In order to investigate the penetration performance of Linear-Shaped Charge(LSC),Embowed LinearShaped Charge(ELSC),and Embowed Linear Explosively Formed Projectile(ELEFP)on T-shaped stiffened plates,a series of near-f...In order to investigate the penetration performance of Linear-Shaped Charge(LSC),Embowed LinearShaped Charge(ELSC),and Embowed Linear Explosively Formed Projectile(ELEFP)on T-shaped stiffened plates,a series of near-field air-burst experiments are conducted.The damage modes and characteristics of the target plates are compared and analyzed.Each flat plate section is completely punctured,resulting in a penetration hole.The damage modes induced by the three charge types on the stiffened plate structure are consistent,characterized by shear failure in the central region of the flat plate due to penetration by the penetrator,localized plastic deformation of the flat plate,and local penetration failure resulting from partial perforation of the central stiffener.The penetration lengths caused by ELSC and ELEFP are 45.1%and 46.1% larger than that of LSC,while the half-width of the penetration hole generated by ELEFP is 54.2% and 24.7% smaller than that of ELSC and LSC,respectively.The penetration height caused by ELEFP are 17.5%and 62.1% larger than that of ELSC and LSC,respectively.The stiffener effectively segments the damage area,enhancing the local structural strength and limiting the extent of plastic deformation in the flat plate section.The comparative results show that the ELSC proves to be more effective for efficient large-scale damage,and ELEFP is more suitable for achieving efficient localized damage.展开更多
To quickly break through a reinforced concrete wall and meet the damage range requirements of rescuers entering the building,the combined damage characteristics of the reinforced concrete wall caused by EFP penetratio...To quickly break through a reinforced concrete wall and meet the damage range requirements of rescuers entering the building,the combined damage characteristics of the reinforced concrete wall caused by EFP penetration and explosion shock wave were studied.Based on LS-DYNA finite element software and RHT model with modified parameters,a 3D large-scale numerical model was established for simulation analysis,and the rationality of the material model parameters and numerical simulation algorithm were verified.On this basis,the combined damage effect of EFP penetration and explosion shock wave on reinforced concrete wall was studied,the effect of steel bars on the penetration of EFP was highlighted,and the effect of impact positions on the damage of the reinforced concrete wall was also examined.The results reveal that the designed shaped charge can form a crater with a large diameter and high depth on the reinforced concrete wall.The average crater diameter is greater than 67 cm(5.58 times of charge diameter),and crater depth is greater than 22 cm(1.83 times of charge diameter).The failure of the reinforced concrete wall is mainly caused by EFP penetration.When only EFP penetration is considered,the average diameter and depth of the crater are 54.0 cm(4.50 times of charge diameter)and 23.7 cm(1.98 times of charge diameter),respectively.The effect of explosion shock wave on crater depth is not significant,resulting in a slight increase in crater depth.The average crater depth is 24.5 cm(2.04 times of charge diameter)when the explosion shock wave is considered.The effect of explosion shock wave on the crater diameter is obvious,which can aggravate the damage range of the crater,and the effect gradually decreases with the increase of standoff distance.Compared with the results for a plain concrete wall,the crater diameter and crater depth of the reinforced concrete wall are reduced by 5.94%and 9.96%,respectively.Compared to the case in which the steel bar is not hit,when the EFP hit one steel bar and the intersection of two steel bars,the crater diameter decreases by 1.36%and 5.45%respectively,the crater depth decreases by 4.92%and 14.02%respectively.The EFP will be split by steel bar during the penetration process,resulting in an irregular trajectory.展开更多
The effects of postweld heat treatment on the microstructure and metallurgical properties of a bronze–carbon steel(st37)explosively bonded interface were studied.Explosive welding was done under 1.5-and 2-mm standoff...The effects of postweld heat treatment on the microstructure and metallurgical properties of a bronze–carbon steel(st37)explosively bonded interface were studied.Explosive welding was done under 1.5-and 2-mm standoff distances and different conditions of explosive charge.Samples were postweld heat treated for 4 and 16 h in the furnace at 250°C and 500°C and then air cooled.Laboratory studies using optical microscopy,scanning electron microscopy,and microhardness testing were used to evaluate the welded samples.Microstructural examinations showed that by increasing the standoff distance and the explosive charge,the interface of bronze to steel became wavier.The microhardness test result showed that the hardness of the samples was higher near the joint interface compared with other areas because of the intensive plastic deformation,which was caused by the explosion force.The results show that increasing the heat treatment temperature and time caused the intermetallic compounds’layer thickness to increase,and,because of the higher diffusion of copper and tin,the iron amount in the intermetallic compounds decreased.Also,because of the increase in heat treatment temperature and time,internal stresses were released,and the interface hardness decreased.展开更多
Ti/Fe clad plate had attracted extensive attention because of its important application. In order to reduce the titanium layer thickness, the explosive welding of TA1 titanium foil to Q235 steel plate was carried out....Ti/Fe clad plate had attracted extensive attention because of its important application. In order to reduce the titanium layer thickness, the explosive welding of TA1 titanium foil to Q235 steel plate was carried out. The interfacial bonding performance was analyzed by micromorphology analysis and mechanical property test, and the formation process of interfacial wave and molten block in the vortex was simulated by smoothed particle hydrodynamics(SPH) method. The results showed that salt as pressure transfer layer used in explosive welding could play a good buffer effect on the collision between flyer and base layers. Regular waveforms were formed on the bonding interface, and the titanium foil/steel clad plate exhibited good welding quality and bonding property. The crest of the observed interfacial wave moved 200 μm from the beginning to the final formation, and it was important of jet on the formation of interfacial waveform. The interface was mainly bonded in the form of molten layer, and the grains near the interface were streamlined. Molten block containing intermetallic compounds and metal oxides appeared in the vortex of wave crest.展开更多
This work pioneers a transient electrical explosive flexible igniter based on a polyurethane-copper composite,achieving unprecedented microsecond-scale plasma initiation(0.75μs threshold at 30 V)through key innovatio...This work pioneers a transient electrical explosive flexible igniter based on a polyurethane-copper composite,achieving unprecedented microsecond-scale plasma initiation(0.75μs threshold at 30 V)through key innovations.A dual-V geometric design concentrating current density.Electroless copper plating(ECP)enabling 80μm conductive layers with flexibility.Capacitive discharge optimization for tunable energy delivery(0.058–1.088 mJ).The flexible architecture demonstrates remarkable mechanical-electrical decoupling-maintaining functionality under 140 kg compressive loads(250%improvement over rigid igniters)and 90°torsional deformation while delivering consistent plasma jets(3–5 mm height,180–580μs duration).Based on the analysis of the multi-physics field simulation re-sults,multiphase energy conversion occurs during the electrical explosion process.The initial Joule heating reaches the melting point of copper,and then an electrical explosion plasma is generated.Voltage-dependent studies identify 50 V as the critical threshold for performance leap,where peak current increases 46.56%and plasma duration extends 214.29%versus 30 V operation.These advances establish a new class of high-speed ignition systems combiningμs-response,140 kg shock resistance,and conformal deployment capabilities for next-generation munitions and micro-propulsion applications.This work extends the application of flexible electronics to the field of transient ignition.展开更多
Reinforced concrete(RC)columns are often subjected to off-central explosion due to the uncertainty of blast locations.However,few studies have focused on the dynamic response of RC columns under offcentral explosions....Reinforced concrete(RC)columns are often subjected to off-central explosion due to the uncertainty of blast locations.However,few studies have focused on the dynamic response of RC columns under offcentral explosions.A field blast experiment was conducted under close-in explosion with varying detonation offset distances(0 m,0.5 m,and 1 m),the overpressure load and dynamic responses of the full-scale RC columns were measured.Compared with the centrally detonated condition,a relative offset distance of 1.67 decreases the maximum and residual deflections of the RC column by 16.8%and 21.4%,respectively,while increasing the maximum and residual support rotations by 24.7%and 17.8%.Based on the experimental results,a theoretical model was proposed that considers the detonation location and charge mass,boundary conditions,axial compression ratio and material properties.The theoretical model exhibited good agreement with the experimental results,with prediction errors below 10%for both maximum and residual deflection.The effects of parameters were analyzed,and it indicated that an increase in offset distance results in decreased maximum and residual deflections but an increased support angle,thereby exacerbating damage.Higher axial load ratio,span-depth ratio,and longitudinal reinforcement ratio reduce both deflections and support angle.Additionally,a rapid method to predict the maximum and residual deflection of RC columns under off-central blast loading was also proposed based on the Generalized Regression Neural Network(GRNN).Eleven features which related to the RC column properties and the blast characteristics were used in the training process of GRNN,and accurate predictions were achieved with prediction errors within 20%.This study fills the gap in predicting the dynamic response of RC columns under off-central explosion,providing valuable references for blast-resistant design.展开更多
To investigate the coupling mechanisms of detonation energy release between the TiH_(2)/PTFE active shell and RDX explosive,an RDX-based active shell thermobaric explosive containing TiH_(2)/PTFE powders was prepared....To investigate the coupling mechanisms of detonation energy release between the TiH_(2)/PTFE active shell and RDX explosive,an RDX-based active shell thermobaric explosive containing TiH_(2)/PTFE powders was prepared.The effects of the TiH_(2)/PTFE mass ratio on the shock wave parameters and afterburning effect of the thermobaric explosives were investigated.The energy release characteristics of the optimal TiH_(2)/PTFE ratio under varying vacuum degrees were evaluated using a 0.9 m3 spherical explosive chamber and colorimetric thermometry method.The experimental results demonstrated that as the PTFE powders content in the active shell increased,the shock wave intensity,explosion fireball duration,and maximum average temperature of the thermobaric explosives initially increased and then decreased,peaking at a TiH_(2)/PTFE mass ratio of 1:1.Compared to the TiH_(2)-based thermobaric explosives without PTFE,the 1:1 TiH_(2)/PTFE formulation exhibited increases of 45.9%in peak overpressure,69.7%in fireball duration,and 7.2%in maximum average temperature.Thus,an optimal PTFE content significantly enhances the energy release efficiency of the RDX/TiH_(2)/PTFE thermobaric explosives.Furthermore,the energy release efficiency of thermobaric explosives was influenced by the vacuum degree,with the maximum average temperature,peak overpressure,positive impulse,positive pressure action time,and fireball duration decreasing by 10.8%,35.3%,52.1%,65.5%,and 46.4%,respectively,as the vacuum degree increased from 0 to 52.4%.展开更多
Gravity-caisson wharves have been widely constructed in coastal and island regions, which are threaten by potential underwater explosions. This work aims to study the dynamic behaviors and propose a damage evaluation ...Gravity-caisson wharves have been widely constructed in coastal and island regions, which are threaten by potential underwater explosions. This work aims to study the dynamic behaviors and propose a damage evaluation approach of caisson wharf against underwater explosion. Firstly, based on both the underwater explosion loading test and underwater explosion test on the reduced-scale caisson specimen, a high-fidelity finite element analysis approach for numerically reproduce the dynamic behaviors of prototype caisson wharves against underwater explosions was proposed and verified. Secondly, the underwater explosion loadings and dynamic behaviors of prototype caisson wharf (14.9 m×8.1 m×10.95 m) against sequential blast wave and bubble pulsation of typical torpedo with a charge weight of 200 kg were studied. The influences of the seabed and cabin infill materials, as well as the explosion standoff distances of 3.4–10.2 m and depths of burst between 1/4 and 3/4 of water depth, on the blast resistance of caisson wharf were further examined through deflection distributions of exterior wall, damage evolution, and overall displacement of caisson wharf. Finally, a performance evaluation approach for prototype caisson wharves against underwater explosions was proposed by comprehensively considering the bearing, storage, and berthing capabilities. The corresponding protective measures and design recommendations were further provided. It indicates that: (i) under the explosion of a typical torpedo, the damage modes of prototype caisson wharf mainly involve the overall vibration, spalling and cracking of the exterior wall, collapse of the upper operating platform and cracking of the top plate;(ii) the blast wave and cavitation zone generated between the bubble and the exterior wall are the two primary causes of damage to caisson wharf;(iii) compared to the saturated calcareous sand seabed, the assumption of rigid seabed underestimates the spalling on the exterior wall, which is not recommended for scenarios where cavitation zones may generate;(iv) rock rubble is the most effective infill material in improving the blast resistance of caisson wharf among four types of infill configurations, i.e., fully filled and half-filled saturated calcareous sand, rock rubble and pure water;(v) the standoff distance of 10.2 m is regarded as a secure protective range in the scenarios discussed currently. As the standoff distance decreases and the depth of burst increases, the spalling of the exterior wall induced by the cavitation intensifies, posing a great threat to the functionality of caisson wharf.展开更多
Auxetic steel systems have been demonstrated to be effective in resisting blast loading demands due to their higher energy absorption,enhanced indentation resistance and higher shear strength compared to conventional ...Auxetic steel systems have been demonstrated to be effective in resisting blast loading demands due to their higher energy absorption,enhanced indentation resistance and higher shear strength compared to conventional systems.However,previous studies reported that such systems still fall short in reducing the pressure values during severe explosions.Therefore,the use of auxetic steel systems to fortify vulnerable structures or armoured vehicles is yet to be explored.To address this gap,the current study develops and validates the blast performance of an enhanced auxetic steel system,namely enhanced reentrant with straight and curved members(ERSAC),that can reduce the pressure values of severe explosions up to a scaled distance,Z,of 0.2 m/kg^(1/3).The design mechanism of the ERSAC system relies on maximizing the specific energy absorption by increasing the number of sequential locking points,thus creating several auxetic cell densification zones.In this respect,a numerical ANSYS/AUTODYN model is developed and then validated against conventional auxetic steel systems(i.e.,re-entrant and arrowhead systems)that were subjected to different scaled distance explosions and quasi-static loading demands in previous experimental programs.The model is then employed to compare the performance of the ERSAC system to the re-entrant and arrowhead systems when subjected to out-of-plane quasi-static and blast loading demands,where all systems are designed to have similar total weights and dimensions.The comparison is presented in terms of the generated pressure,specific energy absorption and total deformations.To investigate the sensitivity of the ERSAC system to its design parameters and geometrical configurations,an interpretability analysis is performed to evaluate the influence of the width,length,cells'thickness,and inclined angle on the generated pressure through 34 possible configurations.The results show that the ERsAC system reduces the pressure values by 40%and 38%compared to the re-entrant and arrowhead systems,respectively,at 0.1 m behind the systems.Overall the average reduction in the pressure values is 18%for Z=0.2 m/kg^(1/3),25%for Z=0.3 m/kg^(1/3),and 15%for Z=0.4 m/kg^(1/3).In addition,the ERSAC system results in higher specific energy absorption values by 37%,41%,and 70%for Z=0.2 m/kg^(1/3),0.3 m/kg^(1/3),and 0.4 m/kg^(1/3)compared to conventional auxetic systems,respectively.The results also show that increasing the width and length reduces the pressure values at near distances behind the ERSAC system.Furthermore,increasing the cell thickness is effective in reducing the pressure values for all distances.The current study provides future research opportunities on the locking mechanisms of auxetic steel systems and their effects on consuming more energy for enhanced blast protection levels.展开更多
To investigate the effects of gas transport on ignition response of polymer-bonded explosives(PBXs)during slow cookoff,this study develops a thermo-mechanically coupled pyrolytic gas transport porous model.The model r...To investigate the effects of gas transport on ignition response of polymer-bonded explosives(PBXs)during slow cookoff,this study develops a thermo-mechanically coupled pyrolytic gas transport porous model.The model resolves dynamically coupled physical fields across thermal,mechanical,gas trans-port,and chemical reaction throughout the slow cook-off.Results are consistent with Sandia Instru-mented Thermal Ignition(SITI)experiments for PBX 9501 in sealed and vented systems.It is revealed that porosity evolves in two stages:the first stage is dominated by thermal expansion,while the second is governed by decomposition.Gas transport pathways are controlled by the coupled evolution of porosity and temperature.Convective heat transfer from gas products contributes less of the total thermal transport,while the concentration effect of gas product within pores is identified as the dominant factor in ignition delay.This study provides a foundational framework for understanding gas transport in the slow cookoff of polymer-bonded explosives.展开更多
The interfacial structure and its regulation play a crucial role in determining the overall performance of advanced functional composites.Weak interfacial interactions between carbon fibers and the matrix present a cr...The interfacial structure and its regulation play a crucial role in determining the overall performance of advanced functional composites.Weak interfacial interactions between carbon fibers and the matrix present a critical challenge limiting the general performance and functional applications of carbon fiberreinforced composites.In this paper,a novel strategy for bioinspired root-soil interfacial structure was presented to enhance the mechanical properties of polymer bonded explosives.A multiscale nanowire heterostructure was constructed through the in-situ growth of morphologically controllable zinc oxide nanowires on the carbon fiber surface via a facile hydrothermal method,with polydopamine as the interfacial reinforcement layer.This structure emulated the function of the"root",and combined with a network-distributed polymer binder representing the"soil",formed a robust root-soil interlocking interfacial structure within the polymer bonded explosives.Due to the multiscale interfacial reinforcement structure,the tensile strength of the polymer bonded explosives was visibly increased by 41%,the strain at the break by 110%,and the creep resistance by 51%with only 0.4 wt%filler adopted.The thermal stress resistance was improved by 57%owing to the synergistic enhancement of thermal conductivity and mechanical properties.This study provides new perspectives and insights for designing and constructing high-performance polymer bonded explosives and other functional composites.展开更多
This study theoretically explored the dynamic response of the liquid-filled cylindrical shell structure experiencing internal explosion shock waves.It analyzed the radial deformation of the liquid-filled cylindrical s...This study theoretically explored the dynamic response of the liquid-filled cylindrical shell structure experiencing internal explosion shock waves.It analyzed the radial deformation of the liquid-filled cylindrical shell structure theoretically.It clarified the protection mechanism of the externally liquid-filled cylindrical shell structure.Based on the improved single-degree-of-freedom system theory,a theoretical model was established via load equivalence and simplification.The radial deformations of unfilled and externally liquid-filled cylindrical shells was investigated under internal explosion shock waves.The influencing factors for structural protection characteristics were explored considering impact load intensity,liquid layer thickness,structural specifications and dimensions,and material properties.The results showed that when the load peak value or the action time was fixed,the maximum radial deformation of the structure increased with the increased load-specific impulse.When the load-specific impulse was fixed,reducing the load peak or extending the loading time decreased the maximum radial deformation of the structure.The protection mechanism of the externally liquid-filled cylindrical shell structure was due to the liquid medium,which acted as an additional mass that con-strained the radial deformation of the structure.The change in liquid layer thickness altered the duration of the liquid's constraint on the radial deformation.The dynamic response of the externally liquid-filled cylindrical shell structure presented three deformation modes,which were determined by the liquid layer thickness,structural specifications,dimensions,and material properties.展开更多
Investigating the detonation reaction zone structures of high explosives is significant for understanding detonation reaction mechanism.This study employed an integrated approach combining machine learning prediction,...Investigating the detonation reaction zone structures of high explosives is significant for understanding detonation reaction mechanism.This study employed an integrated approach combining machine learning prediction,theoretical calculation,and experimental characterization to determine the detonation reaction zone width of CL-20-based aluminized explosive.In this study,the detonation reaction zone refers to the reaction zone between the von Neumann(VN)peak and sonic point,which usually means the so-called detonation driving zone(DDZ).For the machine learning prediction,an ensemble model integrating Random Forest and Support Vector Regression was developed to predict the reaction zone width using a dataset of 19 publicly available samples.For the theoretical calculation,the Wood-Kirkwood(W-K)detonation theory model was utilized to implement numerical calculation of the reaction zone structures,incorporating chemical reaction kinetics to describe the detonation reaction progress.In experimental characterization,the Photon Doppler Velocimetry(PDV)was applied with LiF as the optical window to measure the particle velocity profile of detonation products and derive the reaction zone width.The results indicate that the reaction zone width values are 0.25 mm,0.28 mm,and 0.26 mm obtained from machine learning prediction,theoretical calculation,and experimental characterization,respectively.The corresponding velocities at the Chapman-Jouguet(CJ)point are 1,938 m/s,2,047 m/s,and 1,982 m/s,respectively.The maximum relative deviation in reaction zone width among three methods is approximately 7.7%,while that for CJ particle velocity is approximately 3.3%.These results from all three methods agree well within engineering error.This validates the effectiveness of integrating machine learning prediction,theoretical calculation and advanced experimental techniques for studying the detonation reaction zone structures of high explosives.This research provides insights into the detonation reaction mechanism and reaction zone characteristics of CL-20-based aluminized explosive.展开更多
This paper presents a simplified design tool based on semi-analytical formulations to investigate the dynamic response of an immersed composite cylinder subjected to a far-field underwater explosion.The cylinder is si...This paper presents a simplified design tool based on semi-analytical formulations to investigate the dynamic response of an immersed composite cylinder subjected to a far-field underwater explosion.The cylinder is simply supported,fully submerged and filled with air inside.A classical shell theory using a Double Fourier series solution combined with the first-order Doubly Asymptotic Approximation(DAA1)formulation is adapted to model the fluid-structure interaction.An explicit non-standard finite difference scheme is applied to solve the coupled differential equations in time domain.The validity of DAA1 model is established by comparing the LS-DYNA/USA finite element results with existing experimental data from the literature.Then the proposed semi-analytical solutions are compared to the LS-DYNA/USA results,showing good correlation with a discrepancy of 7%for peak deflections and±9%for maximum stresses at the stand-off point for cylinders with relatively small length over radius ratios.Parametric studies examining the effect of different loading conditions,areal masses,and material configurations reveal that a large charge mass located far from the composite panel turns out to be more damaging than a small mass located nearby due to a broader pressure-time profile.Finally,the proposed model demonstrates a significant reduction in computation time,being approximately 30 times faster than its numerical counterpart,LS-DYNA/USA,making it a valuable tool for the preliminary design stages.展开更多
The gas explosion in residential building has always been a highly concerned problem.Explosions in homogeneous mixtures have been extensively studied.However,mixtures are often inhomogeneous in the practical scenarios...The gas explosion in residential building has always been a highly concerned problem.Explosions in homogeneous mixtures have been extensively studied.However,mixtures are often inhomogeneous in the practical scenarios due to the differences in the densities of methane and air.In order to investigate the effects of gas explosions in inhomogeneous mixtures,experimental studies involving gas leakage and explosion are conducted in a full-scale residential building to reproduce the process of gas explosion.By fitting the dimensionless buoyancy as a function of dimensionless height and dimensionless time,a distribution model of gas in large-scale spaces is established,and the mechanism of inhomogeneous distribution of methane is also be revealed.Furthermore,the stratified reconstruction method(SRM)is introduced for efficiently setting up inhomogeneous concentration fields in FLACS.The simulation results highlight that for the internal overpressure,the distribution of methane has no effect on the first overpressure peak(ΔP1),while it significantly influences the subsequent overpressure peak(ΔP2),and the maximum difference between the overpressure of homogeneous and inhomogeneous distribution is174.3%.Moreover,the initial concentration distribution also has a certain impact on the external overpressure.展开更多
This study represents an important step forward in the domain of additive manufacturing of energetic materials.It presents the successful formulation and fabrication by 3D printing of gun propellants using Fused Depos...This study represents an important step forward in the domain of additive manufacturing of energetic materials.It presents the successful formulation and fabrication by 3D printing of gun propellants using Fused Deposition Modeling(FDM)technology,highlighting the immense potential of this innovative approach.The use of FDM additive manufacturing technology to print gun propellants is a significant advancement due to its novel application in this field,which has not been previously reported.Through this study,the potential of FDM 3D-printing in the production of high-performance energetic composites is demonstrated,and also a new standard for manufacturability in this field can be established.The thermoplastic composites developed in this study are characterized by a notably high energetic solids content,comprising 70%hexogen(RDX)and 10%nitrocellulose(NC),which surpasses the conventional limit of 60%energetic solids typically achieved in stereolithography and light-curing 3D printing methods.The primary objective of the study was to optimize the formulation,enhance performance,and establish an equilibrium between printability and propellant efficacy.Among the three energetic for-mulations developed for 3D printing feedstock,only two were suitable for printing via the FDM tech-nique.Notably,the formulation consisting of 70%RDX,10%NC,and 20%polycaprolactone(PCL)emerged as the most advantageous option for gun propellants,owing to its exceptional processability,ease of printability,and high energetic performance.展开更多
RBOE is a new type of DNAN-based high-energy melt-cast mixed explosive,whose safety under thermal stimulation is significantly affected by heating conditions and venting area of the warhead.Based on the thermal decomp...RBOE is a new type of DNAN-based high-energy melt-cast mixed explosive,whose safety under thermal stimulation is significantly affected by heating conditions and venting area of the warhead.Based on the thermal decomposition reaction characteristics and combustion characteristics of each component of RBOE explosive,the cook-off calculation models of RBOE warhead before and after ignition were established.In addition,closed and vented warheads were designed,as well as fast and slow cook-off test devices.The cook-off characteristics and thermal safety venting area of RBOE warhead were extensively studied.The results showed that the closed RBOE warhead underwent deflagration reaction under both slow and fast cook-off conditions.The calculation result of the shell wall temperature before slow cookoff ignition response of the warhead was 454.06 K,with an error of+1.75%compared to the test result of462.15 K,and the temperature rise rate calculated was in good agreement with the test.The calculated ignition time of RBOE warhead under fast cook-off was 161 s,with an error of+8.8%compared to the test result of 148 s,which verified the accuracy of cook-off model of RBOE warhead before ignition.According to the cook-off calculation model of the warhead after ignition and cook-off test of the vented warhead,it was determined that the thermal safety venting area was 1124.61 mm^(2)for fast cook-off and 530.66 mm~2 for slow cook-off,effectively preventing the reaction of warhead above combustion.Therefore,this study provides a scientific basis for the thermal safety design and evaluation of insensitive warheads.展开更多
Gas explosion in confined space often leads to significant pressure oscillation.It is widely recognized that structural damage can be severe when the oscillation frequency of the load resonates with the natural vibrat...Gas explosion in confined space often leads to significant pressure oscillation.It is widely recognized that structural damage can be severe when the oscillation frequency of the load resonates with the natural vibration frequency of the structure.To reveal the oscillation mechanism of gas explosion load,the experiment of gas explosion was conducted in a large-scale confined tube with the length of 30 m,and the explosion process was numerically analyzed using FLACS.The results show that the essential cause of oscillation effect is the reflection of the pressure wave.In addition,due to the difference in the propagation path of the pressure wave,the load oscillation frequency at the middle position of the tunnel is twice that at the end position.The average sound velocity can be used to calculate the oscillation frequency of overpressure accurately,and the error is less than 15%.The instability of the flame surface and the increase of flame turbulence caused by the interaction between the pressure wave and the flame surface are the main contributors to the increase in overpressure and amplitude.The overpressure peaks calculated by the existing flame instability model and turbulence disturbance model are 31.7%and 34.7%lower than the numerical results,respectively.The turbulence factor model established in this work can describe the turbulence enhancement effect caused by flame instability and oscillatory load,and the difference between the theoretical and numerical results is only 4.6%.In the theoretical derivation of the overpressure model,an improved model of dynamic turbulence factor is established,which can describe the enhancement effect of turbulence factor caused by flame instability and self-turbulence.Based on the one-dimensional propagation theory of pressure wave,the oscillatory effect of the load is derived to calculate the frequency and amplitude of pressure oscillation.The average error of amplitude and frequency is less than 20%.展开更多
While the moisture content of soil affects significantly the blast impulse of shallow buried explosives,the role of surface-covering water(SCW)on soil in such blast impulse remains elusive.A combined experimental and ...While the moisture content of soil affects significantly the blast impulse of shallow buried explosives,the role of surface-covering water(SCW)on soil in such blast impulse remains elusive.A combined experimental and numerical study has been carried out to characterize the effect of SCW on transferred impulse and loading magnitude of shallow buried explosives.Firstly,blast tests of shallow buried explosives were conducted,with and without the SCW,to quantitatively assess the blast loading impulse.Subsequently,finite element(FE)simulations were performed and validated against experimental measurement,with good agreement achieved.The validated FE model was then employed to predict the dynamic response of a fully-clamped metallic circular target,subjected to the explosive impact of shallow buried explosives with SCW,and explore the corresponding physical mechanisms.It was demonstrated that shallow buried explosives in saturated soil generate a greater impulse transferred towards the target relative to those in dry soil.The deformation displacement of the target plate is doubled.Increasing the height of SCW results in enhanced center peak deflection of the loaded target,accompanied by subsequent fall,due to the variation of deformation pattern of the loaded target from concentrated load to uniform load.Meanwhile,the presence of SCW increases the blast impulse transferred towards the target by three times.In addition,there exists a threshold value of the burial depth that maximizes the impact impulse.This threshold exhibits a strong sensitivity to SCW height,decreasing with increasing SCW height.An empirical formula for predicting threshold has been provided.Similar conclusions can be drawn for different explosive masses.The results provide technical guidance on blast loading intensity and its spatial distribution considering shallow buried explosives in coast-land battlefields,which can ultimately contribute to better protective designs.展开更多
The afterburning of TNT and structural constraints in confined spaces significantly amplify the blast load,leading to severe structural damage. This study investigates the mechanisms underlying the enhanced dynamic re...The afterburning of TNT and structural constraints in confined spaces significantly amplify the blast load,leading to severe structural damage. This study investigates the mechanisms underlying the enhanced dynamic response of reinforced concrete blast doors with four-sided restraints in confined space. Explosion tests with TNT charges ranging from 0.15 kg to 0.4 kg were conducted in a confined space,capturing overpressure loads and the dynamic response of the blast door. An internal explosion model incorporating the afterburning effect was developed using LS-DYNA software and validated against experimental data. The results reveal that the TNT afterburning effect amplifies both the initial peak overpressure and the quasi-static overpressure, resulting in increased deformation of the blast door.Within the 0.15-0.4 kg charge range, the initial overpressure peak and quasi-static overpressure increased by an average of 1.79 times and 2.21 times, respectively. Additionally, the afterburning effect enhanced the blast door's deflection by 177%. Compared to open-space scenarios, the cumulative deflection of the blast door due to repeated shock wave impacts is significantly greater in confined spaces. Furthermore, the quasi-static pressure arising from the structural constraints sustains the blast door's deflection at a high level.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.52271307,52061135107,52192692,11802025)the Liao Ning Excellent Youth Fund Program(Grant No.2023JH3/10200012)+1 种基金the Liao Ning Revitalization Tal-ents Program(Grant No.XLYC1908027)the Fundamental Research Funds for the Central Universities(Grant Nos.DUT20RC(3)025,DUT20TD108,DUT20LAB308)。
文摘In order to investigate the penetration performance of Linear-Shaped Charge(LSC),Embowed LinearShaped Charge(ELSC),and Embowed Linear Explosively Formed Projectile(ELEFP)on T-shaped stiffened plates,a series of near-field air-burst experiments are conducted.The damage modes and characteristics of the target plates are compared and analyzed.Each flat plate section is completely punctured,resulting in a penetration hole.The damage modes induced by the three charge types on the stiffened plate structure are consistent,characterized by shear failure in the central region of the flat plate due to penetration by the penetrator,localized plastic deformation of the flat plate,and local penetration failure resulting from partial perforation of the central stiffener.The penetration lengths caused by ELSC and ELEFP are 45.1%and 46.1% larger than that of LSC,while the half-width of the penetration hole generated by ELEFP is 54.2% and 24.7% smaller than that of ELSC and LSC,respectively.The penetration height caused by ELEFP are 17.5%and 62.1% larger than that of ELSC and LSC,respectively.The stiffener effectively segments the damage area,enhancing the local structural strength and limiting the extent of plastic deformation in the flat plate section.The comparative results show that the ELSC proves to be more effective for efficient large-scale damage,and ELEFP is more suitable for achieving efficient localized damage.
基金supported by the Scientific and Technological Innovation Project(Grant No.KYGYZB0019003)。
文摘To quickly break through a reinforced concrete wall and meet the damage range requirements of rescuers entering the building,the combined damage characteristics of the reinforced concrete wall caused by EFP penetration and explosion shock wave were studied.Based on LS-DYNA finite element software and RHT model with modified parameters,a 3D large-scale numerical model was established for simulation analysis,and the rationality of the material model parameters and numerical simulation algorithm were verified.On this basis,the combined damage effect of EFP penetration and explosion shock wave on reinforced concrete wall was studied,the effect of steel bars on the penetration of EFP was highlighted,and the effect of impact positions on the damage of the reinforced concrete wall was also examined.The results reveal that the designed shaped charge can form a crater with a large diameter and high depth on the reinforced concrete wall.The average crater diameter is greater than 67 cm(5.58 times of charge diameter),and crater depth is greater than 22 cm(1.83 times of charge diameter).The failure of the reinforced concrete wall is mainly caused by EFP penetration.When only EFP penetration is considered,the average diameter and depth of the crater are 54.0 cm(4.50 times of charge diameter)and 23.7 cm(1.98 times of charge diameter),respectively.The effect of explosion shock wave on crater depth is not significant,resulting in a slight increase in crater depth.The average crater depth is 24.5 cm(2.04 times of charge diameter)when the explosion shock wave is considered.The effect of explosion shock wave on the crater diameter is obvious,which can aggravate the damage range of the crater,and the effect gradually decreases with the increase of standoff distance.Compared with the results for a plain concrete wall,the crater diameter and crater depth of the reinforced concrete wall are reduced by 5.94%and 9.96%,respectively.Compared to the case in which the steel bar is not hit,when the EFP hit one steel bar and the intersection of two steel bars,the crater diameter decreases by 1.36%and 5.45%respectively,the crater depth decreases by 4.92%and 14.02%respectively.The EFP will be split by steel bar during the penetration process,resulting in an irregular trajectory.
文摘The effects of postweld heat treatment on the microstructure and metallurgical properties of a bronze–carbon steel(st37)explosively bonded interface were studied.Explosive welding was done under 1.5-and 2-mm standoff distances and different conditions of explosive charge.Samples were postweld heat treated for 4 and 16 h in the furnace at 250°C and 500°C and then air cooled.Laboratory studies using optical microscopy,scanning electron microscopy,and microhardness testing were used to evaluate the welded samples.Microstructural examinations showed that by increasing the standoff distance and the explosive charge,the interface of bronze to steel became wavier.The microhardness test result showed that the hardness of the samples was higher near the joint interface compared with other areas because of the intensive plastic deformation,which was caused by the explosion force.The results show that increasing the heat treatment temperature and time caused the intermetallic compounds’layer thickness to increase,and,because of the higher diffusion of copper and tin,the iron amount in the intermetallic compounds decreased.Also,because of the increase in heat treatment temperature and time,internal stresses were released,and the interface hardness decreased.
文摘Ti/Fe clad plate had attracted extensive attention because of its important application. In order to reduce the titanium layer thickness, the explosive welding of TA1 titanium foil to Q235 steel plate was carried out. The interfacial bonding performance was analyzed by micromorphology analysis and mechanical property test, and the formation process of interfacial wave and molten block in the vortex was simulated by smoothed particle hydrodynamics(SPH) method. The results showed that salt as pressure transfer layer used in explosive welding could play a good buffer effect on the collision between flyer and base layers. Regular waveforms were formed on the bonding interface, and the titanium foil/steel clad plate exhibited good welding quality and bonding property. The crest of the observed interfacial wave moved 200 μm from the beginning to the final formation, and it was important of jet on the formation of interfacial waveform. The interface was mainly bonded in the form of molten layer, and the grains near the interface were streamlined. Molten block containing intermetallic compounds and metal oxides appeared in the vortex of wave crest.
基金supported by the National Natural Science Foundation of China (Grant Nos. 22275092, 52102107)supported by the Postgraduate Research & Practice Innovation Program of Jiangsu Province (Grant No. KYCX24_0709)+2 种基金supported by the China Scholarship Council program (Grant No. 202406840160),which provided the opportunity for international collaborationsupported by the Fundamental Research Funds for the Central Universities (Grant No. 30923010920)the State Key Laboratory of Transient Chemical Effects and Control (Grant No. 6142602230201)
文摘This work pioneers a transient electrical explosive flexible igniter based on a polyurethane-copper composite,achieving unprecedented microsecond-scale plasma initiation(0.75μs threshold at 30 V)through key innovations.A dual-V geometric design concentrating current density.Electroless copper plating(ECP)enabling 80μm conductive layers with flexibility.Capacitive discharge optimization for tunable energy delivery(0.058–1.088 mJ).The flexible architecture demonstrates remarkable mechanical-electrical decoupling-maintaining functionality under 140 kg compressive loads(250%improvement over rigid igniters)and 90°torsional deformation while delivering consistent plasma jets(3–5 mm height,180–580μs duration).Based on the analysis of the multi-physics field simulation re-sults,multiphase energy conversion occurs during the electrical explosion process.The initial Joule heating reaches the melting point of copper,and then an electrical explosion plasma is generated.Voltage-dependent studies identify 50 V as the critical threshold for performance leap,where peak current increases 46.56%and plasma duration extends 214.29%versus 30 V operation.These advances establish a new class of high-speed ignition systems combiningμs-response,140 kg shock resistance,and conformal deployment capabilities for next-generation munitions and micro-propulsion applications.This work extends the application of flexible electronics to the field of transient ignition.
基金financially supported by the National Natural Science Foundation of China(Grants No.12472399)。
文摘Reinforced concrete(RC)columns are often subjected to off-central explosion due to the uncertainty of blast locations.However,few studies have focused on the dynamic response of RC columns under offcentral explosions.A field blast experiment was conducted under close-in explosion with varying detonation offset distances(0 m,0.5 m,and 1 m),the overpressure load and dynamic responses of the full-scale RC columns were measured.Compared with the centrally detonated condition,a relative offset distance of 1.67 decreases the maximum and residual deflections of the RC column by 16.8%and 21.4%,respectively,while increasing the maximum and residual support rotations by 24.7%and 17.8%.Based on the experimental results,a theoretical model was proposed that considers the detonation location and charge mass,boundary conditions,axial compression ratio and material properties.The theoretical model exhibited good agreement with the experimental results,with prediction errors below 10%for both maximum and residual deflection.The effects of parameters were analyzed,and it indicated that an increase in offset distance results in decreased maximum and residual deflections but an increased support angle,thereby exacerbating damage.Higher axial load ratio,span-depth ratio,and longitudinal reinforcement ratio reduce both deflections and support angle.Additionally,a rapid method to predict the maximum and residual deflection of RC columns under off-central blast loading was also proposed based on the Generalized Regression Neural Network(GRNN).Eleven features which related to the RC column properties and the blast characteristics were used in the training process of GRNN,and accurate predictions were achieved with prediction errors within 20%.This study fills the gap in predicting the dynamic response of RC columns under off-central explosion,providing valuable references for blast-resistant design.
基金supported by the Natural Science Research Excellent Youth Project of Anhui Educational Committee(Grant No.2023AH020026)and the National Natural Science Foundation of China(Grant No.12272001)the authors would like to thank the foundation for the financial supports.
文摘To investigate the coupling mechanisms of detonation energy release between the TiH_(2)/PTFE active shell and RDX explosive,an RDX-based active shell thermobaric explosive containing TiH_(2)/PTFE powders was prepared.The effects of the TiH_(2)/PTFE mass ratio on the shock wave parameters and afterburning effect of the thermobaric explosives were investigated.The energy release characteristics of the optimal TiH_(2)/PTFE ratio under varying vacuum degrees were evaluated using a 0.9 m3 spherical explosive chamber and colorimetric thermometry method.The experimental results demonstrated that as the PTFE powders content in the active shell increased,the shock wave intensity,explosion fireball duration,and maximum average temperature of the thermobaric explosives initially increased and then decreased,peaking at a TiH_(2)/PTFE mass ratio of 1:1.Compared to the TiH_(2)-based thermobaric explosives without PTFE,the 1:1 TiH_(2)/PTFE formulation exhibited increases of 45.9%in peak overpressure,69.7%in fireball duration,and 7.2%in maximum average temperature.Thus,an optimal PTFE content significantly enhances the energy release efficiency of the RDX/TiH_(2)/PTFE thermobaric explosives.Furthermore,the energy release efficiency of thermobaric explosives was influenced by the vacuum degree,with the maximum average temperature,peak overpressure,positive impulse,positive pressure action time,and fireball duration decreasing by 10.8%,35.3%,52.1%,65.5%,and 46.4%,respectively,as the vacuum degree increased from 0 to 52.4%.
基金supported by National Natural Science Foundations of China(Grant No.52308522).
文摘Gravity-caisson wharves have been widely constructed in coastal and island regions, which are threaten by potential underwater explosions. This work aims to study the dynamic behaviors and propose a damage evaluation approach of caisson wharf against underwater explosion. Firstly, based on both the underwater explosion loading test and underwater explosion test on the reduced-scale caisson specimen, a high-fidelity finite element analysis approach for numerically reproduce the dynamic behaviors of prototype caisson wharves against underwater explosions was proposed and verified. Secondly, the underwater explosion loadings and dynamic behaviors of prototype caisson wharf (14.9 m×8.1 m×10.95 m) against sequential blast wave and bubble pulsation of typical torpedo with a charge weight of 200 kg were studied. The influences of the seabed and cabin infill materials, as well as the explosion standoff distances of 3.4–10.2 m and depths of burst between 1/4 and 3/4 of water depth, on the blast resistance of caisson wharf were further examined through deflection distributions of exterior wall, damage evolution, and overall displacement of caisson wharf. Finally, a performance evaluation approach for prototype caisson wharves against underwater explosions was proposed by comprehensively considering the bearing, storage, and berthing capabilities. The corresponding protective measures and design recommendations were further provided. It indicates that: (i) under the explosion of a typical torpedo, the damage modes of prototype caisson wharf mainly involve the overall vibration, spalling and cracking of the exterior wall, collapse of the upper operating platform and cracking of the top plate;(ii) the blast wave and cavitation zone generated between the bubble and the exterior wall are the two primary causes of damage to caisson wharf;(iii) compared to the saturated calcareous sand seabed, the assumption of rigid seabed underestimates the spalling on the exterior wall, which is not recommended for scenarios where cavitation zones may generate;(iv) rock rubble is the most effective infill material in improving the blast resistance of caisson wharf among four types of infill configurations, i.e., fully filled and half-filled saturated calcareous sand, rock rubble and pure water;(v) the standoff distance of 10.2 m is regarded as a secure protective range in the scenarios discussed currently. As the standoff distance decreases and the depth of burst increases, the spalling of the exterior wall induced by the cavitation intensifies, posing a great threat to the functionality of caisson wharf.
基金support has been provided by the Military Technical College and the Natural Sciences and Engineering Research Council(NSERC)of Canada。
文摘Auxetic steel systems have been demonstrated to be effective in resisting blast loading demands due to their higher energy absorption,enhanced indentation resistance and higher shear strength compared to conventional systems.However,previous studies reported that such systems still fall short in reducing the pressure values during severe explosions.Therefore,the use of auxetic steel systems to fortify vulnerable structures or armoured vehicles is yet to be explored.To address this gap,the current study develops and validates the blast performance of an enhanced auxetic steel system,namely enhanced reentrant with straight and curved members(ERSAC),that can reduce the pressure values of severe explosions up to a scaled distance,Z,of 0.2 m/kg^(1/3).The design mechanism of the ERSAC system relies on maximizing the specific energy absorption by increasing the number of sequential locking points,thus creating several auxetic cell densification zones.In this respect,a numerical ANSYS/AUTODYN model is developed and then validated against conventional auxetic steel systems(i.e.,re-entrant and arrowhead systems)that were subjected to different scaled distance explosions and quasi-static loading demands in previous experimental programs.The model is then employed to compare the performance of the ERSAC system to the re-entrant and arrowhead systems when subjected to out-of-plane quasi-static and blast loading demands,where all systems are designed to have similar total weights and dimensions.The comparison is presented in terms of the generated pressure,specific energy absorption and total deformations.To investigate the sensitivity of the ERSAC system to its design parameters and geometrical configurations,an interpretability analysis is performed to evaluate the influence of the width,length,cells'thickness,and inclined angle on the generated pressure through 34 possible configurations.The results show that the ERsAC system reduces the pressure values by 40%and 38%compared to the re-entrant and arrowhead systems,respectively,at 0.1 m behind the systems.Overall the average reduction in the pressure values is 18%for Z=0.2 m/kg^(1/3),25%for Z=0.3 m/kg^(1/3),and 15%for Z=0.4 m/kg^(1/3).In addition,the ERSAC system results in higher specific energy absorption values by 37%,41%,and 70%for Z=0.2 m/kg^(1/3),0.3 m/kg^(1/3),and 0.4 m/kg^(1/3)compared to conventional auxetic systems,respectively.The results also show that increasing the width and length reduces the pressure values at near distances behind the ERSAC system.Furthermore,increasing the cell thickness is effective in reducing the pressure values for all distances.The current study provides future research opportunities on the locking mechanisms of auxetic steel systems and their effects on consuming more energy for enhanced blast protection levels.
基金support provided by the National Natural Science Foundation of China(Grant Nos.12172050,12172051,12572411,12141201 and 12221002).
文摘To investigate the effects of gas transport on ignition response of polymer-bonded explosives(PBXs)during slow cookoff,this study develops a thermo-mechanically coupled pyrolytic gas transport porous model.The model resolves dynamically coupled physical fields across thermal,mechanical,gas trans-port,and chemical reaction throughout the slow cook-off.Results are consistent with Sandia Instru-mented Thermal Ignition(SITI)experiments for PBX 9501 in sealed and vented systems.It is revealed that porosity evolves in two stages:the first stage is dominated by thermal expansion,while the second is governed by decomposition.Gas transport pathways are controlled by the coupled evolution of porosity and temperature.Convective heat transfer from gas products contributes less of the total thermal transport,while the concentration effect of gas product within pores is identified as the dominant factor in ignition delay.This study provides a foundational framework for understanding gas transport in the slow cookoff of polymer-bonded explosives.
基金supported by the Presidential Foundation of CAEP(No.YZJJZQ2022006)the National Natural Science Foundation of China(Nos.22275173 and 22475179).
文摘The interfacial structure and its regulation play a crucial role in determining the overall performance of advanced functional composites.Weak interfacial interactions between carbon fibers and the matrix present a critical challenge limiting the general performance and functional applications of carbon fiberreinforced composites.In this paper,a novel strategy for bioinspired root-soil interfacial structure was presented to enhance the mechanical properties of polymer bonded explosives.A multiscale nanowire heterostructure was constructed through the in-situ growth of morphologically controllable zinc oxide nanowires on the carbon fiber surface via a facile hydrothermal method,with polydopamine as the interfacial reinforcement layer.This structure emulated the function of the"root",and combined with a network-distributed polymer binder representing the"soil",formed a robust root-soil interlocking interfacial structure within the polymer bonded explosives.Due to the multiscale interfacial reinforcement structure,the tensile strength of the polymer bonded explosives was visibly increased by 41%,the strain at the break by 110%,and the creep resistance by 51%with only 0.4 wt%filler adopted.The thermal stress resistance was improved by 57%owing to the synergistic enhancement of thermal conductivity and mechanical properties.This study provides new perspectives and insights for designing and constructing high-performance polymer bonded explosives and other functional composites.
基金support pro-vided by National Natural Science Foundation of China(Grant Nos.52371342 and 52271338).
文摘This study theoretically explored the dynamic response of the liquid-filled cylindrical shell structure experiencing internal explosion shock waves.It analyzed the radial deformation of the liquid-filled cylindrical shell structure theoretically.It clarified the protection mechanism of the externally liquid-filled cylindrical shell structure.Based on the improved single-degree-of-freedom system theory,a theoretical model was established via load equivalence and simplification.The radial deformations of unfilled and externally liquid-filled cylindrical shells was investigated under internal explosion shock waves.The influencing factors for structural protection characteristics were explored considering impact load intensity,liquid layer thickness,structural specifications and dimensions,and material properties.The results showed that when the load peak value or the action time was fixed,the maximum radial deformation of the structure increased with the increased load-specific impulse.When the load-specific impulse was fixed,reducing the load peak or extending the loading time decreased the maximum radial deformation of the structure.The protection mechanism of the externally liquid-filled cylindrical shell structure was due to the liquid medium,which acted as an additional mass that con-strained the radial deformation of the structure.The change in liquid layer thickness altered the duration of the liquid's constraint on the radial deformation.The dynamic response of the externally liquid-filled cylindrical shell structure presented three deformation modes,which were determined by the liquid layer thickness,structural specifications,dimensions,and material properties.
文摘Investigating the detonation reaction zone structures of high explosives is significant for understanding detonation reaction mechanism.This study employed an integrated approach combining machine learning prediction,theoretical calculation,and experimental characterization to determine the detonation reaction zone width of CL-20-based aluminized explosive.In this study,the detonation reaction zone refers to the reaction zone between the von Neumann(VN)peak and sonic point,which usually means the so-called detonation driving zone(DDZ).For the machine learning prediction,an ensemble model integrating Random Forest and Support Vector Regression was developed to predict the reaction zone width using a dataset of 19 publicly available samples.For the theoretical calculation,the Wood-Kirkwood(W-K)detonation theory model was utilized to implement numerical calculation of the reaction zone structures,incorporating chemical reaction kinetics to describe the detonation reaction progress.In experimental characterization,the Photon Doppler Velocimetry(PDV)was applied with LiF as the optical window to measure the particle velocity profile of detonation products and derive the reaction zone width.The results indicate that the reaction zone width values are 0.25 mm,0.28 mm,and 0.26 mm obtained from machine learning prediction,theoretical calculation,and experimental characterization,respectively.The corresponding velocities at the Chapman-Jouguet(CJ)point are 1,938 m/s,2,047 m/s,and 1,982 m/s,respectively.The maximum relative deviation in reaction zone width among three methods is approximately 7.7%,while that for CJ particle velocity is approximately 3.3%.These results from all three methods agree well within engineering error.This validates the effectiveness of integrating machine learning prediction,theoretical calculation and advanced experimental techniques for studying the detonation reaction zone structures of high explosives.This research provides insights into the detonation reaction mechanism and reaction zone characteristics of CL-20-based aluminized explosive.
基金supported by French Defense Innovation Agency(AID-DGA)(Grant No.ANR-21-ASM2-0002-02)in the framework of the Astrid Maturation SUCCESS+project,a collaborative French research project.
文摘This paper presents a simplified design tool based on semi-analytical formulations to investigate the dynamic response of an immersed composite cylinder subjected to a far-field underwater explosion.The cylinder is simply supported,fully submerged and filled with air inside.A classical shell theory using a Double Fourier series solution combined with the first-order Doubly Asymptotic Approximation(DAA1)formulation is adapted to model the fluid-structure interaction.An explicit non-standard finite difference scheme is applied to solve the coupled differential equations in time domain.The validity of DAA1 model is established by comparing the LS-DYNA/USA finite element results with existing experimental data from the literature.Then the proposed semi-analytical solutions are compared to the LS-DYNA/USA results,showing good correlation with a discrepancy of 7%for peak deflections and±9%for maximum stresses at the stand-off point for cylinders with relatively small length over radius ratios.Parametric studies examining the effect of different loading conditions,areal masses,and material configurations reveal that a large charge mass located far from the composite panel turns out to be more damaging than a small mass located nearby due to a broader pressure-time profile.Finally,the proposed model demonstrates a significant reduction in computation time,being approximately 30 times faster than its numerical counterpart,LS-DYNA/USA,making it a valuable tool for the preliminary design stages.
基金the financial support from National Natural Science Foundation of China(Grant No.52378488)Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX22_0222)。
文摘The gas explosion in residential building has always been a highly concerned problem.Explosions in homogeneous mixtures have been extensively studied.However,mixtures are often inhomogeneous in the practical scenarios due to the differences in the densities of methane and air.In order to investigate the effects of gas explosions in inhomogeneous mixtures,experimental studies involving gas leakage and explosion are conducted in a full-scale residential building to reproduce the process of gas explosion.By fitting the dimensionless buoyancy as a function of dimensionless height and dimensionless time,a distribution model of gas in large-scale spaces is established,and the mechanism of inhomogeneous distribution of methane is also be revealed.Furthermore,the stratified reconstruction method(SRM)is introduced for efficiently setting up inhomogeneous concentration fields in FLACS.The simulation results highlight that for the internal overpressure,the distribution of methane has no effect on the first overpressure peak(ΔP1),while it significantly influences the subsequent overpressure peak(ΔP2),and the maximum difference between the overpressure of homogeneous and inhomogeneous distribution is174.3%.Moreover,the initial concentration distribution also has a certain impact on the external overpressure.
基金supported by a grant from the Ministry of Research, Innovation and Digitization, UEFISCDI, Grant Nos. PN-IIIP2-2.1-PED-2021-1890, PN-IV-P6-6.3-SOL-2024-2-0254 and PNIV-P7-7.1-PTE-2024-0517, within PNCDI Ⅳ.
文摘This study represents an important step forward in the domain of additive manufacturing of energetic materials.It presents the successful formulation and fabrication by 3D printing of gun propellants using Fused Deposition Modeling(FDM)technology,highlighting the immense potential of this innovative approach.The use of FDM additive manufacturing technology to print gun propellants is a significant advancement due to its novel application in this field,which has not been previously reported.Through this study,the potential of FDM 3D-printing in the production of high-performance energetic composites is demonstrated,and also a new standard for manufacturability in this field can be established.The thermoplastic composites developed in this study are characterized by a notably high energetic solids content,comprising 70%hexogen(RDX)and 10%nitrocellulose(NC),which surpasses the conventional limit of 60%energetic solids typically achieved in stereolithography and light-curing 3D printing methods.The primary objective of the study was to optimize the formulation,enhance performance,and establish an equilibrium between printability and propellant efficacy.Among the three energetic for-mulations developed for 3D printing feedstock,only two were suitable for printing via the FDM tech-nique.Notably,the formulation consisting of 70%RDX,10%NC,and 20%polycaprolactone(PCL)emerged as the most advantageous option for gun propellants,owing to its exceptional processability,ease of printability,and high energetic performance.
基金National Natural Science Foundation of china(Grant No.12402468)。
文摘RBOE is a new type of DNAN-based high-energy melt-cast mixed explosive,whose safety under thermal stimulation is significantly affected by heating conditions and venting area of the warhead.Based on the thermal decomposition reaction characteristics and combustion characteristics of each component of RBOE explosive,the cook-off calculation models of RBOE warhead before and after ignition were established.In addition,closed and vented warheads were designed,as well as fast and slow cook-off test devices.The cook-off characteristics and thermal safety venting area of RBOE warhead were extensively studied.The results showed that the closed RBOE warhead underwent deflagration reaction under both slow and fast cook-off conditions.The calculation result of the shell wall temperature before slow cookoff ignition response of the warhead was 454.06 K,with an error of+1.75%compared to the test result of462.15 K,and the temperature rise rate calculated was in good agreement with the test.The calculated ignition time of RBOE warhead under fast cook-off was 161 s,with an error of+8.8%compared to the test result of 148 s,which verified the accuracy of cook-off model of RBOE warhead before ignition.According to the cook-off calculation model of the warhead after ignition and cook-off test of the vented warhead,it was determined that the thermal safety venting area was 1124.61 mm^(2)for fast cook-off and 530.66 mm~2 for slow cook-off,effectively preventing the reaction of warhead above combustion.Therefore,this study provides a scientific basis for the thermal safety design and evaluation of insensitive warheads.
基金financial support from National Natural Science Foundation of China(Grant No.52378488)Postgraduate Research&Practice Innovation Program of Jiangsu Province(Grant No.KYCX22_0222).
文摘Gas explosion in confined space often leads to significant pressure oscillation.It is widely recognized that structural damage can be severe when the oscillation frequency of the load resonates with the natural vibration frequency of the structure.To reveal the oscillation mechanism of gas explosion load,the experiment of gas explosion was conducted in a large-scale confined tube with the length of 30 m,and the explosion process was numerically analyzed using FLACS.The results show that the essential cause of oscillation effect is the reflection of the pressure wave.In addition,due to the difference in the propagation path of the pressure wave,the load oscillation frequency at the middle position of the tunnel is twice that at the end position.The average sound velocity can be used to calculate the oscillation frequency of overpressure accurately,and the error is less than 15%.The instability of the flame surface and the increase of flame turbulence caused by the interaction between the pressure wave and the flame surface are the main contributors to the increase in overpressure and amplitude.The overpressure peaks calculated by the existing flame instability model and turbulence disturbance model are 31.7%and 34.7%lower than the numerical results,respectively.The turbulence factor model established in this work can describe the turbulence enhancement effect caused by flame instability and oscillatory load,and the difference between the theoretical and numerical results is only 4.6%.In the theoretical derivation of the overpressure model,an improved model of dynamic turbulence factor is established,which can describe the enhancement effect of turbulence factor caused by flame instability and self-turbulence.Based on the one-dimensional propagation theory of pressure wave,the oscillatory effect of the load is derived to calculate the frequency and amplitude of pressure oscillation.The average error of amplitude and frequency is less than 20%.
基金supported by the National Natural Science Foundation of China(Grant Nos.12002156,11972185,12372136)Research Fund of State Key Laboratory of Mechanics and Control for Aerospace Structures(Grant No.MCMS-I-0222K01)。
文摘While the moisture content of soil affects significantly the blast impulse of shallow buried explosives,the role of surface-covering water(SCW)on soil in such blast impulse remains elusive.A combined experimental and numerical study has been carried out to characterize the effect of SCW on transferred impulse and loading magnitude of shallow buried explosives.Firstly,blast tests of shallow buried explosives were conducted,with and without the SCW,to quantitatively assess the blast loading impulse.Subsequently,finite element(FE)simulations were performed and validated against experimental measurement,with good agreement achieved.The validated FE model was then employed to predict the dynamic response of a fully-clamped metallic circular target,subjected to the explosive impact of shallow buried explosives with SCW,and explore the corresponding physical mechanisms.It was demonstrated that shallow buried explosives in saturated soil generate a greater impulse transferred towards the target relative to those in dry soil.The deformation displacement of the target plate is doubled.Increasing the height of SCW results in enhanced center peak deflection of the loaded target,accompanied by subsequent fall,due to the variation of deformation pattern of the loaded target from concentrated load to uniform load.Meanwhile,the presence of SCW increases the blast impulse transferred towards the target by three times.In addition,there exists a threshold value of the burial depth that maximizes the impact impulse.This threshold exhibits a strong sensitivity to SCW height,decreasing with increasing SCW height.An empirical formula for predicting threshold has been provided.Similar conclusions can be drawn for different explosive masses.The results provide technical guidance on blast loading intensity and its spatial distribution considering shallow buried explosives in coast-land battlefields,which can ultimately contribute to better protective designs.
基金financially supported by the National Natural Science Foundation of China (Grant No. 52278504)the Natural Science Foundation of Jiangsu Province (Grant No. BK20220141)。
文摘The afterburning of TNT and structural constraints in confined spaces significantly amplify the blast load,leading to severe structural damage. This study investigates the mechanisms underlying the enhanced dynamic response of reinforced concrete blast doors with four-sided restraints in confined space. Explosion tests with TNT charges ranging from 0.15 kg to 0.4 kg were conducted in a confined space,capturing overpressure loads and the dynamic response of the blast door. An internal explosion model incorporating the afterburning effect was developed using LS-DYNA software and validated against experimental data. The results reveal that the TNT afterburning effect amplifies both the initial peak overpressure and the quasi-static overpressure, resulting in increased deformation of the blast door.Within the 0.15-0.4 kg charge range, the initial overpressure peak and quasi-static overpressure increased by an average of 1.79 times and 2.21 times, respectively. Additionally, the afterburning effect enhanced the blast door's deflection by 177%. Compared to open-space scenarios, the cumulative deflection of the blast door due to repeated shock wave impacts is significantly greater in confined spaces. Furthermore, the quasi-static pressure arising from the structural constraints sustains the blast door's deflection at a high level.
