Ultra-high molecular weight polyethylene (UHMWPE) is widely used in the protective field due to its lightweight and exceptional mechanical properties,which can effectively resist projectile impacts.However,the micro-scale anti-penetration mechanism and ballistic impact damage modes of UHMWPE remain to be further investigated. This study focuses on two-dimensional woven and unidirectional (UD) UHMWPE composites,establishing a finite element analysis model for ballistic impacts that considers the microstructural characteristics of fiber-reinforced composites.Numerical simulations of normal and oblique penetration were conducted for composite targets with varying thicknesses and fiber layer counts,and the results were compared with experimental data to verify their reliability.Subsequently,the damage modes and energy absorption characteristics of the composite plates under different impact conditions were investigated.The results indicate that the damage modes of the composite plates are similar across different speeds,with lower speeds resulting in larger deformation areas and less energy absorption,reflecting a tendency for the material to experience extensive plastic deformation rather than localized brittle fracture under low-speed impacts.As the penetration angle decreases,the interaction time between the projectile and the target material significantly increases,enhancing energy transfer and absorption.This study not only delves into the ballistic impact mechanical response of UHMWPE composites,but also clarifies the damage modes and energy absorption mechanisms of the material under different impact conditions,providing a solid theoretical foundation for the design of composite plates with high-efficiency anti-penetration performance.

Solid propellants with crack defects are susceptible to crack propagation under shock wave loading during their service life,significantly affecting their structural integrity.The dynamic mechanical response and defect-induced damage evolution of hydroxyl-terminated polybutadiene (HTPB) propellants under varying shock wave intensities are investigated using a shock tube apparatus,and the schlieren imaging and 3D digital image correlation (3D-DIC) techniques.Shock wave loading experiments are conducted on both defect-free and crack-defected propellant specimens within a pressure range of 0.3 to 0.9MPa,and the dynamic deformation and damage evolution processes of propellant specimens are captured in the experiments.The results indicate that the deformation of the defect-free specimen exhibits a parabolic profile,and The deformation of the sample increases with the increase in impact pressure.The specimens with different crack depths show different degrees of crack growth under 0.9 MPa impact pressure,and the multiple impacts will result in superimposed damage.The critical failure crack depth ratio is 50%-75%.Residual specimen analysis reveales that the matrix cracking,particle debonding,and particle fracture are the primary failure mechanisms.These findings provide valuable insights for assessing the structural integrity of solid rocket motors under ignition shock condition.

In order to investigate the effect of polyurea coating on the protective performance of blast-resistant structure,a multi-layer blast-resistant structure reinforced with polyurea is proposed,and the protective characteristics of blast-resistant structure under the actions of shock wave and fragments are analyzed.The overpressure fitting formula of explosive is calculated and obtained,and out-of-plane displacement of blast-resistant structure is measured using a laser 3D scanner.Experimental results of overpressure and displacement are in good agreement with simulated results.Research results show that the position of polyurea coating has great effects on the protective ability of blast-resistant structure.The protective effect of coating located on blast-facing side of sandwich steel plate is better than those of coating located on the back-blast sides of face plate and sandwich steel plate.It can effectively reduce the penetration rate and impact number of fragments,weaken the energy of the combined load ultimately acting on the back plate,and reduce the vibration amplitude and acceleration at the center of back plate.This study can provide a reference for the design of multi-layer blast-resistant structure.

Coral sand is widely used in military protection projects of islands because of its convenience and well anti-explosion buffering performance.It is necessary to obtain the shock Hugoniot data of coral sand before investigating the high-pressure shock equation of state.A shock wave test system for multi-medium is designed based on continuous pressure-conducted electrical resistance probe.The test system can be used to determine the detonation wave and shock wave time history curves of explosives,standard material and tested material in a explosion test.Then the shock Hugoniot curve of the material under test could be calculated based on the impedance matching principle.A feasibility test is carried out using water as the test material to verify the reliability of the method.Finally,the shock Hugoniot curve,represented by shock wave pressure P and particle velocity U_p, of coral sand is determined using the proposed method,which is compared with the Hugoniot data of quartz sand.The experimental results show that the shock Hugoniot curve of test material can be conveniently and reliably determined based on the continuous testing system of multi-medium shock waves and the impedance matching principle.The exploration work provides a supplement to the experimental research on the shock equation of state for large-scale heterogeneous materials.

To investigate the effects of different machine oil-diesel ratios on the explosive properties of site-mixed emulsified explosives, the viscosity and particle size distribution of emulsion matrices with varying oil-diesel ratios by using digital viscometry, laser particle size analysis, and optical microscopy were examined, the internal phase structure of explosive samples was observed. The density of matrices and explosive specimens were measured through PVC tube simulations of borehole charging configurations. Detonation velocity and brisance were respectively determined by using a detonation velocity tester and lead cylinder compression method. The results reveal that as the oil-diesel ratio in explosive formulations increased from 0:5.5 to 5.5:0, the matrix viscosity rose from 1.5×10⁵mPa·s to 3.7×10⁵mPa·s. Concurrently, the sensitized bubble concentration increased while the bubble size decreased, demonstrating improved uniformity. The dispersed phase droplet size distribution narrowed significantly with distribution width decreased from 86.19μm to 6.33μm, the mean particle size reduced from 13.85μm to 2.78μm, and dispersion index declined from 6.23 to 2.27, indicating enhanced homogeneity. At 0.3% sensitizer content, the explosive density increased progressively from 0.95g/cm³ to 1.10g/cm³. Corresponding improvements in detonation performance were observed: the detonation velocity increased by 24.08% from 3155m/s to 3915m/s showing consistency with theoretical predictions from the B-W method, and the brisance increased by 34.48% from 9.05mm to 12.17mm.With increasing the sensitizer concentrations(0.3%,0.5%,0.7%), the bubble density increased and the explosive density reduced. Distinct performance trends emerged based on oil-diesel ratios: formulations with ratios ≤3:2.5 exhibited initial enhancement followed by decline in detonation parameters, while those with ratios ≥4:1.5 demonstrated progressive reduction in explosive performance characteristics.

Hypersonic warheads usually induce serious aerodynamic heating during flying,and the warhead charge also bears a harsh thermal environment because of the structural heating which may affect its thermal safety.The finite volume method and the two-way fluid-structure interaction method are used to simulate the aerodynamic heating and structural heat transfer processes of hypersonic warheads.The temperature field distribution of pneumatic heating of hypersonic warhead and the thermal-ignition response of charge at different speeds and angles of attack are analyzed based on the chemical reaction kinetics model of explosive.The results reveale that the highest temperature occurs at the head of the warhead under aerodynamic heating and structural heating transferduring the hypersonic flight of warhead,and then it decreases backwards and inward.The temperature distribution is asymmetrical at different angles of attack,the temperature on the windward side increases with the increase in the angle of attack,and the temperature on the leeward side decreases with the increase of the angle of attack.After introducing the chemical reaction kinetics model,the ignition of the charge appears on its head at 35.4s and 574K.the faster the warhead’s speed is,the more severe the aerodynamic heating it experiences is,and the shorter the ignition time of charge is.A thermal protection structure is designed,which can effectively increase the temperatures of warhead’s shell and charge by 79.12% and 71.45% during its 100s flight process as well as ensure that the internal charge does not ignite.This study is of great significance in addressing the thermal safety issues of hypersonic warhead charges.

To address the issues of the lack of structural synergy between ceramic plates in existing spliced ceramic bulletproof plates and the poor dissipation of impact energy,a biomimetic topological interlocking ceramic splicing scheme based on the exoskeletal structure of phloeodes diabolicus is designed.The numerical simulation research is made on the protective performance of the designed bulletproof plates under the impact of bullets. A non-standard bulletproof ceramic plate with a phloeodes diabolicus exoskeletal structure is designed based on the microstructure of biological materials and the principle of topological interlocking in engineering structures.The accuracy of the simulation model is verified through 3D-DIC testing,and the penetrations of 5.8mm DBP 10 rifle bullets into square,hexagonal and biomimetic topological interlocking ceramic spliced bulletproof plates are simulated.The results show that the biomimetic topological interlocking ceramic blocks can effectively enable the surrounding ceramics to dissipate the impact energy,The back bulge height of the biomimetic topological interlocking ceramic bulletproof insert after being penetrated is reduced by approximately 8% compared to that of the hexagonal ceramic bulletproof insert.An individual soldier protective insert plate based on the biomimetic topological interlocking ceramic configuration is designed,and the numerical simulations are conducted on the blunt trauma effects of M80 rifle bullet penetrating the human torso of the protected individual soldier.The results indicate that the blunt trauma energy is primarily borne by the muscles and thoracic ribs,and the peak stress on thoracic ribs reaches 30.7MPa,which potentially leads to bone fractures.The maximum stress in the heart is 930.2kPa,and the maximum stress in the lungs is 777.5kPa,potentially causing myocardial injury and lung soft tissue contusion.

Aiming at the dynamic fragmentation characteristics of reactive material and its effect on the impact energy release behavior,two types of reactive materials,Al/Ti and Al/Ti/W,are selected as the research subjects.Dynamic fragment soft-recovery test is conducted to obtain the fragment size distribution characteristics of reactive material at different impact velocities.Additionally,the impact-induced energy release test is performed to analyze the impact pressure characteristics and reaction processes of Al/Ti and Al/Ti/W.Based on these investigations,a calculation method for impact pressure,which considers material fragmentation characteristics and the critical size of the reaction,is proposed.The results indicate that the fragmentation characteristics of reactive material are crucial in influencing its impact energy release behavior.The cumulative size distribution of fine fragments formed after the impact fragmentations of both Al/Ti and Al/Ti/W materials can be described using a Logistic distribution function.The impact reaction process of reactive material in a reaction chamber can be divided into primary and secondary reaction stages.The calculation error of the proposed calculation method is less than 15% when calculating the quasi-static pressure during the primary reaction stage.

The dynamic response and energy dissipation mechanism of foam aluminum sandwich panel under underwater impulsive load are analyzed to provide a scientific basis for the protection design of ships and marine engineering structures.The consistency between the test and simulated results is verified through the underwater explosion equivalent impact test and simulation.The influences of structural parameters,such as core layer mass ratio,panel thickness,foam aluminum density and impact load on the impact resistance of sandwich panels are quantified.Multi-objective optimization of sandwich panel structure is carried out using neural network and genetic algorithm.The results show that the foam aluminum sandwich panels subjected to underwater impact loading exhibit the deformation patterns such as local collapse and boundary shear.When the mass of sandwich panel is constant,there exists an optimal core layer mass ratio and an optimal wet panel thickness,which increase with the increase of dimensionless impulse.As the thickness of wet panel and the density of core layer decrease,the energy absorption efficiency of the compression deformation of core layer increases.The optimized sandwich panel has significantly reduced deformation and mass.

Exploding foil initiators (EFIs) represents a promising initiation technology for meeting the high requirements of miniaturized and integrated weapon systems for initiation capability.To conduct an in-depth research on the initiation and detonation output characteristics of small-sized charges in the exploding foil initiator system,a synchronous test system for observing the electrical explosion-driven flyer characteristics of metal bridge foils and a particle velocity measurement system for measuring the velocity of particle at the explosive-window interface for flyer-impact-initiated small-sized explosive detonation are built.The velocity and morphological characteristics of flyers and the initiation and detonation reaction behaviors of small-sized Ultrafine Hexanitrostilbene (HNS-IV) explosive under flyer impact were investigated.The results show that the flyer velocity is positively correlated with the initiation voltage.When the initiation voltage ranges from 900V to 1500V, the flyer velocity exiting the accelerator chamber is measured at 2000m/s to 4200m/s.HNS-IV-based explosives demonstrates a short growth distance of detonation under high-intensity impact.For instance,a stable detonation is achieved within just 2.14mm under the action of a 3455m/s flyer.The further analysis of detonation wave structure indicates that HNS-IV has a fast detonation reaction rate,with a reaction time of less than 27 ns and a reaction zone width of only 0.13mm.Under the condition of a 3mm-diameter charge,the main detonation reaction of HNS-IV explosives remaines largely unaffected,but the energy decays rapidly in the late stage of reaction.The detonation reaction rate model is first calibrated with the experimental results,and then the effect of charge size on the energy output is studied through simulation.The results show that the increase in charge thickness is more effective in enhancing the energy output at the end of charge than the increase in charge diameter.

In order to obtain the damage characteristics of the double-layer shell structure under the underwater explosion of the shelled charge, the damage test of the double-layer shell structure under the underwater explosion was carried out with a small explosive tank device, and the influence of the hollow medium at the back cavity of the inner plate, the filling medium between the inner and outer plates, the explosion position and distance and other factors on the damage characteristics of the double-layer shell were analyzed, and the damage mode of the double-layer shell structure under the underwater explosion of the shelled charge was obtained. The results show that under the contact explosion of the underwater shell charge, there are three kinds of damage modes: the overall plastic deformation of the double-layer shell, the tearing of the inner and outer plates in the shape of “mouth”, “grid” and “cross”, and the local bending or fracture deformation of the inner and outer plates and ribs. Under the same underwater contact explosion conditions, when the explosion position is at the intersection of the transverse and longitudinal ribs of the double-layer shell, the damage range caused to the inner and outer plates is larger, and the filling of the water medium between the double-layer shells greatly reduces the impact effect on the inner shell and improves the impact resistance of the inner plate of the double-layer shell.

In order to carry out comparative analysis on the implosion power under atmospheric and vacuum conditions, the implosion experiments were applied for JO-8 explosive in a vacuum explosion tank and the implosion power under different conditions was analyzed. The results show that the peak reflected pressure in the forward direction of explosion product propagation is 1.12 times the value in the side direction in vacuum and the peak quasi-static pressure in the forward direction of explosion products propagation is 1.67 times the value in the side direction. The deformation of the effect target in the forward direction of propagation is greater than that in the side direction, proving that the propagation of explosion products has distinct directionality in vacuum. The peak reflected pressure and peak quasi-static pressure under atmosphere are 1.12 and 1.67 times the values in vacuum respectively. Simultaneously, the deformation of the effect target is greater than that in vacuum, showing that stronger damage power is produced under atmospheric pressure because of the lack of air medium in vacuum.

In order to research the explosion characteristics of HMX-based aluminized explosives with different charge structures in confined space, experiments on the confined explosion of samples with composite charge structures and uniform charge structures were carried out. A closed explosion experimental device with temperature and pressure measurement was established. The explosion pressure and temperature of the sample with composite charge structure were compared with the same sample having the uniform charge structure. The result shows that the peak pressure and quasi-static pressure of the explosion shock wave of the sample with composite charge structure are 12.7% and 8.0% higher than those with the uniform charge structure, respectively. The explosion energy release in confined space can be improved through the composite charge structure, which consists of the outer layer with high detonation velocity explosive and the inner layer with high aluminum/oxygen ratio explosive. The peak explosion temperature of composite charge structure is 621℃, which decreses by 124℃ compared with the uniform charge structure of 745℃, but the samples with composite charge structure can maintain a high temperature around 600℃ in confined space for a long period.

In order to study the ignition and explosion properties of micro-nano self-assembled and physically mixed aluminum powder materials, the ignition sensitivity, flame propagation characteristics and explosion parameters of the materials were studied through a 1.2L Hartmann tube and a 20L ball explosion test system. The results show that compared with Al-T4 micron aluminum powder, nano-aluminum powder can significantly reduce the ignition energy of aluminum powder materials.And the ignition sensitivity of the self-assembly process is further increased compared with that of aluminum powder materials with physical mixed process. In terms of the flame propagation speed, the high reaction rate of a small amount of nano-aluminum powder can accelerate the reaction of micron aluminum powder, and the self-assembled aluminum powder is easy to ignite and the heat transfer is more efficient due to the overall synergistic effect of micro-nano aluminum powder. In the 20L ball explosion test system, the maximum explosion pressure and explosion index of self-assembled and physical mixed aluminum powder with 5% mass fraction of nano content are 0.72MPa, 0.75MPa, 43.21MPa·m/s and 31.49MPa·m/s at 500g/m³. The maximum explosion pressure and explosion index of self-assembled and physical mixed aluminum powder with 10% mass fraction are 0.84 and 0.68MPa at 1000g/m³. The explosion pressure and explosion index of 5% mass fraction of nano aluminum powder increase first and then decrease with increasing the concentration, and the explosion pressure and explosion index of aluminum powder with 10% mass fraction increase with the increase of concentration. The explosion power of the composite system isnot only related to the activity, but also has a certain relationship with the calorific value of the powder.

The effects of altitudes and the decoupled conditions of low pressure and temperature on the blast wave parameters of moving charge were investigated by employing the AUTODYN software. Additionally, a theoretical calculation model was developed to predict peak overpressure of the moving charge under low pressure and temperature. The model was validated subsequently through experimental data and numerical simulations. The results indicate that the model can assess the blast wave peak overpressure of moving charge at low temperature, pressure and coupled high-altitude environment effectively. The peak overpressure of the blast wave generated by the moving charge decreased by an average of 35.6%, the action range increased by 62.0% for altitude increased from 0 to 10000m. With the ambient temperature decreased, the peak overpressure of the blast wave increased by an average of 0.43%, the action range decreases by 11.9%; and with the ambient pressure decreased, the peak overpressure of the blast wave decreased by an average of 36.4%, the action range increased by 83.5%. The increase coefficient of blast wave overpressure resulting from the moving charge at various altitudes closely resembles that of low pressure. In high-altitude settings, the action range and overpressure of the blast wave from the moving charges explosion are predominantly influenced by pressure, whereas the effect of temperature is comparatively marginal.

Aiming at the structural damage caused by the water-entry impact of trans-media vehicle, an auxetic hood load-shedding method is proposed to make use of the special tensile expansion effect of auxetic structure, so that the hood can absorb more impact energy. The arbitrary Lagrangian-Eulerian algorithm is used to analyze the influence law of the auxetic hood on the load-shedding characteristics of the vehicle, and the numerical method is verified by experimental data. The results show that, compared with the traditional load-shedding cowl, the auxetic hood effectively reduces the impact load of the structure entering into water on the basis of structural lightweight, and the peak acceleration can be reduced by 75%, 70% and 68% at the water-entry speeds of 20m/s, 35m/s and 50m/s, which is a good load-shedding cushioning effect. And the load-shedding characteristics of auxetic structure differ greatly under the different parameters of the cell angle, the wall thickness and the length of the sides. The load-shedding characteristics of auxetic hood reaches the optimal effect with cell angle of 20°, cell wall thickness of 0.5mm and cell side length of 1.6 times.

In order to study the impact energy release and crushing behavior of N b₁Zr₂Ti₁W₂ high entropy alloy, the test method of dynamic energy release testing during the bullet-target interaction was provided by ballistic gun and quasi-closed reaction tank. The impact energy release process and dynamic crushing law were analyzed, and the cumulative mass distribution model of fragments was established. The impact induced energy release characteristics of N b₁Zr₂Ti₁W₂ high entropy alloy were studied.The results show that N b₁Zr₂Ti₁W₂ produces “explosion-like” energy release effect under high-speed impact load, which releases a large amount of chemical energy mainly due to the oxidation reaction of Zr element. The 5.07g alloy material can produce 0.176MPa overpressure in the 32.7L quasi-closed vessel at the speed of 1631m/s. The distribution of fragments follows the power law, and the size of fragments is closely related to the energy release.

The improved Hartmann tube device was used for ignition experiments to investigate the flame propagation process and thermal radiation characteristics of MgH₂ dust explosion. A high-speed camera, thermal radiometers, and the infrared thermal imager synchronous control system were used to record the flame propagation, heat radiation flux change, and temperature change process of MgH₂ dust, respectively. The results show that after ignition, the MgH₂ flame continues to expand to form a continuous combustion area and when it reaches the maximum, it begins to decay, and a discrete flame appears. When the mass concentration is 150—1000g/m³, the maximum propagation height and the maximum propagation velocity of the flame front reach 1138mm and 45m/s, respectively, at 750g/m³. In addition, the maximum heat radiation flux of No.3 above the fireball reaches 31.7kW/m², which is much higher than those of No.1 and No.2 on both sides. The temperature is highest in the flame center and gradually decreases around it. The high-temperature zone is concentrated in the upper part of the flame.

Aiming at the expansion fracture mechanism of projectile steel shell under implosion loading, the smooth particle fluid dynamics method(smoothed particle hydrodynamics, SPH)was used to simulate the expansion fracture process and crack distribution law of 40CrMnSiB steel cylindrical shell with several wall thicknesses under implosion loading. The comparative experimental study was carried out by using the explosive water well recovery technology, and the crack formation mechanism was analyzed by combining the macroscopic morphology and microstructure of the cylindrical shell fracture fragments. The results show that the fracture mode of 40CrMnSiB steel cylindrical shell gradually changes from pure shear to tension-shear mixing with the increase of wall thickness. When the wall thickness of the cylindrical shell increases from 4mm to 17mm, the proportion of tension cracks gradually increases from 0 to 4/5, and the circumferential density of the cylindrical shell cracks and the total number of fragments formed decrease by 54.54% and 67.06%, respectively. With the increase of the wall thickness of the metal cylindrical shell, the mass distribution of the final fragments gradually disperses. By analyzing the microstructure of the recovered fragments, it is found that the fracture of the cylindrical shell is actually the result of the interaction and competition between the shear cracks generated on the inner surface of the shell and the tension cracks generated on the outer surface, and there is a phenomenon of mutual shielding between the cracks.

To deeply understand the impact initiation,impact ignition,detonation process,and detonation product states of energetic materials under extreme conditions, the decomposition reaction processes of α-, β-, γ-and ε-CL-20 crystals under shock loading were studied using self-consistent charge density functional-based tight-binding(SCC-DFTB)in combination with multiscale shock technique. The influence of water molecules on the decomposition of α-CL-20 was also studied because α-CL-20 generally exists in the form of hydrate. The results show that γ-CL-20 has the largest compression ratio among these four CL-20 crystals at the same shock velocity. When the shock velocity is 8 km/s, γ-CL-20 completely decomposes, while the other three crystals do not completely decompose until the shock velocity reaches 9km/s. Moreover, the addition of water molecules can significantly increase the activity of CL-20 molecules, and accelerate the decomposition of solid phase α-CL-20. In addition, the initial decomposition path of CL-20 under shock loading is not significantly affected by the crystal forms, but is mainly affected by the shock velocity. When the shock velocity is lower than 8km/s, the decomposition reaction is triggered by the dissociation of N—NO₂ bond. However, when the shock velocity is higher than 9 km/s, the N—NO₂ bond is inhibited by high pressure. The H in the C—H bond may preferentially form a five-membered ring with the adjacent NO₂, and further produces NO and OH.

Due to the issue of high parallel deviation in the explosion heat test results of the composite solid propellants, using the thermostatic calorimeter, carry out the accurate test research of composite propellant explosion heat from the three aspects of clarifying the definition of explosion heat, standardizing experimental conditions and improving experimental devices. The results show that the measured values of the combustion heat release of the propellant using its own oxidizing agent tends to increase significantly with the reduction of propellant particle size and the increase of the sample amount. Therefore, the single quality of the propellant explosion heat test sample should be less than 0.14g, and the quality of the propellant sample should be more than the quality of the sample used to measure stable maximum heat release. The pressure measuring element is installed on the oxygen bomb of the calorimeter to realize the whole test record of the pressure in the oxygen bomb during the calorimetry process, and the pressure detection before ignition guarantees the effectiveness of displacing air in oxygen bomb. The maximum pressure in the oxygen bomb provides a basis for eliminating the outliers of inadequate combustion. Combined with the final pressure and the oxygen bomb volume in the experiment, the test of constant pressure explosion heat is realized.

To investigate the enhancement effects of free hydrogen produced by metal hydrides on the damage performance of fuel air explosive(FAE), A 20L spherical liquid explosion test system and the colorimetric temperature measurement technology were used to study the effects of different matrix liquid fuels and metal additives on the shock wave and thermal damage performance of FAE. The results show that epoxypropane(PO)has the best explosion performances of the three liquid matrix fuels commonly used in FAE. When titanium hydride(TiH₂)powders are added to PO, the explosion overpressure, maximum pressure rise rate and maximum average temperature of the mixed fuels increase first and then decrease with the increase of TiH₂ powders content, reaching the maximum values when the mass fraction of TiH₂ powders was 35%, namely, 1.21MPa, 68.73MPa/s and 2398K, respectively. Compare to Ti-PO mixed fuels, the TiH₂-PO mixed fuels has more continuous combustion flame and more excellent explosion performances at the same mass concentration. The research results indicate that as a potential high-energy additives, TiH₂ could be effectively applied to FAE to improve its explosion characteristics and enhance the shock wave as well as the thermal damage performances.

In order to evaluate the damage effect of block charges with different masses on the surface of concrete pier body,the damage characteristics of the concrete pier under the action of contact explosion were studied by numerical simulation,and the damage effect of the concrete pier body was evaluated by the equal damage curve,and the characteristics of the damage area of the top surface,side and side edge of the pier body under the action of contact explosion were obtained,and then the influence of charge quality and placement position on the damage effect of pier body was revealed. By establishing the calculation model of vulnerable volume,the variation curves of the remaining volume of concrete pier body with the charge mass under the action of contact explosion on the top surface,side and side edge were obtained. On this basis,the block charge with different masses was compared in 8 different positions on the concrete pier body during contact explosion,and the number of large fragments and the maximum fragment volume after the explosion were studied. The result shows that the shape of the damage area on the top surface and side of the concrete pier is approximately circular,and its center coincides with the center of the top surface. The shape of the damage area on the side edge is approximately elliptical. When the charge explodes in contact with the top surface,side and side edges,the damage effect at the center position is the best. When the charge mass is 1-3 kg,the damage effect of the explosive exploding at the geometric center of the top surface of concrete pier is the best. When the charge mass is greater than 3 kg,the damage effect of the explosion at the side geometric center is the best.

To study the influence of thickness on dynamic response and energy-absorption characteristics of foamed concrete(FC)under explosion-load impact,the numerical calculation of anti-explosion of FC under 0.8 m/kg^1/3 ratio-detonation-distance and 0-30 mm thickness was carried out by using finite element software. Subsequently,the anti-explosion tests of FC with thickness of 0 mm,10 mm,20 mm and 30 mm,were carried out to verify the accuracy of the numerical calculation. Through numerical calculation,the damage form and energy-dissipation mechanism of FC under the impact of explosion-load were studied,and the ability of FC to absorb explosion-wave energy was quantitatively analyzed,and the law of the energy absorption characteristics of FC and the deformation response of aluminum alloy plate on the back influenced by the change of thickness of FC was obtained,and the corresponding engineering-calculation-model was derived. The results show that,the size of the FC crushing zone gradually shrinks with the increase of thickness. The FC crushing-zone only accounts for 2.9% of the overall volume when the thickness is 30 mm. FC can effectively absorb and dissipate the energy of explosion wave,and its energy-absorption capacity increases with the increase of thickness. The foam concrete with thickness of 5-30 mm can absorb 42.8%-91.9% of explosion wave energy respectively. The displacement response of aluminum alloy backplane steadily shrinks as FC thickness increases. While the thickness of FC is 30 mm,the displacement response of the center of the aluminum alloy backplane drops to 3.2 mm,which is only 12.6% of that without FC.

In order to study the explosion shock wave propagation law of triacetone triperoxide(TATP)in the air, Raman spectrometer, Fourier transform infrared spectrometer(FTIR)and gas chromatography-mass spectrometry(GC-MS)were used to inspect the structure of homemade TATP. Then the parameters of the explosion shock wave of TATP in the air were tested by the shockwave test system. The variation of peak overpressure, positive pressure duration, specific impulse and shock wave velocity with proportional distance was analyzed. The empirical formulas of peak overpressure, positive pressure duration and impulse of TATP were fitted, and the TNT equivalent of TATP was calculated. The results show that the peak overpressure and specific impulse of TATP decrease with the proportional distance, and the attenuation amplitude also decreases with the proportional distance. The measured average values are 0.87 times and 0.73 times that of TNT, and the TNT equivalent of TATP is 75.39%; The positive pressure duration is affected by both the charge mass and the charge distance. The greater the charge mass and the distance, the longer the positive pressure duration. The average rising rates of the positive pressure duration of TATP and TNT with the proportional distance are 0.066 and 0.100, respectively. In the near field, the positive pressure duration of TATP is longer than that of TNT, and when the proportional distance is greater than 3.646m/kg^1/3, its positive pressure duration gradually decreases smaller than that of TNT. It shows that the explosion shock wave parameters of TATP in the air follow the explosion similarity law, and the empirical formulas obtained by fitting is suitable for the evaluation and theoretical calculation of TATP explosion power.

To investigate the bubble pulsation and water jet characteristics under the gas-liquid-solid multiphase coupling effect of underwater explosions near the seabed, the Euler method was employed to establish a numerical model of underwater explosions near the seabed under different substrate/water depth conditions. The full physical process of underwater explosions near the seabed under muddy substrate conditions was simulated and compared with experimental results, which showed good agreement, verifying the effectiveness of the algorithm in solving the problem of underwater explosion bubbles near the seabed. Based on this, the influence of seabed substrate and water depth on the bubble morphology, radius, period, and water jet of underwater explosions near the seabed was discussed. The results show that under the premise that the bubbles can be split, the harder the substrate, the faster the bubbles split, and the deeper the water depth, the slower the bubbles split. The harder the substrate and the deeper the water depth, the smaller the maximum radius and period of the bubble, the larger the proportion of the bubble in the total bubble volume at the moment of splitting, and the smaller the peak velocity of the two water jets generated by splitting. During the evolution of the downward water jet, a reverse water jet will form. The harder the substrate, the greater the peak velocity of the reverse water jet. In all calculated cases, the depth parameter(H_ref)is in the range of 250—750, and the peak value of the reverse water jet velocity is positively correlated with the H_ref, and the H_ref is in the range of 750—1000, which is negatively correlated.

The concave honeycomb structure has broad application prospects in the automotive industry,aerospace,biomedical and other fields due to their unique deformation mode,excellent impact resistance and energy absorption properties,and lightweight characteristics.Based on the traditional Concave hexagonal honeycomb structure,a deformation-controllable concave honeycomb structure based on rounded corners enhancement is proposed by introducing a rounded corner design and changing the arrangement of the rounded corners,and a deformation-controllable honeycomb structure with deformation modes of Z and Y shapes is designed and prepared using metal 3D printing technology.In order to explore its impact resistance,its deformation mode and energy absorption properties are analyzed through the quasi-static compression and drop weight impact experiments and the finite element numerical simulation.The research results show that the proposed honeycomb structure achieves controllable deformation mode and has higher crushing stability,and the energy absorption performance of the structure is significantly improved through customized Z and Y deformation modes.For the same structure,the energy absorption performance gradually improves as the fillet radius increases.As the speed increases,the structural deformation mode gradually evolves into an I type collapse,the platform force generally shows an increasing trend,and the energy absorption efficiency gradually decreases.Due to the asymmetric arrangement of the rounded corners,the Z shape structure has better impact resistance than the Y shape structure in most cases.The research results can provide reference for the crashworthiness design of new structures under dynamic impact.

In order to quantitatively analyze the effect of explosion impact on the ignition energy of electronic detonator,seven sets of impact experiments with different strengths are made for liquid aluminum electrolytic capacitors by underwater explosion method.The dielectric breakdown behavior and leakage current change rule of capacitor under impact load are studied,and the energy loss path of electronic detonator capacitor is analyzed.An impact-ignition model of electronic detonator is established.The functional relationship between shock wave overpressure and ignition energy is obtained.The results show that the dielectric breakdown of capacitor sample occurs under the shock wave overpressure of 8.5-40.6MPa,and the voltage drop increases exponentially with the increase in shock wave overpressure.When the shock wave overpressure is greater than a critical value,the capacitor cannot heal completely after dielectric breakdown,and the leakage current increases to the mA level with an average value of 1.62mA.The ignition energy of electronic detonator decreases gradually with the increase in shock wave intensity,and when the leakage current increases,the ignition energy drops sharply.

Metal halide perovskites have become a current research hotspot owing to their exceptional optoelectronic properties and significant potential application value. The elemental composition and crystal structure of perovskite material have crucial influence on its performance.To realize the preparation of novel perovskites,this paper focuses on the research of synthesizing cesium lead chloride perovskite (CsPbCl₃) under shock loading.In this study,CsPbCl₃ perovskite powder is synthesized by the shock loading of detonation-driven flyer plates under the conditions of 0.6-0.8 relative densities of powder and 14.2-27.9GPa shock pressures.The characterization results of X-ray diffraction (XRD),scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicate that the recovered products are CsPbCl₃ perovskite powders.Experimental results also demonstrate that the shock pressure and the relative density of precursor are two key factors to the synthesis of CsPbCl₃ perovskite powder.Based on the experimental conditions and analytical characterization results,a formation mechanism of CsPbCl₃ synthesis is discussed.It is confirmed that the proper shock pressure for high-purity CsPbCl₃ powder synthesis is from 14GPa to 17GPa.It is also suggested that the shock synthesis method is a feasible approach for preparing difficult-to-synthesize perovskite.

In order to obtain the slow cook-off response characteristics of HMX-based pressed aluminized explosives under different restraint modes and strengths, a scaled cook-off bomb with charge length-diameter ratio of 5:1 was designed based on a typical supersonic ground penetration warhead. The slow cook-off experiments of HMX-based aluminized explosives under unrestrained and different restrained strengths were carried out. The reaction violence of HMX-based pressed aluminized explosives under unconstrained conditions, and the variation of charge reaction violence with different shell thickness(4, 10, 16 and 20mm)and end cover thread length(10, 12 and 14mm)were obtained. The results show that under the condition of slow cook-off, the HMX-based aluminized explosive reaction includes three stages: gas generation, combustion at the end cap and flame extinguishment. The restraint strength of the slow cook-off bomb affects the ignition time and temperature of the charge, and then affects the increase of the internal reaction pressure of the bomb, and finally leads to different reaction violence. When the thread length(L)is 14mm, with the shell thickness(δ)from 4mm to 20mm, the reaction violence develops from deflagration to explosion and then weakens to combustion; when the shell wall thickness(δ)is 10mm, with the thread connection length(L)increases from 10mm to 14mm, the reaction violence changes from combustion to explosion. When the shell wall thickness(δ)is equal to the equivalent shell wall thickness(δ_e), the restraint strength of the slow cook-off bomb is more uniform, which is beneficial to the continuous growth of the reaction pressure, and finally leads to a more violentexplosion reaction of the slow cook-off bomb.

To study the explosiveness of biomass fuels, TG-DTG thermogravimetric analysis was used to analyze the combustion performance and kinetic parameters of several common biomass fuels(straw, sawdust, peanut shells)and their mixtures. The microstructures of these fuels were analyzed using scanning electron microscopy(SEM). Additionally, an elemental analysis of the wood powder and peanut shell powder mixture was carried out using an elemental analyzer. Based on the elemental composition, the amount of oxygen required for its oxidation reaction was calculated, and an explosion test was subsequently conducted. The results showed that the mixed fuel(wood powder and peanut shell powder in a 1:1 mass ratio)exhibited high stable combustion characteristics, flammability index, and overall combustion performance. The activation energy was moderate, and the surface appeared porous and rough, with more free surfaces and a larger specific surface area, which facilitated combustion. In an experiment,40g of this mixed fuel was loaded into a steel pipe with a diameter of 40mm, a length of 200mm, and a wall thickness of 1.5mm, and filled with 5MPa oxygen. The mixture was successfully detonated by a No.8 electronic detonator without producing toxic gases. The steel pipe was blasted into fragments of different sizes, with most fragments measuring less than 50mm. The research results indicate that biomass fuel can exhibit explosiveness under certain conditions.

To investigate the bubble pulsation and water jet characteristics under the gas-liquid-solid multiphase coupling effect of underwater explosions near the seabed, the Euler method was employed to establish a numerical model of underwater explosions near the seabed under different substrate/water depth conditions. The full physical process of underwater explosions near the seabed under muddy substrate conditions was simulated and compared with experimental results, which showed good agreement, verifying the effectiveness of the algorithm in solving the problem of underwater explosion bubbles near the seabed. Based on this, the influence of seabed substrate and water depth on the bubble morphology, radius, period, and water jet of underwater explosions near the seabed was discussed. The results show that under the premise that the bubbles can be split, the harder the substrate, the faster the bubbles split, and the deeper the water depth, the slower the bubbles split. The harder the substrate and the deeper the water depth, the smaller the maximum radius and period of the bubble, the larger the proportion of the bubble in the total bubble volume at the moment of splitting, and the smaller the peak velocity of the two water jets generated by splitting. During the evolution of the downward water jet, a reverse water jet will form. The harder the substrate, the greater the peak velocity of the reverse water jet. In all calculated cases, the depth parameter(H_ref)is in the range of 250—750, and the peak value of the reverse water jet velocity is positively correlated with the H_ref, and the H_ref is in the range of 750—1000, which is negatively correlated.

In order to investigate the energy release characteristics of the composite charge formed from Al/PTFE reactive materials and highly energetic explosive, three kinds of composite charge samples comprising Al/PTFE reactive materials with various components and mass ratios were prepared, and utilized to explosion tests. Free-field incident shock wave overpressure of several gauging points were measured. The process images of reactive materials scattering, reaction, and the fireball expansion were photographed. The reaction characteristics of reactive materials and the gain mechanism on the shock wave overpressure parameters were analyzed by comparing with the static explosion test of the bare charge. The results show that during the scattering process, reactive materials undergo self-reaction, anaerobic reaction with detonation products and aerobic reaction with ambient oxygen. Compared with bare charge, the secondary reaction enlarges the fireball and highly lengthens the duration of the flame, significantly enhances the shock wave simultaneously. At the gauging point of 2.5 meters, the maximum overpressure value and specific impulse are 1.8 times and 1.5 times of that the bare charge respectively, and the gain effect increases with the increase of aluminum contents in middle and far field range. However, the discrepancy narrows as the propagation distance increases due to the dilution of aluminum powders. By selecting the appropriate composition ratio and quality of Al/PTFE reactive materials, it is beneficial to compensate for the shock wave energy loss caused by the breaking and scattering of materials in the near field. Simultaneously, the after-burning reaction provides energy supplement for the middle and far fields, which is expected to achieve the overall gain of explosion energy release.

In order to improve the impact resistance and energy absorption of thin-walled circular tube,a carbon fiber reinforced composites (CFRP) thin-walled tube with porous array is designed to investigate its impact resistance and energy absorption performance under axial and transverse impact loads,respectively.A finite element model of CFRP thin-walled tube with porous arrays under impact loading is established based on the finite element method (FEM).The effects of different lay-up angles on the impact resistance and energy-absorbing properties of the structure are analyzed.Numerical results show that CFRP thin-walled circular tube with porous arrays has higher specific energy absorption and peak load,which are too high for the protected structure.But the peak impact load and specific energy absorption values can be changed by varying the lay-up angle of CFRP in order to enhance impact damage resistance.The maximum compression load within the effective compression displacement is reduced by about 10.1% and the specific energy absorption value is increased by about 15.1% when the lay-up angle of thin-walled circular tube with porous arrays is changed from [90°/45°/90°/0°]_2S to [90°/0°/90°/0°]_2S under axial impact loading.The preliminary results will be a guide for the engineering application of lightweighting and impact resistance enhancement of CFRP thin-walled tube.

Perovskite is regarded as one potential material for next-generation photovoltaic devices owing to its outstanding photoelectric characteristics which can be easily adjusted by phase transitions.However,the technology for intercepting and preparing the metastable perovskites is still in its infancy.The impact loading method has a significant advantage of high quenching rate,and enables the capture of metastable phases and facilitating their subsequent recovery and preparation.To achieve the impact phase transition treatment of CsPbBr₃,the cylindrical converging shockwaves are generated by the pulsed discharge of cylindrical wire array in water medium for studying the shock-induced phase transition of CsPbBr₃.The delicate control of shock pressure is applied to act on CsPbBr₃ powder by adjusting the charging voltage.After experiments,the samples are recovered and characterized.The characterized results reveale that the shock waves generated by pulsed discharge can induce phase transition in CsPbBr₃ powder under appropriate shock pressures (above 2 GPa).Additionally,the typical phenomena such as grain refinement,lattice distortion and nano-defects are observed in the recovered samples after shock-wave treatment.This study demonstrates that pulsed discharge of cylindrical wire array in water medium is a feasible converging shock wave loading technique,providing a novel approach to shock-induced phase transition loading.

The damage effects of ultra-high performance fiber reinforced concrete (UHPFRC) beams with different strengths subjected to blast loading are studied,with a focus on protecting typical architectural components from explosion.The influences of fiber content and longitudinal reinforcement type on the failure mode and dynamic response of UHPFRC beams are studied througth experiment.The results show that the increase in the fiber content and the use of high-strength steel (HSS) longitudinal reinforcement can improve the bending resistance of UHPFRC beams.A finite element model for UHPFRC beams under blast loading is developed to expand the research on damage effect.The parameters of the K&C constitutive model are calibrated using the single element test method,considering the factors like strength planes,equations of state,shear dilation,damage evolution,and strain rate effects.The quasi-static experiments demonstrate that the modified constitutive model parameters provide a more precise description of the mechanical characteristics of UHPFRC.Furthermore,the accuracy of the finite element model is also validated based on explosive experimental data.Finally,the influences of concrete strength,steel reinforcement type,and charge masses on the damage effects of UHPFRC beams at close range are further analyzed through parameter analysis.

In order to study the damage effect of the near-field strong shock wave on the covered charge,the dimensional analysis method on the sympathetic detonation with covered plate was established theoretically. The shock initiation process of covered-pressed TNT was numerically simulated by nonlinear finite element program ANSYS/LS-DYNA. The influence of covered plate thickness,donor charge mass,length-diameter ratio of donor charge on the detonation distance during non-contact explosion was analyzed. The functional relationship between covered-plate thickness and sympathetic detonation distance was obtained by a non-linear least square method,as well as the functional relationship between donor charge mass and sympathetic detonation distance. The results show that the dimensional analysis results are in good agreement with the fitting formula,which fully demonstrates the validity and accuracy of the fitting formula. The calculated detonation distance of the non-contact explosion decreases with the increase of the covered-plate thickness. While the covered-plate thickness is less than 3 mm,the increase of the covered-plate thickness has a greater impact on the sympathetic detonation distance. While the thickness is greater than 3 mm,further increasing the covered-plate thickness has significantly smaller effect on increasing the shock initiation resistance of explosive. When the length-diameter ratio of the donor charge remaining constant,the detonation distance of the non-contact explosion is linear with the donor-charge radius,and cubic with the donor-charge mass. Under the donor-charge mass remains constant,the detonation distance of the non-contact explosion is the largest when the diameters of the donor-charge and the acceptor charge are equal.