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    31 January 2022, Volume 43 Issue 1
    Contents
    Contents
    2022, 43(1):  0. 
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    Paper
    Stability Design of Spinning Missile Autopilot Considering Parasitical Loop of Roll-pitch Seeker
    ZHOU Jianping, LI Wei, WEN Qiuqiu, XIA Qunli, JIANG Huan
    2022, 43(1):  1-10.  doi:10.3969/j.issn.1000-1093.2022.01.001
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    For the problem that the parasitical loop of roll-pitch seeker affects the dynamic stability of spinning missile, the disturbance rejection rate model of roll-pitch seeker and the mathematical equation of spinning missile are established, and the cross-coupling effect of control system induced by the rotation motion of missile body is derived and analyzed. The relationship between the autopilot gain coefficients and the expected frequency or damping is formulated. The sufficient and necessary condition for the dynamic stability of spinning missiles is analytically derived by stability analysis. The dynamic stability of spinning missile under various conditions is studied by numerical simulations. The results indicate that the stability of spinning missiles is closely related to the disturbance rejection rate and rolling rate of roll-pitch seeker, and the design indices of autopilot. The stability region of design frequency of spinning missile autopilot is obvisously smaller than that of the non-spinning missile, and the low rolling rate is helpful to reduce the effect of parasitic loop of roll-pitch seeker on the stability of spinning missile.
    Application of Multilevel Optimization Algorithm in Artillery Integrated Design
    SHAN Chunlai, LIU Pengke, GU Bin, HE Qi, XU Hongying
    2022, 43(1):  11-19.  doi:10.3969/j.issn.1000-1093.2022.01.002
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    The weapons and equipment are required to have high-mobilility,high-precision,long-range and lightweight in modern warfare. A noverall optimization design method is presented,in which the all aspects of performance of artillery are comprehensively considered. A parametric model of artillery is established,the sensitivity coefficients are calculated using the optimal Latin hypercube experimental design,and a large number of input-output data can be obtained at the same time. The weight values under different firing conditions and different evaluation indexes are calculated from the sensitivity coefficients,and the approximate functions are constructed based on input-output data.A multilevel optimization algorithm is set up based on these results above,and an optimal design scheme would be obtained after the algorithm convergence. The result shows that the evaluation indexes of the optimal design scheme are averagely increased by 22.27%,which is obviously improved compared with the initial design scheme.
    Evaluation Index of Disturbance Superposition Degree in Multi-layer Penetration Acceleration Signal
    MA Mengxin, LI Rong, NIU Lanjie
    2022, 43(1):  20-28.  doi:10.3969/j.issn.1000-1093.2022.01.003
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    The evaluation indexes of layer and inter-layer coefficients for the signal superposition degree is presented to solve lack of measurement criterion of inter-layer superposition in multi-layer penetration acceleration signal. The test and simulated signals are segmented by penetration layers. The layer and inter-layer coefficients of acceleration signal for each layer are calculated by subtracting every amplitude of signal points by former one and summing the absolute values of difference values. The larger the two sets of evaluation indexes are, the more severer the superposition degree is. The calculated results of test and simulated signals are used to demonstrate the efficiency of evaluation indexes. The calculated results of layer and inter-layer coefficients in 3 sets of data show that the layer and inter-layer coefficients are smaller if the disturbance superposition degree is lower, and vice versa. One set of data is extracted from the calculated results of evaluation indexes of acceleration signal for two detonation control circuits in one penetration warhead, and the calculated deviation is less 5%. The calculated result is consistent to the results of qualitative analysis and spectral analysis. The experimental results show that the layer and inter-layer coefficients are efficient for evaluating the disturbance superposition degree in multi-layer penetration acceleration signal.
    Ballistic Damage Characteristics of Cowhide as Skin Surrogate
    XIONG Manman, YAN Wenmin, XU Cheng, QIN Bin, MA Xuejiao
    2022, 43(1):  29-36.  doi:10.3969/j.issn.1000-1093.2022.01.004
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    To explore the similarity between cowhide and human skin, the ballistic impacting experiments were carried out on cowhide in vitro and live creature and the mechanical experiment was carried out on cowhide. The experimental results are used to analyze the mechanical properties, threshold characteristics of cowhide, as well as the impact damage characteristics of creature and cowhide. Results indicate that the tensile failure processes of cowhide and human skin exhibit a similar three-stage pattern: slow rising, linear rising, and rapid falling. The relative errors of strain energy density, failure strength and failure strain are only 6.56%, 6.17% and -4.31%, respectively. The creature and cowhide subjected to the rubber bullet impact have similar partitioned damage characteristics and damage size, that is, the diameters of lesion skin area and kin peeling area are almost equivalent to the bullet diameter, and the diameters of hematoma zone and the fold zone are positively related to the specific kinetic energy of rubber bullet. The perforation threshold specific kinetic energy of cowhide impacted by 6 mm-diameter steel ball is 29.97% higher than that of PMHS skin calculated by the empirical formula. However, considering that the empirical formula is mainly based on the experiments of dead or older cadaver volunteers, the perforation threshold specific kinetic energy data is relatively conservative. It can be concluded that cowhide is similar to human skin in terms of mechanical properties, impact damage characteristics, perforation threshold specific kinetic energy, etc., which is currently a reasonable ballistic skin surrogate.
    Mechanism of High-velocity Projectile Penetrating into Ultra-high Performance Concrete Target
    L Yingqing, CHEN Nanxun, WU Haijun, ZHAO Hongyuan, ZHANG Xueyan
    2022, 43(1):  37-47.  doi:10.3969/j.issn.1000-1093.2022.01.005
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    Ultra-high performance concrete (UHPC) is widely used in the field of protection due to its ultra-high strength and durability. In order to study the phenomenon and laws of projectile penetrating into ultra-high performance concrete, the quasi-static uniaxial compression experiment, split tensile experiment and high-speed penetration experiment of projectile are made on C120 ultra-high performance concrete with 1 vol% steel fibers and C160 ultra-high performance concrete with 2.5 vol% steel fibers. The modified NDRC empirical formula and the empirical formula obtained from dimensional analysis are used to calculate the penetration depths of projectile in the experiments. The results show that the ultra-high performance concrete has a higher tensile-compression ratio and superior ability to resist surface damage of the target compared with ordinary concrete. The area of crater on the surface of target is small, and the crater diameter is about 8-12 times the projectile diameter. The cracks generated in the radial direction are small and short, and the average number of cracks is 4. With the increase in the strength of ultra-high performance concrete, the diameter of crater on the surface of target and the depth of crater decrease, indicating that the addition of steel fiber improves the toughness of the target and reduces the diameter of crater on the surface of target. As compared with ordinary concrete, the penetration depth of ultra-high performance concrete is smaller, but as the strength of target increases, the penetration depth does not decrease significantly. The modified NDRC empirical formula and the empirical formula obtained from dimensional analysis can be used to predict the penetration depth of ultra-high performance concrete under high-speed penetration of projectile.
    Effect of Al Particle Size on the Shock-induced Reaction Characteristics of Al-rich PTFE/Al Composites
    HU Rong, JIANG Chunlan, MAO Liang, QI Yuxuan, CAI Shangye, HU Wanxiang
    2022, 43(1):  48-56.  doi:10.3969/j.issn.1000-1093.2022.01.006
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    The effect of Al particle size on the shock-induced reaction characteristics of PTFE/Al reactive material with a mass ratio of 50∶50 is investigated. 4 kinds of PTFE/Al reactive material specimens with different Al particle sizes were prepared by molding and sintering. The reactive material specimens were tested by using split-Hopkinson pressure bar (SHPB), and the shock-induced reaction processes of PTFE/Al reactive material at different strain rates were recorded with a high-speed camera. The results show that, as the Al particle size increases from 50 nm to 10 μm, the reaction delay rises up to 40% and the reaction duration decreases up to 17%, while the amount of reactive material participating in the reaction decreases, and the reaction intensity and energy release decrease. When the Al particle size increases to 70 μm, it is difficult to ignite under SHPB loading. The strain rate also greatly influences the reactive characteristics of reactive material,and the reaction delay of PTFE/Al reactive material decreases with the increase in the loading strain rate. The results show that Al particle size greatly influences the impact reaction diffusion, reaction speed, and extent of reaction of PTFE/Al reactive material, and its impact reaction property can be adjusted by adjusting Al particle size.
    Hot Spot Temperature Resulting from Elliptical Void Collapse in PBX under Dynamic Loading and Its Semi-empirical Analytical Expression
    LIU Chun, OU Zhuocheng, DUAN Zhuoping, HUANG Fenglei
    2022, 43(1):  57-68.  doi:10.3969/j.issn.1000-1093.2022.01.007
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    The collapse process of elliptical void in a plastic bonded explosive (PBX) under shock loadings is comprehensively investigated through similarity analysis and mesoscale simulation, and the effects of the shock intensity and the void geometry, including the size, position and elongated state, on the hot spot temperature are analyzed. The hot spot temperature generated by an elliptical void can reach up to 2 990 K under the conditions of a certain impact strength, a specific position and elongated state, which is about 54% higher than the hot spot temperature (1 946 K) generated by a circular void in the same area, and this may cause explosive more sensitive. By using similarity analysis of intermediate asymptotics, complete similarity and incomplete similarity, a semi-empirical analytical expression for the hot-spot temperature resulting from the collapse of elliptic void subjected to a shock load is presented to predicate its dependence upon the shock intensity, the void geometry as well as the physical properties of the explosive, and the predicted results are in good agreement with the numerical results.
    Mid-course Reactive Maneuver Penetration and Evading strategy of Ballistic Missile
    FAN Boxuan, CHEN Guiming, LIN Hongtao
    2022, 43(1):  69-78.  doi:10.3969/j.issn.1000-1093.2022.01.008
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    The optimal maneuver penetration of ballistic missiles is studied to improve their penetration capability. Through the simplification and analysis of the motion model, it is determined whether the optimal penetration direction is located in the normal plane connecting the positions of ballistic missile and exoatmospheric kill vehicle. A multi-stage first-order differential motion equation is established based on the motion models of both offensive and defensive parties. The analytical expression of the optimal ballistic missile penetration time is obtained by solving this equation. The error limit of the model parameters that the penetration strategy can support is analyzed. In order to verify the correctness of the obtained optimal penetration time and optimal penetration direction, the two-dimensional and three-dimensional engagement simulations were carried out. The simulated results show that the evading strategy of short-time large pulse maneuver in the direction of the opposite position can be used to effectively penetrate the defense and achieve the maximum miss distance.
    Structural Design of an Insulated Gas Circuit Joint of Short-range Air Defense Missile
    CHEN Ke, KONG Yongfang, FU Xiaogang, WANG Yibo
    2022, 43(1):  79-85.  doi:10.3969/j.issn.1000-1093.2022.01.009
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    An insulated gas circuit joint is proposed to avoid the potential safety hazards brought by traditional refrigeration gas cylinders to missile-borne electronic devices. It is designed by using three-dimensional design software Solidworks.The airtightness of joint structure was simulated by using ANSYS software, and a real gas circuit joint was made for conductivity and ventilation experiments. The simulated results show that the gas circuit joint does not leak under the limit pressure, and has no electric conduction and air leakage in the electric conduction and air tightness experiments. Simulated and experimental results prove that the insulated gas circuit joint has both insulativity and air tightness, and can avoid the potential safety hazards of missile-borne air circuit.
    The Influence of Hydrogen Proportion on the Propagation Characteristics of Hydrogen-kerosene-air Rotating Detonation Waves
    WU Mingliang, ZHENG Quan, XU Han, WENG Chunsheng, BAI Qiaodong
    2022, 43(1):  86-97.  doi:10.3969/j.issn.1000-1093.2022.01.010
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    The influence of hydrogen proportion on the propagation characteristics of rotating detonation waves is studied. Two-dimensional numerical simulation of rotating detonation process was made by solving the Navier-Stokes equation,in which liquid kerosene and hydrogen were used as fuel,and air was used as oxidant. The influence of different working conditions on the propagation characteristics of rotating detonation wave is studied by changing the mass flow rate and the proportion of hydrogen,and the formation process of new detonation wave,the mode conversion process and the mal-distribution of gas and liquid in the combustion chamber are analyzed. Numerical results show that the detonation wave has three propagation modes,namely single wave mode,single wave mode caused by double wave collision and double wave mode caused by double wave collision,under the successful detonation condition. The double wave mode is easily generated by increasing mass flow rate and hydrogen proportion,and the propagation velocity of rotating detonation wave suddenly decreases when propagation mode changes from single wave to double wave. At the end of the first propagation period of detonation wave, the weak shock wave generated during the initial ignition collides with the detonation wave and transmits it. A hot spot is induced by the transmitted shock wave near the slow-burning area and forms a new detonation wave. After a series of collisions,transmitting,and enhancing processes,a stable single wave mode or double wave mode is finally formed. When the detonation wave stabilizes,the internal flow field during the stable propagation of rotating detonation wave in the combustion chamber can be divided into slow-burning area,combustion-rich area,oxygen-rich area and filling area due to the mal-distribution of gas and liquid in the combustion chamber.The formation of hot spots near the slow-burning area is one of the reasons for the formation of new detonation wave.
    Self-learning Fuzzy Grey Method for Plateau Environmental Adaptability Assessment of Air Defense Early-warning Radar
    MENG Guanglei, LI Shufa, LIU Binbin, ZHOU Mingzhe, SUN Donglai, WU Hao
    2022, 43(1):  98-110.  doi:10.3969/j.issn.1000-1093.2022.01.011
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    The harsh natural environment in plateau area brings severe challenges to the normal operation of air defense early-warning radar. In order to improve the efficiency of radar in plateau area and reduce the maintenance cost, the reasonable environmental adaptability assessment should be taken for the air defense early-warning radar in the development stage. In view of the above requirements, a self-learning fuzzy grey method is proposed. A self-learning model based on Bayesian estimation about index weight is established to realize the adaptive adjustment of subjective and objective weight preference coefficients in the combination weighting method by analying the key factors affecting the plateau environmental adaptability of air defense early-warning radar. For the fuzzy relationship among evaluation index factors and evaluation states, the membership function is constructed from the radar failure rates under the influence of various environmental indexes to realize the assignment of valuation index under uncertainty conditions. On the basis of the above work, a self-learning fuzzy grey model for plateau environmental adaptability assessment of air defense early-warning radar is built, in which the influence of information grey value is considered. A simulation experiment of evaluating the plateau environmental adaptability with and without learning process was conducted on various systems and components of an air defense early-warning radar. The results show that the proposed method not only fully considers the subjective experience of experts, but also follows the data law presented by objective facts, which makes the evaluation results more reasonable.
    Ship Magnetic Field Inversion Modeling Method Utilizing the Magnetic Field Difference between Magnetic Sensors
    GUO Chengbao, HU Song, WANG Wenjing, YIN Qiqi
    2022, 43(1):  111-119.  doi:10.3969/j.issn.1000-1093.2022.01.012
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    A method of ship magnetic field inversion modeling utilizing the magnetic field difference of magnetic sensor array is proposed to suppress the influence of environmental noise in magnetic fields, such as geomagnetic field variation and magnetic interference of artificial facility,etc. The formulas for calculating the magnetic field difference between the magnetic sensors in the magnetic sensor array are given for each measurement time. The linear equations for inversing the magnetic source from a ship are constructed by using the three-dimensional ship magnetic monopole array model. Finally,the inversed values of the magnetic source model of ship is obtained by using the regularization technique. The magnetic fields of a typical virtual ship are used to verify the validity of the proposed method. The results show that the proposed method can remove the interference effects of coherent magnetic field noise, and achieve high-precision inversion modeling of the magnetic field of a ship in the magnetically noisy environment. The validity of the proposed method is verified. If the proposed method is used for high precision inversion modeling of ship's magnetic field measurement data in magnetically noisy environment, the geomagnetic reference sensors are not required, and the corresponding facilities are low cost and easy to locate.
    The Influences of Different Mooring Systems on the Hydrodynamic Performance of Buoy
    LU Kuan, RAO Xiang, WANG Huamei, ZHANG Qian
    2022, 43(1):  120-130.  doi:10.3969/j.issn.1000-1093.2022.01.013
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    Hydrodynamic performances of ocean data buoy and mooring system have the important influence on measuring precision of observation parameters. The mooring system has a larger effect on the movement and force of ocean data buoy, so the related research on the hydrodynamic characteristics of mooring system has always been a the focus of the design and development of ocean data buoy. The hydrodynamic performances of three different types of mooring systems under the combined force of wind and waves are studied by using the measured data from the northern Chu Island waters off Weihai through numerical simulation and physical model test. The experimental results show that the different mooring systems have significant effects on the hydrodynamic performance of buoy system. The half-tension-type mooring system performs best for fixed point observation,but has higher requirements on the reliability,which is suitable for the situation of requiring higher observation accuracy. The inverted s-type mooring system is more convenient to lay out,and has stronger resistance to extreme ocean environment,but its swing motion is more obvious,so it is suitable for use in open deep sea areas. The slack type mooring system is fall in between half-tension-type and inverted s-type mooring systems.
    On the Blast Resistance Performance of Large-scale Reinforced Concrete Wall
    WANG Cheng, YANG Jingyu, CHI Liyuan, WANG Wanli, CHEN Tainian
    2022, 43(1):  131-139.  doi:10.3969/j.issn.1000-1093.2022.01.014
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    To study the performance of reinforced concrete blast resistant wall under explosion shock wave, the damage laws of D1, D2 and D3 walls are studied by numerical simulation based on the test with maximum TNT equivalent of 300 kg. Based on LS-DYNA finite element software, a fluid-solid coupling numerical model is applied to calculate the failure modes of the walls under explosion, and the model parameters are corrected according to the test results. ConWep algorithm is used to apply the explosive load, and the failure characteristics of the walls under different overpressures and impulse loads are simulated by controlling the charge mass and explosive distance. Based on the residual dip angle of blast resistant wall after explosion, the numerically calculated results are divided into three damage levels. The overpressure-impulse curve and the charge mass-explosive distance curve obtained by fitting can be used for designing the safety distance of burning explosive plant and the warehouse capacity, and estimating the degree of damage under accidental explosion. By comparing the overpressure-impulse curves of three configurations of walls, it is found that the blast resistance of small size D2 is the weakest; when the peak overpressure of explosion load is small, the blast resistance of D3 is similar to that of D1; and when the overpressure is large, the failure mode of D3 changes, and the overpressure-impulse curve has a tendency of right deviation.
    Dielectric Elastomer-driven Frog-shaped Bionic Soft Robot
    LI Qingzhong, LI Xiaodan, YU Fujie, CHEN Yuan
    2022, 43(1):  140-147.  doi:10.3969/j.issn.1000-1093.2022.01.015
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    A frog-shaped bionic soft robot with a dielectric elastomer as the actuator is designed based on the advantages of frog propulsion method and soft materials for realizing the miniaturization of robot and enhancing its environmental adaptability. According to the tensile properties of material, the manufacturing process was determined and the actuator was simulated by finite element method, and the motion trajectory planning and real underwater test of robot legs were carried out. A propulsion efficiency model was constructed by considering various parameters during swimming, and the most efficient motion parameters were determined. Experimental results show that the maximum swimming speed of the robot is as high as 132 mm/s at a frequency of 2 Hz and a voltage of 5 kV. Compared with the dimensionless model parameters of amphibians, the motion characteristics of the robot are close to those of real creatures, and it has good motion capability.
    Image Dehazing Based on the Optimum of UAV Aerial Image Quality Evaluation
    JIANG Yutong, SONG Haiping, WANG Guanghui
    2022, 43(1):  148-158.  doi:10.3969/j.issn.1000-1093.2022.01.016
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    UAV is an important means of information reconnaissance in modern warfare. The fog seriously affects the quality of UAV aerial images and hinders the ability to perform reconnaissance and recognition. In order to improve the effective utilization of UAV aerial images in the foggy environment,an image dehazing method based on the optimum of UAV aerial image quality evaluation is proposed according to the characteristics and special application background of UAV aerial images.A comprehensive image quality evaluation function is established by combining three image quality evaluation parameters,such as information entropy,standard deviation and image Fourier amplitude. Different atmospheric transmittance values are given,the corresponding dehazing image is solved,and the quality evaluation function value of dehazing image is used as the screening standard. The experimental verification shows that the image dehazing method based on the optimum of UAV aerial image quality evaluation has low computational complexity and simple operation. And the obtained dehazing image has clear visual effects and small result errors.
    Preparation of Elastic Porous Composite Material and Its Energy-absorption Characteristics
    ZHANG Jinming, ZHANG He, DAI Keren, YU Da, YANG Benqiang
    2022, 43(1):  159-168.  doi:10.3969/j.issn.1000-1093.2022.01.017
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    A new design idea of buffering material is put forward for the protection of fuze subjected to multiple high overloads in the process of warhead penetrating into multi-layer target plates. The porous media and elastic polymer are mixed to form a new composite structure in which the particles in porous media are wrapped together by spatial skeleton of elastic fibers. The scanning electron microscope is used to analyze the influence of the mass proportion of elastic polymer on the interior structure of composite films. The influence of the mass proportion of elastic polymer on inner porosity and recoverability were analyzed through the porosity test and multiple static pressure test, and the multiple impact test was conducted by Machete hammer to verify the energy absorption capacity of the material. The test results show that the designed porous material with elastic fiber reticular structure has good energy absorption characteristics and recoverability, and its performance is better than those of the pure porous material, overfilled film material, and polymer material during multiple impacts. It can be used to protect the fuze from damage during multiple impacts.
    Measurement of High-temperature Specific Heat Capacity of SiC Ceramics by Drop Calorimetry Method
    WANG Xuerong, SUN Yan, WANG Qianqian, YAO Kai, MENG Xiangyan, ZHOU Yanping, LIU Yunchuan, MA Yandong
    2022, 43(1):  169-174.  doi:10.3969/j.issn.1000-1093.2022.01.018
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    Specific heat capacity is an important physical parameter of SiC ceramics, which is directly related to its thermal conductivity and thermal diffusivity. It is an important basis for evaluating its thermal properties. Due to the wide application temperature range of SiC ceramics, which can be up to more than 1 000 ℃, it is necessary to study its specific heat capacity in a wide temperature range. To solve this problem,a drop calorimetry method was used to study the specific heat capacity of SiC ceramics in the range from 400 ℃ to 1 000 ℃. The high-temperature specific heat capacity tester for measuring solid materials was calibrated by using sapphire standard reference material. The results show that the error of specific heat capacity of sapphire standard reference material is less than 2%,which ensures the accuracy of the test equipment. The specific heat capacity of SiC sample increases with the temperature increasing. The measured results are basically consistent with the reference values provided in Refs.\[21-22\], and the relative deviation is in the range from 1.8% to 2.9%. It shows that the drop calorimetry method has high accuracy in determining the specific heat capacity of SiC material at high temperature,and it is a feasible method to determine the specific heat capacity of SiC material at high temperature in addition to the mixing method.
    Dynamic Mechanical Properties of Al2O3/SiC Composite Ceramic Subjected to Impact Loading
    DANG Quanyong, GE Yanxin, GAO Yubo
    2022, 43(1):  175-180.  doi:10.3969/j.issn.1000-1093.2022.01.019
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    The study of dynamic mechanical properties and micro-fracture mode of ceramic is the key to understand the damage mechanism of ceramic under impact loading. For the Al2O3/SiC composite ceramic, the split Hopkinson bar apparatus was used to impose the one-dimensional stress wave on a sample, and the SEM analysis was carried out on the recycled granules of fractured sample. Results show that the uniform loading of the sample is achieved by one-dimensional stress wave loading experiment. The strength of Al2O3/SiC composite ceramic is increased with increase in strain rate, which indicates the positive correlation of strain rate sensitivity for the composite ceramic. Due to the microstructure of material, the strength of Al2O3/SiC composite ceramic is close to that of Al2O3 ceramic (AD995, AD999 and so on). And the variaton tendency of ceramic strength with strain rate falls in between those of AD95 ceramic and high-density Al2O3 ceramic. A large number of intergranular fracture zones and a small number of transgranular fracture zones exist in the fracture surface on the side of the sample due to the influence of rarefaction wave on the sample. And a slip line under shear stress occurs in the transgranular fracture zone. However, the fracture surface of debris inside the sample is relatively smooth, and has more transgranular fracture zones and a small number of shear slip lines on it. The micro-cleavage fracture characteristics do not exist in the surrounding grains in the core zone.
    Inversion of Crack Mechanism in Concrete Materials Based on Moment Tensor Theory of Acoustic Emission
    WANG Zonglian, WANG Huaiwei, REN Huilan, ZHAO Mingyan, LUO Zhiqiang
    2022, 43(1):  181-189.  doi:10.3969/j.issn.1000-1093.2022.01.020
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    The locations, types and orientations of cracks on concrete specimens with bilateral openings during the shear failure process under uniaxial compressive loading are inversed to study the temporal and spatial evolution law of cracks based on the improved acoustic emission localization method and the moment tensor theory. The results of moment tensor analysis show that the growth of tensile cracks is dominant in the tensile damage zone, and the growth of shear cracks is dominant in the shear damage zone, which are consistent with the conditions of actual stress and damage in the specimen. This indicates that the moment tensor theory is a useful method to further study the mechanism of damage evolution in concrete,as it can be used for describing the distribution and migration of tensile stress and shear stress effectively. The results of waveform analysis show that the duration of acoustic emission (AE) signal corresponding to tensile crack is about 800 μs, and the frequency range is 7-500 kHz. The AE signals associated with mixed-mode crack and shear crack have frequency ranges from 7 kHz to 500 kHz and from 7 kHz to 250 kHz, respectively, and have higher duration of about 1 720 μs and 1 880 μs, respectively. The main reason is that the energy released by shear rupture is higher than that by tensile rupture, and the average frequency of shear wave released by shear rupture is lower than that of stress wave released by tensile rupture.
    Detection and Analysis of Surface Defects of Si3N4 Cylindrical Roller in Aero-engine Based on Coupled Denoising Algorithm
    LIAO Dahai, YIN Mingshuai, LUO Hongbin, HUANG Jiawen, WU Nanxing
    2022, 43(1):  190-198.  doi:10.3969/j.issn.1000-1093.2022.01.021
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    In order to solve the problem that the traditional single image denoising algorithm based on machine vision has poor effect on the mixed noise signal processing, resulting in the inability to effectively detect and identify the surface defects of Si3N4 cylindrical roller used in aero-engine, a visual detection method based improved coupled denoising algorithm and multi-scale threshold segmentation algorithm is proposed. The surface defect image of Si3N4 cylindrical roller is denoised by the optimized wavelet threshold denoising algorithm and the improved median filter algorithm, and the multi-scale threshold segmentation algorithm is used to segment the defect image, thus identifying and extracting Si3N4 surface defects of cylindrical rollers. The experimental results show that the signal-to-noise ratio of surface defect images of Si3N4 cylindrical rollers denoised by the improved coupling denoising algorithm is more than 24.5%, and the detection and recognition accuracy rate of the multi-scale threshold segmentation algorithm for surface defect images of Si3N4 cylindrical rollers is more than 94%. It proves that the visual detection method has a good image denoising effect and a certain versatility.
    Reliability Evaluation of Aerospace Valves Based on Multi-source Information Fusion
    WANG Bo, JIANG Ping, GUO Bo
    2022, 43(1):  199-206.  doi:10.3969/j.issn.1000-1093.2022.01.022
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    During the development process, the sample size of aerospace valves is small, and the sample rarely fails or even has no failure. In order to solve this reliability evaluation problem, it is necessary to make full use of various existing test data. The tests used for quantitative reliability analysis of valves mainly include temperature test, vibration test and action test. On the basis of preprocessing the temperature and vibration test data, the test data is fused into a unified prior distribution. Then taking the action test data as field data, the reliability evaluation of valves is completed according to the Bayes theory. The research shows that, compared with single-type test evaluation results and large sample evaluation results, the multi-source information fusion method is accurate, stable and credible.
    Collision Behavior between Ball and Cage in Ball Bearing during Oscillating
    ZHANG Wenhu, HU Yusheng, DENG Sier, XU Jia, LI Feng
    2022, 43(1):  207-217.  doi:10.3969/j.issn.1000-1093.2022.01.023
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    For the failure of cage in ball bearing under the oscillating condition, a dynamic analysis model of oscillating ball bearing is established based on the dynamics theory of rolling bearing, and solved by the Gear stiff(GSTIFF) integer algorithm with variable steps. The effects of bearing operating parameters, lubricant traction coefficient and cage pocket clearance on the collision behavior between cage and ball are investigated. The results show that the collision force between ball and cage under the oscillating condition is obviously larger than that at constant speed. The collision force between ball and cage in the loading area is the largest, their collision force in the non-loading area is larger, and the collision force in and out of the loading area is the smallest. The collision force between cage and ball increases with increase in cage pocket clearance. The reduction in stability speed and radial load of bearing, the increase in shifting time and the use of low viscosity lubricant are beneficial to reduce the collision force between ball and cage.
    Research Notes
    Detection Probability of Four-quadrant Circumferential Laser Fuze of Anti-aircraft Rocket Projectile for Swarm Unmanned Aerial Vehicle
    YAO Lixin, ZHAO Xiaoyao, WANG Shuaixiang, YU Yongqiang
    2022, 43(1):  218-225.  doi:10.3969/j.issn.1000-1093.2022.01.024
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    The rendezvous model of the anti-aircraft rocket projectile and the incoming swarm unmanned aerial vehicle (UAV) is described by using the method of spatial analytic geometry. A scheme of a four-quadrant circumferential laser fuze for anti-aircraft rocket projectiles is proposed to detect the incoming swarm UAV, and a detection probability model of projectile-target rendezvous based on Monte Carlo method is established to improve the detection probability of laser proximity fuze of anti-aircraft rocket projectile for the incoming swarm of UAV. The detection probability of the system under the conditions of different rocket projectile and target speeds,laser pulse frequency and detection radius is analyzed.The calculated results show that the probability of the system effectively detecting a target within 8 m is 0.788 8 when the laser pulse frequency is 55 kHz and the rocket projectile rotation speed is 40 r/s.The Monte Carlo calculation model of the system detection probability can provide the theoretical reference for the design of four-quadrant circumferential laser fuze system of air defense rocket projectile.
    Preparation and Properties of Modified Ag/AgCl Marine Electric Field Electrode with Sodium Bicarbonate
    LI Hongxia, SONG Yusu, XIAO Haijian
    2022, 43(1):  226-232.  doi:10.3969/j.issn.1000-1093.2022.01.025
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    An Ag/AgCl marine electric field electrode with high porosity was developed by adding a certain amount of sodium bicarbonate(NaHCO3) foaming agent to the powder pressed Ag/AgCl electrode and utilizing the property that sodium bicarbonate decomposes and produces CO2 gas in the process of sintering at high temperature.The preparation process parameters of NaHCO3-Ag/AgCl electrode were studied from the analyzed and measured results of TG/DSC thermal analysis method and weighing method,and a complete set of preparation method of NaHCO3-Ag/AgCl powder pressed electrode was preliminarily formed. The measured results of electrochemical and detection performances of NaHCO3-Ag/AgCl electrode show that the exchange current density of the electrode is increased,the range stabiliizing time is significantly reduced,and the self noise is reduced.It shows that the electrochemical and detection performances of the developed electrode are improved compared with those before adding sodium bicarbonate.The preparation method of high porosity marine electric field electrode has good feasibility and application prospect.
    Optimization of Temperature Field of Autoclave Frame Mold Based on Fluid Dynamics
    GUO Jingyu, YUE Guang, L Jiamei, REN Lin, PAN Yutian
    2022, 43(1):  233-240.  doi:10.3969/j.issn.1000-1093.2022.01.026
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    Autoclave curing technology has become an important molding technology in the production process of composite materials, and has been widely used in the aerospace. The uneven temperature distribution in the composite material curing process used by this technology leads to the uneven internal structure of the material. For the problem above, a method for optimizing the temperature field of autoclave forming frame mold is proposed based on the influence of fluid flow rate on convection heat transfer. The proposed method is to reduce the circulation area of the working fluid, increase its flow rate, enhance convective heat transfer, and use the change of fluid flow rate to compensate for the temperature loss of the fluid itself due to heat transfer, so as to improve the inhomogeneity of the mold surface temperature distribution and solve the problem of large curing gradient of composite material. The COMSOL multiphysics simulation software is used to calculate the fluid-solid coupling of the “upward convex”, “straight” and “downward concave” variable cross-section molds. The temperature distribution of mold surface is analyzed. The results show that the profile of the “straight” frame-type mold has the best temperature distribution inhomogeneity, and it also has the characteristics of low conversion cost, simple structure, and easy implementation.