This paper reviews the research on the equation of state (EOS) for hydrogen and deuterium in the last twenty years.A quantitative analysis of the wide-range EOS for hydrogen and deuterium is given by combining the modified chemical free energy model and the modern computational techniques such as Quantum Molecular Dynamic (QMD) and Quantum Monte Carlo (QMC).It is demonstrated that the wide-range EOS obtained from ab initio calculations only covers a limited region of density-temperature space, and the H-REOS.3 database, which is obtained by integrating different models, exhibits disagreement with the modern computational results below the temperature of 10⁵ K and its data points distribution is not dense enough.EOS of deuterium is not transformed from the H-REOS.3.Therefore, both the ab initio calculation and the H-REOS.3 are not sufficient for the engineering application, and it is necessary to construct a wide range EOS database for hydrogen and its isotopes, which combines the high-precision experiments, the modern computational techniques, and the analytical or semi-analytical models.

In this study, we developed a sample pre-heating system with the temperature range from room temperature to 180℃, matching with the magnetically driven apparatus CQ-4.The ramp wave compression experiments of bismuth under different initial temperatures (25-148℃) were carried out, using this pre-heating system on CQ-4.The free surface velocity profiles, measured by a dual laser heterodyne velocimetry, show clearly two phase transitions of bismuth during the compression.Furthermore, with the initial temperature increasing from room temperature to 148℃, the characteristic free surface velocities corresponding to the onsets of Ⅰ-Ⅱ and Ⅱ-Ⅲ phase transition decreases from 251.6 and 275.7 m/s to 239.4 and 259.7 m/s, respectively.

The earth was in a molten state at the beginning of its formation.Over time, the magma on the earth's surface began to cool down and solidify, and the earth has gradually become such a trap structure.However, the cooling and liquid-solid transformation process of the earth materials continues until today.This paper presents a statistical analysis of the change of earth's length-of-day after earthquakes, and it is found that the earth's rotation speed is generally accelerated after great earthquakes.We believe that this phenomenon is caused by the cooling and solidification of the magma in the part of the mantle, which causes significant volume collapse of the lower crustal lithosphere.Thus, we set up a crustal dynamic model to explain the interaction and relative motion of tectonic plates.We believe that the dynamic genesis of earthquake and other geological activities are due to the continuous solidification of the melt in the interior of the earth which could lead to a volume shrinkage and pressure drop in the lower part of the earth's crust.The effect of gravity enhances the interaction among tectonic plates, the original mechanical structure becomes unstable, and eventually the massive rock fracture occurs, which can cause severe geological events such as earthquakes, and volcanic eruptions.This conclusion has been further validated based on the thermal and mechanical model proposed in this paper.

BiFeO₃ is one of the most promising multiferroics that exhibits both magnetic and ferroelectric properties above room temperature.The room-temperature structure of BiFeO₃ is a highly rhombohedrally distorted perovskite with space group R3c.In this study, we prepared BiFeO₃ powder under high temperature and high pressure using muti-anvils, and investigated the phase transition of BiFeO₃ in the 0-44 GPa range combinng with Raman spectrum.Upon compression, the low-frequency Raman modes of BiFeO₃ shift to higher angles and become broadening, and the vibrational modes at 145, 177 and 231 cm^-1 begin to decrease.The first phase transition takes place at the pressure of about 5 GPa, shown by the disappearance of the mode at 145 cm^-1 and the emergence of the mode at 217 cm^-1.The second phase transition is indicated by the emergence of the mode at 340 cm^-1 and the disappearance of the mode below 200 cm^-1 at 11 GPa.After this phase transition, the structure of BiFeO₃ transfers to orthorhombic phase Pnma.The third phase transition takes place at the pressure of 38 GPa, all the Raman modes including the mode at 340 cm^-1 disappear, and the structure of BiFeO₃ may transferr to cubic or higher symmetry orthorhombic crystals.

In order to obtain the Grüneisen parameter Γ of unreacted JB-9014 insensitive explosive, we carried out the one-dimensional plane impact experiment on JB-9014 explosive using a gun.In the experiment, the explosive sample was mounted between two copper plates, and two PVDF gauges were installed at the front and the middle of the explosive sample to record the variations of pressure versus time.The copper flyer was accelerated by a gun and then impacted the front copper plate at a certain speed.The right row shock wave was formed in the front copper plate, resulting in the first compression of the explosive sample and then reflected at the interface of the explosive sample and the rear copper plate, causing the second compression of the explosive sample.Supposing the Grüneisen parameter of the explosive sample was constant, we calculated the variations of pressure versus time at the front and the middle of the explosive sample with different Grüneisen parameters.Comparing these calculated values with the experimentally determined parameters enabled optimum values of the Grüneisen parameter to be identified.

In this paper, the launching performance of a developed 20/57 mm two-stage light gas gun was studied, of which the driving energy is supplied by the gaseous chemical reaction.The experimental results show that the relationship between the chemical energy and the kinetic energy of the projectile can be properly fitted with quadratic polynomials.The tests conducted under controlled repeatable conditions indicate good repeatability of system, thus verifying that the system satisfies the requirement of the loading experiments.In addition, we developed a ballistic model of the two-stage light gas gun driven by gas reaction, and calculated the velocities of projectiles, which are in good agreement with the experimental data.

In this study, magnesium oxide (MgO) doped by cobalt (Co) was prepared as pressure-transmitting medium, by solid reaction process.The starting material is a pre-compressed mixture of MgO and cobalt oxide (CoO), which was mixed for 8 h and compressed at 200 MPa, and then treated at 1 200℃.The as-prepared samples were characterized by X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis.The results demonstrate that during the sintering process, the reaction between MgO and CoO was completed and the exchange of metal ions between MgO and CoO leads to a single solid solution phase.Compared to the domestic products (MgO+10wt% Na₄SiO₄), there is no impurity found in Co-doped MgO, which is more stable than the domestic products under high pressure and high-temperature.In addition, the temperature-generation efficiency of the cell assembly with MgO+9mol% CoO as pressure-transmitting medium is also higher than that of the domestic products.

To achieve efficient damage, we simulated the penetration of segmented penetrator with enhanced lateral effect (PELE) on the 4-layer metal target and analyzed the influence of projectile velocity and layer thickness on the terminal effect.The results showed that the segmented PELE projectile performed better penetration than the normal PELE projectile and the diameter of crater produced by segmented PELE projectile was larger than that produced by its rod counterpart.When the projectile passed through the targets, the peak radial velocity of PELE shell increases with the increasing target layer thickness while the length of broken shell did not change with it.The peak radial velocity and length of broken shell was found to increase with increasing segmented PELE projectile velocity after penetrating the first layer and reach a maximum when the projectile velocity was 1.4 km/s after penetrating the second and third layer.After penetrating the fourth layer, the peak radial velocity and the length of broken shell increased with increasing projectile velocity.

Based on the Donnell shell theory and classical shell theory, we established the dynamic buckling governing equation of functionally graded cylindrical shell under axial load using Hamilton principle.According to the expression of the radial displacement based on the circumferential continuity of cylindrical shell, we also obtained the dynamic buckling critical load expression and the buckling solution of functionally graded cylindrical shell under axial loading using the separation variable method.Using MATLAB, we performed the numerical analysis of functionally graded cylindrical shells, and discussed the influence of the diameter-thickness ratio, the gradient index, the number of circumferential mode and axial mode on the critical load of dynamic buckling.The results show that the critical load of cylindrical shells decreases with the increase of the critical length.The constraint conditions have effects on the critical load, and the critical load of the clamped edges is higher than that of the simple support.Moreover, the critical load of cylindrical shells grows as the modal number increases, indicating that the higher the critical load is, the easier the high-stage mode excites.The dynamic buckling modal diagram becomes more complicated as the modal number increases.

In this research, we experimentally investigated the characteristics of the turbulent mixing zone induced by Rayleigh-Taylor (R-T) instability under different accelerations.We used the high-speed shadowgraph to study the evolution of the interface composed with the silicone oil/potassium iodide solution, and analyzed the width of the mixing zone and the obliquity of the interface quantitatively.According to the experimental results, the difference in the evolution of width between horizontal interface and oblique interface exhibits mainly in late stage, and the evolution law is basically same with that in the early and middle stages.There are two different trends in the evolution of the interfacial obliquity.The interfacial obliquity increases with time parabolicaly at first, and then increases linearly.As a result, the fluid interface turns over in the later stage of evolution.There is a competitive relationship between the turbulent mixing induced by R-T instability and K-H instability respectively.

Explosively driven fragmentation of material is a highly complex phenomenon.In this study, we evaluated the influence of explosive on the intrinsic fragmentation characteristics using hollow cylindrical steel shells, and investigated a new universal assessment criteria for the fragmentation of cylindrical shells.The results show that there is a linear relationship between the normalized Payman fragmentation parameter C_u of the shell and the charge/mass ratio C/M, for various combinations of shell material and explosive.The fragmentation parameter C_u of columnar part decreases by a constant value for the presence of end effect, while other factors including the shell thickness and the length of charge vacancy, have little effect on the fragmentation parameter C_u.The fragmentation performance of shell with no charge is relatively low and is only determined by shell material properties.

As the major part of the vehicle front side member, the hat-section beam structure's deformation mode and energy absorption characteristics under the axial impact is the main reference index in the design of automobile passive safety.In this study, we carried out a drop hammer axial impact test and numerical simulation with initial energy of 17.8 kJ for the hat-section beam with chamfering.In addition, keeping the total mass constant, we simulated two other beams with different sections of no chamfering and right-angle bend in the same conditions, aiming to investigate the influences of section geometric parameters on these characterizations as deformation modes, amount of deformation, energy absorption, peak load, the average crushing load and crushing force efficiency within a certain scope.The calculation results of the deformation modes and amount of deformation of the hat-section beam with chamfering are consistent with the experimental ones, verifying the rationality of the computation model.Due to the existence of chamfering in the structure, the pattern of structural deformation was transformed from a non-compact mode to a compact mode, the buffering effect was increased, whereas the maximum crushing load was reduced.When the bending angle changed from 93° to 90°, it only has minor influence on the deformation mode, and the energy absorption of the beam with non-right-angle bending is better than that of the beam with right-angle bending.Therefore, the geometric parameters of the cross section have some influence on the deformation mode and energy absorption characteristics of the hat-section beam structure.

In order to study the loading characteristics of underwater explosion shock wave and bubble near the structural boundary, we designed and tested several plate models.By changing the ratio of stand-off to the maximum bubble radius, the flat thickness and other parameters, we analyzed the bubble pulsation and the low-pressure flow field at the plate boundary, as well as the local and global response characteristics of the slab based on the strain analysis.The results show that a low-pressure (negative pressure) flow field appears at the boundary of the plate during the movement of the bubble in near-flat explosion.The duration of the low-pressure accounts for 60%-80% of the bubble pulsation period and the maximum negative pressure can reach 0.1 MPa.With the reduction of the ratio of stand-off to the maximum bubble radius, the final deformation of the plate changes from elastic and sagging deformation to hogging deformation.

With the wide application of high strength and high impact-resistant steel structures in armor protection of armor, arsenal protective doors and other military facilities, the impact-resistant properties of steel structures become a major focus and hot spot in defense research.In this paper, we simulated the process of hemispherical-nosed projectile penetration through a multilayer steel plate using smooth particle hydrodynamics, compared its results with those from experiment, and analyzed the failure form of the steel plate after being penetrated by hemispherical-nosed projectile, thereby obtaining the von Mises stress distribution and the residual velocity for the hemispherical-nosed projectile and verifying the effectiveness of SPH in the study of the steel plate penetration by a hemispherical-nosed projectile.We investigated the influence of the number of target plates and the thickness of the steel body on the target's penetration-resistant performance using numerical simulation.The results show that the protective strength of the single-layer steel plate is stronger than that of the multi-layer steel plate with a 3 mm thickness; that when the thickness is 9 mm, the multi-layer steel plate has a better protective capability than the single-layer steel plate; and that when the thickness is 12 mm, the multi-layer steel plate and the single-layer steel plate have similar protective strength.

To study the penetration performance of different shapes of a DU alloy fragment, we performed an experiment on a Q235B steel target with a thickness of 20 mm and obtained its terminal ballistic marriage parameters of cylindrical DU alloy fragment penetration.Then, we carried out the corresponding simulation of the key ballistic trajectory using the ANTODYN software.The results from the simulation were found to accord basically with those from the experiment, thereby verifying the simulation results as correct.Furthermore, on the basis of the original simulation, we simulated the cylindrical, cubic and spherical fragments penetrating the target plate with different target positions taken into account.The results show that, in the same quality and at the same velocity, the penetration capability of the cubic fragments in the attitude of the edges and the target cube diminishes in turn with the attitude of the target cube and the spherical fragment, with those in cylindrical and parallel attitude as the weakest.Moreover, hitting the target vertically, the cubic fragment exhibits a stronger penetration than that of the cylindrical, and it shows a better penetration capability when hitting the target in an angular or corrugated attitude.

The extraction of rigid-body deceleration characteristic plays a significant role in the research of anti-hard-target weapons and related areas.In this paper, we investigated the methods of processing on-board recorded penetration deceleration data.The intrinsic mode functions were separated from the raw signals by ensemble empirical mode decomposition (EEMD), and a demarcation point between high-frequency interference functions and the projectile rigid-body acceleration signal functions was distinguished by the consecutive mean square error (CMSE) theory.By discarding the first few high-frequency components without demarcation points, the rigid-body acceleration of projectile was reconstructed with the remaining low-frequency components.The consistency of the integral results between the final curve and the original data shows that, the high-frequency interference is removed effectively and the rigid-body penetration over-load is kept completely.In addition, the difficulty of selecting the filter frequency under different target conditions in the traditional filter method is avoided with the characteristic of signal adaptive in the analysis process.

In this paper, we numerically studied the ballistic resistance of the metal perforated armor to the high-velocity projectile, and analyzed in detail the effects of various factors on its ballistic resistance, including the impact velocity, the oblique angle, the hitting location and the size of holes.The results showed that the effect of hitting position decreases with the increase of the impact velocity near the ballistic limit.Both the normal impact at the asymmetric hitting position and the oblique impact at the symmetric hitting position result in the projectile yaw.The residual velocity of the projectile and the penetration depth decrease dramatically as the oblique angle is larger than 45°, and furthermore, the ricochet appears as the oblique angle is larger than 65°.

In this work, the three-dimensional finite element analysis software LS-DYNA was used to numerically simulate the ballistic performance of explosive reactive armor at different impact points, and the comparative experiments were also carried out in order to obtain the protective envelope of the explosive reaction armor, i.e., the ballistic performance at different impact points on the contact surface between the explosive reaction armor and the jet.The results show that the simulation results agree well with the experimental data.Studies indicate that there is a large difference in the ballistic performance at different impact points.Instead of the responsive armor's symmetrical center and its vicinity, the area with better ballistic performance is located 22.7 and 46.9 times of the jet diameter away from the bottom of the explosive reaction armor.The effective ballistic performance area of the explosive reaction armor accounts for approximately 65.8%, and its ballistic performance increased by about 37.5% compared to that of the border area.Furthermore, the protective capability at the lower part of the reaction armor is better than that at the upper part.

The structural optimization design of filament winding housing for a railgun barrel is introduced.The thickness of fiber laminates, the winding angle and the stacking sequence of fibers for a 50 mm circular bore composite barrel are investigated for structural optimization.Numerical simulation of railgun prestressing has been studied based on continuous solution with birth-death element method.By using a method of stepwise optimization of multi-variable based on random search, the tension profile of fibers is optimized.Optimization of state variables under two different constraints is analyzed and initial stress field and superposition stress field of the prestressed barrel are given.The second type of optimization results show that the profile in this study can meet design requirements of the composite barrel.

Using a pulse decay permeameter, we conducted a combination of laboratory experiments to study permeability evolution of marine-terrigenous facies coal measures shale under reservoir conditions, and obtained the permeability of coal measures shale under different stress states, and furthermore analyzed the permeability of coal measures shale and Wilcox shale.The results show that the permeability of coal measures shale ranges from 2.9×10^-19 to 5.7×10^-18 m² as the effective stress is decreased from 12.5 to 2.0 MPa at constant confining pressure (p_c=17 MPa), and is 2-3 orders of magnitude greater than that of Wilcox shale.The effective stress is given in terms of the external confining pressure and the internal pore pressure by σ_e=p_c-χp_p, where χ is approximately equal to 1.The fitting results of the experimental permeability show that the permeability of coal measures shale and Wilcox shale change exponentially with the effective stress, confining pressure (at constant pore pressure) or pore pressure (at constant confining pressure).