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    31 May 2024, Volume 45 Issue 5
    Electronic edition of this issue
    Electronic edition of this issue
    2024, 45(5):  0. 
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    Contents
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    2024, 45(5):  0. 
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    Optimization Design of a 300kW High-speed Permanent Magnet Synchronous Machine for Aviation Aircraft
    WEI Jialin, WANG Youlong, WEN Xuhui, CHEN Chen, LI Wenshan
    2024, 45(5):  1363-1373.  doi:10.12382/bgxb.2023.0049
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    The temperature rise of the high-speed permanent magnet synchronous machine (PMSM) for aviation aircraft supplied by PWM voltage might be significant because of its high loss density and poor heat dissipation condition. What’s worse, high temperature increases the demagnetization risk of Halbach-array magnets, which impairs the reliability of operation. In allusion to above problems, a multi-objective optimization method of high-speed PMSM based on Nelder-Mead algorithm is proposed. The loss and temperature rise are selected as optimization objectives. Field-circuit coupled finite element analysis method is used to calculate the loss of the machine powered by T-type three-level converter, thus calculating the temperature rise. The optimal design areas are searched by using the optimization algorithm, and the optimal solution is achieved. The flux density distribution and eddy current loss in the Halbach-array magnet are analyzed, and then the design of magnets is optimized to suppress eddy current loss and demagnetization. A 300kW, 30000r/min high-speed PMSM was designed and manufactured. Simulated and experimental results show that the proposed design method could realize multi-objective optimization and suppress demagnetization effectively.

    Real-time Detection of Low-altitude Camouflaged Targets Based on Polarization Encoded Images
    SHEN Ying, LIU Xiancai, WANG Shu, HUANG Feng
    2024, 45(5):  1374-1383.  doi:10.12382/bgxb.2022.1289
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    Polarization can improve the autonomous reconnaissance capability of unmanned aerial vehicle, but it is easily interfered by the variation of detection angle and target materials, which affects the robustness of polarization detection. In this paper, a real-time low-altitude camouflaged target detection algorithm of YOLO-Polarization based on polarized images is proposed. The coded image fused with multi-polarization direction information is used as input, the 3D convolution module is applied to extract the connection features from the different polarization direction images, and a feature enhancement module (FEM) is introduced to further enhance the multi-level features. In addition, the cross-level feature aggregation network is adopted to make full use of the feature information of different scales to complete the effective aggregation of features, and finally combined with multi-channel feature information output detection results. A dataset consisting of polarized images of low-altitude camouflaged targets (PICO) which include 10 types of targets is constructed. The experimental results based on PICO dataset show that the proposed method can effectively detect the camouflaged targets, with mAP0.5:0.95 up to 52.0% and mAP0.5 up to 91.5%. The detection rate achieves 55.0 frames/s, which meets the requirement of real-time detection.

    Refined Dynamics Modeling and Simulation of Special Tracked Vehicles
    WU Rui, YU Huilong, DONG Haotian, XI Junqiang
    2024, 45(5):  1384-1401.  doi:10.12382/bgxb.2022.1070
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    The tracked vehicle dynamics model serves as a foundation for the design of vehicle structure optimization and the development, testing and calibration of control algorithms. However, the user is unaware of the dynamic equations and gradient information of the model created using commercial software, which significantly lowers the efficiency of the optimization of structural parameters and control parameters. Additionally, the poor real-time performance and low solving efficiency of the currently available commercial software have an impact on the development and porting of control algorithm. An improved dynamic model of tracked vehicles, which can satisfy the needs of vertical and horizontal coupling motion simulation, is constructed and simulated based on the derivation of multibody dynamics in order to address the aforementioned issues. A dynamic model of vehicle body considering the three-dimensional coupling motion of space and a dynamic model of track chain including track link are established. By calculating the interaction force between the track links and other components, the vehicle body model, the track chain model and the ground are related, and finally a track vehicle dynamic model with 190 degrees of freedom is constructed. It was compared to the ADAMS Tracked Vehicle Toolkit (ATV) in terms of acceleration, braking, and steering. The simulated results of the proposed simulation model are remarkably compatible with those of commercial software, confirming the accuracy of the approach.

    Research on the Real-time Simulation System for Hydrodynamic Characteristics of Amphibious Vehicle
    CHEN Tairan, GENG Hao, WANG Dian, QIU Sicong, SUN Xuguang
    2024, 45(5):  1402-1415.  doi:10.12382/bgxb.2022.1237
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    A real-time simulation system for the hydrodynamic characteristics of amphibious vehicles is designed to solve the problems of dificultly acquiring the hydrodynamic parameters and slowly predicting the motion attitude of amphibious vehicles. It can realize the driving of simulation models, motion attitude prediction, data monitoring and output. The numerical calculation method(CFD) is used to correct the vehicle dynamics coefficients, which significantly improves the accuracy of real-time simulation system. In addition, a test amphibious vehicle is developed to verify the accuracy of real-time simulation system under different working conditions. The results show that the real-time simulation system can be used to accurately and efficiently simulate the hydrodynamic characteristics of amphibious vehicles, and predict the motion attitude of the vehicle quickly and accurately. It is also applicable to various complex working conditions and has universal applicability for attitude prediction. The system has strong application value and application prospect in the development stage of amphibious vehicles, driver training, semi-physical simulation exercises and complex environment simulation.

    Numerical Simulation of Transcritical/supercritical Injection Characteristics of Diesel Engine Fuel
    LIU Yuhao, XIE Fangxi, LIU Chengjun, LIU Yu, HONG Wei
    2024, 45(5):  1416-1425.  doi:10.12382/bgxb.2022.1012
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    For the complex changes in spray characteristics of diesel engine under working conditions, this paper uses CFD software CONVERGE to simulate and analyze the jet spray characteristics of n-heptane fuel in transcritical/supercritical diesel engine by using large eddy simulation method, and conducts an in-depth study on turbulent subgrid model of LES. The spray characteristics of the transcritical/supercritical jet are compared from mass fraction, density and temperature. The results show that the stochastic turbulence dispersion model can make the predicted values of gas phase and liquid phase penetration distances closer to the test values, and the predicted gas and liquid phase penetration distances for turbulent dispersion coefficient cps=0.16 are more consistent with the test results than those for cps=0.05. Compared with the transcritical jet, the temperature diffusion of supercritical jet spray is faster, and the temperature of spray front is close to the ambient temperature. The similar liquid region in the transcritical jet forms a larger density stratification, which inhibits spray diffusion. Therefore, the flocculent structure in the spray outer layer of supercritical jet appears earlier than that of the transcritical jet. The flocculent structure has a larger range, and the density is closer to the surrounding environment. It is also found that the distributions of temperature, density and mass fraction in the two states show a certain corresponding relationship, that is, the temperature, mass fraction and density are all maximum at the central axis close to the injector, and decrease with the increase of axial and radial distances.

    Study on the Equivalent Full Charge Conversion Coefficient of the Barrel Life Based on the Thermal-chemical Erosion Model
    LI Yanze, QIAN Linfang, FU Jiawei, CHEN Longmiao
    2024, 45(5):  1426-1435.  doi:10.12382/bgxb.2022.0949
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    To explain the paradox between the experimental and theoretical results of equivalent full charge (EFC) conversion coefficient, which can be used to convert the number of firing under various firing conditions to the number of EFC firing, a computational method of that coefficient is investigated on the basis of the thermo-chemical erosion model of the barrel. Supposing that the thickness and composition of the white layer on the inner wall of barrel change periodically after several firings, the relationship among the thermo-chemical erosion volume at the beginning of the rifling and the erosivity of the propellant and the transient temperature field of the inner layer of the barrel is established with the help of the mass diffusion law. During the firing process, the gas temperature in the space behind the projectile and the forced convection coefficient at the innerwall surface of barrel are provided by the classical interior ballistic theory. Hereafter, the model to calculate the transient temperature of the barrel can be developed. In addition, the effect of gas with relative high temperature during the after-effect period is also considered. Eventually, focusing on the firing rate, the charge mass and the charge temperature which have an essential effect on the interior ballistic process, erosion volumes under different firing rates, charge numbers and charge temperatures are calculated. Accordingly, the EFC conversion coefficients under various firing conditions are obtained. It is found that a more severe erosion of the barrel is often related to a faster firing rate, a more charge mass and a higher charge temperature.The EFC coefficient of the supercharge is up to 2.131. The reasonability of the proposed model is verified by using the practical firing data of a 155mm barrel.

    An Improved Quasi-continuous Algorithm for Rotational Shell Magazine Position Control
    CHEN Dong, QIAN Linfang, CHEN Zhiqun, CHEN Longmiao, ZOU Quan, CHEN Junhua
    2024, 45(5):  1436-1448.  doi:10.12382/bgxb.2023.0064
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    Based on the existing researches on quasi-continuous algorithm, a novel improved quasi-continuous controller is designed to improve the precision and robustness of rotational shell magazine position control in the automatic loading process of a large caliber artillery.By combining a sliding mode disturbance observer, the novel controller is independent of the unknown system uncertainty boundary, and no new parameters are introduced, which will lower the difficulties of controller designing and adjusting.The stabilities of controller and close-loop scheme are verified by Lyapunov functions. The simulated and experimental results have demonstrated the superiority of the improved controller over the existing quasi-continuous algorithm.In the presence of unknown time-varying disturbance and uncertain parameters, the improved controller could achieve a higher convergence rate in reaching phase, reduce the overshoot and restrain chattering in sliding phase while performed on the magazine.

    Time-to-go Estimation Method for Anti-ship Missiles with Large Lead Angle in Three-dimensional Space
    WU Hao, LI Dongguang, WANG Yong’an
    2024, 45(5):  1449-1459.  doi:10.12382/bgxb.2023.0613
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    To solve the problem of large initial lead angle or significant change in lead angle when missile terminal guidance starts, a 3D time-to-go(TGO)estimation method for lead angle is designed for various missile guidance laws. The missile velocity and target velocity projections are decomposed to establish the relationship equations of relative motion between missile and target on Oxy and Oxz surfaces of ground coordinate system. Based on this, a three-dimensional missile-target relative motion model is established. A first-order nonlinear differential equation is established by using the relative motion equation and proportional navigation control equation of missile and target. The relationship between missile-target distance and lead angle is analyzed. The first-order nonlinear differential equation is solved by using McLaughlin formula. An appropriate inner frame angle is selected based on the change in line-of-sight angular velocity to compensate for the lead angle, and the median average filtering method is used to reduce the error caused by the fluctuation of lead angle. The simulation experiments are conducted by using the proposed three-dimensional missile-target relative motion model. The simulated results show that, when the small angle assumption cannot be established, especially when the angle control of guidance law results in significant changes in the lead angle, the convergence time and maximum error value of estimated error of the lead angle TGO estimation method are smaller than those of other TGO estimation methods.

    Dynamic Model Uncertain Parameter Identification for A Curved Chain Rotary Shell Magazine
    WEN Hao, HOU Baolin, LIN Yubin, JIN Xin
    2024, 45(5):  1460-1471.  doi:10.12382/bgxb.2022.1196
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    To accurately simulate the nonlinear dynamics of a curved chain rotary shell magazine during the delivery of ammunition, a dynamic model containing uncertain parameters is established according to the system topology and control principle. An uncertain parameter identification model for the dynamic model is developed based on the system test data using the optimization design idea. A functional time series similarity is proposed as the identification criterion. The high-dimensional model representation based on the radial basis function and the radial basis function are used to construct the surrogate models from the uncertain parameters of the mechanical and control systems to the identification criterion, respectively. The sparrow search algorithm is embedded into an island model for multi-population structuring to form an island sparrow search algorithm for optimization. The uncertain parameters of the mechanical and control systems are identified successively by taking the test data of working condition 1 as the benchmark. The results show that the outputs of the identified dynamic model for the two operating conditions are similar to the test data, which verifies the accuracy of modelling and the validity of identification, and provides a reliable sample data source for action reliability analysis and fault diagnosis research.

    Design and Optimization of Secondary Underwater Acoustic Emission Unit for Active Echo Suppression
    WANG Wenjie, YANG Long, ZHAO Xu
    2024, 45(5):  1472-1481.  doi:10.12382/bgxb.2022.0899
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    Traditional coating layer for underwater vehicles mainly depend on material renewal and structure optimization, which is difficult to cope with low-frequency active sonar detection. A lightweight, thin and low-frequency broadband underwater acoustic emission unit with high pressure resistance is designed based on the giant magnetostrictive material. The design and optimization process of the core components are analyzed emphatically, and the finite element simulation results are verified by the PSV-400 laser vibriometer. The optimal boundary constraints of the active emitting element are determined through the modal analysis of a fixed radiation panel. Compared with the performance of the emission unit in the original configuration, it is found that, under the premise of maintaining good directivity of underwater acoustic emission, the highest resonance frequency below 2000Hz is reduced by more than 10% based on the finite element analysis. Based on the acoustic structure coupling analysis, the maximum radiation source level of active emission unit in the low frequency range is 147.48dB, which is increased by 4.65%. The frequency bandwidth of transmitting unit exceeds 1500Hz when the sound source level is higher than 100dB. This means that there is a higher sound power level in this frequency bandwidth range. The emission unit can provide technical support for the application of array in the large-scale acoustic cladding. It has certain academic research value and broad engineering application prospect.

    Numerical Simulation of Lenticular Aircraft during Water-skipping
    REN Fantao, NIU Yusen, JIANG Yi, YANG Baosheng
    2024, 45(5):  1482-1496.  doi:10.12382/bgxb.2023.0102
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    Exploration of the motion and free water surface characteristics of the trans-media aircraft during the water skipping is of significant reference value for the research on the water landing and skipping re-flight problems. The motion and free water surface characteristics of trans-media aircraft during water-skipping are simulated based on the meshless particle method. The effects of different spin velocities, water-entry velocities and water-entry angles on the water-skipping of lenticular aircraft are studied based on the comparison with the experimental values. It is shown that the spin velocity is crucial to keep the smooth water-skipping for lenticular aircraft. The Magnus effect due to the spin velocity causes the lateral motion of lenticular aircraft. Water-skipping process generally includes three stages: stable fall, impact to water and skipping to smooth flight. The free water surface breakage and water burst phenomenon are caused by the impact from the aircraft. During the water skipping, the velocity decay rate and the impact load are less affected by the spin velocity, but mainly by the entry-water velocity and the entry-water angle. The larger the entry-water angle and entry-water velocity is, the greater the velocity decay rate and the impact load are.

    Design of Anti-impact Structure with Novel Star-shaped Negative Poisson’s Ratio and Research on Water-entry Impact
    JIN Zehua, LIU Qingyang, MA Wenchao, MENG Junhu
    2024, 45(5):  1497-1513.  doi:10.12382/bgxb.2022.1212
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    To solve the problem that the trans-media flight vehicle will be subjected to large impact load in the process of entering water, a topology optimization design method for anti-impact structure with of negative Poisson’s ratio based on engineering requirements is proposed. A star-quadrangular honeycomb (SQH) structure with negative Poisson’s ratio which meets the requirements of impact resistance is obtained by adding the elastic modulus and Poisson’s ratio into the objective function of topology optimization design. Based on the theoretical analysis model of SQH structure, the analytical formula of plateau stress under impact load is deduced and verified by numerical simulation. Compared with the specific energy absorption of star-circle honeycomb (SCH) and other negative Poisson’s ratio structures, the specific energy absorptions of SQH structure under low-speed, medium-speed and high-speed impact are 28.74%, 45.2% and 7.03% higher than that of SCH structure, respectively. Through the fluid-solid coupling simulation analysis, the designed SQH sandwich structure is studied for load reduction by water- entry impact, and the influence of the main size parameters of SQH sandwich structure on the impact characteristics of water entry is further discussed. The results show that, within the allowable range of size, the increase in the inclination angle and wall thickness of SQH unit will reduce the peak acceleration of the structure and the transformation of kinetic energy into the deformation energy of the structure, which verifies the effectiveness of the negative Poisson’s ratio structure topology optimization design for engineering requirements.

    Fractional Order Linear Active Disturbance Rejection Control for Electro-hydrostatic Actuator of Ship Rudder
    LÜ Mingming, XIE Huawei, ZHONG Wei, WAN Guolong, TU Chaofan
    2024, 45(5):  1514-1522.  doi:10.12382/bgxb.2022.0922
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    In order to improve the disturbance rejection performance of electro-hydrostatic actuator (EHA) of ship rudder, a fusion control method based on linear active disturbance rejection control (LADRC) and fractional order proportional derivative (FOPD) control is proposed. The mathematical models of the drive motor and hydraulic system are established, respectively. On this basis, a linear extended state observer (LESO) is employed to estimate the total disturbances of EHA, including internal and external disturbances, under different operating conditions. The bounded stability of LESO is also proved. Furthermore, the FOPD control is used as the control law to actively suppress the estimated total disturbance, and the control parameters are determined by frequency response indicators such as shear frequency and phase margin. The joint simulation analysis of EHA model based on AMESim and Simulink shows that the displacement control accuracy of the proposed control method based on LADRC and FOPD is about 1mm when the ship speed is 6kn or 8kn. The self-developed EHA is used to build a semi-physical testing device, on which the reverse rudder and sudden reversal tests are carried out. The results show that the proposed control method has high speed and stability in tracking steering commands under load disturbances and sudden reversal situations.

    Prediction Method and Characteristics of Static Acoustic Scattering from Marine Propellers
    KE Huicheng, PENG Zilong, ZHOU Fulin, CHEN Tianbao
    2024, 45(5):  1523-1533.  doi:10.12382/bgxb.2023.0017
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    For the prediction problem of static acoustic scattering characteristics of propellers, a planar element method combining the layered medium acoustic propagation theory and the discrete surface element thickness information is used to establish a prediction method for the acoustic scattering characteristics of thin plate targets with variable thickness surfaces.The basic idea is to solve the reflection coefficients of all surface elements based on the thickness of surface elements and material property information, and then obtain the total scattered acoustic field of the target. Considering the computational efficiency, the scattered sound field of a complete propeller is predicted by means of mesh topology clone from a single propeller blade. The results show that the predicted values of the frequency response characteristics, angle-distance spectrum and spatial directivity of propeller target strength are in general agreement with the experimental results. This study may be useful for the prediction of acoustic scattering characteristics near the stern of underwater vehicles.

    Research Progress of Aluminum Core-shell Materials Coated with Fluorine-containing Polymer Materials
    GUO Xueyong, ZHOU Jinqiang, LI Hongliang, WU Chengcheng, FANG Hua, DENG Peng, ZHU Yanli, LIU Rui
    2024, 45(5):  1534-1546.  doi:10.12382/bgxb.2022.1022
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    Aluminum (Al) is the most popular metal additive in the field of composite solid propellants due to its high calorific value, high density and low oxygen consumption. In order to improve the performance of composite solid propellant, it is necessary to take measures to modify Al. In recent years, the fluorine-containing polymer coated Al has attracted wide attention due to its excellent comprehensive properties. This paper introduces the different kinds of metal aluminum core-shell materials coated with fluorine-containing polymer materials, the different coating methods, the properties of aluminum core-shell materials and the mechanism of action of fluorine-containing polymers and aluminum. The enhanced ignition and combustion performances of aluminum core-shell materials are due to the surface reaction between the fluorine-containing polymer and the alumina layer, resulting in a violent oxidation process. At the same time, the combustion agglomeration and combustion efficiency of aluminum core-shell material modified propellant are significantly improved. The problems existing in the research of fluorine-containing polymer coated aluminum materials are discussed, and the conclusion, prospect and possible research direction are put forward.

    Effect of Carbon Nanotubes on Properties of Phenolic Resin Matrix Composites
    KONG Guoqiang, AN Zhenhe, ZHAO Huan, YU Qiubing, SHAO Meng, LI Ying, WEI Huazhen, WANG Kang, LIU Wenbo
    2024, 45(5):  1547-1554.  doi:10.12382/bgxb.2022.1042
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    A multifunctional integrated structural composite material with heat insulation, erosion resistance, electromagnetic shielding, etc., is prepared to meet the urgent demand for multifunctional composite materials in weapons and equipment. In this paper, the carbon nanotubes are dispersed in the resin matrix by ultrasonic dispersion process, and the domestic carbon cloth/phenolic composites modified by carbon nanotubes are prepared. The interlaminar shear strength of domestic carbon cloth/phenolic composites modified by carbon nanotubes is increased by 57.4% when the content of carbon nanotubes reaches 1.5%. The bending properties, interlaminar properties and impact resistance of the oriented domestic carbon fiber/phenolic resin composites modified by carbon nanotubes were tested. The test results show that the mechanical properties and modulus of the oriented domestic carbon fiber/phenolic resin composites are significantly improved after the modification of carbon nanotubes. The electrical conductivity and thermal conductivity of carbon nanotube-modified chopped high-strength glass fiber/phenolic resin matrix composites are also studied. The results show that the resistivity of chopped high-strength glass fiber/phenolic resin matrix composites is decreaseed by an order of magnitude with the increase of carbon nanotube content. When the content of carbon nanotubes reaches 14%, the resistivity of the composites decreases from 1010Ω·m to 10-2Ω·m, and The composites change from insulator to conductor. When the content of carbon nanotubes is less than 6%, the thermal conductivity of the composites is improved, but it is improved modestly compared with the electrical properties of the composites.

    Fast Cook-off Thermal Protection Effects of Inner and Outer Heat-insulating Composite Structures of Explosive Charge
    BAI Mengjing, DUAN Zhuoping, BAI Zhiling, ZHANG Yulong, LIU Ruifeng, ZHANG Liansheng, HUANG Fenglei
    2024, 45(5):  1555-1563.  doi:10.12382/bgxb.2023.0065
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    In order to study the thermal protection effects of the inner and outer heat-insulating composite structures (inner heat-insulating material/outer combustion-insulating material) of explosive charges under the condition of fast cook-off (burning), the multi-point temperature measurement fast cook-off experiments are carried out on explosive charges with various forms of inner and outer heat-insulating composite structures. The temperature-time curves of flame and each measuring point of explosive charge and the ignition response time of the charge are obtained. The fast cook-off ignition of explosive charges with different inner and outer heat-insulating composite structures is numerically simulated to obtain the influence law of inner and outer heat-insulating composite structures on the ignition response time of charge under fast cook-off. The results show that the thermal conductivity of the outer combustion-insulating material is increased and its thermal insulation is weakened due to the burning and denaturation of the material during the process of fast cook-off experiment. This effect should be considered in numerical simulation. The ignition response time of explosive charge is delayed with the increase in the coating thickness of both heat-insulating and combustion-insulating materials, whether using separate insulating/combustion-insulating materials or inner and outer heat-insulating composite structures. The inner and outer heat-insulating composite structures have better thermal protection ability and can significantly delay the ignition response time of the charge. The ignition position all occurs at the corner of the end face of the charge, and the reaction intensity after ignition is not affected by the inner and outer heat-insulating composite structures and is always the deflagration. For insulating/combustion-insulating materials within a certainprotection performance range, the composite structure has the best heat-insulating effect when the coating material on the outer surface of the shell is HGN and the coating material on the inner surface of the shell is GXTI, and when the required heat-insulating effect is given, it is possible to consider increasing the coating thickness of the outer surface coating of the shell first to achieve the optimal thermal protection effect of inner and outer heat-insulating composite structures with minimum coating thickness. The research results provide reference for improving ammunition thermal safety design.

    Theoretical Deduction of Ignition Position and Temperature of Two-dimensional Slow Cook-off Model
    ZHANG Kun, ZHI Xiaoqi, XIAO You, WANG Shuai, LUO Ruiheng, ZHANG Yaoyao, HUANG Yunwei
    2024, 45(5):  1564-1572.  doi:10.12382/bgxb.2023.0103
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    According to the theoretical equation of heat conduction of explosives, the non-reactive heat conduction term of explosives is separated from the self-heating reaction heat conduction term by using the superposition principle and the separation variable method, which lays a theoretical foundation for the theoretical analysis of slow cook-off process of condensed explosives and the study on the ignition point of slow cook-off. Therefore the analytical solution of temperature distribution for two-dimensional slow cook-off model of condensed explosives is derived. The variation of the temperature field of self-heating reaction with time and explosive size is calculated and analyzed. The ignition position, ignition temperature and ignition time calculated theoretically are verified by the results of slow cook-off test. The results show that the ignition time and ignition position determined by theory are consistent with those measured by experiment. With the increase of the size, the position of the highest temperature of self-heating reaction of explosive moves from the center to the edge corner. With the increase of test time, the temperature distribution of self-heating reaction tends to be stable. For the RDX explosive with size of ϕ76mm×190mm, the self-heating reaction temperature distribution at the ignition time is consistent with the self-heating reaction temperature distribution at 80000s before ignition.

    Mechanical Properties and Reaction Characteristics of Aluminum Fiber Reinforced Aluminum/polytetrafluoroethylene Reactive Material
    ZHAO Han, REN Huilan, NING Jianguo
    2024, 45(5):  1573-1581.  doi:10.12382/bgxb.2023.0101
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    To investigate the effect of fiber content on the mechanical properties and reaction characteristics of aluminum/polytetrafluoroethylene (Al/PTFE) reactive material, the static and dynamic mechanical responses, and impact reaction experiments are carried out using the universal pressure testing machine and the impact loading experimental techniques for aluminum fiber-reinforced reactive materials prepared by molding and sintering method. The deformation failure mechanism of fiber-reinforced reactive materials is revealed by the micromorphology. The result shows that the random distribution of aluminum fibers improves the quasi-static yield strength and dynamic ultimate compressive stress of Al/PTFE significantly by inhibiting crack propagation within the matrix when the content of aluminum fiber (mass ratio) is between 1% and 4%. The dynamic mechanical properties of Al/PTFE are optimal when the content of aluminum fiber is 1%. Damage caused by aluminum fiber penetrating through the reactive material matrix under impact loading is a major factor limiting the reinforcement effect by the increased fiber mass. On the other hand, the addition of aluminum fibers increases the impact reaction threshold of Al/PTFE under the condition that the theoretical release energy of Al/PTFE is unchanged. The minimum specific incident energy required for the reaction of Al/PTFE increases from 50.7J/cm2 without fibers to 61.3J/cm2with fiber mass of 4%, which increases the impact insensitivity of Al/PTFE.

    Thermal Interaction Mechanisms of Black Powders with Different Particle Sizes and Cellulose as Packing Material during Ignition
    LI Yuxue, TIAN Xiaotao, MA Yifan, LIU Peijin, YAN Qilong
    2024, 45(5):  1582-1592.  doi:10.12382/bgxb.2022.1060
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    In order to study the effect of cellulose shell on the thermal behaviors, including pyrolysis gaseous products, ignition and combustion characteristics of black powder with different particle sizes, a series of black powder/cellulose composite samples are prepared. Various characterization techniques, including scanning electron microscopy(SEM), simultaneous thermal analysis (DSC-TG-FTIR), X-ray diffraction (XRD), bomb calorimetry, and home-made combustion diagnostic system, are used to investigate the prepared composites and their combustion condensed products (CCPs). The results show that the overall heat releases of two black powders are decreased by 66.4% and 58.5% with the cellulose content of 33.3%, respectively. Moreover, the gas phase product analysis shows that the cellulose does not change the pyrolysis pathways of black powder, of which gas-phase products mainly include H2O, CO2 and NO2. The cellulose only affects the energy release process of black powder, but has little effect on the energy release of black powder with different particle sizes, the difference between the energy release changes of these two composites is only 3.1%. It is found that the black powder with smaller particle size and its cellulose composite burns more violently, with larger flame area and higher combustion temperature. However, the cellulose has a negative effect on the combustion performance of black powder, mainly reducing the burning rate and flame radiation intensity of black powder, and decreasing the flame temperature by 273.7℃ and 299.4℃. In addition, the cellulose promotes the agglomeration of condensed phase products of black powder and reduces its combustion efficiency.

    Rheological Property of Double-base Propellant in SC-CO2 Assisted Extrusion Process
    HU Qipeng, YANG Kun, ZHANG He, LI Chunzhi, YING Sanjiu, XIAO Zhongliang
    2024, 45(5):  1593-1601.  doi:10.12382/bgxb.2023.0023
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    To partially substitute the organic solvents used in the extrusion process of propellant, supercritical carbon dioxide (SC-CO2) was introduced into the extrusion process of propellant. Owing to its solvent properties that sharply changing near the critical point, SC-CO2 is rapidly removed from the product after plasticization, paving the way for the complete replacement of organic solvents by SC-CO2. Shear viscosity is adopted as a parameter to reflect the rheological property, and an in-line slit rheometer is used to measure the shear viscosity of material and obtain the rheological curves to investigate the rheological properties of material under various process conditions. The results indicate that the rheological behavior of material in the extrusion process of SC-CO2 assisted double-base propellant can be described by power-law model. The viscosity of material decreases significantly due to the introduction of SC-CO2. And the introduction of SC-CO2 decreases the viscous coefficient of double-base propellant by 17.10% at the content of 4.67 wt%, reflecting the excellent plasticizing effect of SC-CO2 on the double-base propellant. The plasticizing effect provided by increasing the parameter values is limited as the process parameters such as SC-CO2 content, solvent content, and temperature increase.

    Prediction of Peak Overpressure of Underwater Cylindrical Charge Based on PSO-CNN-XGBoost
    LIU Fang, LI Shiwei, LU Xi, GUO Ce’an
    2024, 45(5):  1602-1612.  doi:10.12382/bgxb.2023.0743
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    In order to explore the relationships among the peak overpressure of underwater cylindrical charge and the parameters of its structure and blast distance, the sample data of the charge is regarded as two-dimensional data.A peak overpressure fusion prediction algorithm of underwater cylindrical charge is established. The fusion prediction algorithm is based on particle swarm optimization(PSO)algorithm,1D convolutional neural network(1DCNN) and Extreme Gradient Boosting(XGBoost). Correlation analysis and data visualization methods are used to analyze the correlation among charge structure parameters, blast distance and peak overpressure. 1DCNN deep network is designed to mine the longitudinal temporal relationship among the parameters, including aspect ratio, blast distance, etc., and peak overpressure. XGBoost algorithm is applied to find the lateral nonlinear relationships among charge structure parameters, blast distance and peak overpressure, so as to improve the prediction accuracy of small sample data. PSO algorithm is used to optimize the hyperparameters of 1DCNN and XGBoost, and gain the optimal algorithm structure. In the comparison experiments involving ten intelligent algorithms, the accuracy, stability and fitting degree of PSO-CNN-XGBoost underwater cylindrical charge peak overpressure prediction algorithm are higher than those of other algorithms.

    Effect of Active Material Content on the Near-field Shock Wave of Low Collateral Damage Bomb
    FAN Ruijun, WANG Xiaofeng, WANG Jinying, ZHOU Jie, WANG Shaohong, PI Aiguo
    2024, 45(5):  1613-1624.  doi:10.12382/bgxb.2022.1291
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    In order to improve the near-field damage power of the existing low collateral damage technology scheme, the ratio of material is optimized by adding different contents of pyrotechnic active materials into the heavy metal particle embedding layer of split-type low collateral damage bomb. The static explosion test of different contents of active material in the WC-Al-NaNO3-FKM composite embedding layer was carried out, and the shock wave pressure curve after explosion was measured by the free field pressure test system. The results show that the shock wave overpressure reaches the maximumwhen the active material content increases to 15%, and is increased by 57.5% and 18.2% at 37.5CD (charge diameter) and 50CD, respectively; The maximum increase in specific impulse at 37.5CD was 25.7% when the active material content was increased to 20%. On the basis of the test results, the parameters of Miller item in the afterburning reaction model of active materialare determined by numerical simulation method, and the energy release law of afterburning reaction with different contents of active material and the relationship between the reactivity of active material component and its change with time were obtained. In an ideal situation, the afterburning reaction time decreases with the increase in the active material content. The research results provide a better technical strategy for the near-field enhanced damage element design of low collateral damage warhead.

    A Calculation Modelfor Penetration Depth of Tungsten Ball against Low-carbon Steel Considering Sphere Deformation
    LIU Tielei, WANG Xiaofeng, XU Yuxin, LI Yongpeng, ZHANG Jian
    2024, 45(5):  1625-1636.  doi:10.12382/bgxb.2022.1013
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    In order to study the influence of deformation behavior of tungsten ball on penetration effect under high-speed impact, the penetrationof tungsten ball into a semi-infinite low-carbon steel target is experimentally studied, and the deformation characteristics of tungsten ball and the change rule of penetration depth versus impact velocity of target plate at 1600m/s are obtained through experiment. On this basis, a plastic deformation model of tungsten ball is constructed.A calculation model of tungsten ball deformation penetration depth is established by combining the projectile deformation model with the spherical cavity expansion resistance model. The calculated results of the tungsten ball deformable penetration model and the rigid penetration model at different impact velocities are compared.The results show that the deformable penetration model can be used to more accurately calculate the penetration depth of tungsten ball into the semi-infinite target. The maximum error between the calculated results and test results is 20% (the positive error is 15% and the negative error is 5%), and the calculation accuracy of the deformable penetration model is 42.8% higher than that of the rigid penetration model.

    Contact Explosion Resistance of Steel Plates Reinforced with Polyurea Coating
    LIU Baohua, XU Wenlong, WANG Cheng, YANG Tonghui, GE Meng
    2024, 45(5):  1637-1647.  doi:10.12382/bgxb.2023.0090
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    The blast-resistant performances of single-layer steel plates and polyurea-coated steel plates under contact explosion are studied to address the protection requirements of armored vehicles and other weapons. Both experimental and numerical simulation approaches are employed to analyze the damage modes and protection mechanisms of steel plates with different areal densities and polyurea coating positions. The impact of the ratio of polyurea thickness to steel plate thickness on the blast-resistant performance of the composite structure is also explored. The results show that coating the back face of steel plate with constant thickness polyurea can effectively reduce the perforation and tensile failure on its back and decrease the residual displacement, while coating the front face with constant thickness polyurea can significantly enhance the blast resistance of the structure and greatly reduce the damage to the steel plate under contact explosion. Under the condition of the same areal density, the energy absorption performance of polyurea is positively correlated with its thickness, but the excessive thickness of polyurea may cause greater deformation and reduced stability of the composite structure. Taking into account the deformation, velocity attenuation and energy absorption of polyurea-coated steel plates, the study finds that the steel plate with a polyurea layer on the front face at a thickness ratio of 1∶0.78 has the best blast-resistant performance within the scope of the research.

    Impact Load Characteristic and Regulation Mechanism of Metal/polyurethane Waveform Generator Composite Projectile
    YANG Guanxia, WU Haijun, TIAN Ze, DONG Heng, HUANG Fenglei
    2024, 45(5):  1648-1662.  doi:10.12382/bgxb.2022.0944
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    Using projectile impact to simulate blast/shock loading is an effective laboratory-scale loading method which has attracted great attention. The quasi-static compressive loading-unloading experiments of PWGs with different geometric sizesaremade to investigate the impact load characteristics of metal/polyurethane waveform generator (PWG) composite projectile and the regulation effect of PWG on the load. The basic mechanical properties of PWG, including the qualitative relationship among the stiffness, energy dissipation ratio and the geometric size of PWG, are analyzed. Direct impact tests of metal/PWG composite projectiles with different PWG configurations are performed. Based on direct impact test results, the impact process of metal/PWG composite projectile is systematically analyzed, and the quantitative relationships among the characteristic parameters of impact load, the impact velocity and the PWG geometric size are established, respectively. The regulation effect of PWG stiffness on impact load is explored by the motion equation of single degree of freedom system for projectile direct impact test and the dynamic model of PWG. The results show that the static stiffness coefficient and energy dissipation ratio increase with the increase in diameter, but decrease with the thickness. The results show that the static stiffness coefficient of PWG increases with the diameter, but decreases with the increase in thickness. Compared with PWG diameter, the thickness shows more significant influence on the energy dissipation. The impact load characteristic parameters are significantly correlated with the product of diameter and thickness(D×H) of PWG. With the increase in D×H, the peak pressure decreases exponentially, and the duration and peak specific impulse increase nonlinearly in 2-order and 3-order, respectively. With the increase in the impact velocity, the peak pressure increases nonlinearly in 3-order, the peak specific impulse increases linearly, and the pulse duration decreases nonlinearly in 2-order. In addition, the influence of PWG diameter on impact load is mainly realized by regulating the linear static stiffness coefficient α. The larger the PWG diameter is,the larger the α is, the smaller the peak load is, the greater the impulse is, and the more similar the load shape to half-sinusoid. The influence of PWG thickness on impact load is mainly realized by regulating the nonlinear static stiffness coefficient γ. The smaller the PWG thickness is, the larger the peak load is, the smaller the impulseis, and the more obvious the shape of ‘peak and thin waist’ is.

    Experimental Study of Detonation Wave Propagation Characteristics of Anthracite Pulverized Coal with Different Physical Properties under Ethylene/oxygen Atmosphere
    ZHANG Feng, LUO Yongchen, XIAO Bowen, NI Xiaodong, ZHENG Quan, WENG Chunsheng, XU Han
    2024, 45(5):  1663-1672.  doi:10.12382/bgxb.2023.0022
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    The continuous rotating detonation engine with coal powder as fuel has the advantages of high thermal efficiency of detonation cycle, high volumetric calorific value of powder fuel and adjustable flow rate, etc. However, the operating characteristics of the engine are influenced by the physical properties of coal powder. In order to study the effects of different physical properties of pulverized coal powder on the propagation characteristics of detonation wave, the gas-solid two-phase detonation experiments was conducted with three types of porous 5μm, porous 40μm and flake 5μm anthracite pulverized coals, at different equivalent ratios (0.7, 1.0, 1.3, 1.5). A test setup of constant volume combustion bomb was designed with a high energy ignition system at an initial pressure of 100kPa. In the test cases of detonation with porous 5μm anthracite fuel, the detonation wave speed and pressure continue to increase with the increase in the equivalent ratio, and the maximum detonation wave propagation speed and pressure are achieved when equivalent ratio is 1.5. In the test cases of detonation with porous 40μm pulverized coal fuel, with the increase in the equivalent ratio in the range of 0.7-1.3, the detonation wave speed continues to increase, and when the equivalent ratio is increased to 1.5, the detonation wave speed begins to decrease, but the detonation pressure increases. The detonation wave speed with 5μm porous pulverized coal fuel is better than that with 40μm pulverized coal at the same equivalent ratio ; the detonation characteristics with flake 5μm pulverized coal fuel are the worst and suppress detonation at high equivalent ratio.

    Property and Uncertainty Quantification of Detonation Pressure Based on Shock Hugoniot Relationship
    LIANG Xiao, WANG Ruili
    2024, 45(5):  1673-1680.  doi:10.12382/bgxb.2022.1207
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    The confidential interval of explosive shock Hugoniot parameters is exactly assessed and the uncertainties associated with shock ignition and equation of state are efficiently quantified to improve the robustness and reliability of the model and enormously reduce the calibration cost of detonation pressure. The linear regression method is utilized to calibrate the shock Hugoniot parameters, and the confidential interval of Hugoniot parameters are also deduced from parameter estimation. Moreover, the availability of Hugoniot model is validated through domestic experiment data. On the basis of reasonable assumptions, Chapman-Jouguet theory and shock Hugoniot relationship are combined to the functional relationships among detonation pressure. sample thickness, shock passing time, initial density, Hugoniot slope and 0-presure sound speed are deduced. The input uncertainty is characterized by log-normal distribution and Beta distribution, and it is transformed into independent standard normal random variables by Rosenblatt transformation. Polynomial chaos with basis adaptation is applied to implement uncertainty propagation, and the probability density function and confidential interval of detonation pressure is obtained. The results show that the detonation pressure satisfies the quasi-monotonicity with respect to sample thickness, passing time and detonation speed. The assertion of previous studies is confirmed in specific conditions. The confidence interval is much wider when it is used in PBX9502, which coincides with the prior judgment given by experimental expert. This study develops an efficient uncertainty quantification and propagation method. The result can provide technique support for developing highly predictable and confidential software.

    Experimental Research on Human Lung Injury Induced by Complex Blast Wave
    LI Gang, XU Bingchuan, HU Bin, CAI Meng
    2024, 45(5):  1681-1691.  doi:10.12382/bgxb.2022.1063
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    In order to study the dynamic physical response characteristics of human lung under the blast wave in warfare conditions, a series of tests on damage effects of fuel-air-explosive projectile to an anthropomorphic test device (ATD) and sheeps in the works were carried out under non-contact static explosion conditions. In the tests, the blast test device commonly used in USA military standards and the simple dummies are used as the research objects. The pressure-time curves of ATD are obtained through 6 explosion tests, and the propagation principle of the blast wave on the surface of ATD is analyzed. The assessment of blast wave to human lung injury is compared by Axelsson injury model and UFC 3-340-02 standard. The results show that the main damage elements are blast wave and concrete fragments under the conditions. The blast wave on the surface of ATD thorax is reflected by thorax surface, and then diffracted to the other parts of ATD thorax. The pressure-time curves of ATD show the atypical blast wave characteristics and superposition convergence during propagation. In the positive phase duration interval of typical blast wave characteristics, the chest wall velocity calculated by Axelsson injury model first increases the first peak and then decreases because of the linear damping term of the Axelsson equation. Compared with UFC 3-340-02 standard, the Axelsson injury model is relatively conservative in blast injury predictions. The research results can provide references for engineering application and damage assessment.

    Relationship between Key Process Parameters and Stress Field of Aviation Aluminum Alloy Welded by Laser Beam
    LI Guangzu, WANG Jiangtao, XIE Li, LU Yalin, ZHANG Yongkang, HU Kejun, C. M. CASCIOLA
    2024, 45(5):  1692-1702.  doi:10.12382/bgxb.2023.0935
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    Laser welding process parameters not only affect the residual stress of aluminum alloy structural parts, but also affect their service performance. It is of great significance to explore the relationship between parameters and stress field to improve the quality of welded structural parts.The laser welding of 7075-t7351 aluminum alloy plate with a thickness of 5mm is numerically simulated by using the cone heat source model. The influences of welding speed and laser energy on the welding residual stress field is analyzed. The accuracy of the simulated results is verified by experiments, and the relationship between the laser welding process parameters and stress field of 7075 aluminum alloy is revealed. The results show that the residual stress increases with the increase of welding speed, but when the welding speed exceeds a certain value, the stress in a weld nugget zone does not increase, and the maximum stress gradually expands to both sides. In addition, the larger the laser energy is, the smaller the residual stress is, but the distribution area of maximum residual stress gradually expands. The best process window for laser welding of 7075 aluminum alloy was obtained: welding speed is 5~7mm/s, and laser welding energy is 70~100J/mm. The above research has a certain value and significance in shortening the cycle of laser welding process optimization of 7075 aluminum alloy and reducing its cost.

    Lightweight and Fast Target Tracking Algorithm Based on Ghost-TiFPN
    YIN Guohua, QI Yongsheng, LIU Liqiang, SU Jianqiang, ZHANG Lijie
    2024, 45(5):  1703-1716.  doi:10.12382/bgxb.2022.1272
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    In response to the problems that traditional siamese target tracking algorithm is bulky and difficult to deploy in embedded devices, and has poor effect under the conditions of large changes in target scale and similar object interference, a lightweight and fast target tracking algorithm GTtracker is proposed. The Resnet network is redesigned to build a lightweight G-Resnet network by introducing the Ghost mechanism for fast feature extraction of tracked targets. And then the fusion of feature information is further enhanced by designing a lightweight adaptive weighted fusion algorithm TiFPN to solve the problem of similar object interference. After that, a lightweight area regression network GDNet is introduced for target classification, IoU calculation, and bounding box regression, which applies a new target finder in the tracking stage to enhance the success rate of algorithm tracking. Finally, the algorithm is validated on OTB100 dataset and VOT2020 dataset, and ported to Jetson Xavier NX embedded device for performance testing. Experimental results show the effectiveness and superiority of the proposed algorithm, In comparison with classical siamese target tracking algorithm (SiamCAR), the proposed algorithm can achieve faster operation speed and real-time operation on Jetson Xavier NX, reaching 30 frames/s, under the conditions of the same accuracy and EAO metrics, which can effectively solve the problems of similar object interference and large scale variation.

    An Array Extension Method Based on Combination of Sub-array Covariance Matrices
    LIANG Guolong, LUO Junge, HAO Yu, FU Jin
    2024, 45(5):  1717-1724.  doi:10.12382/bgxb.2022.1076
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    A linear array extension method based on combination of sub-array covariance matrices is proposed to solve the problem of performance deterioration of signal detection and azimuth estimation under low signal-to-noise ratio. The proposed method divides the array into odd and even sub-arrays, and the extended received data is constructed by using the cross-covariance and auto-covariance matrices of the two sub-arrays. Finally, the final extended signal is obtained by combining the extended received data. The proposed method breaks through the physical aperture of array, and avoids the problem of grating lobe when using the cross-covariance of odd and even sub-arrays only to reconstruct the received data. Simulated results show that the proposed method can be used to reduce the sidelobe of beam output, and has good weak target detection ability and azimuth resolution. Compared with the array extension algorithm based on the cross covariance of odd and even sub-arrays, the proposed method can provide higher azimuth estimation accuracy.