Table of Content

29 May 2020, Volume 41 Issue 5

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Contents

2020, 41(5):  0. 

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Paper

The Effects of Initial State Parameters of Projectiles at Muzzle on Their Ground Dispersion

QIAN Linfang, CHEN Guangsong, WANG Mingming

2020, 41(5):  833-841.  doi:10.3969/j.issn.1000-1093.2020.05.001

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The effects of the state parameters of projectiles at muzzle on the dispersion of projectiles are analyzed. Based on the six-degree-of-freedom ballistic equations, the sparse grid numerical integration (SGNI) method is used to obtain the characteristic paramerers of projectiles dispersion considering the error factors of system parameters and the state parameters of projectile at muzzle. The probability distribution of projectiles dispersion is obtained by using the the maximum entropy method. The test examples show that the results obtained by the SGNI method are in good agreement with those obtained by Monte Carlo method, and verify its effectiveness. In addition, an engineering example of 155 mm gun-howitzer is ananlyzed, and the the relation between single state parameter error and multi-state parameter error and the projectiles dispersionis established, which can be provided as reference for the overall design cosidering the dispersion of projectiles. Key

Method for Estimating Sideslip Angle of All-wheel Drive Vehicle Based on Data Fusion

ZHANG Zheng， LIU Chunguang， MA Xiaojun， ZHANG Yunyin

2020, 41(5):  842-849.  doi:10.3969/j.issn.1000-1093.2020.05.002

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A method for estimating sideslip angle based on data fusion is proposed to obtain the driving state parameters of all-wheel electric drive vehicle. On the basis of three-degree-of-freedom vehicle model and tire model, the method fully utilizes the information from a low-cost common vehicle-mounted sensor, in-wheel motor input information as well as driving signals, and the sideslip angle is estimated by using the unscented Kalman filter algorithm. Besides, the sideslip angle is estimated by signal integration method. Combined with vehicle driving conditions and road conditions, the estimated values of the unscented Kalman filtering algorithm and the signal integral algorithm are fused to obtain the final estimation of sideslip angle. A series of simulations were conducted on the hardware-in-the-loop real-time simulation platform. The results show that the proposed estimation algorithm has higher observation accuracy compared with the single estimation algorithm, which can meet the requirements of mass center sideslip angle observation under various driving conditions. Key

Numerical Analysis of Effect of Liquid-gas Two-phase Flow on the Drag Torque Characteristics of Wet Clutch

CHENG Xiao， ZHU Maotao, TIAN Naili

2020, 41(5):  850-857.  doi:10.3969/j.issn.1000-1093.2020.05.003

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For the purpose of reducing the torque caused by oil shear in disengaged clutch discs，a fluid dynamic simulation about the flow field inside two discs is made in considering the influence of oil-gas mixing process. A 3D CFD simulation model including the information about radial groove is built by STAR-CCM+, which calculates the steady state based on Euler two-phase model and k-ε two-layer turbulence model. The calculated results are used to investigate the effects of the flow rate and relative rotating speed on drag torque, which agree with the experimental results with average error of 7.54%. The correlation between oil-gas distribution and drag torque characteristics is observed by changing the structure of groove angle. The research results show that the drag torquel increases with the flow rate. The maximum torque is 4.63 N·m when the flow rate is 7 L/min, and the values of drag torque are reduced by about 20.95% and 33.69%, respectively, when the flow rate is reduced from 7 L/min to 5 L/min and 3 L/min. The groove angle can reduce the drag torque, and the negative groove angle has a better effect in reducing the drag torque. In the single-phase flow velocity zone, the bigger the positive groove angle is, the better the oil liquidity is, and the bigger the drag torque is. In the two-phase flow velocity zone, the continuity of the oil flow is worse, the proportion of oil is smaller and the the drag torque is smaller with increase in groove angle. Key

Damage Behavior of CuCrZr Alloy Rail during Electromagnetic Launching

HUANG Wei， YANG Liming， SHI Gening， ZHANG Yansong， TIAN Kaiwen， LIU Kai

2020, 41(5):  858-864.  doi:10.3969/j.issn.1000-1093.2020.05.004

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The damage behavior of CuCrZr alloy (C18150 alloy) rail is studied through electromagnetic launching test, in which C18150 alloy is used as rail material and 7075 aluminum alloy as armature material. After launching test, the rail material was macroscopically observed, and the 2D and 3D surface profiles were analyzed. The results show that, with the increase in armature velocity, the peak-valley spacing of surface fluctuation increases first and then decreases in the transverse direction. The degree of surface fluctuation decreases with the increase in armature velocity along the direction of armature motion. When the armature velocity reaches its maximum, the rail surface fluctuation is nearly 0 μm. Rail damage presents irregular phenomena in different stages: in the initial stage, the rail damage shows obvious heat damage; in the acceleration stage, it shows strong friction and wear characteristics, and certain melting effect; in the high-speed stage, the rail damage is mainly caused by mechanical wear, showing smooth friction interface and local plastic deformation. Key

The Experimental Study and Prediction of Wrinkles in Sinking Zone of Barrel Forged with Chamber and Rifled Bore

TONG Wei， YANG Chen， YANG Yuzhao， FU Yunfeng， CHEN Xiaoping， FAN Lixia

2020, 41(5):  865-873.  doi:10.3969/j.issn.1000-1093.2020.05.005

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The radial forging process for both chamber and rifled bore is used to improve the coaxiality of rifled bore and the surface quality of chamber. The wrinkles may be formed on the inner surface of barrel during forging. The formation of wrinkles and their evolution are studied. The scanning electron microscope is used to check the inner surface of forged barrel. The results show that the wrinkles are formed in the sinking zone firstly during the radial forging processing. With the increase in deformation, the depth of wrinkles becomes bigger gradually. When the sinking zone turnes to the forging zone, some wrinkles are smoothed under the resistance of the mandrel. Nevertheless, some wrinkles are too deep to smooth and be turned to the fissures. The finite element software ABAQUS is used to simulate the forging process of barrel. It is found that the ratio of radial strain and circumferential strain is nearly same in the sinking zone, and the strain ratio is determined from the forging process parameters. The results show that the wrinkle depth per stroke can be expressed by the ratio of radial strain and circumferential strain [SX(]ε_r[]ε_θ[SX)], and the fitted relational expression is Δd_w=0.058 8[SX(]ε_r[]ε_θ[SX)]+0.052 1. The total depth of wrinkles can be predicted from the number of the stroke required for whole sinking zone and the value of Δdw. The prediction of wrinkle depth helps to prevent the wrinkles from being squeezed into fissure in the forging zone. Key

Research on the Motion Characteristics of Extendable Gripper of Rotary Conveyor Mechanism in Naval Gun

PENG Jinghui, WANG Deshi, ZHANG Hongchao

2020, 41(5):  874-880.  doi:10.3969/j.issn.1000-1093.2020.05.006

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In order to obtain the movement characteristics of rotary mechanism with grippers, the motion theory of extendable gripper of rotary mechanism is studied by simplifying the model, deducing the theoretical formula and analyzing the example. A simplified lever model of mechanism movement is obtained for rotary mechanism with grippers, and the kinematics of rotary mechanism is analyzed according to the change of lever configuration during the movement of extentable gripper, the transformation of multiple coordinate systems and closed vector method. A dynamic equation of extentable grippers of rotary mechanism is established by using force analysis, d'Alembert principle and Lagrange equation. A numerical example is analyzed by MATLAB and ADAMS virtual prototype simulation test based on the geometric parameters and driving parameters of rotary mechanism. Results show that the changes of the theoretical and simulated curves are basically consistent, and the configuration change affects the dynamic characteristics of rotary mechanism. The angular acceleration abruptly changes as the configuration changes, and the existence of eccentric pin can cause the motion track fluctuation but has little influence on the positioning error. In addition, the eccentric pin can cause acceleration shock while reducing acceleration mutation.Key

Research on Coupling Effect of High-power Microwave Front-gate in FMCW Fuze

CHEN Kaibai， GAO Min， ZHOU Xiaodong， HUI Jianghai

2020, 41(5):  881-889.  doi:10.3969/j.issn.1000-1093.2020.05.007

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The field-circuit joint simulation test of the fuze RF front-end was made for the front-gate coupling of fuze under high-power microwave irradiation. A RF front-end model of fuze is established by simulation software, and the coupling effect of front-gate of fuze is analyzed by the test method of irradiation before injection. The test results show that the sensing elements of RF front-end of fuze are easy to be damaged by high-power microwave. The damage effect of high-power microwave is more obvious when the rise time of pulse signal is short; and when the distance between HPM source and fuze is long, the normal ranging function of fuze will be disturbed, but the interference effect caused by the change of flat top width of pulse signal is not obvious. Key

Research on Combined Aerodynamic Parameters Identification Using Flight Data of Multiple Projectiles

LIU Yang, CHANG Sijiang, WEI Wei

2020, 41(5):  890-901.  doi:10.3969/j.issn.1000-1093.2020.05.008

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It may run the risk of becoming trapped into a local minimum when local optimization algorithms are used to identify the aerodynamic parameters of multiple projectiles. And the identified results of the same aerodynamic parameter obtained from multiple projectiles are usually discrepant. A global optimization strategy using multiple flight test data for aerodynamic parameters identification is proposed to improve the accuracy and reasonableness of aerodynamic parameters identification for projectiles. A sole global optimal solution can be achieved by obtaining the search space with local optimization algorithm, taking the flight stability of projectiles as the constraint, establishing the cost function by the use of least-square principle, and applying the differential evolution algorithm to the simultaneous global optimization problem for multiple projectiles. The proposed strategy is validated by processing the yaw-card data of a certain large-caliber projectile. The results indicate that, compared to the identification strategies in the current research literature, the proposed strategy is of smaller cost function value and better computational stability, making the reconstructed trajectory closer to the actually measured one.Key

Calibration of Three-axis Fluxgate Magnetometers with Joint Estimation Iterative Algorithm

SUN Huan, YANG Binfeng, GUAN Hua, WANG Run

2020, 41(5):  902-910.  doi:10.3969/j.issn.1000-1093.2020.05.009

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In the process of geomagnetic field measurement, the three-axis magnetometer is affected by various interference factors and produces various errors which have effect on the measurement accuracy. Based on the analysis of the error sources of measured values of geomagnetic field, an integrated model of three-axis magnetometer measurement is established. An joint estimation iterative algorithm is proposed to calibrate three-axis magnetometer. The performances of the proposed algorithm, extended Kalman filter (EKF) algorithm and nonlinear least squares algorithm are compared. Based on the simulated results, an experimental system was build to verify the proposed method. The simulated and experimental results show that, among the three algorithms, the joint estimation iterative algorithm compensates the error mean and standard deviation to the smallest, and its convergence speed is the fastest. The average error of measured values of three-axis magnetometer can be reduced from 142.4 nT to 12.5 nT, the standard deviation can be decreased from 170.0 nT to 29.2 nT, and the suppression ratio is 84.51%, which provides an effective method for the calibration compensation of three-axis magnetometer. Key

Improved Minimum Variance Distortionless Response Algorithm for Multi-mode Clutter Suppression in Multiple-inputMultiple-output Over-the-horizon Radar

HONG Sheng, LI Jie, DONG Yantao, ZHAO Zhixin, WANG Yuhao

2020, 41(5):  911-923.  doi:10.3969/j.issn.1000-1093.2020.05.010

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For multiple-input multiple-output over-the-horizon radar (MIMO-OTHR), the minimum variance distortionless response (MVDR) is usually used to solve the impact of the ionospheric multi-mode clutter in the received echo on the detection of the target. The output signal-to-clutter-plus-noise ratio (SCNR) of traditional MVDR algorithm is low due to the omnidirectional emission of MIMO-OTHR, the inaccurate estimation of interference-noise covariance matrix, and a few training samples within a finite coherent accumulation time. Therefore, the MVDR algorithm is improved to enhance the multi-mode clutter suppression ability of MIMO-OTHR. A transmit beamspace preprocessing is realized by a second order cone programming (SOCP) to focus the energy on the principal mode angle, which is the transmit angle of the target path reflected by the ionosphere. The echo signal received by array is spatially smoothed to suppress the expected signal of principal mode and improve the estimation accuracy of interference-noise covariance matrix. A bi-iterative MVDR beamforming algorithm based on the beamspace preprocessing is proposed to reduce the computational load and the requirement of training samples. Simulated results show that the improved MVDR algorithm can be used to effectively suppress multi-mode clutter, and obtain higher output SCNR with fewer training samples and less computational load. Key

Calibration of Different-source Cameras for Laser Irradiation Performance Measurement

JING Wenbo, HUANG Bingkun, LIU Jian, YU Hongyang

2020, 41(5):  924-931.  doi:10.3969/j.issn.1000-1093.2020.05.011

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Measuring cameras, including visible light camera and near-infrared camera, are used for imaging measurement of vertical target illuminated by a laser irradiator. The visible light camera is used to capture moving targets, and the near-infrared camera is used to take laser irradiation. For the problem that the cassegrain optical system makes the image distorted during measuring and the optical axes of two cameras are not strictly consistent, the influence of the perspective error is neglected in the long-distance measurement, Zhengyou Zhang camera calibration method is improved, so that the distortion factor in the camera parameters is zero and the camera calibration is realized. A near-field calibration method for camera far-field imaging is proposed. According to the spatial perspective relationship between the imaging planes of visible light camera and near-infrared camera, a dual camera axis consistency calibration method is proposed. The re-projection error of visible light camera calibration is 0.08 pixels, the re-projection error of near-infrared camera calibration is 0.19 pixels, and the camera registration axis consistency accuracy is 0.37 μrad, which meet the needs of laser irradiator irradiation accuracy field test. Key

A Fuzzy Comprehensive Evaluation Method for Attack Effectiveness of the Application Layer of Command Information System

HUANG Yingchun， MOU Xinming

2020, 41(5):  932-940.  doi:10.3969/j.issn.1000-1093.2020.05.012

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The service sharing and opening of command information system lead to more service resource damages and information spoofing risk in its application layer attack. For difficult effectiveness evaluation problem due to the incomplete information and uncertainty in offensive and defensive attack of application layer of command information system, a three-level evaluation index system with index factor number of 2+ 5+17 is established for application layer attack of command information system. A two-factor subjective and objective weighting method is presented to determine the evaluation index weights. The theory of BP artificial neural network is used to establish the fuzzy membership function with learning mechanism and continuously improved capability. A fuzzy comprehensive evaluation method is designed for the single attack efficiency and a variety of attack effectiveness. The experimental results show that the proposed method can be used not only to achieve the fuzzy quantization of single attack effect and fuzzy ranking of multiple attacks, but also have more complete index set, more comprehensive weighting method and more applicable fuzzy membership function. Key

Active Distributed Sonar Multi-target Tracking Based on SMC-PHD Filtering

SHAO Pengfei, WANG Lei, WANG Fangyong

2020, 41(5):  941-949.  doi:10.3969/j.issn.1000-1093.2020.05.013

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An active distributed sonar multi-target automatic tracking method based on sequential Monte Carlo and probability hypothesis density (SMC-PHD) filtering is proposed to solve the problems of large number of clutter, targets uncertainty and observation uncertainty. In the proosed method, the random finite set (RFS) model is used to characterize the target state and observation, and the importance sampling and resampling strategy of sequential Monte Carlo (SMC) method is used to realize the transferring and filtering of probability hypothesis density of multi-target posterior. The multi-target tracking based on SMC-PHD filtering with different number of observation nodes is simulated. The results show that the proposed method can be used to effectively realize multi-target automatic tracking in real time in clutter environment with unknown and time-varying multi-targets. In active distributed sonar system with 4 nodes,the proposed method achieves the high-accuracy tracking with distance estimation relative error less than 0.05 and the completely accurate estimation of targets number. Key

Global Stabilization of Underactuated Asymmetric AUVs with Unknown Model Parameters

DI Qing, ZHOU Jingye, FANG Kai, YAO Jiaqi, LI Jiawang

2020, 41(5):  950-957.  doi:10.3969/j.issn.1000-1093.2020.05.014

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A global feedback stabilization algorithm based on asymmetric model is proposed for unknown model parameters in the control of an underactuated asymmetric AUV on the horizontal plane. An adaptive parameter observer is designed to get the estimated values of the real model parameters by knowing only the upper and lower bounds of the model parameters. The coupling effect caused by the asymmetric items is eliminated through global coordinate transformation. The control system is decomposed into propulsion subsystem and yaw subsystem which are designed, respectively. A second-order filter is introduced to keep the yaw rate with continuous excitation as long as the propulsion system does not converge to the origin. Lyapunov stability analysis indicates that the proposed algorithm can be used to realize the stabilization control under any initial condition without knowing the model uncertainties, and the stabilization errors are globally ultimately bounded. The simulated results show that the proposed controller is effective and robust. Key

Behavior Mechanism Equation of Submarine Acoustic Perception Based on Engagement Process

ZHANG Dongjun, LI Xiao, MI Yang

2020, 41(5):  958-966.  doi:10.3969/j.issn.1000-1093.2020.05.015

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The detection ability of submarine is the prerequisite to obtain the operational advantage in the actual combat. Acoustic detection, as the most important sensing detection means of submarine, is closely related to submarine attitude, relative position, combat behavior and environment. Static acoustic detection index dose not meet the requirements for exercise evaluation. Starting from the relationship between submarine motion and sonar detection capability in actual combat, the composite function of submarine motion equation and sonar mechanism equation based on the engagement process is constructed, an acoustic perception interaction mechanism equation is established according to the relationship between them, and then the case verification is made with the navigation test data. The behavior mechanism equation reveals the law of sonar detection ability changing with submarine attitude, space position, speed and other motion variables, which provides the basis for obtaining and utilizing the detection advantages by changing submarine motion state in actual combat, and is conducive to obtain the combat opportunity for the game between friend and foe in the stage of search and perception. Key

Combat Decision and Correlation Analysis of Warship Integrated Defense Torpedo

ZHANG Leixiao， HU Weiwen， SUN Huiling

2020, 41(5):  967-974.  doi:10.3969/j.issn.1000-1093.2020.05.016

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A new style of underwater warship defense is to integrally defend the acoustic self-guided torpedo with depth charge interception and maneuvering evasion. The correlation analysis for the survival probability of warship and the battlefield situation can provide elaborate reference for training analysis, discussion about tactics and even combat decision-making. In the research process of combat simulation and strategy optimization, two combat strategies of “depth charge interception + backward evasion” and “warship maneuvering + depth charge interception” are formed. The applicable regions of the two combat strategies are roughly divided, and the integral defense effects of the two strategies are analyzed by comparing the survival probabilities of warship under different battlefield situations. The numerical analysis examples of critical regions and the combat suggestions under different battlefield situations are given by using gradient analysis and elastic analysis methods, respectively. This study shows that a corresponding superior combat strategy should be adopted under different battlefield situations, especially, for early warning and detection of torpedo in long-distance and horizontal direction. Key

Analysis of the Scattering Properties of Aggregate with Random-sized Particles in Smoke Screen

ZHOU Mengde， LI Jiayu

2020, 41(5):  975-983.  doi:10.3969/j.issn.1000-1093.2020.05.017

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The optimization of extinction performance of particles in smoke screen is studied based on the phenomenon of particle agglomeration in smoke screen. Based on the theory of cluster-cluster aggregation (CCA), the algorithm program of aggregates with random particle size is established to generate the aggregates composed of different sized particles. On the basis of this model, multi-sphere T matrix (MSTM) method is used to calculate and analyze the scattering properties of the aggregates, of which monomer size follows a lognormal distribution of particles in the smoke screen. The results show that the extinction performance of the aggregate is weakened with the increase in particle size dispersion. In the simulated multi-group aggregate particles, the extinction factor of type A aggregate is increased by 30.9% compared with that of type B aggregate, and the overall scattering energy is decreased by 32.5%. The extinction performance of the aggregate in smoke screen can be effectively improved by avoiding an extremely large size monomer particle which size deviates from the mean of lognormal distribution of particles in the aggregates. Key

Fractional Maxwell Model for Oscillating Flow of a Viscoelastic Elastomer Shock Absorber

WANG Zhiqian, MAO Baoquan, ZHU Rui, BAI Xianghua, HAN Xiaoping

2020, 41(5):  984-995.  doi:10.3969/j.issn.1000-1093.2020.05.018

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The viscoelastic elastomer flowing in a shock absorber has a strong viscoelasticity, and the oscillating flow models for simulating and studying a viscoelastic elastomer in the orifice and gap of shock absorber have been rarely reported. A fractional Maxwell model with quasi-property is proposed to study the oscillating flow of a viscoelastic elastomer shock absorber. According to the actual operating conditions of viscoelastic elastomer shock absorber during periodic reciprocating motion, the oscillating flows in both the orifice and gap of a shock absorber were simplified. The real-world initial and boundary conditions were set, and then the numerical solution of the fractional Maxwell model was obtained using the finite difference method. The velocity distributions at different oscillation frequencies and the influences of the parameters on the stress-strain rate curves were analyzed by comparing the fractional Maxwell model with the Newtonian fluid model. The simulated and experimental results indicate that the non-linearity and frequency dependence of the fractional Maxwell model are stronger than those of the Newtonian fluid model; the stress-strain rate distribution curves of the fractional Maxwell model are all elliptic for different parameters; and the ellipse major axes of stress-strain rate curves of the fractional Maxwell model are counterclockwise rotated as fractional order exponents α and β as well as quasi-state property dimensionless coefficient η increase. The proposed fractional Maxwell model can be used to successfully simulate and predict the shapes and changing trends of hysteretic curves, and the relative average error of energy absorption rate is 3.60%. Key

Analysis of Micro-mesoscopic Thermo-structural Characteristics of Component Materials of 4D Carbon/carbon Composites

ZHU Zhaojun, QIANG Hongfu, WANG Zhejun

2020, 41(5):  996-1006.  doi:10.3969/j.issn.1000-1093.2020.05.019

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The micro-mesoscopic morphologies of composites and component materials are characterized experimentally to study the micro-mesoscopic thermo-structural characteristics of component materials of four-directional carbon/carbon (C/C) composites. The equations of periodic temperature boundary conditions for cubic and hexagonal unit cells are derived. A representative volume element (RVE) model of fiber bundle is established. Based on the homogenization theory and periodic boundary conditions, the proposed method for predicting effective thermo-structural parameters is verified on the isotropic RVE model. The thermo-structural characteristics of different types of RVEs of fiber bundle are studied and compared with the experimental results. The results show that scanning electron microscopy (SEM) can be used to obtain the micro-mesoscopic morphologies of fiber bundle and the 4D C/C composites. The fiber monofilaments are randomly distributed in the fiber bundle. The predicted accuracy of different RVEs of fiber bundle is analyzed by using the proposed method. The method is also suitable for predicting the effective thermo-structural properties of other composites. The effective thermo-structural parameters of fiber bundle RVE satisfy the isotropic properties in the transverse direction. Key

Reaserch on Absorption of Gaussian Laser for the Cutting Surface of 45% SiC_p/Al Composites

KONG Xianjun, WANG Minghai, WANG Ben, ZHENG Yaohui, WANG Yang, YANG Lijun

2020, 41(5):  1007-1015.  doi:10.3969/j.issn.1000-1093.2020.05.020

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In order to investigate the temperature variation of cutting surface of 45% SiC_p/Al composites during Gaussian laser irradiating, the temperature variations of 45% SiC_p/Al composites at different phases are calculated based on the Fourier heat transfer theory and the thermal physical properties of silicon carbide particles and aluminum matrix. A finite element model (FEM) is developed for predicting the temperature field in LAM of 45% SiC_p/Al composites. The influence laws of laser power, laser scanning speed, laser spot diameter, and rotational speed on the laser heating temperature field were obtained by FEM simulation. An empirical formula for the temperature at the cutting point from the workpiece surface is established based on the influence law of cutting parameters on heating temperature. The laser assisted cutting experiments of carbide stools and polycrystalline diamond (PCD) cutters are made based on the temperature field obtained by the empirical formula for the temperature at the cutting point. Carbide tools and PCD cutters are used for laser assisted cutting experiment on 45% SiC_p/Al composites. The results indicate that the ratio of aluminum to silicon content is only 1.187, and the absorption rate of laser is 0.21. However, the ratio of aluminum to silicon is 1.047, and the absorption of laser is 0.23 when the PCD cutters are used. Key

Reliability Analysis of Phased-mission System of Systems for Escort Formation Based on BDD

BIAN Ruibing， ZHANG Yang， PAN Zhengqiang， CHENG Zhijun， BAI Senyang

2020, 41(5):  1016-1024.  doi:10.3969/j.issn.1000-1093.2020.05.021

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The escort formation consists of several ships and is a complex equipment system. The escort formation is taken as a research object, and the concept of phased mission system of systems (PMSoS) is proposed based on the phased mission system (PMS). A mission reliability model is established according to the characteristics of escort formation, and the phased fault tree is simplified according to the common failure basic task. On this basis, the binary decision diagram (BDD) modeling method is adopted to analyze the reliable events of each phase for the formation task, and the flow chart and detailed pseudo code implementation of BDD algorithm for solving the reliability to each stage are given. Finally, the reliability of escort mission process is analyzed and evaluated under the assumption that the life of escort formation system obeys the exponential distribution or the Weibull distribution, and the model and method proposed in this paper are verified. Key

Optimization Design of Homing Trajectory of Parafoil System with Five Segments

GAO Feng, GUO Rui, FENG Zhiwei, JIE Jinliang, ZHANG Qingbin

2020, 41(5):  1025-1033.  doi:10.3969/j.issn.1000-1093.2020.05.022

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The parafoil homing trajectory should be processed and optimized in segments in order to realize the accurate airdrop and easy drop-down control during homing. A high precision 9-degree-of-freedom dynamic model of parafoil system is established. A five-segment homing trajectory optimization model is established, in which the minimum energy consumption is taken as the objective function and the time consumption and turning radius are taken as the input variables. The optimal reference path of homing is given by using the five-segment homing trajectory as the initial condition and using the pseudo-spectral method to optimize the trajectory, and the energy losses in the five-segment homing and direct homing processes are compared and analyzed. The simulated results show that the five-segment homing trajectory optimization strategy proposed in this paper has the advantage of simple control function form and easy application. Key

Research Notes

The Detection of Solidifying Point Temperature of TNT Using Fourier Transform Near-infrared Spectroscopy

GAO Jiaming, SHE Chongchong, CHEN Jun, LI Min, HOU Yunhui, CHEN Lizhen, WANG Jianlong

2020, 41(5):  1034-1040.  doi:10.3969/j.issn.1000-1093.2020.05.023

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In order to detect the solidifying point temperature in TNT production process in real time, the partial least squares method is used to establish a quantitative model for real-time detection of TNT solidifying point by near-infrared spectroscopy combined with chemometrics and spectroscopy. A model established by the preprocessing method with the modeling interval of 9 403.8-4 597.7 cm^-1 and the first-order derivative (17-point smoothing)+SNV is the best compared with six preprocessing methods optimized for the original spectral data. The six methods are standard normal variable transformation (SNV), multiple scattering correction (MSC), first derivative, first derivative + standard normal variable transformation (SNV), first derivative + multiple scattering correction (MSC), and second derivative. The correlation coefficient of the model is R²=0.991, and the root-mean-squares error of cross-validation is 0.178. The results of principal component analysis and model validation show that the maximum deviation between the predicted value of near infrared analysis and the measured value is 0.950 4% when the optimal model is used to predict the solidifying point temperature of nitrates on different samplers. The model has good stability and predictability, and can identify different types of samplers. The solidifying point can be determined by near infrared spectroscopy in a short time. Key