Table of Content

30 June 2021, Volume 42 Issue 6

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Contents

2021, 42(6):  0. 

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Paper

Test and Evaluation of Body Armor Performance Based on 3D Digital Image Correlation Technology

WEN Yaoke， ZHENG Hao， ZHANG Junbin， YAN Wenmin， LIU Fei

2021, 42(6):  1121-1127.  doi:10.3969/j.issn.1000-1093.2021.06.001

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5.8 mm bullet penetration NIJ Ⅲ grade SiC/UHMWPE body armor was test to analyze the transient mechanical response of body armor and the degree of blunt injury of human chest under non-penetrating ballistic impact. 3D digital image correlation technology (3D-DIC) was used to capture the back face deformation (BFD) of body armor, and the deformation height and speed were obtained. The blunt criterion (BC) and abbreviated injury scale (AIS) were used to evaluate the degree of blunt injury when the distance between body armor and chest was 5 mm and 10 mm, respectively. The test results show that the average maximum height of BFD is 22.7 mm, its average maximum static height is 16.3 mm, and its average maximum deformation velocity is 117.7 m/s. When the gap between body armor and chest is 5 mm, the corresponding AIS level is 4-5, indicating that the blunt effect behind body armor can cause serious injury to the human body. However, when the gap expands to 10 mm, the AIS level is less than 3, indicating that the blunt effect after body armor causes slight injury to the human body and even has no affect on the human body.

Robust Adaptive Trajectory Tracking Control Approach for Autonomous Tracked Vehicles

LI Rui， XIANG Changle， WANG Chao， FAN Jingjing， LIU Chunlin

2021, 42(6):  1128-1137.  doi:10.3969/j.issn.1000-1093.2021.06.002

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A robust adaptive trajectory tracking control approach based on robust integral of sign of error is presented for the trajectory tracking control of autonomous tracked vehicles in the field environment. In the proposed approach, the modelling errors, parametric uncertainties, and external random and strong disturbances are taken into account. A kinematic and dynamic coupling model of autonomous tracked vehicles is established based on Lagrangian dynamical equation. The feedforward compensation of the established model is realized by adaptive control approach, and the external disturbances and uncertainties can be suppressed by using the robust integral of sign of error. And then the asymptotical global stability and convergence of the closed loop system is demonstrated by Lyapunov stability theory. The simulated results were verified through real vehicle test. Simulated and experimental results show that the proposed approach can be used to realize the high accuracy trajectory tracking and insure the adaptiveness and robustness for autonomous tracked vehicles in the presence of modelling errors, parametric uncertainties and external disturbances.

The Influence of Inner Ring Tilt Angle on Dynamic Characteristics of High-speed Angular Contact Ball Bearings

CHANG Liping， CHANG Yanan， YANG Leilei

2021, 42(6):  1138-1147.  doi:10.3969/j.issn.1000-1093.2021.06.003

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The tilt angle between inner rings and outer rings of high-speed angular contact ball bearings(ACBB) exist due to the inevitable error of machining and assembly. The tilt angle of the ring has a great influence on the running performance of bearing, and even causes the bearing failure under some conditions. According to the above situation, a bearing analysis and calculation model considering the tilt angle of ring and the centrifugal effect of high speed is proposed. The dynamic characteristics of high-speed ACBB are calculated by using Newton-Raphson method. The results show that the contact stress fluctuation caused by the tilt angle of inner ring becomes weaker but the spin-to-roll ratio and revolution speed fluctuation are enhanced when the rotating speed of inner ring increases. This indicates that the tilt angle of inner ring is more likely to lead to the failure mode associated with bearing heat rather than the common fatigue failure at high speed. For ACBB subjected to combined load, the appropriate tilt angle of inner ring can weaken the contact angle, revolution speed, spin-to-roll ratio fluctuation caused by radial load to some extent, and significantly increase the radial and angular stiffnesses of bearing. In the presence of inner ring tilt angle, the silicon nitride ceramic ball bearings outperform steel ball bearings in terms of contact angle, spin-to-roll ratio,revolution speed and dynamic stiffness. But the contact stress of the ring is more sensitive to the tilt angle of the inner ring than that of the steel ball bearing.

Friction Model of Projectile Engraving Process Based on Temperature Correction

ZOU Libo， YU Cungui， FENG Guangbin， HOU Baolin， ZHONG Jianlin， LIU Xianfu

2021, 42(6):  1148-1156.  doi:10.3969/j.issn.1000-1093.2021.06.004

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During the extrusion of projectile into a barrel，the friction between the cartridge belt and the barrel not only affects the internal ballistic characteristics，but also affects the prediction of barrel life. The friction between the rotating band and the barrel has the characteristics of high speed and high contact pressure during the engraving process of projectile. A friction model for describing the friction characteristics of rotating band and barrel is proposed based on the deformation mechanism of rotating band during engraving process of projectile. In the proposed model，the contact pressure，sliding speed and the effect of elevated temperature on the surface melting of rotating band during burst of fire are considered. A coupled thermo-mechanical finite element model for projectile matching is established to analyze the changes in the stress of rotating band and the temperature during engraving process. The proposed model is compared with the models in Refs.［24-25］. The velocity of projectile after engraving and the surface temperature change of rotating band are analyzed in detail.The result shows that the proposed friction model can accurately describe the frictional characteristics of barrel and rotating band during engraving process.

Impact Deformation Features and Load Characteristics of Truncated Ogival Nose Projectile under Taylor Impact

LI Juncheng， CHEN Gang， HUANG Fenglei， LU Yonggang， TAN Xiaojun， HUANG Weiyin

2021, 42(6):  1157-1168.  doi:10.3969/j.issn.1000-1093.2021.06.005

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The impact deformation characteristics and impact load characteristics of truncated ogival nose projectile are analyzed through theory and experiment. The impact load generated by projectile in Taylor impact test is analyzed. Based on the classical Taylor impact theory of blunt projectile, an impact analysis model of ogival nose projectile was established, and the conservation equation of momentum and impulse was modified. The predicting results of the modified model are closer to the actual results. A series of Taylor-Hopkinson impact tests on the cylindrical projectiles with truncated ogival and blunt nose shape were carried out, the impact-induced deformation characteristics of projectiles and variation characteristics of impact load were specifically analyzed for the two kinds of projectiles, and the overall high g-load that the projectiles were subjected to was further discussed. The results show that the nose shape significantly changes the waveform and pulse duration of impact load, and the impact velocity primarily affects the peak value of impact load. The impact characteristics can be regulated by the nose shape design of projectile and the control of impact speed. The results support the assumption that the Taylor impact test can be applied to high-g loading test.

Performance of Thermal Protection Coating of Fuze and Its Packaging Materials in Cook-off Test

PAN Yue， LI Dinghua， YANG Rongjie， HAN Yanhui， LOU Wenzhong

2021, 42(6):  1169-1177.  doi:10.3969/j.issn.1000-1093.2021.06.006

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A sandwich structural coating with both fire resistance and thermal insulation properties is developed to improve the heat insulation/fire resistance performances of fuze and its packaging box. The use of coatings help to avoid the potential safety hazards caused by thermal stimulation. The slow and fast cook-off tests were made to analyze the thermal insulation performances of different coating structures. The results show that the fireproof coating used alone could not serve as a thermal insulation in the slow cook-off test. After applying an insulation outer coating layer, a strong protective layer could be formed under thermal stimulation. The temperature on the back side of steel plate is reduced by 32 ℃ in the slow cook-off test and 157 ℃ in fast cook-off test. The sandwich structural coating is applied to fuze shells and their packaging boxes. And it plays an important role in heat insulation/fire resistance performance. Compared with the unprotected specimen, the sandwich structural coatings could reduce the temperatures on the back side of steel plate by 21 ℃ and 33 ℃ in the slow cook-off test, and 117 ℃ and 105 ℃ in the fast cook-off test.

Design and Detonation Transfer/explosion Interruption Performance of Micro Initiation Train

XIE Ruizhen， CHU Enyi， DAI Xuhan， SU Qian， XUE Yan， REN Xiaoming， LIU Lan， LIU Wei

2021, 42(6):  1178-1184.  doi:10.3969/j.issn.1000-1093.2021.06.007

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A micro-electromechanical system (MEMS) -based micro initiation train was designed to meet the development requirements of fuze miniaturization. It is consisited of micro initiator， flyer， and MEMS safety and arming device， etc. According to GJB 5309.17—2004(K)， the detonation transfer performance of initiation train in MEMS safety and arming device was test to obtain the ideal design parameters of micro initiation train, namely， the charge desity of initiator of 1.67 g/cm³ and its charge size of 2.0 mm×1.5 mm， and the diameter and height of booster cavity in safety and arming device are 1.0-2.0 mm and 0.65-1.5 mm， respectively. The test results show the initiation train can play a role of normal explosion-proof when the thickness of the slider is less than 0.3 mm， and the function of arming can be realized under the conditions of transmitting overload of 21 000 g and rotating speed of 6 000 r/min. The primary charge and axial dimension of initiation train are effectively reduced by using the booster cavity as accelerating chamber and the flyer initiation mode.

Effect of Central Cone on Working Process and Performance of Liquid-fueled Rotating Detonation Engine

WEI Wanli, ZHENG Quan, LU Jiangtao, WENG Chunsheng, WU Yuwen

2021, 42(6):  1185-1194.  doi:10.3969/j.issn.1000-1093.2021.06.008

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The gasoline/oxygen-enriched air is used as working medium in ring-array rotating detonation engine (RDE) to study the effect of the central cone position on working process and performance of liquid-fueled RDE. The liquid-fueled RDE was studied through experiment. The one-dimensional thrusts of rotating detonation engine at different positions of central cone and its angles were measured，and the variation tendencies of thrust and fuel specific impulse were analyzed. The experimental results show that the position and angle of central cone have little effect on the propagation mode of rotating detonation wave, and the rotating detonation waves are always in double-wave collision modes. Since the double-wave collision point is affected by the tangential injection hole of the pre-detonator, it cannot be stabilized near the outlet of pre-detonator. The velocity and frequency of detonation wave decrease as the central cone moves forward. For l/L=0% where l is the distance from the equal straight segment end of internal wall surface to the end of external wall surface in combustion chamber, L is the length of external wall surface of combustion chamber and θ=20°, the thrust and fuel specific impulse are 951.6 N and 1 151.8 s, respectively, which are the maximum values under all experimental conditions. As the position l/L or angle θ central cone increases, the axial expansion distance of detonation products becomes shorter, the effect of expansion wave is enhanced at the sudden expansion position of central cone, the constraint effect of central cone surface in external flow field is weakened, and the radial expansion of high temperature gas is enhanced. The axial partial velocity of high temperature gas at outlet decreases gradually, and the thrust and fuel specific impulse decrease gradually. For l/L>25.5% or θ>40°, the lowering speeds of thrust and fuel specific impulse increase due to the re-initiation and expansion wave enhancement.

Calculation Method for the Nonlinear Angular Motion Attraction Domain of Spin-stabilized Projectile

YANG Zhiwei， WANG Liangming， ZHONG Yangwei， WANG Yao， ZHANG Xifeng

2021, 42(6):  1195-1203.  doi:10.3969/j.issn.1000-1093.2021.06.009

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An angular motion equation, including geometric nonlinearity and aerodynamic nonlinearity, for spin-stabilized projectile is established to calculate the attraction domain of nonlinear angular motion of projectile. The properties of the origin and its surrounding equilibrium points are analyzed, and the origin in the attraction domain is divided into non-unique stable equilibrium point and unique stable equilibrium point. For the case where the origin is non-unique stable equilibrium point, the attraction domain of the origin is obtained according to the symmetry. And for the case where the origin is the unique stable equilibrium point, the attraction domain is obtained by calculating the limit cycle radius of the subcritical Hopf bifurcation at the origin. The analysis calculation and simulation verification of a 155 mm grenade as an example were made. The results show that the proposed calculation method can be used to accurately calculate the unstable limit cycle around the origin, and the limit cycle is the boundary of attraction domain of the origin. The cubic term coefficient of Magnus moment is the main factor affecting the size of origin attraction domain; in the supersonic range, the area of the origin attraction domain first decreases and then increases with the increase in the projectile’s initial velocity. The greater the air density is, the smaller the area of the origin attraction domain is. The instability of the spin-stabilized projectiles launched from the mobile platform is also caused by the attraction domain.

Trajectory Characteristics of Projectile Obliquely Penetrating into Steel Target with Multi-layer Space Structure

DU Huachi， ZHANG Xianfeng， LIU Chuang， XIONG Wei， LI Pengcheng， CHEN Haihua

2021, 42(6):  1204-1214.  doi:10.3969/j.issn.1000-1093.2021.06.010

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The experiment and numerical simulation investigation of typical ogive-nose projectile penetrating into the multi-layer spaced steel targets at different inclination angles were conducted to analyze the trajectory characteristics of projectile obliquely penetrating into the steel target. Simulation models for oblique penetration of projectile into multi-layer steel target were established by LS-DYNA, the action process of the projectile obliquely penetrating into the multi-layer steel targets was analyzed, and the influence rules of projectile inclination angle, projectile velocity, target thickness and projectile deformation on the trajectory characteristics were obtained. The simulated results agree well with the experimental data. The results show that the trajectory deflection increases with the increase in inclination angle, and decreases with the increase in impact velocity, and its influence decreases with the increase in impact velocity. The trajectory deflection changes from overall downward to overall upward， and the influence of target thickness on the trajectory deflection increases with the increase in its thickness. The trajectory deflection of the rigid projectile is smaller than that of the deforming projectile.

Preparation of Porous Polyacrylate and Its Catalysis on Thermal Decomposition of Ammonium Perchlorate

HUO Junda, YAN Zhenzhan, LU Yuewen, HAN Jimin, YANG Li

2021, 42(6):  1215-1222.  doi:10.3969/j.issn.1000-1093.2021.06.011

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The metal particles are introduced into the polymer chain by the sol-gel method. The porous metal-containing polymer material, which is obtained by freeze-drying, has the features of fluxion, large specific surface area and porosity. These features not only restrain the agglomeration of nano-metal catalyzer, but also provide sufficient catalytic active sites. Two kinds of porous metal-containing polymers (PAA-Cu and PAA-Pb) were prepared. Scanning electron microscope, transmission electron microscopy, infrared spectroscopy, and Brunauer-Emmett-Teller method are used to characterize PAA-Cu and PAA-Pb. TG-IR-GC-MS combination is used to analyze the catalysis of PAA-Cu and PAA-Pb on the thermal decomposition of ammonium perchlorate (AP). The results indicate that the decomposition peak temperature of AP is decreased to 143.1 ℃ under the catalysis of PAA-Cu and 73.7 ℃ under the catalysis of PAA-Pb. Porous PAA-Cu which is of better catalysis compared with PAA-Pb was calcined in this paper. Cu and Cu₂O are produced by in-situ decomposition, while the increasing porosity promotes the exposure of catalytic active substances. The new features obtained by calcination make for the catalysis on thermal decomposition of AP.

Effect of Adhesive on the Zero Drift of Interferometric Fiber-optic Gyroscope in Low Temperature Environment

XU Baoxiang, XIONG Zhi, HUANG Jixun, YU Haicheng

2021, 42(6):  1223-1229.  doi:10.3969/j.issn.1000-1093.2021.06.012

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Adhesive has significant influence on the zero drift of interferometric fiber-optic gyroscope in low temperature environment. The improper selection and use of adhesives can lead to the deterioration in the accuracy of interferometric fiber-optic gyroscope. The effects of temperature and stress on the zero drift of interferometric fiber-optic gyroscope are analyzed，and the influence of the adhesive on the axial stress of fiber when the temperature changes and its influence factors are also analyzed. Through the test of adhesive performance, it is verified that the glass transition temperature，the difference between the curing temperature and the operating temperature，and the bubbles in the adhesive are primary causes to generate the zero drift of interferometric fiber-optic gyroscope in low temperature environment. Theoretical analysis and test results show that the zero drift can be reduced and the accuracy of interferometric fiber-optic gyroscope in low temperature environment is improved by selecting an adhesive with glass transition temperature beyond the operating temperature, small modulus and small temperature coefficient of modulus，and appropriate curing temperature.

Time Series Extraction of Ablation Recession of Hypersonic Vehicle and Its Prediction Based on LSTM Neural Network

YU Zhefeng， XU Jianyu， LUO Yue， YANG Ying， LIU Jinbo， LAN Jingchuan

2021, 42(6):  1230-1237.  doi:10.3969/j.issn.1000-1093.2021.06.013

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The ablation phenomenon of hypersonic vehicle head model in high temperature flow field is studied. The thermal test is made in an arc wind tunnel. The temperature evolution data of the arc wind tunnel ablation model with time is obtained using the colorimetric temperature measurement method of CCD camera image. By tracking the change of the temperature field at the edge of the model, the deformation process of the model during ablation is given, and the time series of stagnation point and other edge points are extracted. Least squares method and long-term short-term memory(LSTM) network method are used to fit and predict the ablation recession data. The LSTM method mainly includes network structure design, network training, objective function setting and algorithm implementation of prediction process. Through comparison between the time series prediction and experiment of ablation recession at different positions of the ablation model, it is found that the least square method is mainly suitable for the fitting and prediction of ablation recession in the linear region; the LSTM method is not only suitable for the linear ablation recession, but also suitable for the fitting and prediction of the nonlinear change of ablation recession.

Tensile Mechanical Properties and Constitutive Model of SiC/polyurea Nanocomposites

LIU Qiang, CHEN Pengwan, SU Jianjun, LI Zhirong, ZHANG Yulei

2021, 42(6):  1238-1249.  doi:10.3969/j.issn.1000-1093.2021.06.014

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Polyurea, as a coating or sandwich material, can be used to improve the protective performance of target structure in the fields of blast and impact. In order to study the tensile mechanical properties and constitutive model of SiC/polyurea nanocomposites, an universal testing machine and split Hopkinson tensile bar (SHTB) apparatus were used in quasi-static and dynamic tests, respectively. The true stress-true strain curves of specimens were obtained in the range of low strain rates (0.001- 0.1 s^-1) and high strain rates (1 260-4 500 s^-1). The effects of strain rate hardening and nano SiC on the mechanical properties of the specimens were discussed. A constitutive model with strain rate effect was constructed based on the hyperelastic theory. The experimental results show that the higher the strain rate is, the greater the flow stress of specimen is, the test specimens show obvious strain rate effects under dynamic loading, and the mechanical characters are enhanced by adding nano SiC into pure polyurea. The relation between the flow stress and the logarithm of relative strain rate is basically linear. The simulation on the dynamic tensile mechanical properties of polyurea shows that the simulated results are in good agreement with the test results, which verifies the accuracy of the stress-strain results in tensile test. Finally, the fitting results of constitutive model are in good agreement with the test results. This indicates that the constitutive model can better describe the tensile mechanical behavior.

Propagation Law of Explosion Wave in Columnar Explosion Tank under Vacuum Conditions

WANG Quan, LU Junwei, LI Zhimin, LIN Chaojian, LI Xuejiao, CHENG Yangfan, LI Rui

2021, 42(6):  1250-1256.  doi:10.3969/j.issn.1000-1093.2021.06.015

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To analyze the propagation characteristics of explosion wave in a columnar explosion tank at negative pressure， the implosion test of a self-designed 320 mm×430 mm adjustable vacuum columnar explosion tank was made to obtain the blast wave propagation velocity u，overpressure Δp，specific impulse i， relative pressure factor α and relative specific impulse factor γ under different vacuum conditions. The results show that the change of vacuum in the tank has a significant effect on the propagation state of explosion wave，and when the initial pressure in the tank decreases，the explosion wave overpressure and specific impulse have different degrees of attenuation. When the initial pressure in the tank is reduced from atmospheric pressure to 0.1 atm， the relative pressure factor α_1max of the first explosion wave Δp₁ is 2.41，and the relative pressure factor α_2max of the second explosion wave Δp₂ is 1.64; the relative specific impulse factor γ_1max of specific impulse i₁ of the first explosion wave is 6.97，and the relative specific impulse factor γ_2max of specific impulse i₂ of the second explosion wave is 3.14. The relative pressure factor α and the relative specific impulse factor α reflect the degrees of attenuation of explosion wave overpressure and specific impulse，respectively，and the blast wave overpressure and specific impulse decay more quickly when α and γ are larger. In addition，the propagation speed of explosion wave changes with the change in the initial environmental pressure，and the lower the initial environmental pressure is，the faster the propagation speed of explosion wave is.

Application of Kalman Filter-based Acceleration Feedback Control in Airborne Opto-electronic Stabilized Platform

WANG Zhengxi, HE Baigen, ZHU Xiaowei

2021, 42(6):  1257-1264.  doi:10.3969/j.issn.1000-1093.2021.06.016

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A method of joining the acceleration feedback control based on Kalman filter in the traditional closed-loop speed control system is proposed to further improve the line-of-sight stabilization accuracy of airborne opto-electronic stabilized platform. Kalman filter collects the input and output signals of the servo system of opto-electronic stabilized platform as its input signal, and outputs the filtered signal of velocity and the estimated result of acceleration. The output speed and acceleration signals are used as the feedback signals of speed loop and acceleration loop, respectively. The simulation and prototype experiment were made. The results show that the acceleration feedback control based on Kalman filter can effectively improve the suppression effect of opto-electronic stabilized platform on the disturbance torque of different frequencies, and the disturbance isolation is better than 20 dB. The step response overshoot is reduced by 40% at least compared to traditional control schemes. The acceleration feedback control based on Kalman filter can effectively improve the servo control performance of opto-electronic stabilized platform.

LSTM-based Fault Prediction Model of Semiconductor Device under Thermal Stress

ZHANG Mingyu, WANG Qi, YU Yang

2021, 42(6):  1265-1274.  doi:10.3969/j.issn.1000-1093.2021.06.017

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For the semiconductor device failure caused by time and stress, starting with multi-source data, a fault predicition model of semiconductor device under thermal stress based on long short-term memory(LSTM) algorithm is proposed to study the change of semiconductor device status with thermal stress level and the cumulative duration of stress, and predict the failure time of semiconductor device. The proposed model uses the advantage of long-term memory ability of LSTM algorithm to build multi-source data stack structure and improve the ability of model fitting the state curve of semiconductor device. The high and low frequency noises are filtered by using the weighted moving average filtering method. The first-order predictor data compression algorithm is used to deal with the feature vectors with continuous and slow variation. And the experimental data is used to test and verify the model. The results show that the model can better reflect the variation trend of semiconductor device status under the action of thermal stress, and the prediction errors of five experiments are within 1.7%, which has high accuracy. The model can predict the failure time in advance, which verifies the feasibility and effectiveness of the proposed model.

Protective Performance of Functionally Graded Foam Lining Subjected to High-speed Rifle Bullet Impact

ZHENG Qiujie, GUO Yingfu, CAI Zhihua, ZHANG Lei

2021, 42(6):  1275-1282.  doi:10.3969/j.issn.1000-1093.2021.06.018

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The mechanical properties of 30 kg/m³, 45 kg/m³ and 60 kg/m³ foamed polypropylene foams with different densities were obtained through material compression experiments, and the cranial response of a dummy under the protection of a functional gradient foam lining subjected to high velocity impact of gunshot was tested and simulated to analyze the cranial biomechanical response under the combination of homogeneous foam, positive and negative gradients, and concave and convex gradients. Based on this, a new type of bulletproof helmet capable of resisting rifle bullets was developed, and the protective effect of functionally graded foam lining in bulletproof helmet was studied. The local and overall energy absorption of the foam was analyzed. The results show that the energy absorption of the layered foam is mainly concentrated in the support layer near the head, accounting for 62.33% of the total energy absorption of the foam; the gradient structure has more significant protection effect than the homogeneous structure when the average density is the same, and the negative gradient is better than the positive gradient in protection; the convex gradient structure increases the energy absorption by at least 19.57% compared with other gradient structures while reducing the overall weight.

Design of A Backstepping Integral Adaptive Controller for Quadrotor UAV

WANG Huidong， ZHOU Laihong

2021, 42(6):  1283-1289.  doi:10.3969/j.issn.1000-1093.2021.06.019

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For the quadrotor unmanned aerial vehicle (UAV) with mass varying in practical application, a mass observer based on adaptive control theory is designed to estimate the real-time mass and correct the mass parameter of UAV. A backstepping integral adaptive controller (BIAC) for trajectory tracking of UAV is developed with the mass observer and the first kind of control error integral on the basis of classical backstepping controller (CBC). The control errors of system are asymptotically stabilized because the design process of controller is based on Lyapunov theory. The trajectory tracking simulation experiment was made in MATLAB/Simulink simulation environment. The simulated results indicate that the real-time mass of UAV can be estimated by using BIAC very well in the case of slow mass change or mass mutation of UAV, and the track error of z_e-axis in earth coordinate system Exeyeze with BIAC is decreased by about 80% compared with CBC.

Generalized Fractional Maxwell Constitutive Model for Mn-Cu Damping Alloy

ZHU Rui, YANG Yuying, MAO Baoquan, HAN Xiaoping, WANG Zhiqian, ZHAO Qijin

2021, 42(6):  1290-1302.  doi:10.3969/j.issn.1000-1093.2021.06.020

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A three-parameter constitutive equation based on the generalized fractional Maxwell model for Mn-Cu damping alloy is proposed. The accuracy of the constitutive model is analyzed and verified by uniaxial cyclic tensile test with constant strain rate. The applicability of the constitutive model is broadened by the mean coefficient method, and the fitting performance of the generalized fractional Maxwell model is studied. The results show that the constitutive relation of the Mn-Cu-based damping alloy has a strong nonlinearity. Its stress-strain curve is like a shuttle, and its hysteresis area increases with the increase in the maximum strain amplitude. The generalized fractal Maxwell model can well describe the nonlinear and hysteresis characteristics of the stress-strain curve of M2052 damping alloy. The mean square deviation of the fitting is between 0.468 4 and 2.651 0, and the coefficients of determination are all greater than 0.992 9. Each parameter of the proposed constitutive model can be determined by strain amplitude without a specific test. The constitutive model can better simulate the nonlinear characteristics of damping alloy compared to viscoelastic models.

Microstructure and Mechanical Property of High-nitrogen Steel with GMAW Welding Wires with Different Nitrogen Contents

MA Liangchao, WANG Dafeng, MA Bing, CHEN Donggao, ZHANG Yingying

2021, 42(6):  1303-1311.  doi:10.3969/j.issn.1000-1093.2021.06.021

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In order to study the structures and properties of high-nitrogen steel welds with different nitrogen content welding wires, three kinds of welding wires with different nitrogen contents of 0.46［N］,0.61［N］ and 0.84［N］ were used in gas metal arc welding (GMAW) tests of high-nitrogen steel, and the nitrogen fixation effect, porosity, microstructure and mechanical properties of the welds were tested and analyzed. The results show that, as the nitrogen content of welding wire increases, the nitrogen content of weld increases, and the porosity tendency increases; the microstructures of three welding wires are composed of austenite and ferrite, the microstructure of weld is mainly determined by the solidification mode of weld, which is determined by the joint action of various alloying elements in the weld; and the mechanical properties of welds are mainly affected by the content and distribution of ferrite. The higher the ferrite content and the distribution along the grain are, the higher the hardness and strength of the weld are, and the worse the toughness is. When the weld solidification mode is A or AF, the nitrogen content of the weld is higher, the tensile property of the weld is better. The pore defect mainly affects the impact toughness of the weld, and the increase in pores reduces the impact toughness of the weld.

Thermal Environment Adaptability of MIN Board for Special Equipment Simulator Computer

LI Yongqiang, L Weimin

2021, 42(6):  1312-1323.  doi:10.3969/j.issn.1000-1093.2021.06.022

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The thermal environment adaptability assessment of most military electronic equipment only refers to the data from high and low temperature alternating experiments carried out according to American military standard，and the fixed high and low temperature standards make the experimental temperature often deviate from reality，which can only qualitatively analyze its thermal environment adaptability and is difficult to be used as a reference basis for task decision-making and maintenance testing.In order to truly reproduce the state of the military electronic equipment in the thermal environment，SolidWorks mechanical design automation software is used to create a CAD model of MD type simulator computer switch input board (referred to as MIN board)，and convert its task state spectrum into an environmental temperature spectrum and electronic component thermal power consumption spectrum，which are the input parameters of Icepak simulation. In addition，with the help of Arrhenius model and the improved C-M equation，the actual failure data of key electronic components obtained from the optimal accelerated degradation tests and the temperature data of electronic components and circuit boards obtained from the simulation are used as the parameters to calculate the thermal degradation failure times of electronic components and the thermal fatigue life of solder joints. At the same time， the competitive failure mode is used to evaluate the predicted life and weak links of MIN board，and the lifetime data is used as a quantitative characterization of its thermal environment adaptability. The simulated results show that the thermal degradation of electronic components is the main influencing factor for the thermal failure of MIN board，and the thermal fatigue of solder joints is the secondary influencing factor. Its weak points are mainly programmable logic devices and three-state buffers，and the predicted lifetimes in the north，east and south regions are 10-11，8-9 and 5-6 years，espectively，which roughly coincides with the actual failure time.

Variational Nonlinear Chirp Mode Decomposition-synchroextracting Transform Method and Its Application in Fault Diagnosisof Rolling Bearing

LI Zhinong, HU Zhifeng, MAO Qinghua, ZHANG Xuhui, TAO Junyong

2021, 42(6):  1324-1330.  doi:10.3969/j.issn.1000-1093.2021.06.023

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When the traditional synchroextracting transform (SET) method is used to process the multi-component non-stationary signals, the instantaneous frequency difference of adjacent components is greater than 2 times of the frequency support range of the window function. Otherwise the time-frequency result is prone to frequency aliasing. However, the actual signal often can not satisfy this condition. In additional, when traditional SET method is used to process complex signal with high noise, its time-frequency resolution is often not ideal. Based on this deficiency, the variational nonlinear chirp mode decomposition (VNCMD) is introduced into SET in this paper, and a fault diagnosis method of VNCMD-SET is proposed. In the proposed method, VNCMD is used to process non-stationary signals with close or even cross frequencies by combining demodulation and variational modal decomposition. The fault signal is decomposed and reconstructed by VNCMD, then the reconstructed signal is processed by SET. The proposed method was compared with the traditional SET method, and was verified through experiment. The simulated and experimental results show that the proposed VNCMD-SET method is superior to the traditional SET method and overcomes the deficiency in the traditional SET method; the proposed method can effectively extract the frequency characteristics of fault signal, suppresses the aliasing, and has a certain anti-noise performance.

Integrated Design of Compressor for Continuous Transonic Wind Tunnel

ZHOU Enmin， GU Yunsong， CHENG Song， LIU Kai， ZHANG Wen， WANG Yitian， XIONG Bo

2021, 42(6):  1331-1338.  doi:10.3969/j.issn.1000-1093.2021.06.024

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In order to meet the special requirements of continuous transonic wind tunnel for the main circuit driven compressor, including wide operating rang, excellent aerodynamic performance, high rotational speed control accuracy, tight sealing, and safe and reliable surge prevention, a compressor was designed for 0.6 m continuous transonic wind tunnel, and the test verification was also made through mechanical running test, air tightness test, rotational speed control accuracy test, thermal performance test, and surge prevention test. The compressor's inlet chamber is integrated with the first corner of the wind tunnel and its outlet chamber is integrated with the second corner by adopting the integrated design concept. The structures of inlet and outlet chambers are compact, the gas flow is uniform, and the pressure loss is lower. The gas seal and cavity are used to effectively prevent the leakage of lubrication oil into the wind tunnel, the leakage of test gas out of the wind tunnel and the leakage of wet air into the wind tunnel. The master-slave control mode and vector control technology are used to realize the synchronous driving of two motors successfully. The test results show that the design of compressor for 0.6 m continuous wind tunnel is reasonable, of which aerodynamic performance is excellent, operation is stable, sealing effect is good, speed control accuracy of compressor is better than 0.03%, and surge prevention is safe and reliable.

Weapon-target Assignment Based on Adaptable Hungarian Algorithm

ZHANG Jin， GUO Hao， CHEN Tong

2021, 42(6):  1339-1344.  doi:10.3969/j.issn.1000-1093.2021.06.025

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When various intelligent optimization algorithms are used to solve the weapon-target assignment problem, they have the disadvantages of long time-consuming and non-unique optimization results. Hungary algorithm has the advantages of short time-consuming and stable optimization results, but its adaptability is poor. Currently, the comparison and analysis of intelligent optimization algorithms and Hungarian algorithm has not been reported. For this phenomenon, the time-consuming and stability of traditional Hungarian algorithm and intelligent optimization algorithms are compared, which shows the advantages of Hungarian algorithm. An adaptable Hungarian algorithm that can be applied to all types of weapon-target assignment problems is established by proposing a unified efficiency matrix. And then some examples are used to verify the correctness of the adaptable Hungarian algorithm.