The influence of aluminum powder content on the energy output characteristics of RDX-based aluminized explosives is studied.The free-field static explosion tests are conducted on aluminized explosives with aluminum powder contents of 20%,30%,and 40%.The overpressure-time curves of free-field and ground shock waves are measured using overpressure sensors,and the propagation processes of incident waves,reflected waves,and Mach waves,as well as the changes in the explosion fireball are captured using a high-speed camera.The JWL-Miller parameters of the aluminized explosives are calibrated based on the test results.The test results show that the peak overpressure and specific impulse of ground reflected wave of the aluminized explosive are slightly affected when the aluminum powder content increases from 20% to 30%.When the aluminum powder content increases from 30% to 40%,the peak overpressure of ground reflected wave is decreased by 2.17% to 7.81%,and the specific impulse is decreased by 0.29% to 12.17%.When the aluminum powder content increases from 20% to 40%,the maximum diameter of explosion fireball increases from 6.48m to 7.12m,and the time when the explosion fireball begins to shrink increases from 20ms to 60ms.The maximum errors of the blast shock wave parameters (peak overpressure and specific impulse) of 30% and 40% aluminized explosives predicted using the JWL-Miller parameters are 16.75% and -8.51%,respectively,compared with the test results,and the average absolute percentage errors are 6.76% and 4.14%,respectively.This study can provide reference and guidance for the prediction of the power field of aluminized explosives.

The crew is the weakness of the ship anti-impact system, and it is helpful to improve the protection design by clearly defining the impact response characteristics of human body.This paper focuses on the impact response regularities of crew in different postures.The impact response characteristics of supine human are studied via the real ship-human underwater explosion (UNDEX) impact test for the first time; A far field UNDEX load-structure-human body integrated response model is constructed based on the Taylor fluid-structure coupling principle, and the vertical response differences of typical organs of human body in different postures under the conditions of typical impact factors (0.30, 0.45 and 0.60) are compared and analyzed.The results indicate that the vulnerable organs of sitting, standing and lying persons are the pelvis, feet and head, respectively, which should be given priority protection.When the human body changes from a sitting position to a standing position, the loads on the organs in the upper part of human body significantly decrease, and the lumbar spine and pelvis are no longer vulnerable parts prone to injury.There is a tendency for the vulnerable parts to shift from the pelvis to the head when the human body changes from a sitting position to a lying position.Under the same impact factor, the response degrees of the organs of human body in different postures directly contacted with the deck are more sensitive to the change of deck mass and show a negative correlation.The research results can provide technical support for the impact protection design.

In order to investigate the performance of different clustering algorithms in processing the finite element resultant stress nephograms,a single-layer ballistic impact finite element model of Twaron^® plain weave fabric is established.Four different clustering algorithms,namely,k-means,Gaussian mixture model (GMM),Mean-shift,and density-based spatial clustering of applications with noise (DBSCAN),are used to cluster the stress nephograms and analyze the results comparatively by taking the resultant images of the stress distributions as an example.The results show that the Mean-shift and DBSCAN clustering algorithms are not suitable for processing a large number of finite element stress stress mapss,the k-means and GMM clustering algorithms improve the processing efficiency by 74.24 and 172.64 times compared with the traditional manual processing,and the GMM clustering algorithm produces errors when the color of the image is not clearly differentiated.The k-means clustering algorithm ensures high efficiency while keeping the error within 0.85%.Therefore,among these four algorithms,the k-means clustering algorithm is the most suitable for fast,objective and quantitative analysis of a large number of stress nephograms.Using k-means clustering algorithm,it is measured that the area of the stress interval of single-layer Twaron^® plain weave fabrics decreases with a stress area change rate of 5.61×10⁷mm²/s for 0-600MPa,and the area of the stress interval increases with a stress area change rate of 5.27×10⁷mm²/s for 600~1200MPa within 1-15μs of the impacts.

The explosive energy release characteristics of thermobaric explosives with different binder systems during detonation are studies.Two types of HMX-based thermobaric explosives with similar formulations are selected for testing of detonation heat，detonation velocity，detonation driving performance，and internal explosion performance.In addition，the influence of differences in the binders on the reaction rate of aluminum powder and the release process of explosive energy in thermobaric explosives is analyzed.The results indicate that the aluminum powders in thermobaric explosives with different binder systems show significant differences in the reaction and energy release processes.Among them，the reaction rate of aluminum powder in thermosetting casting thermobaric explosives is faster than that of aluminum powder in thermoplastic casting thermobaric explosives.Moreover，the aluminum powder involved in aerobic combustion of thermoplastic casting thermobaric explosives is more than that involved in aerobic combustion of thermosetting casting thermobaric explosives，resulting in the expansion mechanical energy converted by its thermal effect compensating for the insufficient mechanical energy converted by shock waves.In summary，this research provides experimental evidence and support for the selection of charges and the estimation of destructive performance for the relevant warheads.

Structures with negative Poisson’s ratios (NPR) exhibit superior energy dispersion and stress homogenization capabilities under impact loading due to their unique auxetic deformation behavior, demonstrating broad application prospects in military protection. However, conventional mesh-based numerical methods such as the Finite Element Method (FEM) often suffer from reduced accuracy or even computational interruption due to mesh distortion when simulating extreme nonlinear behaviors like large deformation and fracture. To address this, the present study employs the Material Point Method (MPM) to systematically investigate the dynamic response and energy dissipation mechanisms of three typical cellular sandwich structures (regular hexagonal honeycomb, re-entrant hexagon, and chiral wave core) under impact loading. Through mesh convergence analysis and experimental validation, the MPM is demonstrated to possess good numerical convergence and physical fidelity in simulating such extreme deformation scenarios. The results indicate that the NPR effect significantly improves the impact resistance of the structures: compared to the conventional hexagonal honeycomb structure (positive Poisson’s ratio), the re-entrant hexagonal structure exhibits a 27.9% reduction in peak reaction force, while the chiral wave cellular structure achieves a reduction of 61.9%. Further mechanistic analysis reveals that the chiral structure facilitates uniform dissipation of impact energy throughout the cellular network via a multi-stage energy absorption mechanism—comprising ring rotation, ligament extension, and pore closure—thereby effectively mitigating local stress concentration and structural failure. This study provides theoretical support and simulation tools for the lightweight anti-impact design of protective equipment such as naval blast protection and personal armor.

To study the energy release behavior of impact ignition and deflagration reactions in fluorinated polymer based reactive materials,Based on experimental observations, cumulative temperature rise ignition mechanism and transient thermal diffusion reaction mechanism were proposed, and thermal coupling simulation of Taylor rod impact ignition process of active material was carried out, and the simulation provided the local hot spot temperature rise under the corresponding mechanism. On this basis, a heat transfer-chemical reaction model for fractured materials was constructed using the bond-based peridynamics thermal diffusion theory and combined with local hotspot information. The solution results were verified and analyzed using infrared temperature measurement experiments. The results showed that the simulation characteristics of deformation and fragmentation of the Taylor rod before ignition reaction are basically consistent with the experimental recorded images, which well reflects the inert response of the reactive material. By superimposing adiabatic shear temperature rise and friction temperature rise, a local area of the rod can form a hot spot region that meets the ignition threshold which basically corresponds to the location of the first flare, the distribution of adiabatic shear temperature rise and friction temperature rise is uneven, with significant differences in starting positions, and adiabatic shear temperature rise plays a dominant role in the total impact temperature rise, implying that the ignition mechanism of cumulative temperature rise can describe the impact ignition characteristics of materials. The simulation of deflagration reaction process proves that the temperature distribution inside the flame is directly affected by the mass and morphology distribution of impact fractured materials; Compared to the heat transfer effect, the reaction heat continuously released as the reactivity of the active site increases plays a crucial role in maintaining the high temperature state of the region.

Explosive shock waves interacting with typical materials at different angles of incidence can lead to severe reflected overpressure, posing significant threats to structures and personnel. However, the accuracy of existing reflected pressure prediction models remains limited. This study develops a theoretical model based on mass and momentum conservation equations, combined with the equations of state for air, granite, and 45# steel. A series of explosion experiments at different charge heights were conducted to measure both free-field and reflected pressures. Theoretical results were compared with experimental data, showing strong agreement. The proposed model effectively predicts reflected overpressure across a range of incidence angles and material types, offering valuable support for shock wave damage assessment and protection design.

The metastable face-centered cubic (FCC) and body-centered cubic (BCC) dual-phase Al₁₅(CoCrFeNi)₈₅ high-entropy alloy has significant application prospects in the field of impact-resistant structural materials. The paper aims to systematically examine its dynamic response and compressive deformation mechanisms. The quasi-static and dynamic compressive mechanical properties of the high-entropy alloy are characterized using a universal testing machine, split Hopkinson pressure bar (SHPB), electron backscatter diffraction (EBSD), and molecular dynamics (MD) simulations. The plastic stress-strain response, strain rate sensitivity, and microscopic deformation mechanisms of the high-entropy alloy are analyzed, and its strengthening mechanism under dynamic compression is elucidated. A dynamic constitutive model for the metastable dual-phase Al₁₅(CoCrFeNi)₈₅ is established. The high-entropy alloy exhibits strain rate sensitivity, of which the flow stress initially increase gradually and then rises sharply at larger strains. The base material is consisted of 71.4% FCC and 28.6% BCC phases. The FCC-to-BCC phase transformation under uniaxial compression is strain-rate-dependent. The ratio of FCC-to-BCC phase transformation under quasi-static loading is approximately 1∶1, whereas it is approximately 3∶7 under dynamic loading. MD simulations confirm the phase-transformation-dominated deformation mechanism. The plastic deformation shifts to full dislocation slip in BCC phases as their fraction increases. The dynamic stress-strain response is predicted using a modified Johnson-Cook constitutive model. These findings can provide theoretical guidance for the design and application of HEAs in impact-resistant structures.

As a novel explosion protection material, sintered fiber network materials exhibit transversely isotropic mechanical properties, posing challenges for engineering design and application. To achieve accurate numerical simulation of sintered fiber network materials, a transversely isotropic phenomenological dynamic constitutive model was established, and a user subroutine was developed to implement the constitutive model algorithms. Constitutive parameters of the sintered fiber network were obtained by fitting experimental stress-strain curves under different loading directions. To validate the constitutive model and parameters, explosion simulation loading tests and corresponding numerical simulations were conducted, revealing the material’s shock pressure attenuation characteristics. Results demonstrate that under varying shock loading directions, the numerical simulations show good agreement with experimental results in terms of shock pressure attenuation and specimen compression deformation. The fiber network material reduces shock pressure by up to 57.4%. The established constitutive model and parameters effectively capture the mechanical behavior of the fiber network material, providing a critical simulation tool for its engineering applications.

The quadruped unmanned combat platform holds significant military application value in future warfare due to its exceptional mobility and adaptability to complex terrains. A rigid-flexible coupled launch dynamics model is established to investigate the impact of shock loads on the vibration characteristics of the platform and firing accuracy. The amplitude, angular displacement and angular velocity variations of muzzle center point around x-axis and z-axis under different shock loads are analyzed through numerical simulation. The firing dispersion characteristics are evaluated using a six-degrees-of-freedom external ballistic model, and the live-fire tests are made on unmanned combat platforms with and without a bidirectional buffering device. The results show that the amplitude of the muzzle center point around the x-axis and z-axis during five-round bursts is significantly reduced, the vibration levels decreases, and the angular velocity tends to stabilize without the continuous increase observed in fixed connections after installing the bidirectional buffering device. The radius of 100% dispersion circle (R₁₀₀) is reduced to 86.4mm with a decrease of 34.6%. Live-fire test data indicates that R₁₀₀ for single-shot and five-round bursts is 75.7mm and 94.5mm, respectively, with the reductions of 21.1% and 32.8%. The test data are in good agreement with the simulated results, validating the accuracy of the numerical simulations. This confirms that the designed damping device effectively suppresses firing-induced vibration, significantly improving the firing stability and accuracy of the quadruped unmanned combat platform. The research findings provide technical support for the structural optimization design of unmanned combat platforms.

For the three-dimensional scene visualization of simulating and reproducing the explosive shock experiments, a virtual simulation system,which is designed for studying and predicting the damage process and effects of explosive shockwaves on targets, is built based on virtual simulation technology and the related explosive field calculation models. The system adopts a layered architecture, covering the scene management, interaction design, power calculation and visualization simulation, and supporting the flexible configuration of explosion parameters, dynamic loading of target models and multi-perspective interaction analysis, which can adapt to different types and scales of explosion scenes. Furthermore, based on Niagara particle system and physics engine real-time rendering technology, the system accurately characterizes the flame, smoke, shockwave propagation and target damage effects, such as concrete crushing, vehicle structure deformation, etc., and optimizes the observation clarity through the dynamic smoke concentration adjustment function. The simulation system provides a highly realistic graphical interface to observe the dynamic processes and physical phenomena of explosive shocks, and supports the multi-perspective and scalable observation in 3D scene. This enhances the intuitiveness and depth of understanding in research, significantly reducing the time and cost of actual experiments, and offering a safe, reliable and cost-effective research method.

To address the issues of large computational scale and low parallel efficiency in the numerical simulation of explosion fields, a distributed shared memory parallel computing strategy based on the Eulerian method is proposed. This strategy improves the parallelization of the pMMIC3D program by constructing a cluster system with a non-uniform memory access (NUMA) architecture and using the message passing interface (MPI) and InfiniBand (IB) high-speed network, thereby enhancing the large-scale computational capability of program. The accuracy, speedup ratio, parallel efficiency and computational scale of the parallel program are tested through the simulation of the explosion in the air. The results show that the proposed parallel computing strategy is accurate and effective, significantly reducing the communication overhead and improving the computational efficiency. In addition, the applicability of this parallel computing strategy in complex scenarios is further validated through the explosion test inside a concrete building structure, and the calculated results are compared with experimental data. The calculated results show that this parallel computing strategy has the ability to handle the numerical simulation of complex large-scale explosion field and is suitable for practical engineering applications.

Sandwich structure is widely used in the field of shock protection, but the traditional cores often suffer from insufficient load stability, which limits their shock resistance performance. Inspired by the cuttlefish bone and incorporating the dynamic enhancement effect of cellular material, a biomimetic gradient double corrugated sandwich structure is proposed. A systematic study is conducted on its shock resistance performance by using graded cellular projectiles as loading means. The results show that, compared with the biomimetic double corrugated sandwich structure without gradient design, the proposed sandwich structure has excellent shock resistance, with an improvement in crushing force efficiency of 26.4%. When the gradient distribution parameters and the axial ratio are controlled within the ranges of 0.1-0.15 and 0.5-0.75, respectively, the crushing force efficiency of the structure remains stable at about 80%. This research provides novel insights and methodologies for the design and evaluation of new protective structures.

The equation of level set function based on DSD (Detonation Shock Dynamics) theory is numerically discretized and solved on uniform 2D/3D Cartesian grid. The obtained TOA (Time of Arrival) for the stable detonation front in the high explosive can be used by program burn algorithm in the hydrodynamic simulations. The boundary condition algorithm, including the selection method of boundary node stencils, and the method of boundary node sort, is simplified and improved based on the previous works. The hybrid MPI (Message-Passing Interface) and OpenMP (Open Multi-Processing) parallel code DSDLS is developed for the efficient solutions of large-scale explosive detonation problems. A series of analytic solutions, semi-analytic solutions, and explosive detonation experiments are used for verification and validation of the proposed improved DSD algorithm, which indicate that the detonation front TOA of numerical simulations conform to the exact solutions and the measured data of experiments. The results of large-scale parallel test on the grid of over 10⁹ nodes indicate that DSDLS is of good parallel efficiency and parallel scalability.

This study addresses the critical challenges in risk assessment of natural fragmentation warhead explosions by proposing a comprehensive parametric analytical methodology. Through systematic integration of key components including stochastic fragment generation, precise trajectory calculation, three-dimensional_h probability evaluation, and quantitative human damage assessment, we have established a multi-scale coupled risk evaluation system. In terms of fragment kinematics modeling, we developed an aerodynamic surrogate model based on artificial neural networks. By introducing fragment sphericity parameters and Mach number as dual variables, the model significantly improves the trajectory calculation accuracy for naturally fragmenting projectiles under random tumbling conditions. For hazard effect evaluation, we innovatively proposed a three-dimensional pie-shaped target model. By incorporating detailed human geometric parameters and considering the relative position between fragment trajectories and human targets, the model enables more accurate calculation of fragment hit probability on personnel. Regarding risk quantification, we constructed a multi-level probabilistic assessment framework that integrates AIS injury scales with fragment kinetic energy distribution. Validation using 155mm projectiles demonstrates that this method can not only describe fragment hazards through uniform annular safety distances but also generate two-dimensional spatial distributions of fragment hazard probability. The research achieves quantitative characterization of the entire process encompassing initial stochasticity, motion complexity, and progressive damage effects of fragments. It provides new analytical tools and decision support for dynamic safety distance determination in ammunition storage and transportation, optimized safety zoning design for firing ranges, and industrial explosion protection.

In order to develop a compressed air-driven variable-sectional shock tube test device for simulating the air explosion shock wave, the classical 1D Sod shock tube problem, compressed air-driven equi-diametric and variable-sectional shock tube tests were firstly numerically simulated based on Ansys Fluent software, respectively. The applicability and reliability of material model parameters, boundary conditions, and numerical simulation method were validated through the comparisons of simulation results with analytical solutions and test data. Secondly, the evolution processes of the pressure pulse in the equi-diametric and variable-sectional shock tubes were analyzed, respectively. It was found that the location where the rarefaction wave catches up with the shock wave is the formation location of the air explosion shock wave; the variable-sectional shock tubes with different expanded angles could generate air explosion shock waves with exponential decay, and the expanded angle of the low-pressure section has little effect on the waveform of shock wave. Further analysis was carried out to analyze the influence of the geometrical dimensions of the shock tube and initial pressure in the high-pressure section on the formation location of the air explosion shock wave and corresponding peak reflected overpressure. It was shown that the formation location of the air explosion shock wave and the above parameters have a nonlinear relationship. The peak reflected overpressure increases with the diameter and initial pressure of the high-pressure section increasing, as well as with the length of the high-pressure section and expanded angle of the low-pressure section decreasing. Finally, based on the simulation results and dimensional analysis, predicted formulas for the formation location of the air explosion shock wave and corresponding peak reflected overpressure were established, respectively. The design process of the compressed air-driven variable-sectional shock tube was given. The test loading capabilities of three typical variable-sectional shock tubes were determined by comparing them with the classical Kingery-Bulmash air explosion shock wave calculation formulas.

To explore the application value of nanoporous material liquid systems (NMLS) in enhancing the blast resistance of fiber shells, experimental and numerical studies were conducted on the blast mitigation effects of nano-porous silica water suspensions. Internal explosion experiments were carried out to compare the blast resistance performance of three different hollow cylindrical composite structures: empty chamber-shell, water-filled chamber-shell, and NMLS-filled chamber-shell. The results showed minimal differences in fiber breakage among these three structures, indicating that neither water nor NMLS exhibited a significant blast mitigation effect. Numerical models matching the experimental conditions were established, and the mechanical behavior of NMLS was described using a compaction equation of state validated by dynamic impact experiments. The simulation results revealed that both water and NMLS significantly increased the internal blast loading on the shell, with peak pressures reaching 1.7 and 1.9 times that of the baseline (no liquid layer), respectively. The more severe loading enhancement caused by NMLS was attributed to the higher initial pressure rise experienced by the shock wave propagating through the NMLS layer under the catch-up effect. Further numerical analyses over a broader range of parameters showed that water consistently exhibits a blast-enhancing effect, while the effect of NMLS transitions from enhancement to mitigation as the standoff distance increases, the charge mass decreases, or the liquid layer thickness increases. This transition was due to a better match between the energy absorption capacity of NMLS and the blast loading, leading to greater attenuation of the shock wave pressure after passing through the NMLS layer.

To study the energy release characteristics of energetic materials after excitation and ensure the safety of the test, a double-layer asymmetric cylindrical explosion protection device is designed with capability of containing 1kg TNT equivalent detonation. Through the structural design, simulation analysis using LS-DYNA finite element software, and full-equivalent detonation dynamic response test with 1kg TNT, the safety of the explosion protection device is evaluated by comparing the theoretical predictions, experimental data and simulated results. Simulated and experimental results demonstrate that the structural design of the double-layer asymmetric cylindrical explosion protection device is reasonable with a sufficient safety margin. In the full-scale 1kg TNT detonation test, the stress corresponding to the measured outer wall strain at typical positions is lower than the yield strength of shell material of the protection device. The peak reflective overpressure measured on the inner l at typical positions is within the range calculated by the empirical formulas. The explosion resistance strength of the protection device meets the test requirements. The design, analysis, and experimental methods in this paper can provide useful references for the design and verification of similar explosion protection devices.

The ceramic/fiber composite ballistic plates are widely used in personal protection equipment. Studying the performance of ballistic plate subjected to multi-impacts is of great significance for reducing the number of casualties in the battlefield.This paper investigates the Al₂O₃/UHMWPE composite ballistic plate,focusing on numerical simulations conducted for various bullet impact points.The reliability of the simulated results is validated by comparing with the experimental results.The relationship between the energy absorption and damage characteristics of the ballistic plate is derived from the ceramic and fiber damage results,and the penetration probability of the next impact is effectively calculated.The results indicate that the damage patterns of ballistic plates are roughly the same and the impact resistance of ceramic layer at the joint decreases.when the impact point of the first bullet is located at the center of a ceramic plate,within the gap between two plates,or at the gap of quadrilateral jointing.Specifically,when the impact point of the first bullet is located at the center of ceramic plate,the subsequent bullets tend to penetrate through the gap between adjacent plates.As the proximity between successive impacts decreases,the energy absorption by the ceramic layer diminishes while the energy absorbed by the fiber layer increases.When two impact points are located parallelly and diagonally apart,the middle ceramic plate does not suffer macroscopic damage due to the joint structure.When the first impact point is in the center of the ceramic plate,the penetration probability of the second impact is 1.04%.When the first impact point is in the center of the ceramic plate,and the second impact point is in the horizontal adjacent center,the four corners of the gap,or the diagonal adjacent center,the penetration probability of the third impact on the ballistic plate is 5.45%,7.35%,and 5.05%,respectively.This method can be used to quickly evaluate the resistance of damaged equipment to multiple penetrations.

In order to study the performance of explosives after the impact detonation of different shaped charges on targets in water,three kinds of shaped charge structures,i.e.,explosively formed projectile (EFP),jetting projectile charge (JPC) and shaped charge jet(JET),are selected for underwater penetration and underwater impact detonation tests.The measured velocities of different shaped charge penetrators before entering water,before hitting a target and after penetrating into a target,the penetration effect on the arc target plate and the impact detonation effect on B explosive behind the target are obtained through the tests.The impact detonation mechanism of different shaped charges in water and the variation law of impact detonation coefficient k at different water medium lengths are compared and analyzed.The results show that the impact detonation performances of EFP,JET and JPC after impacting a target in water decrease nonlinearly with the increase in the length of water medium,and the performance of JPC is better than those of JET and EFP.The critical impact detonation coefficient of explosive B is 18.22mm³/s² after EFP,JET and JPC penetrate the metal target plate with a thickness of 2cm and a length of 0-100cm water medium and a water medium with a length ranging from 0 to 100cm.

The thickness equivalence of composite radome under the far-field explosion loads is studied by taking the fiber-reinforced polymer (FRP) laminate as the research object.A serial artificial neural network (S-ANN) model based on the principle of deflection equivalence is proposed to predict the thickness equivalence relationship between glass fiber radomes with different performances.A finite element model for the dynamic response of FRP laminates under explosive loads is established.The maximum deflection of FRP laminates under the conditions of different detonation distances,laminate thicknesses,densities,and longitudinal elastic moduli is obtained by conducting batch calculations on this finite element model.Based on this,a S-ANN thickness equivalence model is established.The proposed model achieves the thickness equivalence for different types of FRP materials under far-field explosion loads.In addition,the frequency response characteristics of the glass fiber equivalent radome are analyzed using the \overline{A}\overline{B}\overline{C}\overline{D} transmission matrix and a numerical simulation method.The research results show that the longitudinal elastic modulus has the greatest influence on the explosion resistance and equivalent thickness of glass fiber radome under far-field explosion loads.The equivalent thickness has little influence on the amplitude of the radome’s transmission efficiency,but it changes the resonant frequency of the radome’s transmission efficiency.This study can provide reference for the thickness equivalence research and optimization design of radomes.

In order to study the explosion driving characteristics of shell fragments driven by cylindrical charge with cavity and reveal the mechanism of the influence of shaped charge structure on the initial velocity of shell fragments,the explosion driving process and initial velocity distribution of shell fragments under different cavity cone angles are studied through the numerical simulation.The initial velocity distribution function of shell fragment along the axial direction is fitted by analyzing the rarefaction wave propagation path,velocity loss coefficient and fragment acceleration process.The relative error between the calculated and simulated results is less than 15%.The results show that the earlier generation of rarefaction wave and the decrease in cross-section ratio of mass of charge to shell are the main factors contributing to the decrease in the initial velocity of fragments.The initial velocity of the fragments near the non-detonation end decreases with the decrease in the cone angle of cavity and the increase in the cone top height of cavity.The rarefaction wave reflected from the non-detonation end is an approximately planar wave and is at a certain angle to the cavity surface.The instant when rarefaction wave reaches shell is linearly and positively correlated with the axial position of the shell.The cross-section ratio of mass of charge to shell has a quadratic function relationship with k,where k is the ratio of the distance from the cross section to the non-initiating end to the height of cavity cone top.The velocity loss coefficient decays exponentially with the decrease in k.The research can provide a useful reference for the overall structural design,material selection and structural optimization of anti-armour and anti-personnel composite warheads and the deformable fragment warhead with cavity charge structure.

Studying underwater explosions near warships is crucial for hull structure design,explosion impact damage prediction,and personnel safety.To this end,an improved six-equation compressible multiphase flow model based on the diffuse interface method is proposed to resolve thermodynamic state prediction deviation under shock waves and support anti-shock mechanism research and numerical method optimization.The model is improved via a hybrid energy correction equation and a more accurate gas equation of state.A numerical algorithm on an unstructured grid system is constructed,adopting the second-order MUSCL-Hancock scheme (with least-squares reconstruction and Barth-Jespersen limiter) and two-phase HLLC Riemann solver to solve homogeneous hyperbolic equations,and Newton-Raphson iteration for instantaneous pressure relaxation equation.Results show that after total energy equation correction,the model’s simulation of shock wave velocity and interface is highly consistent with the Euler equation’s exact solution,resolving near-interface numerical oscillation.Compared with experimental data,the improved model has a 1.13% relative error and 0.33% higher accuracy; more accurate SG-EOS parameters are obtained by fitting the shock Hugoniot curve.It also clearly shows underwater explosion phenomena:shock wave propagation,bubble expansion-contraction,and bubble collapse water jet.However,it has deficiencies in bubble interface clarity and jet precision,mainly limited by numerical scheme dissipation under extreme gradients.In conclusion,the improved model effectively enhances the accuracy of simulating underwater explosions near naval vessels,supports in-depth warship anti-shock mechanism research,and lays a solid foundation for future numerical method optimization.

Explosion-induced seismic waves have become the main factors inducing secondary disasters such as building collapse and infrastructure damage due to their long wavelength,strong amplitude and fast propagation speed.Based on two kinds of typical explosion-proof equipment,the static explosion tests with different TNT dosages are carried out to study the propagation and attenuation law of explosion-induced seismic waves under three different protection conditions of free-air blast (FAB),steel explosion-proof (SEP) and flexible explosion-proof (FEP).The vibration velocity time-domain responses and main vibration frequency characteristics of SEP and FEP equipment are analyzed.The three-axis peak vibration velocity vector and attenuation models under the protection of SEP and FEP equipment are constructed,and the damage level of building is divided accordingly,which is subdivided into three criteria of safety,slight damage and serious damage.It is found that the vector sum of triaxial peak vibration velocities increases with the increase of TNT charge,and decreases with the increase of detonation distance.The triaxial dominant frequency shows no obvious change rule when the detonation distance or TNT charge increases.Compared with FAB,both SEP and FEP show significant protection performance against the triaxial peak vibration velocity of explosion-induced seismic waves.The research results can provide reference for the structural design of related explosion-proof equipment and the evaluation of explosion-induced seismic wave protection effectiveness.

To develop the electrically-heated composites that have both anti-icing/de-icing functionality and meet load-bearing performance requirements,three types of electrically-heated fabrics containing nickel-chromium alloy wires with parallel spacings of 6.67mm,4.00mm and 2.86mm and their reinforced composites are designed and fabricated based on the tailored fiber placement process.The lowest surface temperature of the composites reaches 87.2℃ within three minutes at 25W.The low-velocity impact properties,electro-thermal properties and compression properties of the composites subjected to 7J impact load are tested and analyzed using a drop weight impact tester,an infrared thermal imager,and a universal testing machine.The results indicate that the impact energy absorption of composite with a the nickel-chromium alloy wire electrically-heated layer is increased by at least 23.6%.The surface temperature of the damaged areas in the electrically-heated composites can still reach above 72.4℃ after impact,and the retention rates of post-impact compressive modulus and compressive strength are 88.73% and 94.97%,respectively.Compared to glass fiber/epoxy composites,the decrease in the parallel spacing of nickel-chromium alloy wires results in a more pronounced delamination phenomenon in the electrically-heated layer under post-impact compressive load.These findings provide practical guidance for the design of electrically-heated composites for aircraft anti-icing/de-icing applications,ensuring a balance between mechanical performance and functional requirements.

In order to study the mechanochemical response behavior of PTFE/Al/W fluoropolymer-matrix reactive materials under shock loading,the drop-weight impact test of fluoropolymer-matrix reactive materials is carried out,and a weak coupling trans-scale numerical calculation method is proposed.Based on this method,a trans-scale numerical simulation model is established for the drop-weight impact loading reaction process of macro-meso scale fluoropolymer-matrix reactive material.The mechanochemical response behaviors and impact activation mechanisms of macroscopic and mesoscopic structures of sample in the drop-weight impact test are discussed and analyzed through trans-scale numerical simulation.The results show that the content of W has a significant effect on the impact activation reaction of fluoropolymer-matrix reactive materials,and the impact activation threshold of the reactive materials system decreases with the increase of W content.The weak coupling trans-scale numerical simulation analysis model effectively simulates the mechanochemical response process of fluoropolymer-matrix reactive materials.The X-shaped shear band is the dominant mechanism for the breakage and activation of fluoropolymer-matrix reactive materials,and its formation,evolution and distribution are greatly affected by W content.

To explore the explosive shock wave characteristics of typical cylindrical explosives with elliptical cross-section,an experiment on the static explosion of variable-section cylindrical explosives in free field is conducted,and a corresponding numerical simulation model is established.The reliability of the numerically simulated results is verified by comparing with the experimental results.The explosions of cylindrical explosives with different cross-sectional shapes in free field are numerically simulated to investigate the influence of cross-sectional shape on the power characteristics of explosive shock waves.The research results indicate that the explosive shock wave generated by the cylindrical explosives with elliptical cross-section produces a wave system structure similar to that generated by the cylindrical explosives with a circular cross section,but there are differences in the propagation characteristics of shock wave at different azimuth angles.The peak overpressure,maximum impulse,and shock wave velocity in the short-axis direction are all greater than those in the long-axis direction.For elliptical cross-section explosives with different aspect ratios of long axis to short axis,the greater the aspect ratio is,the more significant this difference becomes.An equivalent radius is introduced to fit and obtain a formula for calculating the peak overpressure and the shape factor of peak overpressure,which includes the aspect ratio as a variable,and a deviation between the calculated results and the numerically simulated results is less than 10%.

The staggered layout of urban building complex makes the propagation path of explosion shock wave more complicated,thereby increasing the difficulty of evaluating the damage effect comprehensively and accurately.Numerical simulation methods based on computational fluid dynamics can accurately simulate the blast loading,but the calculated amount is large and the calculation time is long.In order to rapidly predict the blast loading in urban building complex,a fast blast loading prediction method based on neural network is proposed.The influence of the number of training samples on the prediction accuracy and the effect of regional division on the prediction performance of the model are analyzed.In order to meet the data requirements for training the neural network model,the explosion simulation software is used to analyze the mesh sensitivity in a typical dense urban building complex and generate a dataset for 80 sets of explosion scenarios while considering simulation speed and accuracy.In order to determine the appropriate model structure,the fully connected neural networks with different numbers of layers are constructed for comparative experiment and analysis.The effects of the number of training samples,the division of region and the construction of dual models on the prediction accuracy of the model are analyzed through comparative experiments.The results show that the prediction error of the proposed method is less than 10% on 16 sets of test data except the training data,and the inference time only takes 2 seconds.The proposed method has a balanced and good prediction ability for various ranges of peak overpressure,and provides a new approach and perspective for realizing the rapid prediction of blast loading in urban building complex.

In order to clarify the injury mechanism of human head under blunt ballistic impact,a finite element model fitting the characteristics of Chinese 50th percentile male adult heads is constructed by the material parameter optimization,proportional scaling and fluid-structure interaction methods based on the total human model for safety (THUMS) model.LS-DYNA (Livermore software technology corporation's dynamic analyzer) is taken as a simulation platform,and the arbitrary Lagrangian-Eulerian algorithm is used to define the fluid characteristics of cerebrospinal fluid,optimize the elastic-plastic material parameters of skull and brain tissue,and realize the localization of head size and anatomical structure through mesh deformation technology.The biomechanical response of the model is verified by comparing the data of Nahum cadaver experiment and THUMS model for the typical vulnerable parts,such as forehead,parietal wall,occipital and posterior fossa,of human body.The results show that the peak values of intracranial pressure in the vulnerable area of the improved model are 150kPa,75kPa,53kPa and 69kPa,respectively,and the error between the improved model and the experimental data is 4%-10%,and the shape of the dynamic response curve is consistent.The maximum von Mises stress of brain tissue (29.5kPa) and the principal stress of skull (18.7kPa) are close to the threshold of Marjoux and Yoganandan simulation experiment,which verifies that the proposed model could effectively predict the risk of craniocerebral injury.The assessment based on NATO AEP-103 standard indicates that the peak value of the forehead intracranial pressure under typical impact is 511.1kPa,far exceeding the threshold of skull fracture (150kPa),which highlights the optimization needs of existing protective equipment.The proposed model has strong applicability and can provide reference and theoretical support for head injury assessment and safety protection under blunt ballistic impact.

Bottom mines are typically deployed on the seabed and are designed to damage the surface ships and submarines during underwater explosion.The casing of bottom mine is the key factor influencing the energy output structure of charge underwater explosion (UNDEX).Based on the theory of UNDEX,the coupled Euler-Lagrange (CEL) method is used to establish a numerical model of the UNDEX of cased charge near the seabed.The characteristics of shock wave loads generated by the underwater explosion of cased charge are studied and the effects of various factors,such as charge shape,detonation mode,casing configuration,casing thickness ratio,and casing-to-charge mass ratio,on the characteristics of shock wave loads generated by underwater detonation of charges are analyzed.Furthermore,a casing with a variable wall thickness suitable for near seabed conditions is proposed,which significantly enhances the shock wave load.The results show that the constraint characteristics of the casing can cause the slower attenuation in the shock wave due to the underwater explosion of charge with distance.The casing with variable wall thickness has an enhancing effect on the shock wave load due to the underwater explosion of charges.The peak pressure of shock wave at 800 mm significantly increases with the increase of δ,and the growth rate can reach 9.74%.It can provide reference for the design of underwater weapons.

The dynamic impacts generated during the transient shifting process of a planetary integrated transmission system for tracked vehicle have serious effect on the service performance and reliability of transmission system.For a certain planetary integrated transmission system,the torsional dynamics models of gear transmission components,clutches and brakes,etc are established,and a dynamics model of transmission system during the shifting process is constructed.The simulation and bench tests of the shifting process of the integrated transmission system are carried out.The changing trends of the simulated and test results are basically consistent,thus verifying the correctness of the dynamics model.The impact loads of typical components during the shifting process are further studied,and the influence laws of the throttle opening and the characteristics curves of oil charging and discharging,etc.on the dynamic torques of the operating components are revealed.The main conclusions are as follows.The reverse dynamic torque of disengaging operating component and the maximum impact torque of engaging operating component gradually increase with the increase in oil discharging delay.With the extension of oil discharging time,the reverse dynamic torque of disengaging operating component gradually increases,and the maximum impact torque of engaging operating component decreases first and then increases.The faster the oil charging is in the fourth pressure increasing stage,the greater the maximum impact torque of engaging operating component is,and the maximum impact value is 11% higher than the minimum impact value.With the increase in throttle opening,the maximum dynamic torque of operating component gradually increases,and the maximum dynamic torque value is 73.8% higher than the minimum dynamic torque value.

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.