The dynamics of phase transition of tin under ramp wave loading was studied with experiment and simulation. The ramp wave compression experiment of tin was carried out with photonic Doppler velocimetry (PDV) and compact pulsed power generator CQ-4. The velocity wave profiles obtained experimentally show that tin undergoes physical processes such as elastoplastic transition and phase transition in the loading section, and the phase transition pressure is about 7.5 GPa. As the increase of thickness of tin, the characteristic velocity corresponding to the onset of phase transition decreased slightly from 676.3 m/s to 636.8 m/s, and the corresponding pressure was from 7.62 GPa to 7.11 GPa. The Hayes multi-phase equation of state and non-equilibrium phase transition kinetic model were employed to simulate the experimental process, and the numerical results can well describe the physical processes such as elastoplastic transformation and phase transformation in the loading section. The calculated results revealed that the correction of the bulk modulus with pressure needed to be considered under ramp wave compression. The influence of typical physical parameters, such as phase transition relaxation time and bulk modulus, on the velocity waveform was discussed. The results show that phase transition relaxation time and initial free energy mainly affect the velocity waveform in the mixing zone, the bulk modulus of the two phases affect the velocity waveform after phase transition and overall velocity waveform respectively.

Based on the first principle of density functional theory, the crystal structure of MgN₈ was predicted in the pressure range of 0–100 GPa by using CALYPSO structure search technique and VASP software. After systematically studying the predicted structure, it was found that the enthalpy of α-MgN₈ crystal with space group P4/mbm was the lowest at ambient pressure. The phase was changed to β-MgN₈ phase of P4/mnc and γ-MgN₈ phase of Cmcm when the pressure reached 24.3 GPa and 68.3 GPa, respectively. And both of the phase transitions were the first order phase transition of corresponding volume collapse. The calculated results of electronic properties suggested that the existence of a band gap of 3.09 eV between the conduction band and valence band of α-MgN₈ phase revealed the non-gold properties of the structure, whereas the obvious metal characteristics appeared in the β-MgN₈ phase and γ-MgN₈ phase. Bader charge transfer calculation showed that the charge which transferred from Mg atom to N atom, increased gradually with the increase of pressure.

The effect of rapid compression on the stability of olivine structure was studied in this work. In the first group, the olivine samples were rapidly compressed to 3 GPa at 293, 373, 473, 573, 673 and 773 K respectively. In the second group, the olivine samples were sintered for 2 h at 873, 973, 1 073 and 1 173 K and then were rapidly compressed to 3 GPa at room temperature. The structure of the recovered samples were analyzed by synchrotron radiation X-ray diffraction, Raman spectroscopy, infrared absorption spectrum and scanning electron microscopy. These results showed that the structure of olivine was stable and there were no phase transition caused by temperature and rapid compression. The micromorphology observation of recovered olivine indicated that the grains were refined. Due to the residual stress and grain refinement in the recovered samples, the Raman vibrational peaks of olivine (822 cm^–1 and 854 cm^–1 at room temperature) showed some broadening and displacement.

Based on density functional theory, a ZrBeO₃ crystal model of perovskite structure was constructed. The binding energy of the crystal model was calculated, and the thermodynamic stability of the structure was calculated. The elastic constant of the structure under different pressures was calculated, and ZrBeO₃ was calculated according to it. The bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, B_H/G_H and other parameters, the calculation results show that the material has mechanical stability, and the material changes from brittle to ductile with increasing isostatic pressure; the hardness of ZrBeO₃ under zero pressure is 34.5 GPa, which indicates that the crystal should be superhard material. The calculated phonon energy spectrum show that ZrBeO₃ is thermodynamically unstable under low temperature and zero pressure. The phonon spectrum, different atomic orbitals and chemical bond values at different pressures show that the Be-O covalent bond formed by the impurity of Be atom is enhanced and the Zr-O bond ion bond component is enhanced with the increase of pressure. The lattice dynamics tend to be stable.

High entropy alloy (HEA) has high strength, high hardness, high wear resistance and corrosion resistance which traditional alloys do not have, and has broad application prospects. The mechanical properties of AlCrFeCuNi high Entropy Alloy (HEA) under axial loading were also studied in this paper. Molecular dynamics method was used to simulate the experimental preparation process of HEA and establish an atomic model. The mechanical properties of AlCrFeCuNi HEA at different temperatures and Al concentrations were studied. The deformation process and the reasons for its high plasticity were analyzed from the point of view of material science. The simulation results show that the AlCrFeCuNi HEA undergoes elastic deformation, yield and plastic deformation stages under tension loads. In the yield stage, the appearance and growth of twins and stacking faults are one of the main reasons for the uneven plastic deformation of the alloy. The analysis shows that the Young’s modulus and yield stress of the HEA decrease linearly with the increase of Al concentration. The HEA have strong temperature effect. The lower the temperature, the smaller the Al concentration, and the greater the decrease in Young’s modulus and yield stress.

This study investigated the applicability of three p-$\alpha $ models and p-$\lambda $ model for predicting shock compaction response of heterogeneous W-Cu powder mixture. Mie-Grüneisen method and Barry isobaric mixing method were employed to predict the Hugoniot of W-Cu powder mixture with the same porosity based on the Hugoniot relationships. At high pressure section, the results were in good agreement with the experimental results, but it deviated greatly at the low pressure section. The p-$\alpha $ models and p-$\lambda $ model were applied to fit the experimental results, and it was found that all the other models were able to describe the shock compression response of W-Cu powder mixture except p-$\alpha $ PL model. The crush strength and compression path of all models are different due to selection of empirical parameters, and they are with poor prediction function.

High-speed particle-laden flow has important applications in astronomy, natural disasters, industrial safety, medical industry, and national defense. In this work, a direct numerical simulation method based on the stratified flow model is used to study the interaction between a planar shock wave and an elliptical column cloud. The influence of the aspect ratio and the tilt angle, the distributions of the flow velocity, RMS velocities along x axis, kinetic energy, internal energy, and turbulent kinetic energy are analyzed; energy values in the upstream region, the elliptical column cloud region and the downstream region of the computational domain are quantitatively analyzed. The 1-D volume-average model is improved for elliptical columns. Based on this model, the appropriate artificial effective drag coefficients are decided by fitting the positions of the reflected shock and the transmitted shock from the direct numerical simulation results, and the distribution of the optimal artificial effective drag coefficients is also discussed.

The high-speed gun is used to study the impact of quartz glass ball on rigid target plate. The crushing process and failure mode of the ball at different speeds are analyzed. When the impact velocity is lower than the critical failure velocity, the quartz glass ball rebounds from the target plate, and the rebounding speed is slightly below the original speed; when the critical speed is exceeded, the sphere exhibits a “compressed fracture zone–surface spalling zone–shear failure zone” failure structure; further increasing the collision velocity, the expansion of the shear failure zone causes the sphere to be fragmented into several “crescent” fragments. At higher impact speeds, the quartz glass ball collapses and spalls at a distance away from the impact end. Furthermore, the discrete element software is utilized to simulate the impact damage process of the sphere. The crushing of the sphere under high-speed collision can be divided into three stages: elastic compression, integral crushing, secondary impact. Before the ball breaks, the Hertz contact theory can describe its impact force well, but the crushing force is much smaller than the theoretical value due to the fracture unloading, and the deviation gradually increases with the increasing impact speed.

Nacre inspired composite materials with different assembly modes were fabricated by photocurable 3D printing. The composite materials consist of two kinds of matrix materials. The tension mechanical properties, fracture and energy dissipation mechanism were analyzed by quasi-static tensile tests combined with scanning electron microscope (SEM). The results show that, keeping the length of the cell constant, the strength of nacre inspired composite materials increase linearly, while the fracture strain decreases linearly with the increasing of in-plane assembly angle. The fracture strain decreases linearly with the increasing of out-plane assembly angle. When the out-plane assembly angle is less than 45°, the strength of nacre inspired composite materials increases linearly with increasing such angle, but it tends to be stable when such angle exceeds 45°. The strength of the material reaches the maximum value when the out-plane assembly angle is 45°. Most of the tension energy is dissipated by pull-out of the hard materials, generation, propagation and combination of micro-cracks at the soft/hard interface and the crack deflection in the propagation process.

In order to study the dynamic response of reinforced concrete wall under impact load, a finite element model of reinforced concrete wall is established by means of ANSYS/LS-DYNA. The impact mass is 2 t and the impact velocity is 3 m/s. The effects of axial compression ratio, wall width and boundary elements on the impact resistance of reinforced concrete walls are analyzed. On this basis, the three stages of wall failure under extreme loading conditions are analyzed, and a criterion of evaluating wall failure under extreme loading is proposed. The influence of axial compression ratio, wall width and boundary elements under extreme loading is analyzed by using the proposed criterion. The results show that, in a certain range, with the increase of the axial compression ratio, the impact resistance of the wall is improved, and the damage area of the wall with axial compression is concentrated. Increasing the wall width and adding edge components can effectively enhance the impact resistance of the wall. Under the ultimate load. When the impact mass is constant, the impact energy required for structural failure decreases with the increasing axial compression ratio.

In order to explore the influence of the scale effects on the timing of fragmentation and shock wave, the key parameters affecting the location of fragmentation and shock wave are determined by the dimensionless analysis and explosion theory for the prefabricated fragment warhead. This paper proposes a method to predict the timing relationship of the prototype warhead fragmentation and blast wave by the scale ratio warhead, and establishes the model of the warhead under different scale ratios. The numerical simulation is carried out with ANSYS/LS-DYNA finite element software. Based on the theoretical and numerical results, we analyze the scale effects of the warhead on the timing of shock waves and fragmentation. The results show that the ratio of the encounter position of fragments and shock waves produced by the scaled model and the prototype model depends on the mass ratio of the two models. Without considering the velocity attenuation of fragments, the ratio of the encounter position in two models is equal to the 0.33 power of the mass ratio. Due to the effects of fragmentation velocity attenuation, the method is applicable to models with a mass reduction ratio of not less than 0.2.

The state equation of water, artificial viscosity coefficient and mesh size have a great influence on the numerical results of underwater explosion shock wave. In order to improve the simulation accuracy of underwater explosion shock wave, the peak pressure and specific impulse of the conventional TNT explosive underwater explosion are taken as the measurement indicators, and the influence of these factors on the numerical simulation results is studied. For the five kinds commonly state equations of water, the specific values of the artificial viscosity coefficients under different working conditions and appropriate grid size for different explosive equivalents are given. These parameters can provide reference for improving simulation accuracy of underwater explosion shock wave under different working conditions. First, through a series of simulations of the commonly used five kinds of state equations of water, the calculation results of peak pressure and specific impulse are compared with the empirical formula, and the error analysis is carried out to give the applicable scope of each state equation. Secondly, the influence of the artificial viscosity coefficient on the calculation results is discussed, and a series of calculations are carried out for the primary and secondary artificial viscosity coefficients under different working conditions. The recommended range of values for the primary and secondary artificial viscosity coefficients under different working conditions is given. Finally, through a series of calculations on 0.1, 0.5, 1, 10, 50, 100, 500 and 1 000 kg equivalent explosives and different grid sizes, the recommended mesh sizes corresponding to different explosive equivalents under the requirement of engineering calculation accuracy are obtained by limiting the relative error of peak pressure less than 10%. The expressions of the recommended mesh sizes corresponding to different explosive equivalents are also given.

The essence of supercavitating projectile penetration is the dynamic response of a special underwater structure subjected to high-speed impact load. In this paper, the damage effect of 12.7 mm supercavitating projectile penetrating typical underwater target shell is studied. Based on LS-DYNA finite element analysis software, the equivalent model of supercavitating projectile penetrating into curved surface target vertically in water environment is established. The combined damage effect of kinetic energy penetration and bubble collapse on target plate during penetration is simulated, and the stress variation and structural deformation law of target plate at different stages are obtained. The results show that the peak pressure of water medium on the head surface reaches 768 N when the velocity of projectile is 200 m/s before penetrating the target, and the surface of the target exhibits obvious concave deformation; with projectile kinetic energy penetration and bubble collapse impact during penetrating process, the impact effect of water medium is less than 2% of that by kinetic energy penetration. After penetrating the target, a water jet with a peak velocity of 42 m/s is formed on the front of the target and further acts on the break. The overall bending deformation of the target plate occurs. In the range of 200 m/s to 300 m/s, the bending deformation decreases with the increase of projectile impact velocity. Ductile perforation occurs locally on the target plate, and the projectile has better perforation effect in water environment. The change of projectile velocity has little effect on the size of the perforation.

In order to study the effect of nose cabin on projectile low speed and high mass during the penetration of metal plates, a finite element analysis model of blunt projectile with nose cabin was established. Based on the mechanical properties, nose cabin can be regarded as equivalent to light foam aluminum material. Numerical simulation of blunt projectile with nose cabin penetrates into metal plates under different working conditions were implemented. The progress of projectile with nose cabin penetrates into metal plate was analyzed. The difference between residual velocity of blunt projectile with and without nose cabin was compared. The results show that there are significant differences in the progress of projectiles penetration into metal plates between blunt projectiles with and without nose cabin. Nevertheless, the failure modes for both conditions are similar. The yield stress of equivalent material of nose cabin has limited influence on penetrative performance of projectile. In conclusion, nose cabin can bring very limited improvement to the penetration capability of blunt projectile, and the effect of nose cabin can be neglected in practical engineering applications.

CH₄-H₂ mixture explosion experiments were performed in a 20 L spherical explosion vessel with the equivalence ratio of 1. Gas proportion and ignition energy were varied to explore their effects on the explosion pressure and intensity. It is found that higher hydrogen proportion causes higher explosion shock wave propagation speed, while the ignition energy has little effects on the explosion shock wave propagation speed. Higher ignition energy can enhance the explosion overpressure, and this enhancement effect is remarkable when the hydrogen proportion is lower, and is not evident when the hydrogen proportion is higher. The effect of ignition energy on the explosion severity index K_G is not evident, but the effect of hydrogen proportion on K_G is remarkable. The positive effect of hydrogen addition on K_G is very slight at low hydrogen proportion while it becomes much more pronounced at higher hydrogen contents. Furthermore, the explosion intensity of hydrogen is approximately tenfold of that of methane explosion with corresponding same equivalent ratio, and therefore, the presence of hydrogen will greatly enhance the explosion hazard of methane.

Lithium-ion battery separators act as the physical barriers to prevent contact between the positive and negative electrodes, and their structural integrity is critical to battery safety. In this paper, uniaxial tensile tests were carried out on four kinds of commercial separators, and the effects of loading angle and linear notch on tensile strength, elastic modulus and fracture mode were analyzed. The results show that the tensile strength of the 0° specimens without notch is the largest and the tensile strength of 90° specimens is the smallest. When the loading angles of two notched specimens are supplementary, their tensile strength is close to each other. For the notched specimens, the failure load is the largest when the notched direction is along 90°. The linear notched specimens have higher elastic modulus, but the plastic deformation is greatly reduced. Both the unnotched specimens and the notched specimens are broken along MD (machine direction) except for the 0° specimens along TD (transverse direction).