As a thermodynamic parameter, independent of temperature and composition, pressure provides a new dimension for material science research and innovation. Pressure has become an important source for developing new concepts, creating new theories and exploring new materials. Here, some advances in optical properties regulation of low-dimensional materials under high pressure are summarized. By changing the exciton binding energy and the distortion behavior of halide octahedra under pressure, the luminescence of low-dimensional halide perovskites experienced a stark change from "0" to "1". Meanwhile, we innovatively put forward the new concept of "pressure-induced emission (PIE)". Through introducing the pressure effect, it is able to regulate the surface ligands of nanomaterials, change the interaction and energy level coupling between the surface ligands and CdSe quantum dots. This will promote the Hirshfeld charge transfer, thus realizing the significant emission enhancement of CdSe quantum dots by nearly one order of magnitude. With the help of high-pressure regulation on energy band structure, we successfully achieved the core/shell configuration transition of CdSe/CdS semiconductor nanocrystals from quasi-type Ⅱ to type Ⅰ core-shell structure. The above work will deepen the understanding of the structure-property relationship of luminescent materials under extreme compression conditions. The research results provide new methods for the design and preparation of low-dimensional materials with specific functionality.

Phase behaviors of α-quartz and coesite at high pressures and room temperature have been investigated by using diamond anvil cells combined with synchrotron X-ray diffraction. α-quartz undergoes a phase transition to a new phase at about 23 GPa, and the phase transition gets finished at about 44 GPa. The high-pressure phase of α-quartz can be observed up to 59 GPa. Coesite transforms to coesite-II at about 22 GPa, and coesite-II undergoes phase transitions above about 36 GPa. Crystalline phase can be observed up to 59 GPa in coesite. Different hydrostatic conditions provided by neon and argon have no crucial effect on high-pressure phase behaviors of α-quartz and coesite. These results not only clarify pressure-induced phase transition pathway of α-quartz and coesite, but also shed light on the transition mechanism of silica under high pressure.

As an important fluid medium in the upper mantle, carbonatite melt has stronger chemical and physical activity than silicate melt. The occurrence of a small amount of carbonatite melt in the upper mantle will significantly affect its many geophysical and geochemical properties, such as electrical conductivity and element composition. Experimental studies at elevated conditions are important approaches to understand the chemical and physical effects of carbonatite melt. The physical and chemical influences of carbonatite melt are closely related to its distribution and geometry in the system, and a key factor of them for the characterization is the dihedral angle. Available studies on the dihedral angle (and various physical effects) of carbonate melt are normally carried out at extremely high temperature exceeding about 1 200 ℃, and the potential problem is that the complex reactions between the melt and solid minerals is inevitable and the experiment is difficult under extreme high temperature. In this work, in order to overcome the problems, the reported dihedral angle distribution in the carbonatite-olivine system at low temperature not exceeding 700 ℃ was measured by a low melting pointing carbonatite mixture. The experiments were conducted at 1 GPa with an end-loaded piston cylinder apparatus, and the dihedral angle distribution in the recovered samples were carefully examined by scanning electron microscopy. The results demonstrate a homogeneous distribution of melt in the system, and the observed dihedral angles are mostly 10°−40°, with the average values of 24°−27°. Consequently, this carbonatite has greater ability in wetting grain boundaries, and provides a new analog for future studies on the behavior and geophysical properties of carbonatite melt inside the Earth.

In our work, a series of Cu/PMMA composites with different components were prepared using the melting blending method, in which particles are randomly dispersed in PMMA matrix without agglomeration. Then again study was conducted on the Cu particles content’s influence on the sound velocity and impact compression behavior of PMMA matrix. The ultrasonic test results show that with Cu particles content increasing, the sound wave attenuation makes a slow decreasing tendency of transversal and longitudinal sound velocities in material, which in turn decreases its bulk sound velocity. Based on the plate impact test, the shock wave velocity-particle velocity (D-u) equations of Cu/PMMA composites in the impact pressure range of 1.1–6.0 GPa were obtained. Owing to the increase of the acoustic impedance of Cu/PMMA composites, Hugoniot parameter shows an increase while the fitted zero-pressure sound velocity tends to decrease, which turns to be consistent with the variation of bulk sound velocity at atmospheric pressure. In addition, pressure-particle velocity (p-u) curves of the composites were discussed on the basis of the p-u model. And a reliable method was proposed to predict pressure-density (p-$\;\rho $) relationship of polymer matrix composites filled with metal particles.

Our work introduces a double-sided top ultra-high pressure die with a steel ring and a carbon fiber composite ring preloading together. Compared with the double-sided top die of the full steel ring, a layer of carbon fiber composite material ring instead of the outermost steel ring is used in this new structure, which overcomes the challenges of manufacturing and processing large-diameter steel rings and makes a new mutual pre-tightening method, in which steel rings and composite material rings are used to pre-tighten the cylinder. Based on the numerical analysis, the mold structure is proved feasible, and it is further indicated that this structure can reduce the circumferential stress, maximum shear stress and equivalent stress of the cylinder to a certain extent. In addition, the failure of the carbon fiber composite ring is also identified in this work.

Due to the machining challenge of high-quality cemented carbide, ultra-high pressure devices are always limited on scale. In our work, a new type of wire wound and split ultra-high pressure die with two-anvil was proposed to try to overcome this limitation. The die is mainly composed of internal split cylinder and external prestressed steel wire. On the basis of the mechanical modeling and via the finite element software, the equal tension winding die was analyzed and the split pressure die as well as steel wire winding layer were studied. The results show that the maximum equivalent stress appears on the inner wall of the pressure die cavity after loading; the dimensional stability of pressure die cavity is proportional to the number of layers of wire winding and the diameter of the wire. The axial stress of the wire in the winding layer is inversely proportional to the diameter of the wire but proportional to the number of layers of the wire.

To better understand crack generation laws and failure modes of various rocks compressed under different strain rates, specimens made from limestone and red sandstone were respectively prepared and their crack formation under different strain rates and stress modes was investigated in both quasi-static and dynamic compression tests. High-speed photography was used to record cracks occurrence as well as failure modes. By analyzing the rocks’ physical properties, stress state, and energy evolution in comparison, reasons for the crack morphology variation in compression under different strain rates were obtained. It is shown that: (1) the failure modes of rock specimens under compression in the quasi-static range vary with strain rates, and the compressive strength of rock specimens are significantly effected by different failure modes; (2) the magnitude of incident energy determines the fluctuation of the dynamic compressive strength curve of the rock sample; (3) under dynamic compression, the circumferential growth rate of crack is positively correlated with the compressive strength of rock.

In order to study the mechanical properties of granite under different unloading confining pressure rates, tests for the granite unloading confining pressure stress path under constant axial pressure were conducted via RMT-150B rock mechanics test system. The results show that: under the same initial confining pressure, the ductility of rock sample gets decreased with the increase of unloading confining pressure rate, which is characterized by brittle failure. The higher the unloading confining pressure rate is, the greater the strain rate is in the duration of confining pressure unloading, but the total deformation keeps small. Under the same unloading rate, the higher the initial confining pressure is, the greater the strain rate as well as the total deformation is. Then using Mogi-Coulomb intensity criterion to fit the test results, it is concluded that the unloading confining pressure rate degrades the cohesion of granite and strengthens the internal friction angle of rock; the smaller the unloading confining pressure rate is, the longer the active period of ringing count is, indicating a slow but complete development of the internal damage in granite samples under low confining pressure release rate.

The mechanical properties of G50 steel and G31 steel under quasi-static, dynamic and detonation loading conditions are compared by tensile test, impact test, Hopkinson bar test and detonation loading test. The results show that the mechanical performances of G50 steel and G31 steel under static and 10³ s⁻¹ strain rate conditions are similar. The G50 steel and G31 steel exhibit similar failure morphology after detonation loading test, indicating that the two materials have similar tensile strength and yield strength under ultra-high pressure and ultra-high strain rate condition. The test results show that G31 steel can apply in the shell of penetrating the warhead.

In this study, axial compression experiments of 99 alumina ceramics at different strain rates were carried out. After soft recovering of the fragments at the corresponding strain rates, and geometrical characterization of the specimen fragments by the sieve residue method, the fragment size distribution curves at different strain rates as well as the energy absorption process in the failure of the specimen were obtained, and the relationship between the external force of the granular ceramic and the relative crushing rate was also established. Digital image correlation (DIC) technology is used to obtain the strain field along the loading direction at different strain rates, and the failure mode is analyzed in combination with the energy absorption process and fragment grading performance. The results show that the fracture strength of 99 alumina ceramics is positively correlated with the strain rate. At the middle strain rate, the energy absorption rate has a negative correlation with the strain rate. Due to the change of the energy absorption mechanism, the sample was fractured at the beginning, but the failure mode became split-crushing mixed failure when the strain rate reached 401 s⁻¹. With the strain rate increasing, the specimen became crushed and damaged. The average particle size decreases, the size of the fragments converges, and the influence of stress concentration gradually weakens. The relationship among energy, destruction process and fragment distribution was analyzed, and finally the fragment distribution law and fragmentation characteristics were obtained.

In this work, a numerical simulation was performed on the dynamic response process of the prestressed reinforced concrete (PC) box-girder bridge under implosion load via three-stage continuous coupling finite element method. Taking gravity and prestress into account, the damage mode of PC box-girder bridge was obtained. Besides, the failure mechanism was analyzed. It is shown that the PC box-girder bridge’s physical process from partial destruction to overall collapse can be theoretically reproduced by the three-stage continuous coupled finite element method. At initial stress stage, the stress of the PC box-girder bridge meets the requirement of the actual project. At local response stage, cracks occur at the connection between the web and the roof, and a break around the top and bottom flanges comes into being in the center. At overall response stage, influenced by the gravity and prestress, the box-girder bridge first arches up, then collapses and finally makes a bending failure.

Boundary condition exerts great influence on the failure mode of square plate under intensive loading. In this paper, a series of experiments of clamped square plates with different boundary chamfer radius were performed in the drop hammer impacting machine, in which the drop hammer was specially designed nearly same as the square plate in dimension and the supporting framework could offer various boundary conditions. The results show that: (1) the failure mode of large plastic deformation, one-side tearing and double-side tearing can be observed, and the square plates are more easily damaged under smaller boundary chamfer radius. (2) The boundary chamfer radius has a minor effect on the plate center displacement and deformation profile, but a major influence on the boundary tearing length and crack forming process. (3) The shear effect on the boundary region of clamped square plate would decrease with increasing boundary chamfer radius, and it is more easier for the plate with smaller boundary chamfer radius to get torn under the same intense impulsive loading. The critical failure strain of square plate is among [0.191, 0.241].

To improve the energy output efficiency of composite warhead, a HEAT-HE composite warhead is presented, which can release explosively formed penetrator, prefabricated fragments and natural fragments. With the numerical simulation software LS-DYNA, we analyzed how the initial detonation mode (including location, diameter and number of detonation points) affects the damage elements formation and energy output. Besides, a possible technical approach for the tunable damage-power warhead was also discussed. The results shows that: (1) When the donation points are wider and further away from the linear, the linear-formed damage element would get a higher tip velocity and a greater tip-tail velocity and length-diameter ratios. The greatest gain of velocity can reach up to 50% so as to lead the transformation from explosively formed projectile (EFP) to jetting projectile charge (JPC). (2) When the detonation points are located on the central axis of the charge, the damage element forming keeps only related to the point closest from the liner. (3) For the prefabricated fragment, the detonation velocity on the 60 mm charge height (P₂) is the highest. Its maximum velocity can get increased with the increasing detonation points with wider diameter, while its minimum velocity always keeps about 600 m/s with little variation. For the natural fragment formed by the shell, there isn’t an obvious variation of the average velocity, but a reasonable approach to detonate can make the fragments more homogeneous and benefit the adjustment of the fragments mass distribution. Therefore, it is feasible to make a tunable damage-power warhead by controlling the initiation detonation mode, but further research into the effects of the initiation mode on the fragment velocity is needed as well.

There is a possibility of gas leakage during the operation of gas distribution stations. The flammable gas mixture generated by the leaked gases may result in explosion accident and bring about great hazards to the public safety. Based on geographic information system (GIS) technology, the geometric model of urban block around a gas distribution station in Nanjing was established and imported in the CFD software FLACS to simulate the gas cloud explosion. The development process and overpressure distribution of gas cloud explosion around the gas distribution station under typical working conditions were revealed. The influences of gas cloud size, ignition position and gas cloud position on the explosion overpressure were discussed. In addition, the damage level of the gas cloud explosion was discussed based on the numerical predictions. The results show that the application of GIS technology can improve the accuracy and efficiency of the model significantly. When the size of gas cloud is larger than 60 m and with obvious restrictions or obstacles in the ignition position, gas deflagration may occur. When the gas cloud is located on the southwest side of the gasholder, the explosion will cause a wide range of minor injuries (damage) to people (buildings), and cause a certain range of serious injuries (damage) to people (buildings). In order to avoid the serious consequences of gas cloud explosion, the existence of tall and dense buildings near the gas distribution station should be avoided.

Explosion venting accidents in underground comprehensive pipe corridors occur from time to time, causing huge losses to ground personnel and property. Based on a pilot project of an underground comprehensive pipe gallery in Chongqing and the material point method, a high-energy combustion model is used to simulate the process of leaking methane gas explosive’s impact on the structure and surrounding rock of the pipe gallery. Through the simulation, the response characteristics of ground pressure and displacement are studied. The results show that: under the effect of explosion, secondary stress waves caused by reflection and refraction of the contact surface will appear in the pipe gallery and surrounding rock. In the transverse direction, the amplitude of the secondary wave increases with the increase of the horizontal distance from the initiation point, while that generated in the longitudinal direction keeps smaller, and the change remains small with the increasing distance. The explosion caused the overall ground subsidence, but the ground bulged near the center of the detonation point. This bulge was composed of a violent bulge formed by the pipe gallery lining broken and gas directly impacting the rock and soil, and a slight bulge formed by the overall vibration of the pipe gallery.

The surface mounted devices (SMD) crystal oscillator is widely used in various electrical and communication equipment or systems. The crystal oscillator is prone to structural damage under shock environment, which may results in abnormal operation of the system. The relationship between the level of structural stress response and the value of related shock response spectrum (SRS) is established and a more reasonable damage boundary form is obtained by analyzing the response characteristics of the single-degree-of-freedom (SDOF) system under shock loads with different frequencies. Based on the mechanical characteristics of the vulnerable component of a typical crystal oscillator, the corresponding simplified analytical model is established, and its structural damage boundary in a large frequency range is obtained. The finite element simulation software is used to simulate the response of crystal oscillator structure under shock loads within the frequency range of 0.5–30 kHz to verify the effectiveness of the structural damage boundary. This paper also provides a feasible method for the reliability study of various micro-components represented by SMD crystal oscillator under shock environment.

In order to improve melt-casting charge quality of the warhead with a large length-diameter ratio, a three-dimensional charge model was established by means of the finite element simulation method, and numerical simulation on the melt-casting charge process was carried out, including traditional casting and hot mandrel process casting. Then combined with the shrinkage principle and mechanism of the traditional hot mandrel process to improve charge quality, a multi-layered hot mandrel with optimized temperature controlling was proposed and its casting process simulation was undertaken to predict how it exerts effects on the charge quality. The results show that the radial solidification order of the grains can’t be changed and shrinkage as well as porosity would appear at the wider area of the explosive room in the traditional hot mandrel casting process. However, the defects of shrinkage and porosity can be avoided by changing the radial solidification order in the improved hot mandrel process, which just corresponds to our expectation.