In this paper, to find out about how the inlet pressure influences the supersonic liquefaction of natural gas mixtures, we established a three-dimensional mathematical model for the supersonic condensation flow of the methane-ethane mixture gas, obtained the axial parameters along the Laval nozzle, and conducted experiments to verify the gas condensate phase transition of double condensable components.It was found that the numerical simulation is in good agreement with the experimental results, thereby proving the mathematical model and the calculation method as correct.We also investigated the influences of the inlet pressure on the supersonic liquefaction of methane-ethane mixtures.The results indicate that, when the temperature and composition of the Laval nozzle inlet remain the same, the nucleation position of the mixed gas moves forward, the nucleation rate, the mean droplet radius and the liquid mass fraction all increase with the increase of the inlet pressure.The greater the inlet pressure, the more apt for the condensation of the gas mixture in the Laval nozzle to occur.In the actual production, the condensation of natural gas mixtures can be promoted by adjusting the inlet pressure, and the liquefaction efficiency of the Laval nozzle will be improved.

The structural, elastic and thermodynamic properties of Mg₂Si and Mg₂Ge phases under pressure were calculated using the first-principles based on the density functional.The calculated results indicated that the lattice parameters under 0 GPa are fairly consistent with the experimental value and other theoretical data.The ratio of a/a₀ and V/V₀ decreased as the external pressure increases.An appropriate pressure (0-25 GPa) can improve their stiffness and plasticity because the bulk modulus B, shear modulus G, and Young's modulus E almost linearly increase with pressure.The brittleness of the material turns to ductility at 15 GPa.Finally, the effect of temperature and pressure on the Debye temperature, bulk modulus, heat capacity and linear thermal expansion coefficient was studied using the quasi-harmonic Debye model and Gibbs software.

In this paper we developed an experimental technique and numerical simulation method that we then adopted to investigate the Rayleigh-Taylor instability in metallic materials driven by explosion.We studied experimentally and numerically the growth of the Rayleigh-Taylor instability in an explosion-driven aluminum flyer and showed that the perturbation amplitude growth follows an exponential law over time.The numerical results agree with the experiment qualitatively, but not quantitatively.This is because the aluminum strengthens under high pressure and at high strain rate, and the Steinberg-Guinan constitutive model used in the simulations underestimates the strength of the aluminum as being not great enough to suppress the perturbation growth.By investigating numerically the effects of the initial shear modulus and the initial yield strength on the development of the Rayleigh-Taylor instability of the metallic material, we also found that the initial shear modulus in a specified range does not affect the dynamic yield strength and the increase in the initial yield strength can improve the dynamic yield strength significantly to stabilize the perturbation growth.In other words, the material strength dominates the interface perturbation growth.

A high-precision and resolution shock capturing scheme is of great significance for numerical simulation of the complex flow field containing shock waves.In this study, to improve the convergence accuracy of the conventional third-order WENO-Z scheme at the critical points, we firstly derived the sufficient conditions for satisfying the convergence precision of the third-order WENO scheme from the theoretical derivation, then determined the parameters of the constructed scheme using the Taylor series expansion for satisfying the sufficient conditions, and proved using the accuracy test that the proposed scheme converges to the third order precision in smooth flow field including the critical points.Furthermore, we selected the Sod shock tube, the Rayleigh-Taylor instability and some other classic examples, verifying that the improved scheme WENO-NN3 was capable of giving more precision and high resolution results of the complex flow field structures compared with other WENO schemes such as the WENO-JS3, WENO-Z3, and WENO-N3.

In this paper we analyzed the shock wave breakout time shift at the sample/window due to the flyer velocity shift and the time sequence relationship in the simultaneous measurement of the dynamic emissivity and the radiance.Then, we designed the fiber pins with a total reflection coating film at their edges to trigger the illumination pulse laser.The distance between the fiber pins and the sample was designed elaborately and the design residue was analyzed briefly.In the tests of two shots, the expected flyer velocity was 4.1 km/s and the measured velocity shift of the flyer was 70 m/s and 210 m/s respectively, but the dynamic emissivity signals were successfully superimposed on the thermal radiation of the sample/window interface at the time expected, and the time sequence controlling satisfied the demand of the simultaneous measurement experiments.

In this paper we measured the Hugoniot data for JB-9014 explosive by measuring the times when the shock wave reached the surfaces of the explosive sample and the particle velocity at the sample/window interface on a gun using PDV.Calculating the difference between the times when the shock wave reaches the front and the back surfaces of the sample explosive and its thickness, we figured out the propagation velocity of the shockwave in the sample, and found that the combined standard uncertainties of the shock velocity and the particle velocity were 0.54% and 1.7% within the pressure range of 3.1-9.7 GPa, through uncertainty analysis.Moreover, we also derived the relation between the pressure and the density of the JB-9014 explosive sample from the simultaneous equation of the Hugoniot relation and the Rankine-Hugoniot relationship of the shock wave form and obtained the fitted p-ρ curve in the sample along the (p, ρ) surface under heat-insulated shock.

In the present work, we conducted the quasi-static compression-shear experiments on the closed-cell aluminum foams using an improved testing machine and installing beveled bars and a column sleeve.By changing the angle of the inclined beveled bars we obtained the mechanical properties of the aluminum foams in different compression-shear loading paths, and then figured out the aluminum foam's experiment yield surface from the force analysis of the specimen used.At the same time, we simulated the compression-shear process of the closed-cell aluminum foams using the finite element software LS-DYNA.The simulated yield surface is in good agreement with the experimental yield surface.The results show that, for the aluminum foams of the same density and in a given range of the cell size, the yield strength of the closed-cell aluminum foams increases with the increase of the cell size, and so does its load capacity.

Reinforced concrete structural members subjected to impact loads behave quite differently as compared to those subjected to quasi-static loading, with their failure mode becoming more complex.In this work, by introducing the strain rate effect of reinforcement in the trilinear model of the reinforcement, we simulated the structural responses of reinforced concrete beams under different impact loadings based on the dynamic analysis module of ABAQUS.The curves of impact-time and mid-point deflection-time were observed to agree well with those from the experiments.Based on this model, we simulated the responses of beams with the reinforcement ratios of 2.56%, 2.66%, and 2.76%, respectively.The comparison shows that the bearing capacity and deformation resistance of the beams increased with the increase of the reinforcement ratios; the enhancement effect of the reinforcement ratio weakens gradually as the impact velocity increases; when the impact velocity is 4.85 m/s, the reinforcement ratios have slight effect on the failure mode of beam at low impact velocities; in addition, when the impact velocity is higher than 4.85 m/s, the failure mode changes from shear failure to bending failure with the decrease of the reinforcement ratio.

In this paper, we studied the mechanical properties of tungsten alloy spheres in sintered and polished states using the quasi static test and the dynamic loading test, observed their metallographic structure and damage mode before and after the test using SEM, and analyzed the causes leading to their difference.The result showed that the surface microstructure of the tungsten alloy sphere in the sintered state was more uniform than that in the polished state, which accounts for its better mechanical properties.

To identify the properties of the three-wave point for aluminized explosives in the near-earth air blast, we simulated the explosion process of 3 kinds of RDX-based aluminized explosives, i.e. HL-01 (RDXph), HL-02 (85% RDXph+15% Al) and HL-03 (70% RDXph+30% Al), using the ANSYS/AUTODYN software.The results show that the pressure histories and the near-earth overpressures obtained from the simulation almost overlapped those measured from the experiment, indicating that the chosen model and parameters were appropriate.The comparison of the simulation results with those from the empirical chart shows that it was not suitable to calculate the height of three-wave point for aluminized explosives from the empirical chart, while it was so by simulation.At the same explosion height, the height sequence of three-wave point was HL-03 > HL-02 > HL-01.For the same explosive, the height of three-wave point increased with the decrease of the explosion height.

In the present study, we redesigned the structure of a depleted uranium alloys liner to analyze its penetration performance using numerical simulation results on the basis of a copper liner, and compared the penetration capability of two liners, made of copper and uranium-niobium alloys respectively by penetration experiments.The results show that, with almost the same quality of the main charge, the maximum penetration depth of the depleted uranium liner was 33.4% bigger than that of the copper liner.

A monolithic metal plate is usually replaced with a double-layered metal target with the same thickness to improve the ballistic limit in practical engineering.This paper presents a theoretical study of the perforation of a double-layered metal target without spacing by a flat-nosed projectile.Based on the previous analytical work and experimental observations a new theoretical model was proposed to predict the peroration of the double-layered metal target in comparison with the test data available.It was found that the predictions made from the present model are in good agreement with the test data.It was also found that the ballistic limit for a double-layered metal target is considerably higher than that for a monolithic one when its thickness is larger than the critical thickness at which adiabatic shear plugging occurs; that the ballistic limits are more or less the same for both targets when the total thickness is below the critical value.

Aiming at the problems concerning the application of tantalum in a shaped charge warhead, we investigated the influences of the arc-cone tantalum liner's structural parameters (cone angle, wall thickness and radius of curvature) on the formation and penetration performance of EFP using the LS-DYNA finite element software, revealed how these various structural parameters affected the formation performance of EFP:the cone angle of the liner determines the capacity of the axial tension and the radial shrinkage of EFP, the head velocity and tail fracture and outward expansion of EFP are determined by the thickness of the liner, the head shape and the absolute solid length of EFP are determined by the radius of the curvature.The range of the structural parameters of the tantalum liner with better formation performance of EFP was obtained:the cone angle ranged from 143° to 147°, the thickness and radius of the curvature ranged from 0.024 to 0.026 and 0.7 to 0.8 times of the charge diameter.The order was found out in which various structural parameters exert their influence on the penetration depth and aperture of EFP:the radius of the curvature, the cone angle, the wall thickness and cone angle, the wall thickness, the radius of the curvature.The optimal combination of the structural parameters of the tantalum liner that would bring about a better formation and penetration performance of EFP was proposed:the cone angle is taken for 145°, the thickness and radius of the curvature are taken for 0.025 and 0.70 times that of the charge diameter.

In the present work the process of the jet penetrating the interval target of a water protection layer was observed using flash X-ray photography, the variations of the jet tip velocity and the distribution characteristics of the metal particles and shock waves in water were obtained, and the phenomenon in the experiment were discussed in combination with the mechanism of water on the metal jet at high temperature.The result shows that the jet tip velocity would drop during the jet penetrating the water protection layer.This is mainly due to the fragmentation resulting from the high pressure (9-10 GPa) and high temperature after the shock wave of the jet.Besides, the fragmentation of the jet tip is the most serious in the early stages of the jet entering the water protecting layer, which results in a fast consumption of the jet tip and the false image of the jet tip's velocity drop in the test of the flash X-ray measurement.

In the present study we fabricated a thermobaric explosive with 3 kinds of aluminum powders (40 nm, 3 μm and 35 μm) to study the influence of the aluminum particle size on the explosive energy output of the thermobaric explosive in a confined space.We measured its shock wave pressure histories at 1.0 m, 1.2 m and 1.5 m of the explosion chamber, and obtained the overpressure and impulse values by analyzing the curves.We also studied the thermal decomposition of thermobaric explosives with different particle sizes of aluminum powder using the DSC.The results show that the aluminum particle size has a great influence on the explosion energy of the thermobaric explosive in a confined space, the overpressure of 2^# sample with particle size of 3 μm is at least 6.0% and 10% higher than 1^# and 3^# sample at each distance, the thermal stability of the 3 samples reduces with the decrease of the aluminum particle size, the biggest falling range of the activation energy is 31.1%, and the maximum value of T_P0 is reduced by 11.7℃.

The initiation criterion of heterogeneous explosives is important for weapon design and safety evaluation.In this paper, based on Kim's elastic-visco-plastic "hot-spot" model, we numerically solved a temperature rising model of a local hot-spot inside the explosive, and obtained the initiation thresholds for TATB and HMX under different shock loading pressures.We quantitatively analyzed the influence of explosives' porosities on the shock initiation thresholds, and compared the calculated thresholds with experimental results.We drew the following conclusions:under a pressure of 1-10 GPa, the calculated initiation thresholds agree well with the one-dimensional shock initiation experimental results; the corresponding initiation thresholds of the explosives are approximately constant; under a pressure above 10 GPa, as the pressure rises gradually, the dominant shock initiation mechanism of the heterogeneous explosives transforms from the uneven heating of the local hot spot, to the shock's direct heating of the bulk of the explosive.Furthermore, we also verified that, within a given pressure range, the initiation threshold dropped as the explosives' porosities increased.

In this study experiments were carried out in a round tube, 5 800 mm in length and 48 mm in inner-diameter, filled with orifice plates, to investigate the detonation of hydrogen-air mixtures and stoichiometric hydrogen-methane-air mixtures, and the DDT (Deflagration-to-Detonation Transition) limits were determined.The blockage ratio of the orifice plates was 0.56, and the spacing was divided into two, i.e., S=D and S=2D, in which S and D are the obstacle spacing and the tube diameter.The flame velocity was obtained using photodiodes mounted on the tube wall.The results show that the flame regime observed is the quasi-detonation or the choked flame.The flame velocity measured for S=2D is larger than that for S=D, and the velocity fluctuation is more significant.This indicates that the cycle of the detonation failure and re-initiation is longer for S=2D, which is similar to the "galloping detonation".For hydrogen-air mixtures, detonation re-initiation occurs more aptly at S=2D, and the limits correlate well with d/λ≈1.In the case of hydrogen-methane-air mixtures, the DDT limits for S=D and S=2D are both consistent with d/λ≈1, where d and λ are the inner diameter of the orifice plate and the detonation cell size.The results indicate that the obstacle spacing has a significant effect on the propagation of detonation, i.e., detonation propagates more aptly for increased spacing.To generate the quasi-detonation, the opening of the orifice plate has to be large enough to contain at least one cell size while the spacing has to be large enough to form detonation re-initiation.

In the present work we calculated the shock wave energy and bubble energy of thermobaric explosive to study the afterburning reaction of the thermobaric explosive using the double container gas charging device and underwater explosion test.Through the study of the energy output structure of the underwater explosion of the thermobaric explosive, the energy released by the afterburning reaction in different gas atmospheres was calculated.As a comparative reference, the same experimental study was carried out on TNT under the same experimental conditions.The experimental results show that when the pressure of the oxygen was 2.5 MPa, the specific shock wave energy of thermobaric explosive with the aluminum powder content of 40% were maximum, the specific bubble energy and total energy of thermobaric explosive with the aluminum powder content of 50% were maximum.It was respectively 1.99, 1.62 and 1.55 times TNT equivalent under the same experimental conditions and, with the increase of the oxygen content in the gas, the afterburning effect was enhanced.The energy of TNT released by the afterburning reaction in the oxygen is 1.94 times that in the air.The energy of the thermobaric explosive released by the afterburning reaction in the oxygen was 2.70 times that in the air.

Detonation velocity is one of the main parameters in explosive welding where glass microsphere is used as a sensitizer and diluent.In this paper, the effect of the glass microsphere on detonation velocity of emulsion explosive was explored.The honeycomb-structured explosive manufactured using a honeycomb aluminum panel and a low detonation velocity emulsion explosive with the detonation velocity of 2.230 km/s was used to carry out explosive welding of Al-steel clad plate.The results showed that the density of the explosive decreased with the increase of the glass microsphere content.The emulsion explosive misfired when the content of the glass microsphere was less than 2% or greater than 35%.The detonation velocity of the emulsion explosive decreased with the increase of the glass microsphere content when the content of the glass microsphere was greater than 7% and less than 35%.The sensitization effect and detonation velocity adjustment effect of small-size glass microspheres produced a better welding quality than those of large-size glass microspheres.The honeycomb aluminum structured explosive used for Al-steel explosive welding was able to achieve superior bonding quality.

In this paper we studied the variation of the minimum ignition temperature of coal dust layer with its metamorphism, particle size and thickness using the minimum ignition temperature measurement system.The results showed that, with the gradual increase of its degree of metamorphism, the minimum ignition temperature of coal dust layer varied from 290℃ to above 400℃; and that when the coal dust layer of lignite, long flame coal, non-stick coal, gas coal were ignited, an obvious flame was observed; and that, as the coal dust particle size decreased, the minimum ignition temperature of different kinds of the coal dust layer exhibited a significant reduction trend.It was found that when the thickness of the layer is 15 mm, with the particle size decreasing from 0.5 mm to 0.075 mm, the minimum ignition temperature decreased by 31.0%, 26.7%, 28.1%, 25.8%, 28.6%, 27.8%, 18.9% and 15.0%, respectively, indicating a very obvious effect of the coal dust particle size.With the increase of the layer's thickness, the minimum ignition temperature of different kinds of the coal dust layer exhibited a decreasing trend, while the trend of anthracite was the least significant.

In order to explore the effects of high pressure on the texture and quality of fruits and vegetables in different varieties, we selected 5 kinds of fruits and vegetables with different density, water content, microstructure and texture to analyze their data under different conditions of ultrahigh pressure treatment.The results showed that the texture of fruits and vegetables could affect their pressure resistance.Softer texture and less vacuolar structure exerted a good influence on pressure resistance whereas the volume of fruits and vegetables was apt to be compressed with more vacuolar structure and harder texture.There is great difference in volume variation because fruits and vegetables have different textures.The texture index would decrease more obviously after high pressure treatment, when the fruits and vegetables have higher density and greater hardness.The prolongation of the holding time will further damage the texture and structure of fruits and vegetables.