Abstract:

Abstract:

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: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: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: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: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.

Abstract:In order to investigate the shock initiation of warhead charge by multiple explosively formed projectiles （MEFP） impacts， the shock initiation experiments of covered Composition B by single EFP and dual EFP were conducted to test the shock initiation capacity of single EFP and dual EFP on covered Composition B. Moreover， the numerical simulations on shock initiation of covered Composition B by EFP were carried out by AUTODYN finite-element software， the formation processes of single EFP and dual EFP and their shock initiation processes of covered Composition B， were analyzed respectively， and the critical cover plate thickness （H_c） for the detonation of Composition B was obtained. Further， an engineering calculation model of the critical initiation condition of covered charge with dual EFP was established. The experimental results show that the length of EFP is 18 mm and the diameter is 19 mm. The critical cover plate thickness range is 10 mm≤H_c<15 mm for shock initiation of covered Composition B by single EFP impact， while the critical initiation cover plate thickness range is 15 mm≤H_c<20 mm for dual EFP impacts. Besides， the numerical simulation results show that the critical cover plate thickness is 13 mm for shock initiation of covered composition B by single EFP. While for the action of double EFP， the critical initiation cover plate thickness is 19 mm， which is 46.2% higher than that for single EFP. The numerical simulation results are consistent with experimental results. Finally， the calculation model can provide a good prediction of the critical initiation condition of the covered charge with dual EFP.

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: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: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: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.