The 6061 aluminum alloy is an important raw material for aluminum liner carbon fiber full-wrapped composite gas cylinders, whose hydrogen compatibility determines to a great degree the safety and reliability of gas cylinders.However, the data is lacking in China concerning its hydrogen compatibility.In order to investigate the effects of high pressure hydrogen on the mechanical properties of the domestically fabricated 6061 aluminum alloy, the slow strain rate tests and fatigue crack growth rate tests for it were carried out under two heat treatment conditions.The test results show that the 6061 aluminum alloy has good compatibility with hydrogen, and hydrogen has little effect on its slow strain rate tensile properties and fatigue crack growth properties.Meanwhile, it was also found that heat treatment has little influence on its hydrogen embrittlement sensitivity.

We designed a built-in graphite heating assembly, called "Bridge", based on a domestic 6-8 type static high pressure apparatus and using the cut-apex three-segment 36/20 assembly, and obtained the relationship between the heating power and the temperature using the high pressure in-situ measurement technology.We also achieved a stable p-T (2.5-10.4 GPa; 0-1 650/1 800 ℃) region.Moreover, we successfully synthesized a centimeter sample under high pressure and at high temperature, one that can reach 13 mm.We discussed the relation between the resistances of the assembly and the heating temperature, and analyzed the cause of the resistance change.The temperature distribution of the assemble was reflected by the characterization of the sample.This study will broaden the applicability of the domestic hinge-type cubic-anvil press 6-8 type static high pressure apparatus, and offer a better practicability.

Ternary Al_xGa_1-xN alloy is an important semiconductor for devices in the ultraviolet and visible parts of the spectrum.So far, most studies of high Al content Al_xGa_1-xN alloy were mainly focused on their properties under ambient pressure and at room temperature but few on their high-pressure behavior.In this work, high Al content Al_0.86Ga_0.14N was investigated using the in-situ Raman scattering spectrum, and the intrinsic AlN and GaN were also studied as a comparison.The results show that the substitution of Ga by Al can be regarded as a kind of chemical pressure, and the pressure effect caused by the internal substitution can reach that caused by the external compression for GaN and the internal extension for AlN.Due to the crystalline anisotropy, the pressure effect caused by the internal substitution is more significant along the c-axis than that perpendicular to the c-axis.Moreover, the negative pressure, caused by the internal substitution, has a more significant influence on the high-pressure behavior of the AlN-like mode than that of the GaN-like mode.

The high pressure effect on layered lithium cobaltite oxides (LiCoO₂) was investigated using synchrotron X-ray diffraction (XRD) up to 20.3 GPa.In this pressure range, no structural transition was observed and the crystal structure of LiCoO₂ keeps stable; therefore, the compressibility of the parameter c was 4.5 times that of the parameter a, exhibiting a larger anisotropic compression; the isothermal equation of the state of LiCoO₂ was fitted using the second orders Birch-Murnagha of state.Moreover, the ionic conductivity of LiCoO₂ was measured by electrochemical impedance spectroscopy up to 16.8 GPa.The results of the high pressure impedance spectroscopy demonstrated that the Li ionic conductivity decreased rapidly with the increase of pressure.This research provided deep insight into the complex relationship of crystal structure with Li ionic conductivity in LiCoO₂.

In order to study the influence of the interaction between the jet and the target on the penetration performance, a pure copper target and a carbon steel target were penetrated by a titanium alloy shaped charge jet.The results show that both the hole diameter and the penetration depth of the pure Cu target is much greater than those of the carbon steel target.After static armor-piercing tests, the microstructures of the pure copper target and the carbon steel target around the ballistic trajectory were investigated in detail.The micro-structural analysis reveals the penetration mechanisms of the titanium alloy shaped charge liner penetrating the pure copper target and the carbon steel target, and the influence of the interaction between the jet and the target on the penetration performance.

Using a two-stage light gas gun and FPGWI (flier-plates with graded wave impedance), the free surface velocities of 93 tungsten alloy (93W) were measured at the impact velocities of 2.12 km/s and 5.02 km/s respectively and the experimental data were analyzed based on the shock wave theory.The results show that at a low impact velocity the pressures and temperatures of 93W alloy after repeated shock compression are higher than those after a single shock compression, and that at a high impact velocity the reverse is true.The phenomenon is results from the change of the Hugoniot parameters and the volume stress after multiple compressions.

Numerical simulations were carried out to study the perforation of 12 mm thick Weldox 460E steel targets subjected to impact by 20 mm diameter rigid projectiles.Assuming the same mass, the cone angle of the conical-nosed projectile varied ranging from 10° to 180° and the caliber radius head of the ogive-nosed projectile varied from 0.5 to 4.0.The analysis was focused on the influence of the projectile nose shape on the ballistic limit and the failure mechanism, with the effect of the friction between the projectile and the target also taken into consideration.The results show that the cone angle of the conical-nosed projectile exerts significant effect on the ballistic limit.An increase in the projectile cone angle changes the failure mechanism of the target from ductile hole enlargement to shearing plugging.The caliber radius head of the ogive-nosed projectile exerts significant effect on the ballistic limit for ψ≥3.0, and the plate is perforated through the ductile hole enlargement mechanism with ψ≥1.0.The influence of the friction increases with the increase of the sharpness of the projectile nose.

The dynamic processes of the fragments driven by single and double layer charges were numerically simulated using LS-DYNA and the initial velocity and the distribution of the preformed fragments were obtained.The effects of the initiation positions and the explosive parameters of the double-layer charge on the fragment-driven process were calculated and analyzed.The results show that the calculated values are in good agreement with the experimental results.Compared with the single charge, the double layer charge can make the fragments more focused, and the total kinetic energy of the fragments also increases by more than 12%.The comprehensive damage efficiency of the fragments can be further improved by changing the initiation mode and the explosive type of the double layer charge.

Based on the mechanism of explosive interaction between the armor and the jet, the present study aims to design a new structure for the reactive armor with a greater resistance against the jet interference, called multi-layered angle reactive armor with a variable angle.The effects of different armor structures and their response to the jet interference were investigated using numerical simulation, and the results were compared with the jet interference resistance capability of multi-layered reactive armor with different angles based on ANSYS/LS-DYNA.The resistance capability of the multi-layered reactive armor with a variable angle was measured based on the size of the trace of the jet penetration left on the jet-interference plate.The results of the comparative analysis showed that the jet interference resistance capability of W-shaped reactive armor is greater than that of V-shaped one, that of multi-layered reactive armor with a variable angle is the greatest when the angle of W-shaped armor is 22°.

K9 glass is often used to study the generation mechanism of failure wave and the dynamic fracture property of brittle materials under impact loading.However, the research on the optical property of K9 glass is often ignored due to the impact pressure limit.In this work, through the plane impact experiment combining the Doppler pin system (DPS) with the laser wave length of 1 550 nm, the velocity history of different optical testing interfaces during the spread process of the shock wave was obtained.Based on an analysis of the temporal correspondence between the original interference signal and the interface velocity profile, the pressure range within which the K9 glass maintains impact transparence and elastic response was achieved.The results show that when the impact pressure is less than 8.0 GPa the K9 glass can maintain good transparent property, and its dynamic refractivity changes linearly with the density.

Symmetric plate impact experiments were performed using a two-stage light gas gun to investigate the dynamic response and optical properties of polymethylmethacrylate (PMMA) under shock loading.The particle velocity of the flyer/sample interface, the shock velocity, and the refractive index of the sample were measured using a Doppler pin system (DPS).The measurements produced accurate Hugoniot data for PMMA, with the uncertainty of the shock velocity below 1%.The velocity correction at 1 550 nm of the wavelength under shock pressures ranging from 6 to 50 GPa was also obtained.The relationship between the refractive index and the density under shock compression was deduced from the measurements.Moreover, the shock velocity was distinctly captured by DPS and its relationship with the actual shock velocity was examined.

The high pressure micro water jet nozzle is often seriously worn and its resolution is difficult to further improve.To address this problem, a new method of the micro water jet under the constraint of the gas flow was presented in this paper.Using numerical simulation, the process of the jet was explored and the flow field distribution of the micro water jet under the constraint of the gas flow was obtained.The results show that the scheme proposed was feasible, capable of reducing effectively the wearing of the jet nozzle and improving its resolution.

Concrete is a widely used engineering material and it is of great significance to study its dynamic properties.The tensile strength of concrete materials is obviously affected by the strain rate's hardening effect.Obvious difference exists in the relationships of the dynamic increase factors (ψ_DIF) and the strain rates as a result of difference between a low strain rate and a high strain rate.In the present study, a mass of test data collected from the published literatures were compared and discussed.The relationships in different strain rate regions between the ψ_DIF and the strain rate were analyzed.The influences of the test methods, such as spalling, split and direct tension, on the tensile strain rate effect were researched.Finally, the relationships between the ψ_DIF and the strain rate of the concrete material, including compression and tension, were proposed.The results show that the values of the ψ_DIF of the tensile strength of the concrete increase with the increase of the strain rate, and approximately satisfy the linear relationship; that the strain rate hardening effect of the tensile ψ_DIF of concrete at high strain rates is obviously different from that at low strain rates; and that in both the low strain rate region and the high strain rate region, the relationships between the ψ_DIF of the tensile strength of concrete with different test methods and the strain rate have similar regularities.

Porosity and water content are typical properties that have a significant influence on the macroscopic dynamic behavior of rock materials, which further on affect the cratering behavior under high velocity impact.This paper was focused on the impact cratering morphology and studied the characteristics of dry and wet rock materials by conducting numerical and the high velocity impact experiments.Based on the hypervelocity fragment acceleration platform, experimental studies on the impact cratering of rock materials were performed using numerical simulation, and comparative analysis of the cratering effect, cratering morphology and characteristics of the dry and wet rocks was presented.The results indicate that, in high-velocity cratering, the target of dry sandstone leads to smaller crater sizes compared with those of the water-saturated target.The transient crater reaches a larger diameter in the water saturated sandstone.The water within the pore space reduces the porosity and counteracts this process, which influences the impact cratering of rock materials.

Recently, the moving mesh method has received plenty of attention in the numerical computation areas owing to its capability to improve effectively the calculation precision on the shock waveplane.This paper describes a moving mesh method that simulates the shock wave's propagation in condensed matter based on the variation principle.The generation of the moving meshes consists of the iterative computation of the Euler-Lagrange equation and the governing equation's mapping from the physical plane to the computational plane.We have studied the effect of computational efficiency using different iterative methods.Finally, the numerical results show the validity of the arithmetic.

The blast load generated by energetic materials in a confined space consists mainly of transient shock waves and the long-lasting quasi-static overpressure.In order to investigate the effects of the size of venting holes on the characteristics of the quasi-static overpressure in a confined space, a 3D high resolution hydro-code was developed in the present work implementing the third-order WENO scheme based on the FORTRAN platform.First, the problems of the Sod shock tube, the interacting blast wave and the shock entropy wave interaction were simulated to validate the code.Then, the validated code was used to simulate the blast waves generated by condensed explosives in a confined space.A simplified analytical model was proposed to describe the quasi-static overpressure, which agreed well with the simulation results.The research done in this paper can be used to provide reliable input load for the design of anti-explosion engineering structures.

Propane is one of the major constituents in petroleum gas, and its concentration distribution and flammability in the air is the basis of safety measures for petroleum gas.The influence of concentration distribution on the flammability of the propane-air mixture was analyzed using numerical simulation and experiment.The FLUENT, a computational fluid dynamics (CFD) software, was adopted to simulate the three-dimensional gas mixing process and the combustion process at a low flammability limit in non-adiabatic vessels with length-to-diameter ratios (L/D) of 1, 3, 5 and 7, respectively.The results show that the concentration distribution of the propane-air mixture is inhomogeneous by gravity, and the concentration distribution is the prime cause of the spark location affecting the combustion behavior of the propane-air at a low flammability limit.With the increase of the length-to-diameter ratio, the peak overpressure decreases.

To study the specific kinetic energy threshold of impacting initiation covered explosive B by six-prismed tungsten fragment, an experiment of impacting covered explosive B by fragments was designed and carried out.Based on the experiment data, using the Autodyn-3D finite software, simulation models were established and used to calculate the specific kinetic energy threshold of impacting initiation covered explosive B by six-prismed tungsten fragment.Based on the proven simulation, specific kinetic energy threshold of impacting initiation of typical size fragments were calculated by the up-down method, and the related curves were drawn.The specific kinetic energy threshold and velocity threshold were compared in the same circumstance.The results show that the specific kinetic energy thresholds of impacting initiation of experiment is 34.780 MJ/m² and, with a given charge and shell, fragments with a larger length to diameter ratio will have a higher kinetic energy to initiate the explosive.

In order to avert the mutual interference that occurs between the armor piercing discarding sabot and the muzzle brake when the armor piercing projectile ejects out of the gun barrel, a novel sabot was designed based on the traditional saddle-shaped sabot.The discarding mechanism of the novel sabot was analyzed, and the discarding experiments of the sabots were carried out.The results show that by adopting a series of measures such as adjusting the tilt angle of the windward side, reducing the volume of the windward and the leeward troughs, distributing uniformly the opened cylindrical holes in the sabot's leading edge, the discarding angle of the sabot can be reduced, thereby averting the mutual interference between the armor piercing discarding sabot and the muzzle brake.

On the basis of the interaction of the plate charge with the shaped jet and in view of the greater penetration capability required for the large caliber plate's more concentrated charge, this article contrasts and compares the shaped jet interference capability of the single plate charge, the double parallel plate charge and the multi-layer parallel plate charge using theoretical analysis and numerical simulation.It was found that the shaped jet interference capability of the plate charge is greater with the increase of the plate layers.The distance between the plate charges determines not only the jet interference capability but also the size of the reactive armor.The article represented the process of the interaction between the plate charge and the shaped jet using the ANSYS/LS-DYNA 3D software, and compared the residual velocity, the residual energy and the after effect of the shaped jet at some point and obtained the optimum distance (δ=25 mm) between the plate charges, thereby not only ensuring the interference effect of the multi-layer parallel plate charge on the shaped jet but also effectively controlling the size and the weight of the reactive armor.The results can serve as reference for development of new reactive armors.