In this work we prepared sample primary material for synthesis of jadeite jade adopting the sol-gel method, reduced the bubbles in it by melting it many times at high temperature and, after it, obtained bulk transparent glass materials containing the jade chemical component (NaAlSi₂O₆). In order to promote its plastic deformation, reduce its residual stress and prevent its cracking, we treated the sample by compression and decompression at high temperatures and under high pressures. The jadeite sample so synthesized maintains good forms as blocks, and its phase composition and microstructure are all highly close to those of natural jadeite judging by the analysis of X-ray diffraction (XRD) and scanning electron microscope (SEM). It is found that the major influence on the quality of sample jade synthesized under high pressure is the microstructure of the jadeite jade crystallized from the primary glass material, i.e. the volume, morphology, alignment, compactness, etc. of the crystalline grain.

PbTe is the only thermoelectric material that has been commercially used for power generation in the medium temperature. It has been found that the n-type PbTe with high performance can be synthesized by high pressure method, but so far there has been no report on similarly prepared p-type PbTe, which is also needed for the application of thermoelectric materials. In this study, we successfully synthesized PbTe with an excess of Te using the high pressure method, and studied their thermoelectric properties at room temperature. It turns out that the main carriers of PbTe with 6% excess Te are holes, indicating that they are p-type semiconductors. By changing the content of Te, we optimized the electrical transport properties of PbTe and decreased their thermal conductivities. The maximum figure-of-merit, 0.21, was obtained for p-type PbTe_1.12, which is about 50% higher than that of PbTe with standard stoichiometric ratio synthesized by the same method. All the results show that the high pressure method, combined with the adjustment of the stoichiometric ratio, can prepare p-type PbTe thermoelectric materials that possess high thermoelectric performance.

An equation-of-state (EOS) calculation model was presented for a multi-component mixture by assuming that all components of the mixture are in a locally thermodynamic equilibrium state, which means that they are isothermal and isobaric, and that the sub-volume of each component is additive. Thermodynamic quantities of the mixture, such as internal energy, pressure, constant-volume specific heat, pressure coefficient and isothermal sound speed, can be constructed with the EOS of each component. Based on this model, we calculated the EOS of a 4-component tungsten alloy, which is remarkably consistent with the result achieved from the wide-range equation of state.

Laser interferometry for measuring velocities and wedge-shaped test explosive were used to study the Hugoniot of unreacted insensitive high explosive JBO-9021 and, on the basis of the wedge-shaped design, the velocities of the particles and the shock wave under different pressures were obtained from the experiment by measuring the particles' velocities at different positions of the test explosive. Based on the experiment data achieved, the Hugoniot parameters of the unreacted JBO-9021 explosive were derived from our theoretical analysis and non-linear interpolation. Moreover, the equation of state of the unreacted insensitive high explosive JBO-9021 was also derived from the simultaneous equations of the Hugoniot relation and Rankine-Hugoniot relationship of the shock wave front.

The Richtmyer-Meshkov (RM) instability in a twice-shocked heavy gas (SF₆) cylinder surrounded by ambient air is experimentally studied using the particle image velocimetry (PIV) technique, and the velocity and vorticity fields as well as the circulation of the flow are quantitatively characterized. The results show that after the first shock-interface interaction, the evolution of the interface is dominated by the formation of a primary vortex pair, whose strength undergoes little change over a relatively long time; but after a reshock, for a short endwall distance, a secondary vortex pair, with its rotation opposite to the primary vortex pair, is formed whose strength is significantly weaker than that of the primary vortex pair, while, for a long endwall distance, no large scale vortex structure is formed. The circulation of the primary vortex pair decreases over time after the reshock, which suggests that the energy is being transferred from the large scale structures to the smaller ones in the flow. The circulations of the primary and secondary vortex pairs are remarkably consistent with the predictions by the theoretical models.

The classic front tracking (FT) method, using the segments between the tracer points to represent the interface and the interface motion is simulated by the movement of tracer points, is valued for its typical high precision, but it is unable to deal with interfaces which have complex topological changes. In this paper, we have made an improvement on the basis of the classic FT algorithm and proposed a new data structure to solve problems involving the topological property. We simulated the movement of the interfaces by using the line segments between the tracer points and wrote a related program. In addition, two typical examples were applied to verify the reliability of the improved FT algorithm and the results are convincingly satisfactory.

A constitutive model based on ice particulate-reinforced material is developed to visually describe the dynamic mechanical properties and the stress-strain relationship of frozen soil. In view of the fact that soil breaks layer by layer under impact loading, we brought the strain rate into consideration as an important factor in constructing the model by assuming that the dynamic modulus of soil changes with strength decreasing step by step. A split Hopkinson pressure bar (SHPB) was used to test the dynamic mechanical response of frozen soil at different temperatures and high strain rates. The experimental results show that frozen soil produces an obvious strain rate effect and temperature effect, and are in good agreement with the theoretical analysis, verifying the constitutive model as both valid and applicable and having significant application value in engineering.

In the present work the dynamic response of the V-shaped aluminum foam sandwich panel and that of the flat panel under blast loading were simulated using the dynamic explicit algorithm based on the three-dimensional nonlinear program LS-DYNA. In our simulation the deflection of the panel faces, the core layer compression and the energy absorption of the core layer were examined with special consideration of different working conditions. The advantage of the V-shaped panel has been exhibited when in comparison with the simulation of the flat panel. When the thickness of the face is constant, the deflection of the top face, the core layer compression and the energy absorption of the core layer increase as the included angle of the V-shaped panel increases whereas, when the included angle of the V-shaped panel is constant, the deflection of the top face, the core layer compression and the energy absorption of the core layer decrease as the thickness of the face increases. The simulated results can serve as a reference for the protection design of motors and other devices.

In order to quantitatively and comparatively investigate the transient responses of cylindrical shells induced by moving and simultaneous impulsive loads, we studied in this work the law of average strain difference varying with geometric parameters by numerical simulations where the two kinds of loads were respectively applied on cylindrical shells with different dimensions.The results show that, for the cylindrical shell, the average strain difference varies with the diameter-thickness ratio, d/t, and the length, that the influence of the shell thickness on the average strain difference is insignificant for specific diameters and lengths.The average strain difference decreases with the increase of the diameter-length ratio d/l, and that when d/l≤0.45 the average strain difference is below 20%.Our results and conclusions provide a theoretical support for relevant experiment design and evaluation.

In order to explore an expression formula for the stress undergone by the nose of the projectile during cratering in the process of penetration, penetration performance in the surface layer of the concrete target was analyzed using the stress wave damage theory.The crater-forming mechanism was explained based on the theory of stress wave obliquely reflection, and the expression formula was established for the stress endured by the nose of the projectile.By conducting numerical simulations and experiments, the depths of the carter were measured to verify the engineering model.The results indicate that the resistance is related to the velocity and the nose shape of the projectiles.A comparison of the theoretical and numerical results with the experimental data demonstrates an improved agreement between them.The new model, which is capable of overcoming the shortcomings of the Forrestal method, successfully describes the relation between the penetration velocity and the crater depth and can be applied to the calculation of the resistance for projectiles penetrating into concrete targets.

The movement state of a flyer driven by two head-on colliding detonation waves is an important problem in weapon physics, about which, up to now, experimental studies have mostly focused on the external characteristics of collision behavior in the later evolution period but, in spite of the strong correlation between the diagnosis results in the later period and the early response behavior of the collision region, relatively little has been done concerning the precise diagnosis of this behavior's early period.In this paper, such materials as W, Cu, etc., whose basic properties are already known, were selected as experiment samples, and a precise experimental diagnosis platform was built using our own developed high speed photoelectric camera.The platform was used to study the collision processes of shock waves and the response of the flyer.Deformation conditions of the flyer surface before and after the collision of the shock waves were obtained.Moreover, clear evolution images of the early bulge in the collision region of the flyer were also successfully achieved.It is expected that these results can serve as significant reference for state analysis and numerical simulation on bulge behaviors of the collision region.

A good understanding of the temporal and spatial distribution characteristics of the railgun contact heat is an important basis upon which to suppress armature melting, design the rails cooling system, and control the thermal management.In this work, based on the calculation models of the contact pressure and contact resistance of the armature and rail, the calculation model of the railgun contact heat temporal and spatial distribution was built, the temporal and spatial distribution of the contact heat was simulated, and the distributional characteristics were analyzed.Aiming at the problem of the relative concentration of the contact heat in the initial stage of the armature movement, the effect of the armature pre-acceleration on the temporal and spatial distribution of the contact heat was examined.The simulation and analytical results show that the contact heat originates mainly from the current's Joule heat, the curves of whose power and driving current have great similarity; most of the contact heat is conducted to the rails in the initial stage of the armature movement, which is the primary cause for the rail erosion; both the contact heat conducted to the unit length rail in the initial stage and that accumulated in the armature during the launching process decrease with the increase of the armature initial velocity.

An armature is the key component in the device for energy exchange in an electromagnetic coil launcher (EMCL).In this work, in view of their working principle and structural characteristics, mathematical models of the induction solid armature launcher (ISAL), induction coil armature launcher (ICAL), series current coil armature launcher (SCCAL) and parallel current coil armature launcher (PCCAL), were deduced, and their simulation system was built with MATLAB based on the equal circuit method so that their performances as an electromagnetic launcher were examined and compared.A series of parameters including the dimension and material of the solid armature, the diameter of the winding coil armature, the initial velocity and the initial position of the armature, the positions order of the armature in a multi-stage launcher were simulated and analyzed.The conclusions reached show that a pulling effect exists in the initial and the last stages of the ISAL and ICAL that leads to the decrease of the muzzle velocity of the armature and the payloads, that no pulling effect occurs in current coil armature launcher (CCAL), that the muzzle velocity can be improved when the diameter of the armature of ICAL and SCCAL increases and the diameter of the coil armature of the PCCAL decreases, and that CCAL is more suitable for accelerating the payload at a low velocity with a launcher of fewer stages.Our work is of great significance for guiding the selection and design of the armature structure.

When the equation of state (EOS) and physical parameters of the projectile and the target plate materials are unknown, it is impossible to estimate accurately the peak value and the pulse width of the shock wave pressure on the impacting surface based on the existing theoretical models.To solve this problem, using the dimensional analysis, we studied the factors influencing the peak value and the pulse width of the shock wave pressure, and established an empirical model of the peak value, and that of the pulse width of the shock wave pressure respectively, with a clear physical meaning specified for each component in the formulas.This kind of model successfully avoided the problem of unknown EOS of the projectile and target materials.The obtained formulas can be used to predict the peak value and the pulse width of the shock wave pressure.We applied this model to an actual experiment of 45 steel impacting on a Ni plate, and found that the peak values and the pulse widths of the shock wave pressure calculated by this model match well with the measured results, which proves the feasibility of our model.

As uncertainty always exists in the modeling and simulation of complex engineering problems, the identification and analysis of its source and the quantification of its degrees play an important role in assessing the credibility of the modeling and simulation results.In this paper, the concept of uncertainty as well as uncertainty quantification process was presented in the modeling and simulation, with the blast wave problem used as a typical example to illustrate the detailed process for the quantification of the aleatory uncertainty.The expectations and variances of density, pressure, velocity and internal energy were calculated and, moreover, the probability density function of the shock wave position was obtained using the Monte-Carlo and the non-intrusive polynomial chaos (NIPC).The results were consistent with each other, which verified that the NIPC method is an efficient approach in the uncertainty quantification of a complex nonlinear system.

With the development of radiography technologies, the synchrotron radiation facilities can emit highly coherent and energy-tunable X-rays with a large flux, making X-ray imaging techniques widely applicable in various fields.The X-ray imaging techniques have evolved from simple radiography to phase-contrast imaging, microscopy, and coherent diffraction imaging, and X-ray diffraction techniques provide structural information for crystal materials with long-range periodicity.In contrast, however, the X-ray imaging techniques are highly visible, and provide direct measurements for all kinds of materials (alloy, amorphous, liquid) from micro-, meso-, to macro-scales.In recent years, the X-ray imaging techniques have been applied in high pressure researches.For example, the equation of state of amorphous materials, the ultrasonic velocities under high pressure, the molten iron transport properties in the Earth's mantle, the strain distribution in the crystalline, and the structural evolution of the phase transformation, can be extracted by X-ray imaging techniques.In this paper, we sum up the studies of the high static pressure research using X-ray imaging techniques, which we expect will facilitate future studies in this area.