Table of Content

28 February 2022, Volume 43 Issue 2

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Contents

2022, 43(2):  0. 

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Paper

Unified Motion Planning Method for Heterogeneous Tracked Vehicles

WANG Boyang, GUAN Haijie, GONG Jianwei, CHEN Huiyan, ZHAO Huijing

2022, 43(2):  241-251.  doi:10.3969/j.issn.1000-1093.2022.02.001

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A motion planning method based on the offline generation and online extension and selection of motion primitives is proposed for planning the motion of heterogeneous tracked vehicles under a unified algorithm framework. The heterogeneous tracked vehicle studied refers to a tracked vehicle equipped with three different steering mechanisms. The optimized generation of motion primitives takes trajectory smoothness as the goal. A motion primitive library that meets the motion planning requirements of heterogeneous tracked vehicles is generated by comprehensively considering the differentiated behavior constraints of heterogeneous tracked vehicles, platform kinematics model constraints, smooth transition constraints, etc. The extension and selection of motion primitives are based on a unified algorithm framework, which comprehensively considers the attributes of the motion primitives, reference lines, expected velocity, obstacles, and other factors. By selecting the appropriate primitives from the motion primitive library to form the primitive sequences, the coordinated motion at the level of trajectory and velocity is planned. The results show that the proposed unified motion planning method for heterogeneous tracked vehicles, with the help of differentiated behavior constraints when primitives are generated, and unequal selection weights set according to primitive attributes, generates a motion planning result that reflects the difference in characteristics of heterogeneous tracked vehicles and meets real-time requirements.

Generating Method and Process of Load Spectra for Tracked Vehicles Based on Prediction of Manipulating Action

XU Baorong, WANG Tao, LIANG Zi

2022, 43(2):  252-259.  doi:10.3969/j.issn.1000-1093.2022.02.002

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A new generating method of load spectrum for tracked vehicles is proposed based on load spectrum blocks and training subjects to cope with the problem of insufficient sample size. Action of vehicles and driving behavior are predicted by using path planning algorithm and action planning algorithm. Training subjects and geographic information are used as input data, the predicted vehicle situation and driving behavior are taken as indexes to get load spectrum blocks, and the time domain load spectrum are generated by spliced load spectrum blocks. The verification test results show that the load data samples generated by splicing method can reflect the vehicle working conditions correctly, and it can be used to generate load samples rapidly.

Vertical Drop Impact Characteristics of Flat Base Projectile without Package and Fuze with Bottom-down

JIN Luxuan, WEN Quan, WANG Yushi, WANG Guangyu, ZHANG Zhibiao

2022, 43(2):  260-272.  doi:10.3969/j.issn.1000-1093.2022.02.003

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A formula for the impact characteristics of flat base projectile and fuze when the projectile drops vertically is proposed for studying the vertical drop impact characteristics of a flat base projectile without package with bottom-down involved in the design of fuze setback arming device. On the basis of simplified assumption, the theoretical calculation formulas are derived to calculate the peak acceleration and impact duration of the projectile dropping vertically and colliding with ground targets by using elastoplastic mechanics theory. A 152 mm caliber flat base projectile is used as a benchmark, the processes of projectiles with different calibers dropping vertically and colliding with ground targets are simulated by using software ANSYS/LS-DYNA. Based on simulated peak impact acceleration and duration of impact, the theoretical formulas are corrected through modification of constant coefficient. The formulas for the impact characteristics of projectile and fuze when the flat base HE projectile drops vertically downward were obtained. The results show that the larger diameter of the projectile is， the smaller peak impact acceleration is and the longer duration of impact is. The drop height only changes the peak impact acceleration. The impact recovery coefficient only changes the duration of impact. In the case of fully elastic collision， the projectile falls to any target at the same height， the product of peak impact acceleration and duration of impact is constant.

Effect of Flame Inhibitor of the Muzzle Flame of Large Caliber Gun

WANG Danyu, NAN Fengqiang, LIAO Xin, XIAO Zhongliang, DU Ping, WANG Binbin

2022, 43(2):  273-278.  doi:10.3969/j.issn.1000-1093.2022.02.004

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Because of the complexity of charge components and large charge weight of the large caliber gun, the muzzle flame is more serious during firing, which is easy to bring threat to personnel or battlefield camouflage. A chemical reaction model considering flame inhibitor for a 155 mm gun is established to study the generation and evolution of muzzle flame. PISO algorithm is used to simulate the muzzle flow field of gun with or without adding flame inhibitor. The simulated results show that the mass fractions of combustible components ( C and CO) in the gun muzzle decrease obviously and the maximum temperature outside the muzzle decreases from 3 000 K to 2 200 K after 1.5% K₂SO₄ is added into the propellant. This explains that the flame inhibitor can effectively inhibit the generation and evolution of muzzle flame. By comparing the simulated results with the experimental images, it can be seen that the shapes and sizes of simulated and experimental muzzle flame profiles are consistent. Also, it is found that the error is less than 5% after using the element grid to estimate the fireball area outside the muzzle.

Preparation and Properties of Copper Azide Initiating Film with Low Electrostatic Sensitivity

YAN Zhenzhan, LI Long, YANG Li, HAN Jimin

2022, 43(2):  279-286.  doi:10.3969/j.issn.1000-1093.2022.02.005

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The high electrostatic sensitivity of copper azide limits its practical application，and carbon fiber as a frame material can effectively reduce its electrostatic safety. A carbon-based copper azide initiating film was prepared using the cheap and easily available copper acetate as the raw materialby carbonization and azide. The prepared copper azide composite film has certain flexibility, and the copper azide nanosheets are uniformly grown on the surface of carbon fibers. The excellent electrical conductivity of carbon fibers can reduce its electrostatic sensitivity. The precursors, carbide intermediates, and copper azide films are all characterized in detail by scanning electron microscope, infrared, X-ray diffraction, specific surface area test and thermogravimetric analysis etc. The test results show that the electrostatic sensitivity of the prepared copper azide initiating film is reduced to 1.2 mJ and the sensitivity to flame is increased to 45 cm since carbon fiber has the excellent electrical and thermal conductivities. The 0.65 mg copper azide initiating film can successfully ignite at a voltage of 10 V or more under the discharge condition of a 33 μF capacitor, and can pit the lead plate.

Macro-meso-scale Cook-off Simulations of DNAN-based Melt-cast Explosives

LIU Ruifeng, WANG Xinjie, HUANG Fenglei, HUANG Hengjian

2022, 43(2):  287-296.  doi:10.3969/j.issn.1000-1093.2022.02.006

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The melting of DNAN and the phase transformation of HMX crystal occur in 2,4-dinitroanisole (DNAN)/octogen (HMX) melt-cast explosives during cook-off test. A melting reaction kinetics model is developed for DNAN, and a four-step reaction kinetics model of HMX is used to study the melting, phase transformation and ignition response of DNAN-based melt-cast explosives at the macro-meso scale. Macroscale calculation shows that DNAN melts at about 377.00 K, HMX undergoes a phase transformation at about 450.00 K, and the ignition temperature is 531.34 K. The ignition position locates at the annular area between the upper and lower ends and the side of the explosive, the error between the calculated and experimental ignition times is 0.5%. The mesoscale calculation results based on the macroscopic ignition area show that the ignition position locates at HMX crystal, and the evolution rules of DNAN melting and HMX phase transformation are obtained: at different times, the statistical distribution of liquid-phase DNAN is U-shaped, and δ-HMX is approximately normal. The macro-meso scale cook off simulations of DNAN-based melt-cast explosives are of great significance for understanding the thermal ignition mechanism of energetic materials.

Evaluation Method for Migration Invalidation of Deterred Double-base Gun Propellants

LIANG Hao， DING Yajun， LI Shiying， ZHAO Xianzheng， XIAO Zhongliang

2022, 43(2):  297-304.  doi:10.3969/j.issn.1000-1093.2022.02.007

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The traditional aging invalidation evaluation of gun propellants is mainly for the chemical stability of propellants during storage without considering the migration of deterrent in the aspect of physical change. Based on the diffusion principle and the relationship between the deterrent distribution and the combustion performance, a migration invalidation evaluation method is established for testing the percentage increase in the maximum dynamic vivacity of deterred double-base gun propellants by closed vessel experiment. Through the closed vessel and ballistic experiment, the linear growth model of the increasing percentage of the maximum dynamic vivacity of deterred double-base gun propellants with the aging time was obtained, and the validity of the established method was verified. The variation of the stabilizer content with aging time is analyzed by gas chromatography. It is revealed that the invalidation time of deterred double-base gun propellants caused by the aging migration is earlier than that of the chemical stability. The aging invalidation evaluation of the deterred double-base gun propellants should follow the “double threshold principle” to ensure their storage safety and use safety.

Multi-body Dynamics Analysis Method for Ejection Launching of Submarine-borne Missile Considering the Flexibility ofMissile Body and Its Canister

ZHANG Zihao， WANG Hanping

2022, 43(2):  305-315.  doi:10.3969/j.issn.1000-1093.2022.02.008

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In the process of vertical launch of submarine-borne missile, the attitude of missile is the key to the successful launch. A dynamics analysis method for ejection launching of submarine-borne missile considering flexibility of missile body and its canister. An improved model of flexible point-to-curve high pair is used to simulate the compression and bending loads of the adapters. Based on the assumption of element linear distribution of hydrodynamic force and water inertial force attached to missile body, Hermite shape function is used to simplify the element distributed load to a concentrated force on element nodes, and the loading is realized by GFOSUB subroutine development. The simulated results are in good agreement with the experimental data, which proves the practicality and credibility of this method. The proposed method provides a new idea for modeling the ejection launching dynamics of submarine-borne missile considering the flexibility of missile body and its canister, and also gaves a new approach for the simplified modeling of contact between flexible bodies.

Dynamic Inverse Compensation Method of Flow Rate Dead-zone of Electro-hydrostatic Actuator Considering Viscosity-temperatureCharacteristics of Oil

HAN Xiaoxia, FENG Yongbao, XIE Jian, WEI Liejiang, WANG Yaqiang, WEI Xiaoling

2022, 43(2):  316-327.  doi:10.3969/j.issn.1000-1093.2022.02.009

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The highly integrated electro-hydrostatic actuator (EHA) has been reduced in size and weight, but the poor heat dissipation and rapid increase in system oil temperature have been brought, thus leading to the time-varying characteristics of flow rate dead-zone of EHA resulting from the reduction of oil viscosity. This makes accurate control of EHA more difficult. For the above problems, a mathematical model of EHA flow rate dead-zone is established, in which the viscosity-temperature characteristics of the oil are considered, and the variation law of flow rate dead-zone is analyzed. Furthermore, a dead-zone dynamic inverse compensation method for flow rate based on the system model information is proposed. The compensation effects of proposed method at different speeds and loads are compared and analyzed, and verified through experiment. The results show that the flow rate dead-zone of EHA increases with the rise in temperature, and the proposed dynamic inverse compensation method can compensate the flow rate dead-zone of EHA under light load conditions, which is conducive to improving the control performance of the system.

Two-stage Optimization Strategy of Assignment for Operating Modes of Early Warning Radar

YIN Kangyin，JIANG Zhimin，FENG Yajun

2022, 43(2):  328-336.  doi:10.3969/j.issn.1000-1093.2022.02.010

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A two-stage optimization strategy of assignment for operating modes of early warning radar is proposed to improve the efficiency of early warning radar. In the first stage, the demand to radar resource is calculated by line programming based on the task environment, target distribution and special target with the object of high data rate and covering region. In the second stage, an optimization model of radar operating modes is proposed by 0-1 programming with the detection effectiveness of radar operating modes,in which the detection probability and contribution rate of detection source are considered. The methods of standardized processing of radar sector and prediction of detection effectiveness are proposed to improve the optimization model.The optimization model was validated through simulation experiment.The result shows that the mastery ratio of target and the matching ratio of radar operating modes are above 90%, respectively. It is a preference to improve the efficiency of early warning radar.

Key Generation Method Based on Generative Adversarial Network and Its Application in Low-light-level Image Encryption

LI Jinqing, LIU Zefei, MAN Zhenlong

2022, 43(2):  337-344.  doi:10.3969/j.issn.1000-1093.2022.02.011

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Generative adversarial network (GAN) is a deep learning model, which is one of the most promising methods for unsupervised learning in complex distributed environment in recent years. The random numbers generated by GAN and chaotic systems have many similar advantages, such as randomness and sensitivity. But at the same time,the random numbers generated by GAN have the features that the random numbers generated by chaotic systems do not have, such as non-reproducibility.The random number generated by GAN training shows its rapidity and higher security in the encryption of low-light-level images with low signal-to-noise ratio and few gray levels. GAN is introduced into the random key generation. The pseudo-random number generated by quantum cellular neural network (QCNN) system is used as the training set of GAN, and a completely random key pool is obtained through GAN to learn and train the random key generated by hyperchaotic system. For the application of the proposed key generation method in low-light-level image encryption, a new low-light-level image encryption algorithm is proposed, which uses a 2D-pointer related to the plaintext to randomly select two phase masks in the key pool to achieve the security of low-light-level images. The results show that the encryption key generated by the learning key generation scheme can pass all the random tests of The National Institute of Standards and Technology, and the scheme can resist differential attacks by cryptanalysts, known/chosen plaintext attacks, and various statistical analyses. The performance comparison with other similar algorithms also shows the superiority of the proposed cryptosystem.

Improved YOLOv3 Algorithm and Its Application in Military Target Detection

YU Bowen， L Ming

2022, 43(2):  345-354.  doi:10.3969/j.issn.1000-1093.2022.02.012

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Military target detection in a complex environment is the basis and key to improving battlefield situation generation and analysis capability. For the military target detection tasks, the detection performance of traditional detection algorithms in complex environment is low. A military target detection algorithm based on improved YOLOv3 algorithm is proposed to automatically detect the military targets in complex environment through deep learning. A military target image dataset is constructed to provide a testing environment for various target detection algorithms. The detection accuracy and speed of deformable target are improved by introducing the deformable convolutional improved ResNet50-D residual network as feature extraction network. In the stage of feature fusion, a dual-attention mechanism and feature reconstruction module are introduced to enhance the characterization ability of target features, suppress the interference, and improve the detection accuracy. The loss function of target detector is redesigned by using DIOU Loss functions and Focal Loss to funther improve the detection accuracy of military targets. The experimental results show that the improved YOLOv3 algorithm improves the average detection accuracy by 2.98% and the detection speed by 8.6 frames/s compared with the original YOLOv3 algorithm. The improved YOLOv3 algorithm has better detection performance and can provide effective auxiliary technical support for battlefield situation generation and analysis.

The Influence of Waves on the Impact Load during High-speed Water-entry of a Vehicle

YANG Xiaoguang， DANG Jianjun, WANG Peng, WANG Yadong, CHEN Cheng, LI Deying

2022, 43(2):  355-362.  doi:10.3969/j.issn.1000-1093.2022.02.013

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The load characteristics of a vehicle entering into water at high-speed under wave conditions are key factors influencing the overall plan and structural design of vehicle. VOF multiphase flow model and dynamic grid technology are used to establish a numerical simulation method of high-speed water-entry, and the accuracy and applicability of the simulation method are verified by experiments. The influences of water entry angle and wave parameters on the axial impact load during high-speed water-entry events are numerically studied. The results show that the peak axial impact force coefficient increases with an increase in the water-entry angle, and has a linear relationship with the tangent function of water-entry angle. The different wave phases change the actual angle between the vehicle and the water surface at the water-entry moment. When entering into the water at 90° or 270° wave phase angle, there is little difference between the axial impact load and that in static water environment; when entering into the water at 0° wave phase angle, the peak value of axial impact load is the largest, and it is basically the same as the axial impact load at the corresponding water-entry angle on static water surface; when entering into the water at 180°wave phase angle, the axial impact load is the smallest, but it is prone to ‘jump’ and cause failure in the water-entry. The actual water-entry angle should be the coupling value of the wave inclination and the vehicle attitude at the entry point under wave conditions, the peak axial impact force coefficient can be obtained by interpolating the peak coefficient curve of impact load in static water environment.

Electrochemical and Electric Field Response Performances of Nitrogen-doped Carbon Fiber Electrode Modified with HydrazineHydrate

SUN Jiuzhe, ZHAO Honghao, HAN Yongkang, XU Jiawei, FU Yubin

2022, 43(2):  363-371.  doi:10.3969/j.issn.1000-1093.2022.02.014

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The modification on the surface of carbon fiber by nitrogen doping is expected to improve its electrochemical performance and electric field response performance. A new type of ocean electric field electrode was prepared using hydrazine hydrate as the nitrogen source to modify the viscose-based carbon fibers, and the changes in electrochemical performance and electric field response performance of electrode before and after modification were explored. The results show that the electrochemical performance and electric field response performance of the modified carbon fiber electrode are significantly improved. The high-temperature heat-treated nitrogen-doped sample after modification with hydrazine hydrate has the best performance, and its specific capacitance reaches 102.5 F/g, and is 18.99 times that of the blank group; the charge transfer resistance and the low-frequency capacitive reactance are greatly reduced respectively. The potential stability of electrode is improved, and the electrode can stably respond to 1 mV, 1 mHz low frequency and low intensity electric field signals; and its response sensitivity and accuracy are also significantly improved.The modified electrode can be used to prepare high-performance marine electric field sensors and improve the detection capability of underwater electric field.

Electromagnetic Pulse Coupling Characteristics of a Vehicle in High Altitude Nuclear Explosion Environment

NIE Kunlin, ZHAO Wei, LI Peng, WEI Yongli, LIU Xin, LI Xiaoqiang, ZHANG Xiong, ZHU Zhizhen, ZHU Xuezheng, ZHENG Yi

2022, 43(2):  372-382.  doi:10.3969/j.issn.1000-1093.2022.02.015

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Electromagnetic pulse coupling threshold is the basic basis for the decision-making of operational employment of equipment in the nuclear explosion environment and the optimization of its anti-nuclear reinforcement. On account of the fact that the immunity to electromagnetic pulse of a vehicle is unknown, the coupling characteristics of high altitude nuclear electromagnetic pulse (HEMP) are studied. The finite-difference time-domain (FDTD) method is applied to the research on the coupling characteristics of HEMP of a vehicle. The FDTD method for the research on HEMP coupling effect was verified through the radio antenna irradiation test of the vehicle, and the change of electric field inside the vehicle in HEMP environment is analyzed systematically starting from the observation hole of the vehicle. It is found that the amplitude of the coupling electric field in most of the space within the vehicle is less than 2 kV/m, and the amplitude of the electric field near the observation hole is higher when HEMP is normal incident. The suggestions of electromagnetic pulse protection are proposed from the relevant distribution laws of the electric field in the vehicle: the electronic equipment and wiring in the vehicle should be as far away from the observation hole as possible; the amplitude of coupling electric field at the observation hole is reduced by using shielding glass; and when receiving the warning information related to nuclear explosion, the electronic equipment should be quickly moveed as far away from the observation hole as possible to prevent damage.

Prediction Model for Ignition Probability Function of Ullage in Aircraft Fuel Tank

LUO Liang， PEI Yang， HOU Peng， ZHANG Mengtao， LI Mingsuo

2022, 43(2):  383-390.  doi:10.3969/j.issn.1000-1093.2022.02.016

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The ballistic experiment of shooting a projectile at a simulated fuel tank is made to study the ignition probability function of ullage in aircraft fuel tank, and the conditions of igniting to fuel tank by projectile at different speeds are obtained. The impact damage criterion of fuel tank (BC criterion) is put forward. Based on the experimental research, an ignition probability function prediction model of the ullage in aircraft fuel tank is obtained through Logistic regression analysis. The research results show that the error between the predicted value of the ignition probability function based on BC criterion with the predicted value of the empirical formula and the frequency at experimental point is small, and the proposed prediction model can be used to predict the ignition probability of fuel tank under the given conditions with good accuracy. The research methods and related conclusions can provide a reference for the research on the damage criterion of aircraft fuel tank and the aircraft vulnerability assessment.

Seismic Collapse Resitance of NFB700 High-strength Steel Plate

XU Gancheng, YUAN Weize, CHEN Linheng, LI Chengxue, XIE Xuhu, NIE Mengqi

2022, 43(2):  391-400.  doi:10.3969/j.issn.1000-1093.2022.02.017

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In order to study the seismic collapse resistance of NFB700 high-strength steel plate with high yield strength and good toughness, the field explosion tests were carried out on four targets. Through the observation of damage state of the test model and data analysis, the ability of high-strength steel plate to resist the seismic collapse of the target was studied. The numerical simulation analysis of the ultimate seismic collapse resistance of double-layer concrete-steel structure is carried out. The results show that the micro-strain of the target mostly decreases with the increase in the thickness of concrete slab, but the change of the micro-strain with the distance from the explosion center is not obvious, and the target with high-strength steel plate and thicker concrete slab has fewer cracks and finer cracks on it. And most of them have surface cracks. The target with ordinary steel plate has more cracks on it, of which are wider and longer, with the maximum length of 770 mm; as the thickness of concrete slab increases, the deformation of high-strength steel plate on the back decreases successively, and the concrete crater depths decrease successively; the deformation of the ordinary steel plate target is about twice that of equal thickness high-strength steel plate target, the overall deformation is V-shaped, and the center of the concrete is completely broken, indicating that the use of high-strength steel plate as the back plate can greatly improve the seismic collapse resistance of the target; For the structure of using 8 mm-thick high-strength steel plate as the back slab and reinforced concrete composite structure, the seismic collapse coefficient is about 0.147.

Test Method for Pulse Response of Field-induced Insulator-metal Transition Material

ZHAO Min, QU Zhaoming, WANG Qingguo, ZHOU Xing, CHEN Yazhou

2022, 43(2):  401-409.  doi:10.3969/j.issn.1000-1093.2022.02.018

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The field-induced insulator-metal transition material can meet the urgent demands of self-adaptive efficient protection of electronic information equipment under strong electromagnetic pulse. However, the pulse response test method of the material is not clear at present, which is a theoretical subject to be urgently solved. A micro-strip line test method with wide test range and fast response time is proposed based on the principle of micro-strip line, and a corresponding test system is developed. The equivalent circuit model of the test system in terms of horizontal polarization is established, and the formula of material's resistance after phase change applied by electromagnetic pulse is derived. The accuracy and feasibility of the theoretical model and test method are verified by resistances equivalent test and material sample performance test. The theoretically calculated and test results show that the proposed test method can satisfy the requirements of pulse response test with resistance range of 1 Ω-30 kΩ, the resistance, response time and recovery time of the material after the phase transition can be calculated, which provides a theoretical and technical support of quantitative evaluation of pulse response characteristics of the field-induced insulator-metal transition materials and new material design.

Transient Aerodynamic Interference between Rotor and Fuselage for a Quadcopter

ZHU Yifei, LIN Defu, MO Li, YE Jianchuan

2022, 43(2):  410-422.  doi:10.3969/j.issn.1000-1093.2022.02.019

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The rotors of a quadcopter cause transient aerodynamic interferences to the fuselage, which impacts the overall aerodynamic characteristics. Based on a typical quadcopter model, the computational fluid dynamics (CFD) method is used to obtain the transient changes in force and moment under the condition of forward flight with the assumption of rigid body and incompressible flow. Wind tunnel test was implemented for verifying the rationality of CFD method and the accuracy of calculated result. The fast Fourier transform (FFT) method is adopted to obtain the modal of aerodynamic interference for further investigating of the change frequencies and amplitudes of interference force and torque. The results show that the aerodynamic interference is highly correlated with the rotation rate of rotors. Such interference can be fitted by a fifth-order Fourier series. In this model, compared with the rear rotors, the front rotors have larger impact on the fuselage. The change in the lift force can be simplified and described by the first-order Fourier series, the change in the drag force can be described by the first-third-order Fourier series, and the major periodical variation of pitching moment changes can be described by a single second-order Fourier series. The first-fourth-order Fourier series are capable of describing the detail of variations.

Design and Volumetric Efficiency of Micro High-pressure Two-dimensional Piston Pump

CHEN Yong, LI Sheng, RUAN Jian, WU Changsheng, ZHANG Hao

2022, 43(2):  423-433.  doi:10.3969/j.issn.1000-1093.2022.02.020

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A micro hydraulic piston pump based on two-dimensional micro-pump structure was developed to meet the stringent requirements on space and weight of hydraulic equipment. The piston of this pump has two degrees of freedom of movement: rotation and linear movement. With the cooperation of guide rail and roller, the rotation of piston is converted into reciprocating motion, thereby completing the function of sucking and discharging oil. The pressure characteristic equation is solved to obtain the numerical solution of discharge chamber pressure and then the flow rate loss and volumetric efficiency of each part, and find the trapped oil and backflow phenomena. By analyzing the flow rate curve, it is found that the flow rate loss is mainly attributed to backflow flow rate loss and gap leakage. The backflow flow rate is proportional to the rotation speed, accounting for about 50%-78% of the total loss. A test bench was set up to test the volumetric efficiency. The experimental result show that the volumetric efficiency increases from 82.7% to 85.8% when the rotation speed increases from 2 000 r/min to 7 000 r/min at 30 MPa, and the maximum difference between the experimental value and the simulated value is about 6%.

Electrochemical Properties and Marine Electric Field Response of Amino Acid-modified Carbon Fiber Electrode

HAN Yongkang, ZHAO Honghao, SUN Jiuzhe, XU Jiawei, FU Yubin

2022, 43(2):  434-441.  doi:10.3969/j.issn.1000-1093.2022.02.021

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The electrochemical properties and electric field response of carbon fiber are improved significantly by introducing oxygen- and nitrogen-containing functional groups on the carbon fiber surface. Glutamic acid, glycine and lysine are grafted onto the surface of carbon fiber as the carrier of oxygen- and nitrogen-containing functional groups. The carbon fiber surface is characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The electrochemical properties and electric field response performance of carbon fiber surface are studied from the cyclic voltammetry curve, electrochemical impedance spectrum and electric field response curve. The results show that the modified carbon fiber electrode has larger electric double layer capacitance and lower low-frequency capacitive reactance; the average daily drift of potential difference between paired carbon fiber electrodes is less than 5 mV/d, and the electrochemical self-noise is less than 5 nV/Hz; and the modified paired carbon fiber electrode can better respond to 1 mV and 1 mHz sinusoidal electric field signal, and the linearity of modified glutamic acid group is 0.058%, which is the lowest among the modified groups. These results are much related to its special electric double-layer structure.

Properties of Aerogel Modified Quartz Fiber Reinforced Silicone Wave-transparent Composites

KONG Guoqiang, WANG Kang, YU Qiubing, LI Ying, WEI Huazhen, SHAO Meng, BI Weidong, LIU Benxue, YIN Lei, SUN Xiaodong

2022, 43(2):  442-450.  doi:10.3969/j.issn.1000-1093.2022.02.022

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Quartz/silicone composites were prepared by using SiO₂ aerogels, Al₂O₃ aerogels and ZrO₂ aerogels as modifiers, methyl phenyl silicone resin as matrix, and quartz fiber as reinforcing material. Thermogravimetric analysis, dynamic thermomechanical analysis, mechanical properties test, dielectric properties test and SEM test were made for quartz/silicone composite. The effects of different aerogel modifications on the thermal, dielectric and mechanical properties of quartz/silicone composite were studied. The results show that the thermal stability and mechanical properties of quartz/silicone composite increase with the addition of aerogels. Al₂O₃ aerogels increase the mechanical strength of composites. The compressive strength and flexural strength of quartz/silicone composites are 145 MPa and 192 MPa, respectively, which are increased by 122% and 81% compared with unmodified composite. The dielectric constant of quartz/silicone composites increases with the addition of aerogels, but their dielectric constants are all less than 3.5 and their dielectric loss tangents are less than 0.01.

Reliability Analysis of Electric Aircraft Drive System with Feedback Loop

JIANG Xiuhong， LI Jiaxin， LIU Yanjuan， WANG Yuying

2022, 43(2):  451-457.  doi:10.3969/j.issn.1000-1093.2022.02.023

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Due to the existence of feedback loop, the reliability of electric aircraft drive system cannot be analyzed by using GO methodology directly. If the feedback loop is disconnected directly, the accuracy of the analysis results will be reduced. To solve this problem, a reliability analysis method of system with feedback loop is proposed by establishing Boolean equation. The feedback signal is set as a system input, and Boolean equation with the feedback signal can be established according to the signal flow direction and the operational rules of GO operators.The expressions of each feedback signal are derived by using Boolean equation and the equations of other feedback signals, and then the analysis results of system reliability is obtained. For the PMSM drive system of an electric aircraft, the system reliability model is established based on GO methodology. The two cases of system without and with feedback loops are analyzed and compared. The results show that the proposed method for feedback loops is feasible, which can improve the accuracy of analysis results and extend the application range of GO methodology.

On Factors Affecting Fatigue Life of Stranded-wire Helical Spring

ZHANG Rui, YI Lili, LIU Zhipeng

2022, 43(2):  458-466.  doi:10.3969/j.issn.1000-1093.2022.02.024

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Stranded-wire helical spring (SWHS) is a kind of cylindrical helical spring formed by twisting multiple steel wires into steel strands. At present, there are few studies on fatigue failure of SWHS. For the fatigue failure of SWHS in practical application, the influences of the fracture characteristics of SWHS steel wire and the geometrical parameters of SWHS on SWHS fatigue life are analyzed and studied. The analyzed results show that the surface defect of steel wire is the main reason that causes crack initiation and reduces fatigue life, and the geometric parameters of SWHS have also an effect on its fatigue life. The surface defects of steel wire include the line patterns, scars, pits, etc. In addition, the micro-holes and micro-cracks inside the steel wire material would accelerate the crack growth and reduce the fatigue life of spring. Among the geometric parameters of SWHS, the restoring force under the maximum vibration amplitude is taken as a variable, the effect of spring helix angle α on fatigue life of SWHS is the greatest, followed by spring winding ratio C and steel wire twist angle β.

Comprehensive Review

Review on Mechanical Mechanism of Blast-induced Traumatic Brain Injury and Protection Technology

CAI Zhihua, HE Wei, WANG Jianhui, WANG Xing, ZHANG Lei

2022, 43(2):  467-480.  doi:10.3969/j.issn.1000-1093.2022.02.025

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Blast-induced traumatic brain injury (BTBI) is the main form of injury for individual soldiers in the new war mode. Especially in the frequent terrorist attacks and explosion safety accidents in recent years, more and more civilians are suffering from such kind of trauma. So far, the domestic and foreign scholars have studied the brain injury caused by blast waves, but the injury mechanism, damage threshold, protection technology and injury assessment technology have not been clarified yet. Based on the extensive investigation on the latest research frontiers at home and abroad, the generation of blast waves, the types of brain injuries and its pathological characteristics, the research methods, the injury mechanism, the damage threshold and the protection methods are reviewed, focusing on analyzing the current research status and hot spots, the existing main problems and the future research direction.