Table of Content

29 January 2021, Volume 42 Issue 1

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Contents

Contents

2021, 42(1):  0. 

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Paper

A Guidance Control Method for Air-to-ground Missiles with Laser Seekers

ZOU Ruping， CHEN Shichao, CHEN Yun, ZHANG Jianling

2021, 42(1):  1-10.  doi:10.3969/j.issn.1000-1093.2021.01.001

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A guidance control method based on attitude measurement gyro midcourse and laser homing terminal is proposed for timely precise attacking of air-to-ground missiles (AGMs) with laser seekers. The guidance feature of AGM with laser seeker is analyzed in detail. Attitude control of a missile being merely provided with gyro is conducted in pitching, yawing, and rolling channels. Stable missile body control and high target acquisition probability are realized by fusing rolling angle stabilization control, attitude control, proportional guidance control, and programming control together. Meanwhile, the determination of the laser illumination time is studied. Experimental results show that the stable control of AGM with laser seeker can be realized by using the proposed method. The results of trajectories and altitudes obtained from flight experiment coincide to the theoretical design.

Rollover Prevention Control for In-wheel Motor Drive Vehicle Based on Model Prediction Control

WANG Zhifu, BAI Jin, HUANG Kanglun, WANG Jun, WANG Yang, LIANG Changchun, WANG Rui

2021, 42(1):  11-25.  doi:10.3969/j.issn.1000-1093.2021.01.002

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An active anti-rollover control strategy based on the model predictive control is proposed for the rollover stability of 8×8 in-wheel motor drive vehicle. In order to make full use of the independent controllable characteristics of the torque and turning angle of each wheel, a hierarchical control structure is used to design a control strategy for the distribution of wheel angle and motor torque, and then design an active anti-rollover control strategy based on the model predictive control. And the rolling optimization algorithm is simplified to reduce the amount of calculation to ensure real-time performance. Through MATLAB/Simulink and Trucksim co-simulation and proportional model vehicle test, it is shown that the vehicle rollover instability can be avoided and the driver's desired travel trajectory can be tracked as well by using the proposed hierarchical control strategy and the active anti-rollover control strategy based on the model predictive control.

Data Processing of Test of Fuze Arming Distance Measured Using Langlie Method Based on Bayesian Method

ZHAO Xin, JI Yongxiang, LIU Shefeng, CHEN Zhong, NING Xiaolei

2021, 42(1):  26-32.  doi:10.3969/j.issn.1000-1093.2021.01.003

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For the contradiction between smaller sample size and large evaluation error in measuring the fuze arming distance by Langlie method, Bayesian method is used to process the data of fuze arming distance measured by Langlie method. A Bayesian mathematical model is established, and the prior distribution choice and the posterior distribution form are clarified. The prior data hyperparameters are determined from the experimental data, and the posterior distribution is solved from the prior information. The simulated and experimental results show that the influence of the Langlie method on accuracy of variance can be improved, and the accuracy of variance can be increased by 20%. The error of 95% and 5% points of the fuze arming distance that can be reduced is controlled within 5%. The inconsistent test results that are caused by test conditions are corrected to reduce the influence of condition errors on the mean and variance, and obtain the relationship between modified mean and variance. Bayesian method can modify the variance of Langlie method, and also weaken the influence of the test conditions on the results.

Oscillation Characteristics of Pressure in Combustor with Rotary Valve for Solid Rocket Engine

XI Yunzhi, WANG Ningfei, LI Junwei, ZHANG Zhihui

2021, 42(1):  33-44.  doi:10.3969/j.issn.1000-1093.2021.01.004

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The pressure-coupled response function test system of solid propellant based on rotary valve is difficult to perform the measurement of phase angle, and the analysis of pressure oscillation and internal flow field. A set of cold-flow experimental system with rotary valve was designed, and a corresponding theoretical calculation model of pressure oscillation and a three-dimensional transient flow field simulation model based on dynamic mesh technology were established. Cold flow experiment and theoretical calculation at different exhaust frequencies were made, and the experimental and calculated results were compared with the simulated results. The results show that the periodic swing motion of a single-rotor exhaust duct can replace the unidirectional rotary motion of the multi-rotor exhaust duct in the simulation calculation, and the error is less than 1%. The errors of the exhaust cycle obtained by simulation calculation and experiment are less than 1.2%; the simulated peak-to-peak pressure is smaller than the experimental one, and the difference value is reduced from 0.019 MPa at 20 Hz to 0.001 MPa at 300 Hz, which verifies the effectiveness of the simulation model.

The Characteristics of Explosives Initiated by Precursor Shock Waves in Shaped Charge Jet Penetrating a Bulkhead at DifferentTemperatures

ZHAO Pin， CHEN Lang， LI Jinhe， LU Jianying， WU Junying

2021, 42(1):  45-55.  doi:10.3969/j.issn.1000-1093.2021.01.005

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The reaction mechanism and response law of ammunition under the impact of shaped jets are of great significance to the study of ammunition safety. The initiation caused by shock waves formed in bulkhead and the effects of explosive temperatures in experiment and numerical simulation are mainly researched. An experimental device was designed for the large-sized shaped-charge jet penetrating the different thick bulkheads to initiate heated explosives. The upper and lower ends of explosive charge are heated, and its side keeps warm to achieve the uniform heating and temperature control of the charge. Jet-penetrating initiation experiments of RDX-based aluminized explosives (mass ratio of RDX, Al and adhesivein explosive formulation is 61%∶30%∶9%) were performed under the conditions of different temperatures and bulkhead thicknesses. Flash X-ray high-speed radiography was used to observe the jet penetration process and detonation wave. A temperature-dependent simulation model of jet initiating explosives was established, and large quantities of numerical simulations were made on the initiation caused by shock waves, which were formed in jet penetrating the bulkhead. It is found that the precursor shock waves are formed in bulkhead by jet penetrating the thick bulkhead, and reach the surface of the explosive earlier than the jet does, and the explosive is detonated after the shock waves propagate in the explosive at a certain depth. When the incident pressure is between 3.1 GPa and 5.13 GPa, the explosive is detonated by shock waves formed in bulkhead. When the incident pressure is higher than 5.13 GPa, the impact initiation occurs. The explosive temperature has a great influence on the precursor shock wave initiation mechanism. It is suggested that the shock sensitivity of the explosive to the jet decreases with the increasing temperature at 25-110 ℃, mainly because of binder softening. However, at 110-170 ℃, the influence of the soften binder is weak, and the shock sensitivity increases when the temperature exceeds a certain value, which depends on the increasing sensitivity of RDX.

Equivalent Simulation of Soil Motion Characteristics under the Action of Ground Shock Induced by Nuclear Explosion

RONG Jili, SONG Yibo, WANG Xi, GUO Zhen, XIANG Dalin, WU Zhipei

2021, 42(1):  56-64.  doi:10.3969/j.issn.1000-1093.2021.01.006

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Nuclear explosion induces the problems such as multi-field coupling, strong nonlinearity and large deformation of rock and soil media, which makes the ground shock wave composition complex and difficult to simulate the ground shock effect of nuclear explosion accurately. In order to solve these problems, an accurate method for describing the combined effect of induced ground shock wave and direct ground shock wave is proposed, and a simulation analysis model is established. The method is used to simulate a ground motion test which was carried out by the U.S. Army. Ground shock waves induced by the overpressure shock front were obtained, which shows that the surface and subsurface targets are subjected to the effects of induced ground shock wave while being hit by the air shock wave, and the round shock effect of entire nuclear detonation is the combination of airblast-induced ground shock and direct ground shock. The simulated results of soil velocity fit well with both test data^［3］ and calculated values in TM 5-858-2^［8］, proving the validity of this numerical simulation model.

Availability Modeling of Military Ad Hoc Network Based on Markov Chain

FU Yanfang， WANG Zan， SU Yichang， DAI Fei， ZHONG Lianjiong， GUO Dengdeng， LU Ying， LIANG Hongtao

2021, 42(1):  65-73.  doi:10.3969/j.issn.1000-1093.2021.01.007

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Nowadays, the scale and complexity of military communication network are increasing, so a high availability network is urgently needed to meet the needs of users for high reliability services, and the quantitative study of network availability is of great significance to evaluate the reliability of tactical ad hoc network. For the mobile model and fault characteristics of tactical ad hoc network, a network availability model based on Markov chain is established,the delay model of the main factors affecting network service is studied by analyzing the CSMA/CA transmission mechanism. On the basis of the proposed model, the statistical principle is used to propose a fault-based quantitative evaluation model of service availability of mobile ad hoc network. And taking a typical combat communication network of an army unit as an example, the relationship between network availability and core indexes such as number of nodes, transmission rate and message length is analyzed, and the effectiveness of the analyzed results is verified by simulation.

Modeling on Exposed Area of Suppressing Jamming Based on Radar Antenna Beam Pattern

XIA Dong， WANG Shouquan， BAO Zhonghua， CAO Yunhe

2021, 42(1):  74-82.  doi:10.3969/j.issn.1000-1093.2021.01.008

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Current radar exposed area model is imprecise as the influnce of antenna beam pattern needs to be considered. In order to implement the optimized penetrating strategy of protected targets, the radar antenna beam pattern was introduced in calculating burn-through distance, and a new radar exposed area model modified by radar antenna beam pattern was built. On basis of analysis of the new model,the penetrating strategy of protected targets when radar is interfered by just one jammer is presented, in which the penetrating direction should be selected at radar antenna sidelobes' maximum. Radar exposed area of moving platform under suppressing jamming of multiple jammers was simulated and analyzed, and a targets penetrating strategy with multiple jammers was built. When an angle between multiple jammer and radar is less than a certain value and equal to the angles corresponding to radar antenna sidelobes' maximum, the radar exposed area has few glitches, which leads to good suppressing effect with wide scope of penetrating direction. The simulated results show that burn-through distance obtained by the proposed model varying with directions is consistent with experimental results.

A Real-time Discrimination Method for Operating State of Terminal Guidance Radar in Complex Electromagnetic Environment

LEI Zhenshuo, LIU Songtao, WEN Zhenming, GE Yang

2021, 42(1):  83-90.  doi:10.3969/j.issn.1000-1093.2021.01.009

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The accurate judgment of operating state of terminal guidance radar is one of the important preconditions to infer the threat degree of enemy missile and evaluate the jamming effect of electronic warfare system. For low discrimination accuracy of operating state of terminal guidance radar due to inaccurate and incomplete signal in complex electromagnetic environment, a new method for real-time discrimination of operating state of terminal guidance radar in complex electromagnetic environment is proposed. A status breakpoint discrete method is used for discriminating. The samples with the same working state and similar eigenvalues are classified into one class by using this method, which makes the division of the discrete interval reasonable, and the anti-noise capability of the discrimination method be enhanced. A basic probability assignment (BPA) correction method based on incomplete information is also used in discrimination.In this method, the BPA output from support vector machine is corrected by using the similar correction factor, and the incomplete information is utilized without introducing human error. The simulated results show that the proposed method can improve the discrimination accuracy of operating state of terminal guidance radar.

A Bullets Fast Matching System Based on Single Point Laser Detection

PAN Nan， PAN Dilin， JIANG Xuemei， LIU Yi， QIAN Junbing， ZHAO Chengjun

2021, 42(1):  91-99.  doi:10.3969/j.issn.1000-1093.2021.01.010

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The traces of bullets rifling are not easy to be destroyed, difficult to be disguised and unique, and have good identification value. The traces are of great significance to create batch firearms file and determinate the guns for crime. For the disadvantages existing in traditional microscope inspection, segmented photography and other methods, such as time-consuming, low efficiency, great influence of subjective factors on trace detection, and more difficult quantitative analysis, a fast matching system for bullets based on single-point laser detection was designed. The system adaptively adjusts the center position of bullet and the cylindrical axis, and a laser displacement sensor is then used to detect the rifling traces on the surface of bullet along the circumference. After multiple detection data are superimposed, the generalized morphological filtering is used for noise reduction of detection data, and then the matching of trace similarity is calculated using Pearson correlation coefficient, eventually achieving the fast matching of bullets. The experimental results show that the rapid matching system has the advantages of high detection accuracy, fast matching speed and no damage to the surface texture of bullets. It can be used for one-to-one data matching between bullets, and one-to-many data matching. It can be effectively applied to the batch filing of guns and the determination of guns for committing crimes.

Domain Computing Method Based on Partially-averaged Navier-Stokes Turbulence Model

LUO Qian， HU Changli

2021, 42(1):  100-107.  doi:10.3969/j.issn.1000-1093.2021.01.011

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A partially-averaged Navier-Stokes（PANS）method is proposed to calculate different regions of flow field with different values of f_k, which imposes the different turbulence models to be set at the same time. The proposed method is applied to simulate the single-phase flow around the two-dimensional square cylinder and the unsteady cavitating flows around Clark-y hydrofoil, respectively. The modified PANS model well predicts the pressure coefficient distributions on the surface of square cylinder and the velocity distribution at different sections of flow field. In addition, it can well capture the time evolutions of the cavities around the Clark-y hydrofoil and the fluctuation of lift coefficient of hydrofoil.

Effect of Appendages on Hydrodynamic Characteristics of Submarine in Stratified Fluid

LIU Shuang, HE Guanghua, WANG Wei, GAO Yun

2021, 42(1):  108-117.  doi:10.3969/j.issn.1000-1093.2021.01.012

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The effect of appendages on the flow field and resistance characteristics around submarine in density stratified fluid is investigated. A Reynolds-averaged Naiver-Stokes-based CFD model was established for simulating the navigation of submarine in density stratified fluid. The convergence study was carried out with a SUBOFF submarine model, and the proposed numerical model was validated by comparing with experimental data. The hydrodynamic characteristics of submarine with different appendages navigating at various speeds were simulated, and the simulated results were analyzed combined with the changes of pressure. Results shows that the effect of appendages on hydrodynamic characteristics of submarines is related to navigational speed; the coefficients of wave-making resistance of submarine reach the highest around Fr (Froud number)=0.5. The sharp curvature around appendages on the surface of submarine causes sharp change of pressure. The proposed model shows the hydrodynamic characteristics of submarine navigation, and can be used for the selection of simulation method for navigation of submarine in density stratified fluid and the design optimization of submarine appendages.

Application of Electro-thermal Coating in Infrared Decoy

YANG Hui, HE Chao, PAN Jialiang, JIA Qi, HE Meng, XU Xin

2021, 42(1):  118-123.  doi:10.3969/j.issn.1000-1093.2021.01.013

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The electro-thermal coatings were theoretically and experimentally studied to improve the camouflage effectiveness of decoy effectively. The electro-thermal coatings with different resistivity gradients simulating the target temperature are analyzed, which achieve excellent infrared decoy. The coatings with different conductivities were prepared by designing the components of the electro-thermal coating, and after they were connected in series into the circuit, three infrared gradient patterns were formed. And then the camouflage performance of electro-thermal coating was confirmed by applying it in a decoy prototype. The result shows that the electro-thermal coatings with different resistivity gradients can be used for the infrared simulation of target, and have good camouflage effectiveness.

Mechanical Properties and Ballistic Performance of Ti-6321 Alloy

HUANG Junhao, WANG Lin, LIU Xiaopin, XU Xuefeng, LIU Anjin, Tayyeb Ali, ZHOU Zhe, NING Zixuan, YANG Jiabin, ZHANG Binbin, CHENG Xingwang

2021, 42(1):  124-132.  doi:10.3969/j.issn.1000-1093.2021.01.014

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A series of mechanical experiments and ballistic performance tests were conducted on Ti-6321 titanium alloy with three microstructures of equiaxed, bimodal and Widmanstatten structures. The macro- and micro-damage characteristics of Ti-6321 targets were analyzed. The effects of microstructure and mechanical properties on ballistic performance of titanium alloy with different microstructures were investigated. The experimental results demonstrate that the equiaxed Ti-6321 targets exhibit the best ballistic performance and good mechanical properties. The dynamic mechanical properties, including dynamic flow stress and impact absorbing energy, exhibit a positive correlation with ballistic performance. Besides, the micro-damage analysis of the targets show that target with equiaxed structure has the least number, short lengths, and less bifurcations and convergences of adiabatic shear bands on it, while the target with Widmanstatten structure has the largest number, long lengths, and more bifurcations and convergences of adiabatic shear bands on it.

Anti-collapsing Performance of POZD Coated Reinforced Concrete Slab

YANG Jianchao， WANG Jianhui， CHEN Li， KONG Defeng， ZHAO Hongxiang

2021, 42(1):  133-140.  doi:10.3969/j.issn.1000-1093.2021.01.015

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Different TNT equivalent tests of three test models were made to study the anti-collapsing behavior of POZD coated reinforced concrete slab. The failure mode and anti-collapsing mechanism of POZD coating were studied and analyzed by observing the damage states and data statistics of the test models. The results show that POZD coated reinforced concrete slab has superior anti-collapsing performance, and with the increase in coating thickness, the anti-collapsing capacity increases gradually, and K_z decreases linearly. After spraying 8 mm-thick POZD coating on reinforced concrete slab, its anti-collapsing capacity is much better than that of 3 mm-thick Q235b steel plate. The damage model of POZD coating is conically bulged under the contact explosion of group charge, which is caused by large plastic deformation under the combined action of concrete fragment and shock wave. When the shock wave load exceeds the ultimate tensile strength of POZD material, the coating can remain intact and effectively restrain the concrete fragments except for the small circular hole shear failure at the tip of the cone. Under the action of high strain and strong dynamic load, POZD coating can still maintain the characteristics of large deformation and high plasticity. Through the large deformation of POZD coating, it absorbs the energy of shock wave, constrains the concrete debris, and plays a good anti-collapsing effect.

A Multi-agent System Flocking Model with Obstacle Avoidance in Complex Obstacle Field

ZHANG Chaosheng, WANG Jian, ZHANG Lin, WANG Ya

2021, 42(1):  141-150.  doi:10.3969/j.issn.1000-1093.2021.01.016

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A multi-agent system flocking model with obstacle avoidance in complex obstacle field is established for the obstacle avoidance of robot flock in the ground battlefield. In this model, the complex obstacle is geometrically described with polygon shape, which reduces the probability of channel narrowing or blocking caused by the least circumscribed circle(ball). Based on the artificial potential method, a mathematical model and the solving flow are presented for the interactions between agents, agent and surrounding obstacles, agent and its target. When solving the model, the rejective edge and rejective area of polygon obstacle are determined from the relationship among the outer center of agent and the geometric properties of polygon obstacle, including inner center, outer center and edge, and the capturing edge of polygon obstacle and the temporary target of agent are determined from the relationship among the outer center of agent, the edge of polygon obstacle and the target, thus overcoming the defect that the agent is usually captured by the edge of polygon obstacle. The simulated results show that the proposed model can be used to control the flocking with obstacle avoidance of multi-agent system whether for static target or dynamic target.

New Hydrodynamic Ejection Dynamic Characteristics of Unmanned Aerial Vehicles

ZHANG Zhenhua, WU Xiangyang, LI Chunping, ZHANG Jizhi, WEI Liejiang, WANG Fei

2021, 42(1):  151-158.  doi:10.3969/j.issn.1000-1093.2021.01.017

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For the complicated structure and limited power of pneumatic ejection of active unmanned aerial vehicles(UAV)，a hydrodynamic ejection scheme is proposed，in which the reverse thrust generated by high-pressure water jets as power is used to take off the VAU quickly.A non-linear ejection dynamics model is established, which couples the air chamber state equation and water chamber momentum equation of ejector，the energy and momentum equations of jet，and the force balance equation of catapult load. The variations of ejection speed and displacement，spurt speed and reverse thrust，ejector air chamber pressure，and the influences of ejector diameter，jet diameter and inflation pressure on catapult performance are numerically analyzed. The results show that, as the catapult time increases，the catapult speed and displacement increase approximately in a logarithmic curve and an exponential curve, respectively，and the ejection speed，the reverse thrust of jet and the air chamber pressure decrease significantly in a parabolic state. When the ejector diameter is 200 mm，the ejector length is 2 400 mm，the jet diameter is 20 mm，and the inflation pressure is 31.5 MPa，the 150 kg UAV can be accelerated to 25.02 m/s in the range of 16.62 m. Increasing ejector diameter adversely affects ejection performance.The increase in jet diameter has little effect on the maximum ejection speed，but it significantly shortens the catapult time and distance，and increases the catapult overload.Under the premise of catapult overloaded，an appropriate increase in inflation pressure can reduce catapult time and distance，and help to increase catapult speed.

Integrated Navigation Algorithm of Depth Camera/MEMS IMU

ZHANG Fubin， LIN Jiayun

2021, 42(1):  159-166.  doi:10.3969/j.issn.1000-1093.2021.01.018

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GPS, radio positioning and other positioning methods are difficult to use in the indoor environment. Wheel odometer is easy to slip or idle in stairs and other occasions. Single vision sensor or micro-electromechanical system (MEMS) inertial measurement unit (IMU) is difficult to achieve high-precision autonomous positioning. The traditional vision/MEMS IMU integrated navigation algorithm is complex, computationally expensive and of low accuracy. In order to solve these problems, a loose coupled navigation algorithm based on depth camera/MEMS IMU is proposed for indoor application. The pre-integration results of MEMS IMU are used as the initial value of the iterative closest point (ICP) algorithm, which greatly reduces the number of iterations. The position of a carrier is calculated by depth camera and MEMS IMU, respectively. The position difference is obtained by subtracting the two positions. The errors of MEMS IMU is estimated and the result of dead reckoning is corrected by using the position difference as the measuring information of EKF. The results of experiments with Kinect v1 and MTI 100-IMU show that the improved ICP algorithm based on MEMS IMU can effectively reduce the number of iterations by about 50%. The depth camera/MEMS IMU loose coupled algorithm based on position difference can make the position errors less than 10% of the total mileage.

Dissolution and Precipitation Rule of Carbides in 30Cr2MoV Gun Barrel Steel

HE Xing, HU Chundong, WANG Zimeng, CHEN Yuewei, WEI Xicheng, LI Junsong, DONG Han

2021, 42(1):  167-174.  doi:10.3969/j.issn.1000-1093.2021.01.019

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The important development direction of gun barrel steel is to use the secondary hardening effect for ensuring a high temperature strength. This type of steels is generally of low toughness. The dissolution and precipitation behaviors of carbides as well as their effects on the toughness of a new 30Cr2MoV secondary hardened gun barrel steel were studied to improve the steel toughness. The carbides were characterized by using scanning electron microscope, transmission electron microscope, carbon replica and phase analysis technologies. The results show that, as the quenching temperature is raised from 850 to 1 050 ℃, the dissolution quantity of carbides increases, then so does the precipitation kinetics of secondary hardened phase. At the quenching temperature of 950 ℃ (slightly lower than the total solution temperature of MC carbides), undissolved MC at the austenite grain boundaries can effectively inhibit the growth of original austenite grains, and the impact energy remains high (107 J). As the tempering temperature increases from 600 to 700 ℃ after quenching at 950 ℃, the dissolution of M₃C and the precipitation of M₂C increase, the precipitation of M₇C₃ starts at a temperature slightly lower than 650 ℃, the content of MC remains almost unchanged, and the total content of carbides is decreased by about 14%. The impart fractures show quasi-cleavage, cleavage and ductile fracture, respectively, at the tempering temperatures of 600, 625 and 650 ℃. The cleavage fracture at 625 ℃ may be correlated with the transition from M₃C to M₂C, which causes intragranular strengthening and grain boundary weakening, segregation of impurity elements at grain boundaries and coarsening of carbides.

An Analysis Method for Nonlinear Structural Reliability Based on Gradient Search Method

CHEN Pengfei, HE Peng, YU Tailong, LIU Qiaoling

2021, 42(1):  175-184.  doi:10.3969/j.issn.1000-1093.2021.01.020

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Many engineering structures have strong nonlinear characteristics and their functions are implicit. It is difficult to analyze the reliability of engineering structures accurately and efficiently. A sensitivity analysis method of strong nonlinear structural reliability based on gradient search method is proposed. Based on the implicit function of engineering structure, the gradient information near the initial sampling point is calculated by using the difference method. Then the gradient search method of checking point is used to obtain the limit state point at the minimum distance from the limit state surface corresponding to the sampling point, through which the limit state surface is linearly expanded by Taylor expansion method. A set of training samples near the limit state surface are obtained through several iterative searches. On this basis, the polynomial function and response surface function are used to fit the limit state equation to calculate the reliability and reliability sensitivity. The numerical and engineering examples show that the proposed method has the advantages of high accuracy and less sampling times compared with the previous methods, and it is suitable for the reliability analysis of strong nonlinear implicit structures.

Magnetoacoustic Emission Characteristics of Q235 Steel under Static Load Tension and Low Cycle Fatigue

LI Zhinong, ZENG Wenjun, WEN Qinsong, SHEN Gongtian, SHEN Yongna

2021, 42(1):  185-191.  doi:10.3969/j.issn.1000-1093.2021.01.021

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A force-magnetic coupling model of Q235 steel under static load tension and a low cycle fatigue life model are established to study the relationship between stress and magnetoacoustic emission (MAE) and the relationship between magnetoacoustic emission and fatigue state of ferromagnetic metal materials. From the perspective of finite element simulation, the generating mechanism of magnetoacoustic emission signals under static load tension is analyzed. According to the simulated results, the low cycle fatigue test of MAE is designed, and a self-built test platform is used to verify the proposed models. The law of magnetoacoustic emission signals under static load tension and low cycle fatigue was studied. The experimental results show that the permeability shows a linear increasing trend with the increase in the tensile stress in the elastic range under static tension, which leads to the increase in the loss on the specimen and the weakening of MAE signal. The root mean square voltage and envelope area of magnetoacoustic emission signal show a downward trend. However, during low cycle fatigue, the low cycle fatigue life of Q235 steel can be predicted by Smith-Watson-Topper model, and the amplitude and pulse counting characteristic parameters of Q235 steel decrease with the increase in cycle number. The obtained results clarify the influence of stress on MAE and fatigue state on MAE.

Optimal Assignment of Accompanying Rush-repair Tasks of Equipment

WANG Shaohua， L Huiqiang， DONG Yuansheng， ZHANG Yuan

2021, 42(1):  192-198.  doi:10.3969/j.issn.1000-1093.2021.01.022

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For the characteristics of field rush-repair of army equipment, such as high task intensity, short available time and distributed human resources, the organization and implementation procedure of battlefield accompanying rush-repair was proposed. The optimal selection and assignment of rush-repair tasks are discussed in considering multiple rush-repair teams. To solve the decision-making issue, the available repair time is taken as a hard constraint, and the objective function is brought forward according to the quantity of repaired equipment and consumed time, and then a decision-making model is built. Considering the problem brought by high dimensional decision-making space, a solving method is proposed by using genetic algorithm. The feasibility of the proposed model and the solving method was verified through case study.

Simulation Evaluation of Mission Success Probability of Synthetic Forces during Wartime Considering Random Common CauseFailure

WANG Shuangchuan， JIA Xisheng， HU Qiwei， CAO Wenbin， GUO Chiming

2021, 42(1):  199-208.  doi:10.3969/j.issn.1000-1093.2021.01.023

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Common cause failure (CCF) is a common phenomenon in the process of equipment carrying out combat tasks, which plays an important role in the evaluation of equipment mission success probability during wartime. The combat mission profile of synthetic forces is developed based on the level analysis of equipment of synthetic forces, and the characteristics of equipment CCF and equipment maintenance support of synthetic forces are analyzed. The mission success requirements of synthetic forces are proposed by taking the mission during attack phase as the research object. In thoroughly considering the impacts of random common cause failure (RCCF), multiple equipment, cooperative operation of multiple combat units, random mission time and replacement repair time on combat mission success probability of synthetic forces, a simulation evaluation model of mission success probability of synthetic forces during wartime is established based on the Monte Carlo method. And then the feasibility and validity of the evaluation model based on simulation is verified by an analytical example. The research results present that the proposed model can be used to evaluate the mission success probability of combined arms during wartime and optimize the time of combat mission; the reasonable allocation of carrying quantity of various spare parts contributes to the improvement of mission success probability of synthetic forces during wartime.

Research Notes

Calculation Method of Firing Trajectory of High Spinning Projectile Adapted to Wide Altitude

DING Tianbao， HE Zhao, WANG Liangming, LIN Zhiwei

2021, 42(1):  209-213.  doi:10.3969/j.issn.1000-1093.2021.01.024

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A new method which gives priority to the idea of theoretical calculation and simulation with data of a few tests is proposed to improve the traditional method of firing table development which depends on live firing test radically. A nonlinear motion equation of projectile coupled attitude is established, which is used to calculate the influence of initial disturbance on mean trajectory. The model of the variation of projectile resistance coefficient with the altitude is improved on the basis of the relational model of the ballistic coincidence coefficient and the firing angle of gun. Based on the feature information extracted from a few of high-precision ballistic test data, the theoretical calculation firing table is modified to achieve higher precision. In order to reduce the principle error of the intersection for two firing tables used on plateau and plain individually, a method of smoothing the connection of two firing tables is created. The correctness of the proposed method is proved by the results of the live fire tests, and the precision of the firing table is high enough, which is fully suitable for the applications at the altitude from 0 m to 4 500 m.

Reactive Molecular Dynamics Simulation of Microscopic Mechanisms of Femtosecond Laser Ablation of RDX

WU Junying, YANG Lijun, LI Yaojiang, CHEN Lang

2021, 42(1):  214-224.  doi:10.3969/j.issn.1000-1093.2021.01.025

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The femtosecond laser can be used for the precise machining of explosives and the preparation of energetic nanomaterials because of its ultra-short pulse duration and ultra-high energy density. Deep understanding of the femtosecond laser ablation mechanism of energetic materials is the basis for rational use of femtosecond laser machining technology. The molecular dynamics calculations of RDX ablated by femtosecond laser were conducted based on ReaxFF/lg reactive force field. The decomposition reaction pathway and particle diffusion of RDX were analyzed, and the ablation mechanism of RDX under different femtosecond laser energies was discussed. Results show that the ablation mechanisms of RDX are different under the action of different femtosecond laser energies. When the laser energy is high enough (e.g., 1.0 mJ/pulse, 51 J/cm²), RDX is rapidly decomposed to generate high-temperature and high-pressure plasma. In addition, there are many single atoms, ions and small molecular fragments in the products; when the laser energy is relatively low (e.g., 0.2 mJ/pulse, 10.2 J/cm²), the explosive is removed by a photomechanical ablation mechanism, RDX in laser focal zone escapes as its starting molecular structure. During the femtosecond laser ablation, the high-speed particles in focal zone quickly escape outward and become difficult to transfer the energy to the surroundings, by which the explosive can be removed effectively without causing thermal diffusion. Therefore, the “cold” machining of explosives can be realized.