Abstract:A lateral annular slit charge was proposed in order to improve cutting effect in hard rock tuunels. Firstly， the blasting effects of the charge were analyzed theoretically. Then， the distributions of blasting strain and blasting crack after the charge blasting were studied through the model experiments. Finally， field tests were implemented to explore the applied efficacy of the charge. Results showed that the lateral annular slit charge could induce an energy accumulation effect at the slit position， which results in the rock mass at the slit position being subjected to stronger blasting loads and thus having stronger crack propagation ability. The lateral annular slit tube could reduce the blasting strain in the non-slit direction and increase the blasting strain in the slit direction. The strain distribution characteristic proves the energy accumulation phenomenon in the slit direction of the lateral annular slit charge. According to the macroscopic crack propagation， the crack propagation ability of lateral annular slit charge in the slit direction has been significantly improved. Compared with conventional column charge cutting blasting technique， the lateral annular slit charge cutting blasting technique could improve drivage efficiency and reduce cost in hard rock tunnels， which verifys that the lateral annular slit charge is preferred in hard rock tunnel cutting blasting.

Abstract:In order to improve the dispersibility and energy output of nano-boron powder， n-B/NC/F₂₆₀₂ core-shell nanofibers were prepared by coaxial electrospinning method. The morphology of the samples prepared with different core solution mass fraction， shell solution mass fraction， working voltage， distance from needle to collector and injection rate were analyzed by scanning electron microscope（SEM）， and the optimum preparation conditions were explored. Scanning electron microscope （SEM）， X-ray photoelectron spectrometer（XPS） and infrared spectrometer （IR） were used to analyze the morphology of the samples prepared under the best preparation conditions. The combustion performance test， thermodynamic simulation and DSC-TG were used to analyze the combustion performance. The results show that the optimum preparation conditions is 15% of the core layer solution， shell solution mass fraction 15%， working voltage 16 kV， distance between needle and collector 12 cm， core flow rate 3.6 mL·h^-1， shell flow rate 6 mL·h^-1. The average diameter of the spinning product was 1.32 μm. The combustion performance test shows that the highest peak of combustion pressure is 0.51 MPa， and the average pressure boost rate is 0.61 MPa·s^-1， showing excellent combustion performance. Thermodynamic simulation showed that the average molecular weight of the product was 29 g·mol^-1， and the combustion was sufficient. DSC-TG showed that the weight gain of boron in n-B/NC/F₂₆₀₂ was 43.43% more than that of the original boron powder， and the peak exothermic temperature of boron in n-B/NC/F₂₆₀₂ was 41 ℃ lower than that of the original boron powder. The coaxial electrospinning method could better optimize the nanostructure of the fibers.

Abstract:Quantitative characterization of its physical structure is crucial for regulating and enhancing the performance of PBX. Utilizing micro-CT， image processing， and statistical analysis， we researched the quantitative acquisition of characteristic parameters for molding granules. We conducted research on image processing and statistical analysis to quantitatively obtain the characteristic parameters of molding granules based on micro-CT. The characteristic parameters of TATB-based molding granules were characterized by this method， and an evaluation of the characterization method was conducted. The results suggest that this method can implement the quantitative characterization of the size， morphology， porosity， density， and packing characteristics of the molding granules. The granule size and sphericity of the TATB-based molding granules approximately follow the exponential Gaussian and Weibull distributions， respectively. The intrinsic density is 1.35 g·cm^-3， with a visible porosity of 2.3%（@spatial resolution 14.3 μm）， and a volume fraction of 0.69. Evaluation experiments demonstrate that the method exhibits good accuracy， stability， and repeatability. The characterization results of granule size are consistent with those of the sieving process， and the relative deviation of the characterization results of main characteristic parameters in different periods is less than 1%. The results of morphology and properties are relatively significantly influenced by the packing state of granules and the spatial resolution of micro-CT.

Abstract:To investigate the influence of SiC mass fraction， SiC particle size， Al particle size， and their interactions on the mechanical properties of PTFE/Al/SiC （PAS） reactive materials， a 2³ factorial design criterion was employed to design and prepare eight different compositions of PTFE/Al/SiC reactive materials， and quasi-static compression tests and split Hopkinson pressure bar （SHPB） experiments were conducted. Significant factors were selected using the t-value ranking method， and their contribution rates and disturbance trends were analyzed. Additionally， response surface methodology was employed to analyze significant interaction effects. The results indicate that a higher SiC mass fraction positively impacts the mechanical properties of PAS materials. With a sudden change of strain rate， SiC particle size exhibits opposite disturbance trends on the material mechanical response. The effect of Al particles on the mechanical response of the PAS material system is limited. Strong interaction effects between factors should not be overlooked. With low strain rate loading， the interaction between SiC mass fraction and SiC particle size is significant. When the SiC mass fraction is high and the particle size is small， the particle dispersion state and interfacial bonding strength can be optimized， thereby improving material mechanical response. With high strain rate loading， PAS materials with a higher SiC mass fraction exhibit higher dynamic mechanical response， and the interaction between SiC particle size and Al particle size is significant. When the particle sizes of SiC and Al are close， the dynamic response of the material can be effectively improved.

Abstract:Energetic materials are of great strategic value in both national defense and civil application. The thermal decomposition characteristics are one of the most important characteristics directly related to the effective application of energetic materials. It is of great significance to clarify the thermal decomposition behavior and mechanism of energetic materials for further improving the thermal decomposition efficiency and inhibiting their unstable decomposition. Three typical energetic materials， cyclotetramethylene tetranitramine （HMX）， hexanitrohexaazaisowurtzitane （CL-20） and 3，4-dinitrofurazanofuroxan （DNTF）， were studied. The basic physical and chemical properties related to the thermal decomposition characteristics were present， and the thermal decomposition behavior and mechanism were summarized， with emphasis on the structural characteristics of materials and the types of additives that influence the thermal decomposition. It is found that the removal of nitro group is the key step in the thermal decomposition， and the metallic materials rich in active sites and organic complexes with abundant active groups tend to interact with nitro groups to accelerate the thermal decomposition process. Inorganic non-metallic materials can also contribute to the decomposition behavior due to the large specific surface area and excellent gas diffusion ability. Three methods， including eutectic， coating and adding desensitizing agent， are widely used to improve the thermal stability of these three energetic materials. Based on the research of the thermal decomposition mechanism， the design and development of thermal decomposition accelerators and inhibitors can be carried out， which will effectively promote the innovative development of thermal application of energetic materials and become the focus of future research on the thermal decomposition characteristics of energetic materials.

Abstract:Photoacoustic signals were induced on slices of black powder and its components， which was radiated by 1064 nm laser pulses with 10 ns duration. The laser pulse energies were adjusted by regulating the number of fused silica plates on the laser path as attenuators. An optical fiber-based Michelson interferometer was utilized to detect the generated acoustic signals. Acoustic wave energy was estimated. A primary model was proposed to estimate the reaction rate of black powder. Detected phase changes were similar to each other， but the dimensions varied with laser pulse energy. Thermal reaction of blackpowder was not significant under laser radiation， but other reaction mechanism existed and enhanced the photoacoustic signal. Relationship between laser pulse energy and integration of absolute value of phase change is approximately linear. Reaction rate of black powder is positively related to laser energy， except for high-energy pulse. The maximum of reaction rate was about 20 mmol·s^-1， which was achieved when laser energy is around 10 mJ.

Abstract:The safety issues of weapons and ammunition are essential that they matter the survivability and effectiveness of weaponry. The complex and harsh enviroments faced by ammunition lead to the high requirment of ammunition safety that the development of safe ammunition is the only way. Ammunition safety mainly depends on inherent safety and safety enhancement technology. Using insensitive explosives is the key way to improve the inherent safety of ammunition， while the enhancement and protection of charge and structure are important means to improve ammunition safety . In order to meet the requirements of high damage power and safety of ammunition， it is necessary to balance and coordinate the prominent contradiction between high energy and insensitivity of explosives from the multi-scale structures， such as molecules， crystals and mixed systems of explosives. Safety enhancement technologies such as charge structures， weak link structurse of projectiles and protection enhancements can effectively control the accidental ignition， reaction violence and evolution ammunition charges， and furthermore improve the safety of ammunition under abnormal environment and accident conditions. Therefore， the design ideas and technicalapproches for safety ammunition systems were proposed， including strengthening the foundation of multi-scale material design and performance control of insensitive explosives， complementing the shortcomings of charge structures， protection enhancement， and accidental ignition and reaction control， and exploring and developing the integrated design of material，- structure- and function .

Abstract:To study the influence of liner offset on the jet forming and armor breaking process of shaped charge， the numerical model verified by pulse radiography and penetration depth tests was used to investigate the evolution of the pressure distribution on the liner surface， molding parameters and penetration depth under different offsets ranging from 0~0.05D_k. The allowable range of liner offset that meets the requirements of good jet performance was obtained. In addition， the variation law of jet shape and lateral velocity under the coupling of liner deflection and deflection was discussed. The results show that the liner offset affects the symmetric distribution of liner surface pressure at 10μs and 12 μs after initiation （middle and late collapse process）， and a negligible effect observed at 10 μs and 12 μs after initiation（early and finally collapse process）. When the liner offset is 0.0125D_k， the jet maintains good collimation and continuity， and the penetration depth decreases by 6.6% compared with the axisymmetric case； When the offset exceeds 0.0125D_k， the jet bends in a bow shape and breaks at severe bending， with the decrease of penetration depth exceeding 10%. When the deflection angle of the liner is -0.015α， and the deflection changes from 0 to -0.0125D_k， the bending direction of jet changes， and the bending degree decreases first and then increases.

Abstract:The matrix explosives in cast explosives are molten when being ignited under thermal stimulation， thus the hot gas released by reaction expands and reacts in liquid explosives in the physical form of bubble clouds. Considering the scale distribution and activated developing mechanism of burning-bubble clouds， a regulation model for the evolution of burning-bubble clouds after ignition of cast explosives is established. This model well reflected the dependence of reaction evolution and final reaction violence on intrinsic burning rate， shell confinement strength， charging structure size， reserved air-gap volume and pressure relief venting area. Furthermore， the flexibility of this model was verified by comparing the calculated results with the experimental data. Results show that with the increase of shell confinement strength and charge size， the self-sustaining enhanced combustion and reaction violence level increase. Moreover， with the combined design of pressure relief structure venting threshold and pressure relief venting area， the reaction violence of the charge is controlled. Under the charging condition in this paper， when the ratio of pressure relief venting area to shell surface area is up to 8.6‰， the charge reaction violence level is controlled as burning. This work provides a theoretical basis for the thermal safety design and reaction violence evaluation of explosives.

Abstract:Ultrafine 2，6-diamino-3，5-dinitropyrazine-1-oxide （LLM-105） possesses high safety performance and low impact initiation threshold， showing promising applications in the initiation sequence. Solid-phase ripening is the main aging behavior of ultrafine LLM-105 during the storage process， which leads to the growth of particle size and performance degradation. Temperature and humidity are important environmental factors that affect solid-phase ripening， but the microscopic mechanism is still unclear. In situ small angle X-ray scattering （SAXS）， Scanning electron microscope （SEM） and in situ Atomic force microscopy （AFM） were used to capture the structural evolution of ultrafine LLM-105 particles under different temperature and humidity environments， and the solid-phase ripening mechanism was analyzed. Ultrafine LLM-105 had obvious solid-phase ripening after 30 days at 120 ℃， and its specific surface area （SSA） decreased by 41.6%. The ripening mechanism was dominated by Ostwald Ripening （OR）， accompanied with Smoluchowski Ripening （SR）. Humidity significantly accelerates the solid-phase ripening of ultrafine LLM-105 by promoting OR. After 30 days at 60 ℃ and 90% relative humidity， SSA decreased by 35.8%.

Abstract:In order to understand the effect of initial free cavity on the violence of confined octogen （HMX）-based PBX-3 in slow cook-off， the weak restricted test setup was designed with initial free cavity volume ratios of 1.0% and 7.4%， respectively， referring to Sandia instrumented thermal ignition（SITI）. The confined HMX-based PBX-3 explosives were heated at the same rate in slow cook-off tests. The temperatures of different locations at the center plane of explosive and shell surface were acquired using small-sized K type thermocouples， the shell velocity after thermal explosion was measured using the heat-resistant probe of photonic-Doppler-velocimeter（PDV）， and the wreckage of test setup was recycled in the slow cook-off chamber. The results show that the confined PBX-3 explosives are ignited in the center region for the same restricted strength and heating process， no matter with the initial free cavity volume. When the initial free cavity volume ratio is 1.0%， the shell surface temperature and the overall temperature of the explosive are higher when thermal explosion occurs， the shell accelerates faster and the maximum velocity is higher after thermal explosion， the wreckage fragments of test setup are smaller， and the reaction violence is higher. It is analyzed when the initial free cavity volume ratio is 1.0%， the stress of explosive is larger before thermal explosion， resulting in more serious damage. When thermal ignition occurs at the center of the explosive， the larger thermal stress causes a higher pressure induced by the gas accumulation， and the burning rate of explosive is higher. The high-temperature gas generated by the combustion is easier to enter the microcracks， resulting in stronger convective burning， faster pressure growth rate and more violent reaction.

Abstract:In order to explore the effect of 3，4-dinitrofurazan （DNTF） on the explosive energy release process of layered composite thermobaric charges， various double-layer composite charges were prepared， with the content of aluminum powder in the outer charge adjusted from 60% to 94%， and the content of DNTF adjusted from 40% to 0. Then， explosion tests were carried out in a closed tank under nitrogen and air environment. Based on the correlation between quasi-static pressure and effective mechanical energy， the released energy of charges at different reaction stages was obtained. Moreover， the afterburning process of aluminum powder from different charges was analyzed according to the evolution of fireball. The results reveal that the dispersed DNTF particles are easy to be ignited and grow rapidly after being shock-dispersed when the mass fractions of DNTF in the outer charge is 40%， which can improve the anaerobic combustion rate of aluminum powder and the aerobic combustion rate of aluminum powder at the edge of the cloud， thus the combined mechanical energy released during detonation and anaerobic combustion is raised 12% than that of the homogeneous charge with same composition. Whereas， when the DNTF in the outer charge is replaced by polytetrafluoroethylene （PTFE） in the same proportion， the combustion rate after dispersal is significantly reduced as well as shock wave overpressure and temperature， and the total mechanical energy released decreased by about 22% than composite charge containing DNTF in its outer layer. Moreover， when the outer charge is all replaced by aluminum powder， intensely aerobic combustion with longer duration will occur in the high-concentration aluminum powder cloud， the total mechanical energy released drops by only 5%， while the combined mechanical energy released by detonation and anaerobic combustion drops by 32%， and the peak shock wave overpressure has a considerable reduction. The above indicates that DNTF in the outer layer of the composite charge plays an important role in enhancing the combustion rate of the aluminum powder cloud and energy release rate in the early explosion stage.

Abstract:In order to obtain the thermal decomposition properties and melting crystallization kinetic parameters of the lowest eutectic mixture of 3-amino-2，4，6-trinitroanisole （ANTA）/N-methyl-2，4，6-trinitroanisole （TNA）， the thermal decomposition properties of the lowest eutectic mixture of ANTA/TNA were studied by differential scanning calorimetry （DSC）， and the thermal decomposition kinetic parameters were calculated. The effects of additives （HMX and RDX） on the melting process and crystallization process of the lowest eutectic mixture of ANTA/TNA were studied by microcalorimetry. The non-isothermal melting and crystallization behaviors of the eutectic mixture were analyzed by Šatava-Šesták method and Avrami method， respectively. Results show that the lowest eutectic mixture has good thermal stability， and the thermal decomposition kinetic parameters are close to that of ANTA and TNA. The melting process of eutectics conforms to the first-order reaction kinetics， and the heating rate has a great influence on the melting kinetic parameters. Additives can reduce the dependence of melting kinetic parameters on the heating rate to a certain extent. The crystallization process of the lowest eutectic mixture gradually shifts to the low temperature region with the increase of cooling rate， and the crystallization rate decreases with the increase of crystallinity. In HMX medium， the crystallization rate is less affected by crystallinity， and the crystallization rate in RDX increases with the increase of crystallinity.

Abstract:In order to study the morphology evolution of 1， 1-diamino-2， 2-dinitroethylene （FOX-7） particles under thermal stimulus and its influence on mechanical properties and mechanical sensitivities， four kinds of FOX-7 particles with typical size and morphology differences were selected. By controlling heating time and temperature， the morphology， mechanical properties and mechanical sensitivities evolutions of FOX-7 particles after heating were studied by scanning electron microscope， compressive stiffness experiment and mechanical sensitivities tests. The results show that the surface cracks of FOX-7 particles appear after heating and returning to room temperature. With the increase of heating temperature or heating time， the surface cracks of large-size particles （>100 μm） grow and break through ， thus the particles crack in layers and exfoliate. While， the surface cracks of small-sized particles （<100 μm） do not grow with the increase of heating temperature or heating time. Kawakita equation was used to fit the compaction curves of FOX-7 particles before and after heating. It is found that the modulus of FOX-7 particles increase after heating， and the increase is even greater for small particle size. Under the condition of larger particle size， FOX-7 has relatively low mechanical sensitivities， and still maintains low mechanical sensitivities after being heated and returning to room temperature. When the particle size is small， the mechanical sensitivities of FOX-7 are relatively high， and after heating and returning to room temperature， the mechanical sensitivities increase significantly， which may be related to the greater increase of modulus.

Abstract:In order to increase the density and detonation energy of the explosive， hydroxyl-terminated fluorine-containing binder （HTFB， 1.40 g·cm^-3） was applied to the formulation of casting PBX explosive （polymer bonded explosive）. The effects of toluene diisocyanate （TDI）， isophorone diisocyanate （IPDI）， hexamethylene diisocyanate （HDI） and hexamethylene diisocyanate trimer （3HDI） on the viscosity and curing process of the binder system were studied， and the effects of curing agents on curing and mechanical properties were also investigated. Results show that the curing agent can significantly reduce the viscosity of the binder system. In the temperature range of 25-70 ℃， the higher the temperature， the lower the viscosity of the binder system was. Above 60 ℃， the viscosity of HTFB binder system changed gently and the difference of each system was small. As curing agent， the viscosity， opening time and gel time of trifunctional isocyanate are more suitable for the preparation process of casting PBX explosive. Based on the formulation of aluminum-containing casting explosive with 88% solid content and the preparation process of pinch-vacuum injection-curing， the influence of HTFB binder on the preparation process and properties of explosive was studied in comparison with HTPB. The HTFB based PBX explosive show decent casting rheological properties and curing quality， and the density and detonation heat are 1.96 g·cm^-3 and 7790 J·g^-1， which are 6.52% and 6.55% higher than that of HTPB based PBX explosive， respectively.

Abstract:Aluminum hydride （AlH₃） is a new energetic material with higher energy density than aluminum. A large amount of hydrogen produced in the combustion of AlH₃， which significantly reduced the average molecular weight of gas products. AlH₃ can be used as an energetic component of explosives. However， the crystal transformation process of AlH₃ is extremely dangerous and the unstable impurity phase is difficult to separate， thus it is challenge to obtain the pure stable phase α-AlH₃. The preparation of AlH₃ complexes can avoid the danger of crystal transformation of AlH₃， AlH₃ complexes retain the structural unit of AlH₃， avoid the dangerous crystal transformation process， and can be purified by recrystallization， which has a broad application prospect. This paper reviews the synthesis methods， coordination modes， types and applications of AlH₃ complexes， and focuses on the effects of different ligands， such as tertiary amine， tertiary phosphine， ether and carbene， and different coordination structures on the thermochemical properties of AlH₃ complexes. The future research direction of AlH₃ complexes is clarified.

Abstract:In order to study the effects of hydrogen storage tantalum powder （HTa） on the material density and energy density of Al/PTFE reaction materials， four different Al/HTa/PTFE cylindrical specimens were prepared with varying HTa contents （5%， 10%， 20%， 30%）， and Al/PTFE cylindrical specimens without HTa were also prepared. A comparative study was conducted through Hopkinson pressure bar experiments and ballistic gun penetrating target experiments to analyze materials" dynamic mechanical properties， ignition thresholds， impact damage， and energy release characteristics. The results indicate that both Al/PTFE and Al/HTa/PTFE are elastoplastic materials with consistent stress-strain behavior. The ignition thresholds of the four Al/HTa/PTFE materials were measured as 4470 s^-1， 5620 s^-1， 5135 s^-1 and 3948 s^-1 respectively， with the ignition delay time decreasing and then increasing with increasing HTa filler content. In comparison with the Al/PTFE reactive materials， the reaction zone of Al/HTa/PTFE projectiles significantly expands between spaced targets， resulting in severe black scorch marks on the target plate and the generation of carbon deposition effect. The penetrating ability and secondary fragment damage were improved， further enhancing the material"s target penetration damage level.

Abstract:Aiming at solving the problems of the structural design and the applicability of the penetration performance of dual-mode warhead， a dual-mode warhead with arc-cone combined shaped liner of variable wall thickness is designed. Using ANSYS / LS-DYNA simulation software， the influence of shaped charge structure parameters on the characteristic parameters of dual-mode damage elements is studied. Based on the optimized structure， the damage of different damage elements to concrete targets is studied. Through the range analysis， the optimal combination of the structural parameter of dual-mode warhead is obtained： the cone angle of the liner is 80°， the arc radius is 8 mm， the upper wall thickness of the liner is 2.22 mm， the lower wall thickness is 5.44 mm， the length-diameter ratio of the charge is 0.88， and the shell thickness is 5 mm. The X-ray imaging test is carried out to verify the optimization results. The results show that the simulation results are in good agreement with the X-ray test results. Compared with the shaped charge jet （JET）， the rod-shaped charge jet （JPC） has obvious advantages in surface collapse and opening performance when penetrating concrete targets， while the penetration depth of JET to concrete targets is significantly improved compared with JPC. The research results can provide reference for the design and application of warhead structure.

Abstract:In order to obtain a new type of alloy fuel with excellent thermal oxidation and energy release performance， the spherical aluminum-tungsten alloy fuel powder （Al-25W） was prepared by the combination of aluminothermic reduction and ultra-high temperature gas atomization. The phase structure， oxidation behavior， and energy properties of the alloy powder were studied. The results show that the metastable Al/W alloy phase in the spherical Al-25W alloy powder particles is uniformly distributed in the pure Al matrix， and transform into the Al₁₂W phase after the stabilization treatment， and the energy is released to the outside. The spherical Al-25W alloy powder has higher oxidation heat release and oxidation weight gain than pure Al powder. It can be completely oxidized in air at 1400 ℃， with all W atoms oxidized to WO₃ and volatilized in the gaseous form. The residual oxidation product is only Al₂O₃. The measured volumetric combustion enthalpy of the spherical Al-25W alloy powder is higher than that of pure Al powder （83000 J·cm^-3） calculated theoretically， up to （83132.1±608.5） J·cm^-3， and the gaseous combustion product WO₃ is generated during the violent combustion.

Abstract:Fluoropolymer-matrix reactive materials are a new type of material with energy release characteristics of impact reaction. It has a wide application prospect in the military field. In order to master the energy release and damage characteristics of fluoropolymer-matrix reactive materials and promote its application in high-efficiency damage warhead， the research status of impact-induced chemical reaction behavior of fluoropolymer-matrix reactive materials and the coupling damage effect of ignition， detonation， invasion and explosion are reviewed. The research progress in energy release characteristics of split Hopkinson pressure bar （SHPB） experiment， quasi-closed ballistic experiment and explosive loading experiment is emphatically introduced. In terms of damage characteristics， the research progress of reactive projectile， fragment and reactive jet is summarized， the application design of fluoropolymer-matrix reactive materials in shaped charge and the research results of reactive jet forming are emphasized. Besides， the related reaction model and numerical simulation are introduced. On this basis， the future research direction is discussed： establishing a systematic response model and simulation method； regulating its performance by formula， process and other parameters； innovating and exploring the observation and characterization technology of energy release reaction and giving engineering application designs.

Abstract:In order to study the burning damage characteristics of polyurea anti-blast layer under the action of explosion transient temperature field， experimental tests were carried out for the polyurea coated capsule liquid-filled container with different thickness （1 mm， 4 mm and 6 mm） under the condition of close-in explosion. The macro-micro damage characteristics of the polyurea layer after explosion transient high temperature burning were obtained by explosion experiment， and the burning mechanism of the explosion temperature field on polyurea was analyzed using the colorimetric temperature technology and the numerical simulation method. The results showed a maximum explosion temperature of passivated hexogen （RDX） of about 3792 K under the described experimental conditions， which was higher than the initial decomposition temperature of the polyurea material （231.2 ℃）. The burning phenomenon occurred on the surface layer of the polyurea. When the thin layer between the surface layer and the internal hole was broken by penetration， the detonation product entered the internal hole of the material， thus resulting in a significant increase in the burning depth of the polyurea and the formation of a spotted burning outer layer. The ignition degree of polyurea was positively correlated with the density of detonation products and the propagation velocity of detonation products along the thickness of the polyurea layer. Besides， ignition occurred when the mass per unit area of detonation products acting on the polyurea layer reached 0.0195 g·cm^-2. Heat conduction was the main reason for the thermal decomposition of polyurea. Overall， the research method and results could provide reference for the engineering protection evaluation of polyurea and the modification of anti-blast polyurea.

Abstract:Limited by the size of model test chamber， the reflection wave generated by explosion load on the boundary of test chamber would inevitably affect the expected results in the centrifugal tests of underwater explosion. Therefore，reducing the boundary effect will substantially restore the actual test situation and improve the test accuracy. Numerical simulation on centrifuge model test of underwater explosion was conducted based on the Coupled-Eulerian-Lagrangian（CEL） method，. Through comparing experimental results with theoretical results and analyzing mesh sizes of 1， 2， 4， 6， 8 and 10 mm， the reliability of the numerical model was verified. Based on that， the shock wave propagation characteristics in centrifuge tests of underwater explosion with boundary energy absorbing materials of rubber and foam （thicknesses of 5， 10， 15 and 20 mm） were compared， and the mechanism of wave absorption and energy dissipation was analyzed. The results show that the Euler mesh size of 2 mm could balance the calculation efficiency and accuracy of calculation results. Laying rubber or foam materials on the inner wall of the model chamber could effectively reduce the reflection effect of underwater explosion shock waves. The rubber material is more effective in shock wave absorption than the foam material for the condition of 5 mm thickness. However， with the increase of material thickness， the foam material has a better absorption effect than rubber. Both rubber and foam materials have a certain inhibitory effect on low-frequency signals of shock waves， but the inhibitory effect on high-frequency signals is weak.

Abstract:To study the jet formation and failure characteristics of penetrating concrete and rock targets of shaped charge with large barrier， the jet formation by using X-ray cinematography and static armor-piercing into concrete and rock targets were carried out. Meanwhile， the evolution process of detonation wave， the rod jet formation of shaped charge with large barrier and penetration process of concrete and rock targets are simulated by ANSYS/AUTODYN software. Combined with the experimental results， the penetration damage characteristics of the shaped charge rod jet to concrete and rock targets were analyzed. Results show that the Lee-Tarver equation of state can accurately describe the propagation process of the internal detonation wave， and the maximum error of forming jet parameters （projectile length， jet length， jet head velocity and jet diameter） is 12.8% compared with the test. The continuous rod-like jet with large aspect ratio can be formed after detonation of the shaped charge with large barrier. There are obvious craters in the penetrated concrete and rock targets， and the jet has no obvious reaming effect during the penetrating concrete process. The penetration depth and hole diameter of the penetrated concrete target are 46.7% and 48.1% larger than those of rock target in the test. However， the surface of the rock target is seriously damaged and the crater area is larger. Compared with the concrete target， cracks in rock target are continuously generated and developed significantly in the process of jet penetrating and the length and width of cracks formed are larger than those of concrete targets. The damage range around the rock target penetration channel is larger， and the internal damage of the target is serious.

Abstract:To select and optimize the formulation components of high-energy Fuel air explosive， petroleum ether， propylene oxide， and ethyl ether （liquid fuel）， isopropyl nitrate and nitromethane （liquid sensitizer）， and metallic aluminum powder （solid component） were used as the research objects. The explosion pressure and explosion temperature of FAE with different composition ratios was investigated by EXPLO5 calculations. The cloudburst experiments of liquid and liquid-solid FAE formulations were also conducted under unconstrained conditions， and the parameters such as explosion field and temperature field were analyzed for the damage effect. The results show that the mixed liquid FAE， composed of petroleum ether （mass accounted for 55%-70%）， propylene oxide， and isopropyl nitrate， shows a better detonation performance.. The liquid-solid mixture of FAE with a liquid-solid ratio of 1∶1 has a better detonation performance and shows the best cloud dispersion state in the unconstrained cloud dispersion experiment. Two systems of FAE formulations in the 1 kg of secondary detonation charge under the cloud burst can be a stable response to achieve the detonation state. They all have superior results in terms of destructive capacity. Also， the effects of heat damage and overpressure damage were quantified and evaluated for each system.

Abstract:By using penetration experiment and numerical simulation methods， the damage characteristics of the multilayer thin steel target penetrated by reactive materials （RMs） under hypervelocity impact condition was investigated. The two-stage light gas-gun was used to study the damage mode of PTFE/Al based RM and Al-based all-metal RM to multilayer thin steel target， the influence of material type and penetration velocity on damage effect is presented. The results show that， compared with inert metal， both of RMs have lateral damage enhancement effect on multilayer thin steel target， which the broken hole size of the second layer can reach more than 4 times of the bullet dimeter （BD）. The AUTODYN numerical simulation software was used to prove the efficiency of the RM parameters and then the damage effect numerical simulation of RMs were carried out. The results show that the damage characteristics of PTFE/Al-based RM and Al-based all-metal RM to multilayer thin steel target can be described by J-C model combined with Lee-Tarver model and J-C model combined with Shock equation respectively. Additionally， the phenomenon that the increase in penetration speed can hardly improve the lateral damage enhancement effect of the PTFE/Al-based RM but can significantly improve that of the Al-based RM to the multilayer steel target， which is mainly due to the difference in energy releasing mechanisms between two kinds of RMs.