock wave energy was established and the condition of sympathetic detonation was given. The results showed that the detonation wave propagates from the top left to the bottom right and explodes at the bottom right, and the critical sympathetic detonation distance of the fuze explosive train is 9.7 mm. When the shock wave energy was greater than the critical detonation energy, the sympathetic detonation occurs in the fuze explosive train.

Using vinyl ester resin prepreg and winding method, a ECR corrosion resistant glass fiber reinforced epoxy resin matrix composite pressure vessel was manufactured. The strain variation of the pressure cylinder was measured in the hydraulic test using the electrical method.And the strain response of the pressure vessel with internal delamination defects under external loadings was predicted by Abaqus/Explicit finite element simulation. The experimental and simulation results show that the error between the results of the finite element model and the experimental results is less than 12%. When the composite pressure vessel containing internal delamination defects (defect diameter 10, 20, 30, 40 and50 mm) is subjected to displacement load, the circumferential strain is the main strain, the maximum longitudinal strain and Mises stress position coincide with the loading position, and the maximum Mises stress increases with the increasing delamination area.

Based on the Kirchhoff thin plate theory and Hamilton principle, the vibration control equation of composite plate is established. The equation is simply supported on three sides and fixed on one side with initial geometric imperfections. The expression of buckling critical load is obtained. The numerical calculation is carried out by MATLAB programming. The effects of initial geometric imperfections, initial phase, ply angle, buckling mode order and layer number on the critical buckling load of the plate are discussed. Results show that the critical buckling load is decrease with the increasing of the critical length, the decreasing of the laying thickness, the increasing of the initial geometric defect coefficient, and the decreasing of the initial phase of the mode function. In addition, the smaller the angle between the laying angle of each layer and the load direction is, the greater the buckling critical load is. And the buckling critical load tends to be stable when the layer number of symmetrical laminate reaches seven.

Inspired by the microstructure of natural bamboo, a new bio-bamboo thin-walled tube was designed by introducing double-rhombic ribs between inner and outer tubes on the basis of the traditional double-circular tube structure. Based on the theory of simplified super folding element, theoretical models of bio-bamboo circular tubes under axial compression were established. Finite element software ABAQUS was used to simulate the axial compression of these models. For crashworthiness and deformation mode of bio-bamboo thin-walled tube, the effects of those number of double-rhombic ribs, diameter of inner tube, wall thickness were analyzed, and it was compared with the traditional structure. The results show that the theoretical prediction is consistent with numerical simulation, and the errors of average compression force and specific energy absorption are less than 10%. Compared with traditional double-circular tube, the specific energy absorption of the bio-bamboo thin-walled tube is increased by 83.61% and the compression force efficiency is increased by 198.65%. The number of ribs has a significant effect on the crashworthiness of the structure. With the number increase of double-rhombic ribs, both specific structural energy absorption and peak crushing force increases. When the number of ribs is small, the structure appears local buckling deformation, which affects the energy absorption crashworthiness. The smaller the diameter of inner tube, the higher the initial peak force, and the larger the diameter of inner tube, the smaller the energy absorption.

Based on the half-disk layered rock sample with central straight cutting groove, tests on fracture performances of layered phyllite were conducted, and the finite element numerical model of layered rock was developed. The influences of bedding dip angle, bedding strength, bedding thickness, span and different cutting angle on the fracture performances of layered phyllite was systematically studied. The results show that with the change of bedding dip angle from 0° to 90°, model Ⅰ fracture toughness value increases gradually, and the peak load and peak displacement also show increasing trend. When the bedding dip angle is 0°, the tensile failure occurs. When the bedding dip angle is 15°−45°, the shear failure is dominant, and when the bedding dip angle is 60°−90°, the tensile failure is dominant. When the bedding dip angle is 0°, the failure mode is less affected by the bedding strength. For cases with angle of 15° and 30°, with the increase of bedding strength, the specimen changes from shear failure to tensile-shear coupling failure. As the angle ranges from 45° to 90°, the specimens show tensile-shear coupling failure. With the increase of bedding strength, the specimens seem to fail by tension. When the bedding distance is small, the crack shows an obvious ladder-like growth along the bedding plane.

To study the response characteristics of the fuse with venting structure, the self-designed fuse venting device is used to study the effect of venting device on the reaction violence of the fuse under cook-off. The results show that under slow cook-off, the reaction violence of fuse is deflagration without venting structure, and the fuse structure is destroyed. The reaction violence with the venting structure is combustion. Under fast cook-off, the reaction violence fuse is deflagration when there is no venting structure, the bottom end cover of the fuse is damaged, and the reaction violence is burning with the venting structure. The temperature inside the explosive is obtained through numerical simulation. The ignition point of slow cook-off is located at the center of the booster, and the ignition point of fast cook-off is at the bottom of the booster. Different ignition positions make the pressure release process of the booster different. Slow cook-off uses the pressure of the center ignition to form an exhaust channel from the center to the venting structure to release the internal pressure. In the fast cook-off test, after the venting structure releases part of the pressure, the remaining pressure causes the bottom end cover to burst.

In order to study the problem of preliminary ballistic deflection when a penetration warhead with truncated ovate nose penetrates target obliquely, the theoretical model and simulation model are set up to analyze the effects of truncated ovate nose diameter on the preliminary ballistic deflection of penetration. The defection function and deflection angular velocity of warhead penetrating target are calculated in the same penetration condition with different truncated ovate nose diameters. It is concluded that the angle between axis of warhead and normal of target decreases with the action of deflection moment caused by the warhead of truncated ovate nose penetrating target. Both the deflection moment and the deflection angular velocity increase with the increase of truncated ovate nose diameter. When the truncated ovate nose diameter increases to 1.5 times, the deflection moment will increase to about 1.2 times. When the truncated ovate nose diameter increases to 2.0 times, the deflection moment will increase to about 2 times. Under the condition of the same truncated ovate nose diameter, the defection moment and the deflection angular velocity are increased with the shape coefficient of warhead.

To study the influence of different algorithms on penetration simulations of granite target subjected to projectile, Lagrange, SPH-Lagrange coupling and SPH (smooth particle hydrodynamics) algorithms are used for penetration simulations, based on Lagrange and SPH algorithms within LS-DYNA software. By comparing the numerical results through calculation efficiency, penetration depth, velocity attenuation, target damage and Mises stress distribution, the advantages and disadvantages of three algorithms are obtained. The results show that: Lagrange algorithm has the highest calculation efficiency and accuracy, but it has some problems such as element distortion, no impact sputtering, and no back-pit area. Although SPH algorithm has the lowest calculation efficiency, the calculated target damage is basically consistent with experiment. SPH-Lagrange coupling algorithm has both advantages, but it can produce stress hysteresis and unstable stress wave attenuation. Lagrange and SPH-Lagrange coupling algorithms are preferred in large-scale simulation.

Aiming at the research on the penetration behavior of rigid oval short rod projectile to semi infinite thick steel target, the ballistic test of $\varnothing $12.7 mm projectile penetrating 45 steel at different landing speeds is carried out by using 12.7 mm ballistic gun. The penetration behavior of the projectile in the process of penetration is analyzed with numerical simulation. The results show that the critical cratering velocity of $ \varnothing $12.7 mm projectile to 45 steel is 75 m/s, and the core shows rigid penetration behavior in the range of projectile velocity. The increasing trend of penetration resistance of the core is basically the same under different impact velocities. When the impact velocity is greater than 400 m/s, there will be a constant resistance stage after the end of cratering until the end of the penetration. At the same time, the penetration depth of the standard projectile to 45 steel is linearly proportional to the target kinetic energy, and the relationship between the dimensionless penetration depth and the dimensionless kinetic energy is fitted.

The overpressure and its oscillation of gas explosion in long straight space will endanger personnel and structures. In order to reduce the potential hazards, a numerical model of gas explosions in long straight tube was established based on the CFD software FLACS and was verified by using the existing experimental data. Based on the validated numerical models, the suppression of CO₂, N₂ and water vapor on the CH₄/air mixture explosions with stoichiometric concentration was investigated. The influence of the volume fraction of inert gas and water vapor on the explosion overpressure and its oscillation was considered and discussed. It is shown that for every 10% increase in the volume fraction of CO₂, water vapor and N₂, the final overpressure of the gas explosion in the closed tube drops by 81, 47 and 65 kPa, the final overpressure in the end-vented tube decreases by 81, 47 and 65 kPa. When the volume fractions of CO₂, water vapor and N₂ are 25%, 26%, and 30%, respectively, the explosion is completely suppressed. CO₂, water vapor and N₂ can effectively suppress the oscillation of explosive overpressure, both the pressure amplitude and the pressure oscillation frequency decrease with the increase of the volume fraction of added gas. CO₂ has the best suppression effect on explosion overpressure and its oscillation, followed by water vapor, and N₂ is the weakest. This phenomenon is related to the differences in the physical properties of the three gases and the suppression mechanisms.

A large number of methane explosion accidents show that premixed methane/air gas explosion is easy to cause huge casualties and property losses. The influence of the water mist cooperating with sliding device on the explosion characteristics of methane was explored by using the 10 cm × 10 cm × 100 cm transparent experimental pipe, and the explosion flame and overpressure was analyzed emphatically. The results show that the effect of water mist on the overpressure in the combustion zone is little under the synergistic effect. It has a significant attenuation effect on the peak overpressure in the unburned zone, and the maximum attenuation is 44.41% when the methane concentration is 11.5%. The water mist can destroy the finger flame and accelerate the flame propagation. When the methane concentration is 11.5%, the flame propagation speed increases by 62.50%. The sliding device reversely compresses the flame to the water mist action area to accelerate the flame extinction. When the methane concentration was 9.5% and 11.5%, the flame quenching time decreased significantly, which are 20.76% and 29.65%, respectively. When the methane concentration was 7.5%, the flame quenching time decreased by 3.5 ms.

In order to predict evolution of permeability for reservoir in the process of coal measure gas exploitation, based on the stress-strain constitutive of reservoir and the cubical relation of permeability and porosity, the model of the effective stress-permeability of reservoir was presented, which considers the kinetic diffusion of gases in the matrix. The analytical models of reservoir under constant volume and uniaxial strain conditions were established respectively. Furthermore, the effectiveness of the two models are investigated using permeability data from field and laboratory tests respectively. The results show that, compared with the model under constant volume condition and C-M model, the permeability model under uniaxial strain condition can better fit the permeability data from the field and laboratory. It is very important to take the dynamic diffusion of gas in the matrix into consideration during establishing the permeability model. Besides, the effect of model parameters on permeability was studied. It is shown that the model parameters have a significant influence on the permeability evolution and rebound pressure.