Dynamic fracture behavior of rocks under blasting loading are a major concern in civil engineering, mining, oil and gas industries. This study presented herein is on the borehole blasting-induced fractures in rocks. The paper consists of two parts: the first part gives a brief description of a constitutive model for rocks subjected to dynamic loading, which is mainly based on a recently developed model for concrete; the second part deals with numerical simulations of borehole blasting-induced fractures in rocks. The values of various parameters in the constitutive model for granite are first estimated and then employed in the numerical simulations. It is demonstrated that the numerical results in terms of peak pressures and crack patterns predicted from the present model are in good agreement with the experimental observations made both in cylindrical granite sample reported in the literature and in square granite specimens conducted in our own laboratory. Moreover, the analysis shows that the experimentally observed crack patterns are mainly caused by tensile stress, while the smaller cracks around borehole are created largely by compression/shear stress.

High-entropy alloys have excellent mechanical properties, such as high hardness, high strength, high resistivity, excellent wear resistance, excellent magnetic properties, and high-temperature mechanical and oxidation resistance. This also makes high-entropy alloys have a very broad application prospects. In the application of high-entropy alloys, there will be pre-existing plastic strains in the alloys. However, the mechanical properties of plastic deformed high-entropy alloys (such as the hardness under micro-scale compression) were less studied. In the micro-indentation test, it is necessary to eliminate the influence of the scale effect by adopting the corresponding micro-indentation test theory. Dynamic pre-compressions of CoCrFeNiMn high-entropy alloy at room temperature and high temperature (600, 800, 1000 ℃) were performed with split Hopkinson pressure bar in this paper, so that the alloy has different pre-compression plastic strains, and Nix-Gao which describes the scale effect is adopted. The hardness of dynamic pre-compression specimens with different plastic deformations was characterized at the micro-scale with the micro-scale indentation theory model. The results show that different plastic deformations under macro-precompression have a significant effect on the micro-scale indentation hardness of the alloy. Compared with axial compression, the hardness that eliminates the scale effect is greater than that of sample under radial compression. This research method establishes the relationship between the macroscopic plastic deformation and the micro-scale indentation hardness, and also provides a new idea for the realization of the micro-scale indentation test to determine the research method of the internal plastic deformation of materials.

In this paper, an independently-designed system for explosion experiment is used to investigate the dynamic response law of hollow tempered laminated glass with plane size of 300 mm × 300 mm and 1000 mm × 1000 mm under explosive load. The influence of layer thickness of PVB glue, thickness of air layer, explosive quantity and explosion distance on the anti-explosive performance of hollow tempered laminated glass is analyzed. The results show that: (1) the anti-blast performance of hollow tempered laminated glass is enhanced with the increasement of the plane size; (2) for both large-size and small-size hollow tempered laminated glass, with increasement of the thickness of the PVB glue layer, both the overall strength of the structure and the load-bearing capacity of the sample increase gradually when the thickness of the intermediate air layer increases, the overall stability of the structure decreases and the anti-explosion ability become weaker; (3) changing the amount of explosives and the explosion distance has a strong influence on the dynamic response of the hollow tempered laminated glass. With the increasement of the explosive amount and the reduction of the explosive distance, the damage degree of the hollow tempered laminated glass increases gradually.

In order to investigate the dynamic response behavior of clamped square plates under the impact of the large-scale hammer, a large-scale hammer head was designed in combination with the drop hammer tooling. The impact tests of clamped square plates under different impact strength were carried out, and the typical failure modes of clamped square plates under the impact of large-scale hammer were obtained. Based on the experimental results and the impact dynamics theory, the deformation evaluation method of clamped square plates under the impact of large-scale hammer was established. In addition, the boundary tearing criterion of clamped square plates was established by combining simulation analysis. The results indicated that the energy dissipation of clamped square plates under the impact of the large-scale hammer mainly depended on the plastic hinge and in-plane plastic hinge, and the initial tearing firstly occurred in plate boundary. Moreover, the plastic deformation evaluation method of clamped square plates established by the plastic hinge energy dissipation mechanism was in good agreement with the experiment results. In addition, the value of the stress triaxiality at the initial tearing position was nearly 0.6 during the tearing process of the clamped square plates. According to failure criterion established in this paper, the value of B_h was 1.6 times plate thickness. The evaluation method and failure criterion presented in this paper further improve the research on the dynamic response behavior of clamped square plates under the impact of the large-scale hammer.

The effect of solution temperature on the dynamic mechanical properties and microstructure of near-β-phase TB6 titanium alloy was studied. Dynamic compression tests were carried out through the split Hopkinson pressure bar (SHPB) system, with untreated and treated TB6 titanium alloy specimens. The results indicate that both the untreated and treated TB6 titanium alloys perform the strengthening effect of strain rate, and their compression mode is exhibited as the typical shear failure. The solution temperature that converts the strain hardening of TB6 into strain softening is ranging from 700 ℃ to 750 ℃. The microscopic performance characterized by optical microscope (OM), X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods show that the primary α-phase in TB6 is partially dissolved and the strength decreases after a solution treatment at 700 ℃. When the solution treatment is equal to or greater than 750 ℃, the primary α-phase is completely transformed into β-phase. The β grain becomes bigger and the strength increases, but the plasticity decreases evidently.

To study the mechanical properties of glass fiber reinforced plastic composites under static and dynamic loading, compression experiments were conducted in two directions using a materials testing system (MTS) and a split Hopkinson pressure bar (SHPB). The typical damage pattern of the composites was obtained by scanning electron microscopy (SEM). The results show that the material has strong strain rate sensitivity and anisotropy. Delamination damage and interlaminar crush are the factors that caused the in-plane and out-of-plane loading damage, respectively. The microscopic analysis of the fracture shows that the degree of fiber-matrix fragmentation is higher under dynamic loading. The force between the fiber-matrix interface is stronger, which may be one reason for the difference in the dynamic and static mechanical response of the material. A compressive constitutive model with strain-rate and damage effects was developed to accurately describe the dynamic compressive stress-strain behaviors of the composite along the two perpendicular directions.

In this paper, Al/W active materials with different W additions were prepared by molding and sintering processes. Based on the split Hopkinson pressure bar (SHPB) technology, copper sheets and rubber sheets were used for wave shaping, and dynamic compression and destruction characteristics of Al/W materials with different ratios were evaluated. The experimental results showed that with the increase of W additions, the pores and microcracks inside the Al/W material gradually increased. With different W additions, the dynamic compression deformation and failure characteristics of the Al/W material exhibited obvious differences. When the mass fractions of W are 44% and 64%, the stress-strain curves of Al/W under different strain rates exhibited elastic-plastic strengthening deformation characteristics, and the failure strain increased with the increase of strain rate. Al/W materials with a W mass fraction of 83% exhibited the strain softening characteristic in the plastic deformation stage. When the W mass fraction reached 91%, the Al/W material failed quickly after reaching the breaking strength, and the breaking strain is maintained at about 0.03. With the increase of W additions, the transformation of Al/W deformation mode is the result of the interaction between the reinforcing phase W and the internal defects of the material.

A combination of numerical simulation and theoretical analysis is used to study the dynamic response of foamed aluminum filled pipes under lateral explosion loads. The finite element software ABAQUS/EXPLICIT was used to carry out a numerical simulation study on the plastic deformation of the aluminum foam-filled tube under lateral explosive load, and the influence of the relative density of the foam aluminum, the diameter and wall thickness of the outer tube and other factors on the dynamic response of the structure was analyzed. Based on the ideal rigid-plastic foundation beam model, combined with the modal analysis method, a theoretical analysis model for predicting the mid-span deflection of the foamed aluminum filled pipe under lateral explosive load is established, and a dimensionless analysis is carried out. The change of the dimensionless deflection of the mid-span with the elementary impulse is obtained. The error between the theoretical prediction and the numerical simulation result of the foamed aluminum filled pipe mid-span deflection is within 20%, indicating that the established theoretical analysis model is reasonable and feasible. The relative density of foamed aluminum has a great influence on the mid-span deflection of the filled pipe under lateral explosive load. As the relative density of foamed aluminum increases, the mid-span deflection of the filled pipe decreases. As the diameter and wall thickness of the outer tube increase, the mid-span deflection decreases. The two modal functions assumed in the theoretical analysis have little effect on the mid-span deflection of the filled pipe.

Rock mass is a discontinuous medium composed of intact rock and joints, whose mechanical properties are mainly determined by the geometrical and mechanical characteristics of joint. It is significantly valuable to explore the influence of joint on the mechanical behaviors of rock mass. In this paper, a synthetic rock mass model (SRM) is established by PFC2D software at first. Then the influence of joint geometrical parameters on rock mass mechanical properties, such as the strength indices and failure modes under uniaxial compression are studied. Through the orthogonal experimental analysis, the influence of the joint geometrical parameter on the strength index of rock mass is discussed. The analysis results show that when the joint dip angle is between 10° and 50°, the joint length, dip angle, spacing and rock bridge length have significant effect on the uniaxial compressive strength and elastic modulus of rock mass. When the joint dip angle is between 50° and 90°, the influence of the rock bridge length on the uniaxial compressive strength and elastic modulus of rock mass is not significant. The joint step angle has no significant influence on the uniaxial compressive strength and elastic modulus of rock mass no matter how much the joint dip angle is. The failure mode of rock mass is mainly affected by the joint dip angle and step angle. The research results provide valuable reference for the stability analysis of rock mass and the support design.

Iron is one of the typical d-orbital transition metals. Its melting behavior and melting curve at high pressure are of great importance for revealing the composition, thermal structure, and thermal evolution of the Earth’s core. Creating the extreme high pressure-temperature conditions and measuring the melting temperatures of the condensed matters in the laboratory are quite challenging, resulting in a long-term controversy on the melting curves of iron at high pressures among various experiments and between experiments and theories. With the development of various experimental techniques, the results between experimental and theoretical studies are generally consistent with each other. This review presents the main static and dynamic compression techniques that have been used to study the high-pressure melting curve of iron in recent years; it also explores the advantages and disadvantages of melting diagnostics for iron and transition metals. The possible reasons for the discrepancy in the melting curves of iron are also discussed. Based on the experimental and theoretical results of the melting curve of iron, the melting temperature of iron can be anchored to 5900–6300 K at the pressure of the inner core boundary (ICB, about 330 GPa). Summarizing the current researches on the melting behaviors of iron under static and dynamic compression has an important implication for studying the melting curves of other transition metals, as well as the melting mechanism.

Dynamic pressure loading/unloading device is one of the most important devices which has been paid much attention recently in high pressure research field. It can be effectively used for the preparation of metastable materials, phase transition kinetics, ultra-high pressure chemistry and so on. And it shows many other important application prospects in materials science, condensed state physics, chemistry, and geonomy and so on. In this project, the research progress of dynamic pressure loading/unloading devices and in-situ characterization technology in recent years are summarized, and a novel dynamic pressure loading/unloading device with large pressurization rate and measurable pressure range is developed, which is also combined with both time-resolved spectroscopy test system and in-situ heating/cooling system. It will be a new breakthrough in the research field of high pressure science and technology. And this device can effectively improve the basic research facilities and improve the research on discovering novel structure and functions of materials in the field of high pressure science and technology.

A novel B-C-O compound, B₄C₆O₄, was predicted by combining the candidate structure generated by the particle swarm optimization algorithm and first-principles stability analysis. B₄C₆O₄ has a direct bandgap semiconductivity characteristic with a bandgap width of about 2.25 eV. B₄C₆O₄, B₂CO₂ and B₄CO₄ have similar structures and belong to the BC_xO series. It was found that the decrease of carbon content led to the increase of the band gap of the system, and the molecular formula volume decreased synchronically with the decrease of carbon content, and the high pressure of 100 GPa compressed the volume of the three as high as 20%. The band gaps of B₂CO₂ and B₄C₆O₄ continue to decrease due to the effect of high pressure, while the band gap of B₄CO₄ rise first and then fall. The stress-strain simulation results showed that the three BC_xO compounds (x = 3/2, 1/2, 1/4) all have high ultimate tensile stress, and the strain would affect the band gaps of the three BC_xO compounds. The mechanical properties of three BC_xO compounds showed that they all had high modulus of elasticity and hardness. The highest phonon vibration frequencies of BC_xO under chamber pressure are higher than 30 THz, and the relationship is B₄CO₄ > B₂CO₂ > B₄C₆O₄. The effect of high pressure will cause the continuous enhancement of the bond energy of the system.

δ-(Al,Fe)OOH is regarded as a potential water carrier to core-mantle conditions, thus its high pressure structural behavior is important for understanding water circulation in the Earth’s interior. In this study, the compression behaviour of 8 mol.% Fe-bearing δ phase (δ-Fe8) is investigated using diamond anvil cell combined with synchrotron X-ray diffraction. The obtained pressure-volume (p-V) data show that δ-Fe8 experiences phase transitions from order to disorder of hydrogen and high spin to low spin of iron in the pressure range from ambient pressure to 78 GPa. The order to disorder transition of hydrogen takes place at 9.7 GPa characterized by the subtle kinks in the p-V profiles and the inversion of pressure dependence of a/c and b/c axial ratios, which accompany with a change in the crystallographic symmetry from P2₁nm to Pnnm. The isostructural iron spin crossover occurs between 31.5 and 39.5 GPa accompanied by 2% volume collapse. The compressional parameters are derived from fitting of p-V data using Birch-Murnaghan equation of state. The mixed-spin state of δ-Fe8 within the spin crossover region is treated as an ideal solid solution of the high spin and low spin state, then the fraction of low spin state is obtained by fitting experimental data. The calculated bulk moduli and bulk sound velocity soften across spin crossover, indicating that an accumulation of δ-Fe8 in middle part of lower mantle possibly leads to low bulk velocity anomalies. The linear relations between ferric content and structural transition pressure in δ-(Al,Fe)OOH are given with the combination of this study and previous results.

In order to analyze the influence of different initial conditions on the interior ballistic performance of hydrogen-oxygen detonation gas gun, a two-dimensional numerical model of hydrogen-oxygen detonation gas gun was established by using FLUENT software, which is based on the computational fluid dynamics method. The validity of numerical model was verified by launching experiments of 40 mm caliber gas gun. The influence mechanisms of initial pressure, nitrogen content and reaction gas ratio on the interior ballistic performance of hydrogen-oxygen detonation gas gun were revealed by numerical calculation. The results show that, increasing the initial pressure and nitrogen content of the gas chamber can effectively improve the projectile launching speed, while nitrogen can reduce the average temperature of the gas chamber and improve the energy utilization rate of the reaction gas. The results indicate that there exists an optimal ratio of reaction gas dose, injecting nitrogen with proper content can improve the energy utilization and get higher launch speed under the same initial pressure.

In order to analyze the mechanical response and damage-ignition process of typical explosive charges in projectiles during penetrating concrete targets, the combined microcrack and microvoid model (CMM) were used to investigate the compressive wave propagation, damage and temperature rise mechanism of PBX charge in penetration process. The constitutive model parameters of two kinds of explosives were calibrated. Meanwhile, the difference between two typical PBXs (pressed PBX04 and casted GOFL-5) in response to penetration process is compared. The results show that, the yield strength, hardening modulus, initial microcrack density and microcrack size of GOFL-5 are lower than those of PBX04. The damage of microcrack in the head of PBX04 is higher than that of GOFL-5 in the initial loading stage. During the whole penetration process, the most serious microcrack damage areas of the two kinds of explosives are the head and tail. Shear-crack hotspot is the dominated ignition mechanism for PBX04, and the temperature rise of GOFL-5 is lower than that of PBX04.

In order to study the overall damage characteristics of hull girder subjected to non-contact underwater explosion, a numerical method was established in which an explosive charge was located at the mid-span of the hull girder. The effectiveness of this method was verified by the model test. The damage mode and frequency response were studied to analyze the overall response of the hull girder. Results showed that the numerical method can simulate the response period and amplitude of the hull girder during the first bubble pulsation phase. When the bubble pulsation frequency approximated the first wet frequency of the hull girder, the response mode of girder will transform from whipping motion to sagging with the decrease of the ratio of stand-off to maximum bubble radius.

This paper is focused on a special-shaped projectile with ribbed plate head. In order to explore its penetration ability and trajectory stability, the 152 mm diameter light gas gun was used to launch projectiles to penetrate concrete targets of 300 mm thickness at different angles within the speed range of 250–350 m/s. In the meantime, numerical simulations of ogive-nose projectile and ribbed-head projectile perforating concrete targets with different velocities and inclination angles were implemented with LS-DYNA, and the simulation results are in good agreement with the experimental results. The experimental and simulation results show that oblique penetration will reduce the penetration ability and affect the trajectory stability of projectile. Under experimental conditions, the main damage of the target plate includes the open pit area and the shear plug area. The crater area will increase the attitude angle of projectile, while the caving zone will reduce the attitude angle. Compared with the ogive-nose projectile, although the penetration ability of the special-shaped projectile decreases due to the increase of the action area, the rib structure of the special-shaped projectile makes the missile body suffer less deflection moment when the projectile intrudes into the target, which makes the projectile body have an excellent anti-deflection effect and trajectory stability.

In order to find a new way to improve the output performance of explosives, the coupling of external electrical energy and explosive energy of the explosive itself was studied. At the same time, an explosion-electricity coupling (EEC) device was designed and set up, and a flat RDX plastic explosive was selected as the research object. The detonation velocity measured by the detonation velocimeter and the detonation pressure measured by the photonic Doppler velocimetry were used as the main characteristic parameters of the EEC gain to study the effect of the EEC on the output performance of the explosive. By analyzing the electrical properties of explosives in the process of EEC, the reaction process of EEC was qualitatively analyzed, and the possible mechanism of the EEC of RDX plastic explosives was proposed. The research results show that the EEC can effectively deposit electrical energy in the explosive reaction zone. In the premise of ensuring the same other conditions, the EEC can increase the detonation velocity, von Neumann spike pressure and Chapman-Jouguet pressure of RDX plastic explosives to a certain extent. The above work puts forward a way to enhance the output performance of explosives through theoretical and experimental research on EEC, which has a certain theoretical value and guiding significance for the research on the enhancement of explosive performance in the future.

Based on the fire and explosion-proof mechanisms of porous materials, pipeline explosion system, pressure sensor, high-speed camera and other equipment were used to study the suppression effects of natural luffa sponge (different filling positions: 1.9 and 4.4 m from the ignition location; different filling lengths: 5, 8 and 10 cm) on the explosion pressure and flame propagation in premixed methane/air gas with methane concentration of 9.5% by volume. The experimental results show that: under different conditions, luffa sponge has inhibitory effect on the explosion pressure and flame propagation. Meanwhile, it has the obstruction pressure effect. When the luffa was filled at a distance of 1.9 m from the ignition location, its inhibition effects on the explosion pressure and flame propagation rate are better than those of filling position at 4.4 m. When the filling position of luffa is constant, the filling length exerts significant influence on the explosion pressure and flame propagation rate. When the material was filled at a distance of 1.9 m from the initial detonation point, the flame propagation was completely blocked by the three lengths of loofah, and the material with the filling length of 10 cm has the best explosion suppression effect. Compared with unfilled condition, its maximum explosion pressure and maximum explosion pressure rising rate decrease by 73.90% and 71.72%, respectively.

Aiming at the transient dynamic response of drone aircraft cushion landing with airbag, the explicit dynamic calculation method and pressure equalizing airbag model are adopted to analyze the dynamic response of drone aircraft fuselage and wings under impact during cushion landing with airbag, and the attitude and strength characteristics and airbag parameters in the recovery process of drone aircraft are obtained. The effects of airbag cushion parameters (orifice area, initial internal pressure and exhaust threshold) and drone aircraft state on the fuselage of drone aircraft during landing are discussed. The results show that: under the standard conditions, the aircraft’s attitude and strength meet the requirements of safe landing after buffering with airbag. Through the analysis of different landing parameters, it is found that the area of the airbag exhaust vent has a great impact on the cushioning effect, while the threshold of the airbag exhaust pressure and the initial internal pressure have little impact on it. The same airbag has high adaptability to different initial landing speeds of drone aircraft. The local stress of the later landing fuselage of the drone aircraft with pitch angle is too large. This method can be widely used in the dynamic calculation of aircraft airbag cushion. Combined with the airbag drop test, the corresponding airbag parameters and fuselage structure response data can be obtained, which provides a basis for the design of target aircraft.