TATB (1, 3, 5-triamino-2, 4, 6-trinitrobenzene), as one of the typical high-energy insensitive explosives, has important research value in national defense and military applications. Based on the Science Challenging Program (SCP), this work provides a detailed overview of the research progress on physical properties of TATB under extreme conditions in terms of experimental technology and experimental results. This paper systematically introduced the spectral test system and some instruments about high temperature and high pressure independently designed and built by our research group, and studied the light absorption and the structural evolution on TATB under high pressure. Additionally, the structural stability of explosives under low temperature and thermal stability of explosives under high temperature and the effect of pressure on the chemical decomposition process and thermal decomposition mechanism of the sample were elaborated and discussed.

HMX is a high-energy explosive with excellent performance and is widely used in weapons. The phase transition law of HMX, especially under non-hydrostatic pressure, is controversial. In this work, a high-pressure Raman experimental study of HMX crystals under non-hydrostatic pressure was carried out using different pressure-transmitting media. The HMX crystal undergoes three phase transitions at pressures of 4.9, 13.9 and 17.5 GPa, respectively. Under the pressure of 13.9 GPa, HMX began to undergo phase transition from structure Ⅱ to structure Ⅲ, and the two phases existed simultaneously within a certain pressure range; another new phase (structure Ⅳ) began to appear from 17.5 GPa. The three-phase coexistence of structure Ⅱ, structure Ⅲ and structure Ⅳ appeared in the pressure range of 17.5−23.6 GPa. Importantly, the phase transition process of HMX crystals under non-hydrostatic pressure is completely different from the phase transition path under quasi-hydrostatic pressure, and the pressure gradient under non-hydrostatic pressure environment is the reason for the difference.

A ramp wave compression experiment of (100) RDX single crystal under 35 GPa was carried out with the magnetic driven 10 MA device and laser interferometry, and then the interface velocity data of RDX single crystal/LiF window were obtained. The experimental results show that the velocity wave profile shows a three wave structure, which corresponds to elastic wave, plastic wave and phase transition wave from low to high pressure. The onset pressure of α-γ phase transition is 3.1 GPa. One dimensional hydro-dynamic simulation of ramp wave compression process of RDX single crystal was also carried out by combining the modified Hayes multi-phase equation of state and non-equilibrium phase transformation dynamic model. The calculated and experimental data are basically consistent.

The crystal structure, phase transition and microstructure changes of explosive crystals have important influence on the properties of explosives. In order to study the high temperature phase transition of HMX crystals and the effect of the cracks caused by them on ignition, we performed in situ high temperature Raman spectroscopy and X-ray diffraction on HMX crystals. Moreover, drop weight experiments were also carried out for HMX crystals with different cracks and phase structures. The effects of different temperature loading and post-treatment methods on the phase structure and microstructure of HMX crystals were identified by Raman spectroscopy and X-ray diffraction spectroscopy. Samples with different phase structures and cracks were prepared, and the decoupling of the HMX phase structure and the effect of cracks on ignition was realized. The results of the HMX crystal drop-weight impact experiment showed that the order of sensitivity of the three types of HMX crystals under the drop-weight impact was: crack-containing β-δ phase > β phase with cracks > β phase without cracks. And the reasons why high temperature phase transition and cracks can improve the crystal sensitivity of HMX were also analyzed.

At high temperature loading, the thermal expansion and solid-solid phase transition firstly occur in HMX-based PBXs prior to the melting and decomposition of HMX crystal, thereby inducing the abrupt change of mechanical and safety properties. A constitutive model integrating with several deformation mechanisms, including thermal expansion, and phase transition was developed to investigate the effects of heating-induced phase transition on damage evolution. The influence mechanisms of phase transition in binder-bonded HMX single crystal on the volumetric deformation, stress states and crack nucleation and growth were revealed from the viewpoint of mechanics. The effects of heating rate on phase transition and crack related damage evolution were quantitatively analyzed. The calculated results show that, as the increase of loading temperature, tension stress formed due to the thermal expansion and $\,\beta $→$\delta $ phase transition in unilateral-restrained HMX crystal and local shear stress formed due to mutually compression between crystal and binder, contribute to the nucleation and growth of HMX crystal. The number density of cracks exhibits a remarkable growth near the phase transition temperature, thereby inducing the irreversible damage. The heating rate has a significant influence on the nucleation and growth of cracks. Large heating rate will increase the crack related damage level of crystal, thereby increasing the number density of potential hotspots and risks of inadvertent ignition.

The coal measures sandstones in hard rock roadways were collected as the research samples, and a modified dynamic and static combined split Hopkinson pressure bar (SHPB) system was adopted to perform one-dimensional cyclic impact compression tests with the axial pressure of 5, 15 and 20 MPa and the impact pressure of 0.8, 1.0 and 1.2 MPa. Experimental results indicate that the peak stress of sandstones increase and then decrease with the increase of the impact times, while the peak strain, maximum strain and average strain rate show the opposite trends in the whole cyclic impact process without considering the axial pressure and impact pressure. Under the same impact pressure, the peak stress and cumulative cyclic impact times decrease with the increase of the axial pressure, while under the same axial pressure, the peak stress increase with the increase of the impact pressure, and cumulative impact times increase and then decrease. Under the action of one-dimensional coupled static and cyclic impact loads, the whole impact process of sandstone could be divided into the compacted stage, the internal crack development stage and the accelerated failure stage. The results of this experimental study show that the high probability of deep underground mine prop is caused by the interaction between static and dynamic loads, and the frequent disturbance of dynamic load is one of the key influencing factors.

Spall fracture is one of the most important issues in the study of dynamic damage for materials. The damage characteristics and mechanism show obvious phased rules with different loading strain rates. At present, the study on spallation characteristics, laws and mechanisms of materials under ultra-high strain rate has become an important part of the research on dynamic response characteristics of materials under extreme conditions, and is of great significance in the field of engineering application and basic research. In this paper, the spallation experiment of aluminum under femtosecond laser driven shock loading is carried out. The velocity profile on free surface of aluminum is measured by using the self-designed ultrafast chirped frequency domain interferometry system. The spallation strength of aluminum under 10⁹ s⁻¹ strain rate is about 7 GPa, and the variation of spallation strength with strain rate is analyzed.

Electronic interconnected conductive adhesive has a wide range of application prospects in portable electronic products. It is often subjected to drop impact conditions during service, resulting in a relatively high strain rate at the bonding point of tiny conductive adhesive. Therefore, the research on the mechanical behavior of conductive adhesive under a higher strain rate and the drop reliability of bonding point is particularly important. Herein, the rate-dependent properties of the epoxy resin-based isotropic conductive adhesive (ICA) with silver conductive particles were investigated by using the universal testing machine and the split Hopkinson pressure bar. Furthermore, the numerical simulation analysis of the conductive adhesive interconnection package structure under drop impact was carried out. The dynamic results show that the cured ICA is sensitive to strain rate. It is clear that the key bonding point appears at the four corners, and the small-angle drop is more dangerous than that of the horizontal drop. The long-side drop mode results in a relatively large stress and strain at the key bonding point in comparison with that of the short-side drop mode.

In order to study the dynamic response and damage of square steel tubular structural components under near-field multiple blast loads, the explosion resistance performance of square steel tubes is obtained from the number of equal parts, the charge mass ratio and the initiation time interval at the same total explosive charge based on the explosion test. The results show that when the total explosive is equally divided with simultaneous detonation, the deformation on the front surface and the deflection of the tube under multiple blast loads are both larger than that of the tube under single blast load by 17.5% and 32.1%, respectively. For two explosive loads, when the mass of the two explosives is close, the deformations on the front surface and the deflection are greater than that the mass of the two explosives is quite different by 18.3% and 19.7%, respectively. For multiple blast loads, when the distance between the explosive center of each explosive and the mid-span of the tube is equal, the deformation on the front surface of the tube with non-simultaneous detonation is smaller than that of the tube with simultaneous detonation by 4.3%, and the longer the initiation time interval is, the smaller the deformation will be. When the distance between the explosive center of each explosive and the mid-span of the tube is not equal, if the initiation time of the explosives is appropriate, the deformation on the front surface of the tube with non-simultaneous detonation can be larger than that of the tube with simultaneous detonation by 13.9%.

The dynamic compression experiments of ZL101A aluminum alloy were carried out under room and high temperature conditions by using split Hopkinson pressure bar (SHPB) system and high temperature heating equipment. The dynamic compressive stress-strain curves under the conditions of strain rate range of 2900−6100 s⁻¹ and temperature range of 20−600 ℃ were obtained. The experimental results show that ZL101A aluminum alloy has a strain rate hardening effect, and the strain rate hardening effect gradually decreases with the increase of temperature. Meanwhile, ZL101A aluminum alloy has obvious temperature softening effect at different strain rates, and the plastic deformation induced adiabatic temperature rise enhances the thermal softening effect. In order to quantify the influences of strain rate and temperature on the flow stress of ZL101A aluminum alloy, the strain rate effect and the temperature effect were decoupled. A suitable constitutive model for ZL101A aluminum alloy was established by analyzing and fitting the experimental data. After comparing the predicted results from the model with the experimental data, it was found that the established constitutive model can well describe the flow stress characteristics of ZL101A aluminum alloy.

The study on damage and fracture in superconducting Nb₃Sn is an indispensible part of understanding the origin of strain sensitivity in Nb₃Sn. In this paper, by using molecular dynamic simulations, the fracture and crack propagation behavior of single crystal Nb₃Sn with ideal lattice and with central crack at extreme low temperature are studied, respectively. The strain rate effects on the crack initiation and growth in both Nb₃Sn sample cases are also carefully analyzed. The results show that for stressed Nb₃Sn single crystal with ideal lattice, it slips with the dislocations plugging emerging on the slip band, which contributes to stress concentration and atomic bond breaking, resulting in the failure of Nb₃Sn. While for Nb₃Sn single crystal with central crack, the atomic bonds break due to the stress concentration concurring at the crack tip, microcracks form and propagate to induce the Nb₃Sn fracture. The analysis on the damage fracture and failure mechanism of single crystal Nb₃Sn at different strain rates reveals that it shows brittle fracture at low strain rate and ductile fracture at high strain rate.

Bionic design structures have received wide attention for their excellent mechanical properties and potential applications in engineering fields. In the bionic context, a new horsetail bionic thin-walled structure is designed and its energy absorption characteristics under axial compression are investigated. The results show that the specific energy absorption (SEA) of the bionic thin-walled tube is increased by 34.74% and the compression force efficiency is increased by 37.50%; the specific energy absorption of the bionic thin-walled structure increases monotonically with the wall thickness; the impact resistance of the thin-walled structure is the best when the number of ribs is 4 for a certain mass; the SEA is almost not lost when the rib thickness is constant. The initial peak force of the thin-walled structure can be reduced by adjusting the rib angle with constant rib thickness. To further improve the energy absorption capacity of the thin-walled structure, a multi-objective optimization was performed using the internal radius, rib angle and rib thickness as design variables. The response surface methodology (RSM) and genetic algorithm (NSGA-Ⅱ) were used to maximize the SEA while minimizing the peak crushing force. The SEA of the optimized thin-walled structure was improved by 13.42% compared to the initially designed thin-walled structure.

Structural integrity is an important basis for the design and manufacture of hydraulic accumulator. In order to determine the maximum bearing capacity of an accumulator shell under internal pressure, the plastic limit load and failure location of the shell are studied based on elasto-plastic analysis, numerical simulation and experiments. The results show that the perfect elasto-plastic analysis is obviously higher due to the lack of consideration of the wall thickness. Although the strain strengthening effect is ignored, the calculation result of nonlinear finite element method using step-by-step iteration of load factor is very close to the measured value of the blasting test with an error of only 3.5%, and the predicted plastic failure is consistent with the actual fracture. It shows that the Risk method is more accurate and can be used for the analysis and design of simple thin-walled pressure vessels.

In order to study the energy release law of a charge with a non-circular cross-sectional structure under the influence of initiation modes, the energy release characteristics of the charge with a non-circular cross-sectional structure under different initiation modes were calculated by AUTODYN simulation software, then effects of initiation modes on the evolution of detonation waveforms, and masses and initial velocities of fragments were analyzed. The results show that, due to particularity of the charge’s structure, energy distribution of the charge is uneven when using single-endpoint initiation, which results in a large number of invalid fragments with small masses in some areas, and a large fluctuation of initial velocities of fragments at different positions. When the two-endpoint and three-endpoint initiation modes are adopted, the detonation energy is homogenized, the number of invalid fragments is reduced, and the consistency of fragments’ initial velocities is improved. It proves that the energy output structure of a charge with a non-circular cross-sectional structure could be effectively regulated by adjusting the initiation mode, and the circumferential energy field could be homogenized.

In order to improve the design level of anti-explosion capability of protective structure of ships, it is necessary to reveal the influence of changes in typical structural parameters of ships on their damage characteristics. The trapezoidal cross-section girder, of which the size and structural characteristics are close to those of a typical military ship the real ship is designed. The underwater explosion load of each calculation condition is obtained by using Geers-Hunter theoretical formula. Based on ABAQUS finite element numerical analysis method, the structural response characteristics of the girders with different parameters such as length, outer plate thickness, depth and width subjected to underwater explosion were compared and analyzed. A dimensionless structural strength factor that can characterize the influence of each typical structural parameter on the overall structural strength of the girder is proposed. The results show that the coupling between bubble pulsation and structure natural frequency leads to sagging deformation when the pulse duration of bubble is close to the natural frequency of the girder. The increase in the length causes the reduction in bending resistance of the structure. The initial hogging deformation increases slowly and the maximum sagging deformation increases significantly; the increase in the outer plate thickness, depth and width lead to the decrease in the initial hogging deformation and maximum sagging deformation of the structure during the response. The initial hogging deformation is less sensitive to the change of structural parameters than the maximum sagging deformation. The dimensionless structural strength factor proposed in the paper can characterize the overall strength of the girder structure.

In order to enable warhead to have multiple directional damage modes and to achieve a certain degree of controllable damage, a deformable directional fragment warhead with fan-shaped charge is proposed. It can realize an axial-expanding mode and an lateral-expanding mode. The AUTODYN software is used to carry out the numerical simulation of the fragment field. Firstly, the position of the initiation point at 25 mm away from the central axis is determined based on the analysis of the unit constituting the warhead. Secondly, for the axial-expanding mode, the influence of the axial-expansion angle on the fragment flying speed, the quantity and the spatial distribution of fragments are obtained. The results show that the damage effect of the warhead is better when the axial-expansion angle is in the range of 60°–75°. Thirdly, for the lateral-expansion mode, the velocity and the spatial distribution of fregments are analyzed. It showes that the fragments under the lateral-expansion mode have directional flying quality.

An explosion in the subway station will lead to huge losses of personnel and property. In order to study the response law of subway platform and surrounding rock of a subway station project in Shanghai under the action of solid explosive explosion, HJC model is embedded in the open source material point method program. The results show that the response pressure of platform roof and floor will decrease rapidly after reaching the peak in a short time under the influence of explosion wave, and the platform structure forms tension zone and compression zone during explosion. Due to the superposition of stress wave and reflected wave, overpressure sudden change zone will appear at the platform side wall. The whole platform structure sink under explosion. Moreover, the surrounding rock directly below the detonation point forms a collapse pit, and the surrounding rock directly above the detonation point and the station structure rises up. The damaged area is mainly concentrated in the bottom plate of the structure, and the damaged area is oval. The blast resistance of platform with column area is stronger than that without column area.

In order to study the influence law and degree of premixed gas length, pipeline spacing, pipeline thickness and pipeline yield strength on the failure of the adjacent pipeline under the action of natural gas explosion in the gas compartment of the utility tunnel, a three-dimensional model of the gas compartment is established based on the actual case by using the nonlinear finite element software ANSYS/LS-DYNA to obtain the ovality change of the adjacent pipeline. The results show that under the action of natural gas explosion, the ovality of the adjacent pipeline is positively correlated with the length of premixed gas, and negatively correlated with the thickness and yield strength of the pipeline; the ovality of the adjacent pipeline is negatively correlated first and then positively correlated with the pipeline spacing, the safest pipeline spacing in this gas compartment is 0.74 m; the yield strength of the pipeline has the least influence on the ovality of the adjacent pipeline; the change rate of influencing factors is in the range of 1%–12%, 13%–18% and 19%–25%, the factors that have the greatest influence on the ovality of the adjacent pipeline are the length of premixed gas, pipeline thickness and pipeline spacing. This research can provide a reference for the design of the gas compartment in the utility tunnel.

Deep coal seam has high geostress, high gas content and low permeability coefficient, which seriously threaten the safety and efficiency of coal production, so it is necessary to strengthen the permeability enhancement and improve the gas extraction rate. Hydraulic blasting has the characteristics of high energy transfer efficiency and good safety, and can be better applied to the permeability enhancement of deep coal seam. In order to study the crack propagation regularity of hydraulic blasting in deep coal seam, LS-DYNA numerical method was used to analyze the effect of fracture of coal seam under different geostresses, uncoupling coefficient and coupling medium. The results show that the geostress can reduce the impact load caused by hydraulic blasting. With the increase of geostress, the crack length of coal seam becomes shorter and the range of crack zone decreases. When the geostress is within the range of 1−20 MPa, the attenuation trend of blasting stress wave weakens gradually with the increase of geostress. With the increase of the uncoupling coefficient, the range of crushing zone decreases, the range of fracture zone increases at first and then decreases. When the uncoupling coefficient is in the range of 1.0−3.0 and the uncoupling coefficient is 2.0, the blasting cracking effect is the best. When blasting in different coupling media, and the range of blasting fracture zone in water is larger than that in air. The maximum effective stress produced by blasting in water is 1.35 times higher than that in air, the water is more beneficial to the propagation and development of coal seam cracks. This research results have a certain guiding role for the engineering practice of crack propagation and permeability enhancement caused by hydraulic blasting in deep coal seam.

The fracture characteristic of mineral component interface refers to the stress, strain and other processes generated by the bonding interface under the action of external load. It is of great significance for studying the dissociation of component minerals and improving the efficiency of ore crushing. To further study the characteristics of mineral accumulation and non-uniform distribution of useful minerals in the ore, the internal rock facies analysis and the mineral interface in-situ loading experiments were carried out. Based on these two experiments, the non-linear, multi-scale modeling platform DIGIMAT was employed to construct the coincident group. The representative volume element (RVE) model of the mineral microstructure is divided, and the in-situ crushing simulation of the ore RVE model is carried out through the DIGIMAT-ABAQUS coupling. It is suggested by these results that: (1) The useful minerals in the studied wolframite ore are distributed in granular form inside the ore, mainly in the quartz mineral and the bonding interface with the siliceous rock mineral. (2) The mechanical properties of the bonding interface with different components are related to the physical properties and morphological characteristics of the constituent minerals. The minimum fracture stress range of the quartz-siliceous rock interface is 1.1785–1.4820 GPa, and the minimum fracture stress range of the quartz-tungsten interface is 1.3355–1.5420 GPa; (3) Although the peak stress of ore crushing has no obvious effect when the loading rate is 0.010 or 0.005 kN/s, it has a greater impact on the internal deformation of the ore. When the loading rate is 0.010 kN/s, the stress suddenly decreased and constantly fluctuated during the strengthening stage. (4) The damage caused by in-situ loading mainly occurs at the boundary of the loading area. The fracture mechanical characteristics of quartz minerals in the two sets of interfaces are greater than that of tungsten minerals and siliceous rock minerals. Quartz minerals in the interface composition minerals are preferentially formed and destroyed.