Liquids are an intriguing state of condensed matter with a density close to that of the solid-state but with all atoms undergoing continuous diffusive motions, resulting in an absence of long-range structural order. Understanding the structural evolution of liquids under extreme conditions is important for fundamental physics, chemistry, materials and planetary science. Two or more liquid states may exist even for single-component substances, which is known as liquid polymorphism, and the transition between them is called liquid-liquid transition. In situ experiments and atomic simulations can provide crucial insight into the nature of liquid-liquid phase transitions, paving the way toward understanding the complex phase diagrams and melting behavior under high pressure. In this paper, we reviewed the research progress on the structure of metallic molten Sn and Bi, and discussed how to gain a more physically understanding of the existence of two or more liquids in a single-component substance but also provided information for in-depth understanding of liquid properties and complex phase diagrams.

Exploring the structures and properties of halide perovskite under pressure have triggered great interest among scientists in recent years. However, there is still little understanding on the potential properties and applications of their amorphous phase under high pressure. In this paper, we utilized diamond anvil cell, combined with in situ high pressure synchrotron radiation X-ray diffraction, Raman spectroscopy and electrical resistance measurement to investigated the amorphization of quasi-one-dimensional halide perovskite CsCu₂I₃ under high pressure. It was observed that CsCu₂I₃ started to transform to a reversible low-density amorphous phase Ⅰ above 35.9 GPa. An irreversible high density amorphous phase Ⅱ was realized at higher pressure, which can be maintained to ambient pressure. With the application of pressure up to 136.0 GPa, the initially insulating CsCu₂I₃ transform to a metallic phase. In addition, the metallic amorphous phase Ⅱ can be preserved to at least 90.0 GPa. These results provide an important scientific basis for further exploring the potential properties and applications of amorphous perovskite.

The millimeter-size tetragonal PbTeO₃ single crystal was synthesized by hydrothermal method under saturated vapor pressure of water at 230 °C. Crystal structure, microscopic morphology, thermal stability and other properties of the sample were studied. The compression behavior of the tetragonal PbTeO₃ crystal under high pressure was investigated by diamond anvil cell (DAC) with in-situ synchrotron X-ray diffraction. The results show there is no phase transition observed in the tetragonal PbTeO₃ up to 37 GPa. Using the Birch-Murnaghan equation of state to fit the observed pressure-volume data of the tetragonal PbTeO₃ sample, a bulk modulus B₀=42(1) GPa, $ B_0'$=5.5(0.2) for tetragonal phase was obtained. The variation of lattice parameters with pressure shows that the crystal is easier to compress in the c-axis direction.

According to the requirements of target structure design and experimental data processing in multilayer target quasi-isentropic compression experiments, an interlayer transfer method for multilayer targets was proposed based on the backward integration method, the backward calculation of multilayer targets from the measuring surface to the loading surface or laser ablation surface was realized. Through the forward and backward integration numerical experiments and the application in laser driven experiment, the effectiveness of the backward integration method in multilayer targets was verified, and the backward integration processing accuracy of multilayer targets can reach within 1% in most of the calculation area. The waveform design of quasi-isentropic compression multilayer target experiments was carried out by backward integration method, and the influence of multilayer targets with different thicknesses of glue on quasi-isentropic compression experiments was analyzed.

In order to study the effect of strain rate (loading rate) and multi-walled carbon nanotubes (MWCNTs) content on the mechanical properties, energy evolution law and damage failure characteristics of MWCNTs-reinforced concrete samples, the RMT-150B rock mechanics test system was used to carry out a series of uniaxial compression tests on MWCNTs-reinforced concrete samples with different content of MWCNTs under different strain rates. The results show that the ductility of MWCNTs-reinforced concrete samples increases with the increase of the content of MWCNTs. When the strain rate is constant, the uniaxial compressive strength of the MWCNTs-reinforced concrete with 0.10% MWCNTs content is the highest; when the content of MWCNTs is constant, the uniaxial compressive strength of the MWCNTs-reinforced concrete samples reaches the maximum under strain rate of 5×10^–3 s^–1 (0.5 mm/s); when the strain rate is large, the mean value of the energy dissipation of MWCNTs-reinforced concrete accounts for 28.29% of the total energy at the peak stress. When the strain rate is small, the energy dissipation phenomenon in the pre-peak stage is significant, and the mean proportion of dissipated energy at the peak stress is as high as 37.34%. When the strain rate and MWCNTs content are small, the energy absorbed by the MWCNTs-reinforced concrete before failure is largely transformed into dissipative energy, and the energy release rate of the samples after peak stress is small, which is characterized by mixed failure of local tension and shear. When the strain rate and MWCNTs content are large, the energy absorbed by the MWCNTs-reinforced concrete before failure is mainly stored as releasable elastic strain energy, and the energy release rate of the concrete samples is faster at failure, and the MWCNTs-reinforced concrete samples are relatively broken at failure, showing the characteristics of impacted damage to a certain extent.

To determine the mechanical properties and failure modes of ultra-high molecular weight polyethylene (UHMWPE) fiber composite laminates under static and dynamic compressive loading, a universal material testing machine (UTM) and a split Hopkinson pressure bar (SHPB) experimental system were used to obtain the stress-strain relationships of UHMWPE subjected to out-of-plane compression at different strain rate loading. After experiments, the microscopic failure morphology of the material was observed through scanning electron microscopy (SEM), then the failure mode of the material was analyzed. The results show that the UHMWPE fiber composite laminates performs a rate-independent behavior at low strain rates (6.7×10⁻³ s⁻¹ to 6.7×10⁻² s⁻¹); while a rate-dependent at high strain rates (2.05×10³ s⁻¹ to 5.27×10³ s⁻¹). The compression strength increases with the rising strain rate, and the dynamic enhancement factor gradually increases, with an obvious strain rate strengthening effect. Under static compression, the main damage mode of UHMWPE is the stretching and fracture of the fibers, while at dynamic situation, the main damage mode of the material is the longitudinal dislocation delamination.

In this paper, the mechanical properties of glass fiber/epoxy vinyl ester resin (GF/epoxy VER) composite after hygrothermal aging were studied. The GF/epoxy VER composites laminates were fabricated by vacuum assisted injection molding technology. According to the stress characteristics of composite pressure vessels during service, bending and shearing samples were made by water cutting technology. Considering the working environment of pressure vessel, accelerated aging tests were carried out on the samples soaked in water to analyze the changes of the mass and mechanical properties of the composites at different temperatures and periods. Results show that bending and shear properties of composite materials decrease with the increase of water immersion time. The effect of temperature on the properties of composites is more significant than that of soaking time. If immersed in 90 ℃ water for 6 weeks, the shear strength, flexural strength and flexural modulus of the composite are reduced to half of the initial value.

To study the improvement mechanism of polyisocyanate oxazodone (POZD) on the blast resistance of steel plate, and analyze the dynamic response of steel/POZD composite structure, close-range air blast tests and finite element numerical simulations were conducted. Deformation failure modes of steel/POZD composite structures were studied and analyzed by observing the damage of tested structures and dealing with related date statistics. The accuracy of numerical simulation method was verified by comparing the results of numerical simulations with those of tests. The mid-span displacement change and energy absorption characteristics of steel/POZD composite structures were analyzed. Results show that steel/POZD composite structures have better blast resistant performance than single steel plates. Steel plates exhibit three different deformation failure modes. In the case of a steel/POZD composite structure with no crevasse, the plastic strain energy of steel layer gives a most contribution to the total energy absorption. The maximum central displacement of steel/POZD composite structure gradually increases, and meanwhile, its deformation velocity first increases and then decreases. The research results can provide references for the anti-explosion protection design of steel/POZD composite structures in engineering field.

Due to the low cost, high toughness and energy absorption characteristics of hybrid honeycomb structure under low velocity impact, an Al/carbon fiber reinforced plastics (CFRP)/hybrid honeycomb aluminum composite sandwich multilayer structure was designed. The kinetic energy of the projectile was supposed to be effectively absorbed and the protection was supposed to be achieved through gradually reducing the velocity of the projectile layer by layer. In order to investigate the damage evolution law and energy absorption characteristics, numerical analysis was carried out, and the impact energy effect on the penetration resistance of multilayer structure was discussed. It is found that, compared with the Al/CFRP composite structure, the reaction force given by the structure becomes larger for hybrid honeycomb aluminum. Hence, with an identical energy, the time of the projectile acting on the plate becomes shorter. In the process of anti-penetration of Al/CFRP/hybrid aluminum honeycomb composite sandwich multilayer, the Al plate and CFRP core mainly resist the penetration, and the honeycomb aluminum mainly absorbs the energy of the projectile. When the impact energy is 40 J, the total absorbed energy is 36.79 J, and the specific energy absorption is 0.217 J/g, the honeycomb aluminum core layer absorbs the main part of the energy with the proportion of 30.3%; as the impact energy increases, the proportion increases to 56.2%. This indicates that the energy absorption of the honeycomb aluminum core layer is better when the impact energy increases.

In this study, a novel type of the intorsion hierarchical honeycomb-like (IHH) structures was proposed based on the cell geometrical design. The out-of-plane mechanical behaviors and deformation characteristics were studied by numerical simulation, and the results were compared with that of ordinary honeycomb (OH) structure as well as the honeycomb structure filled with circular tube (HFCT). It is found that the intorsion hierarchical design makes the constraint effect inside the cell. Through multi-order hierarchical design, the constraint effect can be further strengthened, so as to improve the mechanical behaviors. In addition, parametric studies were carried out to reveal the influence of the change of relative density on mechanical performance. Based on the simplified super folding element (SSFE) theory, a theoretical model of IHH was established. The results show that the proposed IHH exhibit the progressive folding deformation mode and attain the optimal energy absorption efficiency among all the competitors. The theoretical model can effectively predict the mean stress of IHH. The results in this study can provide guidance for the mechanical performance optimization of multi-cell structure.

In this paper, a slamming model of composite laminate is established based on the Euler-Lagrangian fluid-structure interaction method. The reliability of the numerical simulation method is verified through the comparison between numerical and experimental results. On this basis, a fluid-structure interaction slamming model of carbon fiber reinforced composite sandwich panels is established, and the progressive damage evolution mode of composite sandwich panels is investigated by VUMAT subroutine. The hydrodynamic force, flow jet, and water pressure distribution as well as slamming damage characteristics of composite sandwich panels are analyzed. Finally, the effects of slamming speed and deadrise angle on the slamming damage characteristics are investigated. The results show that the hydrodynamic force has gone through four stages including the initial growth stage, fluctuating stage, sharp rise stage and rapid decreasing stage during the slamming process. The matrix tensile damage and delamination damage of composite sandwich plates are accumulated under slamming loading. With the increase of the slamming speed and deadrise angle, the hydrodynamic force and slamming damage significantly increase.

The double-layer plate air-container set in the liquid-filled structure can effectively reduce the harm caused by the hydrodynamic ram. In order to study the influence mechanism of the spacing and position of the double-layer plate on the hydrodynamic ram process, the numerical simulation of projectile penetration into the double-layer plate liquid-filled structure was carried out based on the material point method (MPM). The validity of the MPM numerical model is verified by experiments. The cavitation process, the residual velocity of projectile, the peak pressure of liquid at fixed points, the deformation of entry wall, exit wall and the double-layer plates were analyzed. The results show that with the increase of the spacing of the double-layer plate, the deformation of the liquid-filled structure shows a trend of first reducing and then increasing. The closer the position of the double-layer plate to the entry wall, the stronger the obstruction of the transmission of pressure shock wave, and the better the penetration resistance of the liquid-filled structure.

In order to study the influence of off-axis initiation on shaped charge jet, the finite element software LS-DYNA was used to simulate the jet forming and armor breaking process under different eccentricities (0.025D_k–0.125D_k, D_k is shaped charge diameter). The asymmetric collapse degree of the liner, jet shape and lateral velocity were investigated. A theoretical model was established to analyze the lateral velocity distribution of jet under different eccentricities. Based on the orthogonal experimental design theory and analysis of variance, the significant difference of the influence degree of each factor on the evaluation index was discussed. The results show that the degree of asymmetric collapse and lateral velocity of jet are positively correlated with the offset. When the offset is 0.025D_k, the percentage of penetration depth was only 0.7%. However, when the eccentricity was 0.050D_k, the percentage of penetration depth suddenly jumped to 12.4%. Moreover, the penetration depth continues to decrease with the increase of offset, seriously affecting the jet’s penetration performance. In addition, the influence of off-axis initiation on jet lateral velocity can be compensated by increasing the thickness of liner and the explosive height above liner.

To study similar law of the fragmentation effect of penetrator with enhanced lateral effects (PELE) penetrating a metal target plate, breaking length of the PELE jacket and scattering radius of the fragments behind target are selected as two physical parameters to measure the fragmentation effect of PELE. A similar analysis on the fragmentation effect of PELE was conducted based on dimensional theory. Four groups of scaling model simulations were carried out using AUTODYN software, and two groups of scaling model verification tests were done. It is determined that the fragmentation effect of PELE satisfies geometric similar law through the similar theory analysis, and in the range of 800–2000 m/s impact velocity, the normalized breaking length of jacket and dispersion radius of fragments both increase linearly with the impact velocity in the simulation and test results, which proves that the fragmentation effect of PELE penetrating the metal target satisfies the geometric similarity law.

For exploring the new technologies of hydrogen explosion prevention and the development of new barrier and explosion-proof materials, the effects of anti-magnetic aluminum wire and ferromagnetic nickel wire on premixed hydrogen-air explosion pressure were carried out. The CHEMKIN-PRO software was used to simulate the reaction path and temperature sensitivity changes during hydrogen explosion. The experimental results show that the two metal wires have a dual effect on the explosion of hydrogen-air mixture. When the volume fraction of hydrogen in the mixture is less than 20%, the metal wire material inhibits hydrogen explosion, and the larger the filling amount of the material, the stronger the inhibition. When the volume fraction of hydrogen in the mixed gas is higher than 25%, the two metal wires promote hydrogen explosion, and the larger the filling amount, the stronger the promotion. In the stage of promoting explosion, the effect of nickel wire is weaker than that of aluminum wire, in the explosion suppression stage, the explosion suppression effect of nickel wire is better than that of aluminum wire. The inhibition or promotion effect of metal materials on gas explosion is determined by the concentration and properties of gas and the filling amount of materials. Changing the filling amount of materials will lead to changes in the performance of inhibiting/promoting hydrogen explosion. The simulation results show that •H, •O, and •OH are the key free radicals in the process of hydrogen explosion, and the change of reaction rate and sensitivity directly determine the explosion intensity. Among the main elementary reactions that affect hydrogen explosion, R2 has the greatest impact on the formation rate of hydrogen, and R1 has the greatest impact on hydrogen and temperature during explosion. The main elementary reactions that affect the change of temperature sensitivity have a promoting effect on explosion. The influence mechanism of different magnetic wires on hydrogen explosion was revealed by experiment and numerical simulation.

The design of annular combustion chamber and pre-detonation tube of rotary detonation engines is the key factor affecting the ignition performance of the engines. In order to obtain the detonation initiation mechanism in an annular combustion chamber, the multi-frame short-time shutter-opening method was used in experiment to study the propagation process and mode of the detonation wave of acetylene and oxygen with different argon dilutions entering an annular channel tangentially through a straight pipe. We focus on the mechanism of detonation wave failure and reinitiation. By analyzing the cellular mode, it is found that the propagation mode of the detonation wave in the annular channel can be divided into three states: subcritical, critical and supercritical. The detonation wave in the annular channel propagates clockwise and counterclockwise at the same time. Depending on the initial pressure and the width of the channel, there can be a mode of complete detonation, a mode of detonation-reignition, and a mode of no detonation at all, corresponding to subcritical, critical and supercritical states. The order in which the three states appear in the clockwise and counterclockwise directions are not consistent, and the counterclockwise propagation is more likely to be extinguished. The study also found that reinitiation is achieved in two ways. One is by decoupling the reflection of the detonation wave from the inner wall surface and the subsequent lateral detonation wave, and the other is by burning to detonation. By analyzing the critical tube diameter of the straight tube, it is found that the critical tube diameter approaches the unstable detonation in the classical diffraction problem as the width of the channel increases, regardless of whether the detonation wave of acetylene and oxygen is diluted by high concentration or low concentration of argon gas. The experimental results can provide technical support for the structural design of the combustion chamber and pre-detonation tube of rotary detonation engines.

The initiation delay time seriously affects the efficiency of tunnel blasting excavation. It is of great significance to study the improvement of rock fragmentation effect and tunneling efficiency under the electronic detonator initiation condition via precise control blasting. The similarity model test of delay time between the cutting holes and the caving holes in tunnel blasting was conducted, and the rock fragmentation characteristics under different delay time were analyzed. The results show that it can be seen from the model test that the electronic detonator has obvious advantages in improving the blasting effect in tunnel blasting for its precise delay ability. In addition, the similarity relationship of the initiation delay time between the model and field tests was summarized. According to the field test, when the best delay time between the cutting holes and the caving holes is 15−25 ms, the utilization rate of the blast-holes is the highest. Guided by the similarity theory, the optimum delay time drawn from the model test is 8–24 ms, showing a good agreement with the field test. This paper is of reference for the selection of delay time between the cutting holes and the caving holes in tunnel blasting.

To ensure the face stability of the super-large rectangular shield tunnel, based on a super-large rectangular shield tunnel, the theoretical analysis, numerical simulation and field monitoring are used to study the ultimate support force of the super-large rectangular shield tunnel crossing the high-speed railway in the composite stratum. The critical failure mode of excavation surface of super-large rectangular shield tunnel crossing high-speed railway in a composite stratum is proposed, and the calculation method of ultimate support force is deduced based on the ultimate equilibrium theory. The results of numerical simulation and field monitoring show that the errors between the proposed ultimate support force calculation method and numerical simulation as well as the proposed ultimate support force calculation method and field monitoring are 10.40%–18.30% and 11.19%–16.85%, respectively. The formula of ultimate support force is safe and reliable, and can be applied to practical engineering. The research conclusion can provide a reference for the stability control of excavation face in similar projects.