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Model of CEL for 3D Elements in PDMs of Unidirectional Composite Structures

Computer Modeling in Engineering & Sciences 2019年第1期118卷 157-176页

作者： Tianliang Qin Libin Zhao Jifeng Xu Fengrui Liu Jianyu Zhang Beijing Key Laboratory of Civil Aircraft Structures and Composite Materials BASTRI of COMACBeijing102211China School of Astronautics Beihang UniversityBeijing100191China Key Laboratory of Spacecraft Design Optimization and Dynamic Simulation Technologies Minisitry of EducationBeihang UniversityBeijing 100191China State Key Laboratory for Strength and Vibration of Mechanical Structures Xi'an Jiaotong UniversityXi'an 710049China College of Aerospace Engineering Chongqing UniversityChongqing400044China.

Progressive damage models(PDMs)have been increasingly used to simulate the failure process of composite material *** accurately simulate the damage in each ply,3D PDMs of composite materials have received more attention recently.A characteristic element length(CEL),which is an important dimensional parameter of PDMs for composite materials,is quite difficult to obtain for 3D elements,especially considering the crack directions during damage *** this paper,CEL models for 3D elements in PDMs of unidirectional composite structures are presented,and their approximate formulae are *** damage in unidirectional composite materials can be divided into fiber cracks and inter-fiber *** fiber crack and inter-fiber crack directions are considered in the CEL derivations,and thus,the CELs of 3D elements that have various damage modes and damage directions could be obtained relatively *** tensile and compressive tests of open-hole laminates were conducted,and the corresponding numerical analyses by the progressive damage method,including the proposed CEL models and those models from the literature,were *** numerical results are in good agreement with the experimental results,which proves the fidelity and effectiveness of the proposed CEL *** addition,the proposed CEL models have better performance in improving the mesh independence of the numerical models.

关键词： Laminates finite element analysis(FEA) mechanical testing progressive damage analysis CEL.

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MOVING SHIP DETECTION and MOVEMENT PREDICTION in REMOTE SENSING VIDEOS 24

MOVING SHIP DETECTION and MOVEMENT PREDICTION in REMOTE SENS...

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2020 24th ISPRS Congress - Technical Commission II

作者： Wang, Y. Cheng, H. Zhou, X. Luo, W. Zhang, H. Department of Aerospace Information Engineering School of Astronautics Beihang University Beijing102206 China Beijing Key Laboratory of Digital Media Beijing102206 China Key Laboratory of Spacecraft Design Optimization and Dynamic Simulation Technologies Ministry of Education Beijing102206 China

With the rapid development of remote sensing technology, it is possible to obtain continuous video data from outer space successfully. It is of great significance in military and civilian fields to detect moving objects from the remote sensing image sequence and predict their movements. In recent years, this issue has attracted more and more attention. However, researches on moving object detection and movement prediction in high-resolution remote sensing videos are still in its infancy, which is worthy of further study. In this paper, we propose a ship detection and movement prediction method based on You-Only-Look-Once (YOLO) v3 and Simple Online and Realtime Tracking (SORT). Original YOLO v3 is improved by multi-frame training to fully utilize the information of continuous frames in a fusion way. The simple and practical multiple object tracking algorithm SORT is used to recognize multiple targets detected by multi-frame YOLO v3 model and obtain their coordinates. These coordinates are fitted by the least square method to get the trajectories of multiple targets. We take the derivative of each trajectory to obtain the real-time movement direction and velocity of the detected ships. Experiments are performed on multi-spectral remote sensing images selected on Google Earth, as well as real multi-spectral remote sensing videos captured by Jilin-1 satellite. Experimental results validate the effectiveness of our method for moving ship detection and movement prediction. It shows a feasible way for efficient interpretation and information extraction of new remote sensing video data. © 2020 International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences - ISPRS Archives.

关键词： Remote sensing

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design optimization of a low-cost three-stage launch vehicle with modular hybrid rocket motors 2

Design optimization of a low-cost three-stage launch vehicle...

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2023 2nd International Conference on Aerospace and Control Engineering, ICoACE 2023

作者： Wenzhi, Hao Hao, Zhu Wei, He Zhiguo, Zhang School of Astronautics Beihang University Beijing100191 China Key Laboratory of Spacecraft Design Optimization and Dynamic Simulation Technologies Ministry of Education Beijing100091 China Yu Menglun Intelligent Rocket Laboratory Institute of Astronautical Systems Engineering Beijing100076 China

This article investigates the impact of modular propulsion system design on the performance and cost of a three-stage hybrid rocket. Furthermore, it conducts a multi-objective optimization of unit payload cost, take-off mass, and payload mass ratio, considering factors such as the number of motors and layout considerations. The optimization design scheme for the three-stage hybrid rocket is divided into four cases. In the first case, each stage is equipped with a fixed single motor, and each stage is independently optimized without modular design. The second case considers the use of multiple motors in the first and second stages, still without modular design. The third case also involves multiple motors in the first and second stages, but all motors in each stage have identical parameters except for the nozzle expansion ratio, implementing a modular design. In the fourth case, the number and layout of the motor design method are the same as those in the third case, with independent optimization in the third stage using partial modular design. The results indicate that the unit payload cost of the multi-motor non-modular design case can be reduced by 13.12% compared to the single-motor non-modular design case. Within the modular case, the full modular design case is slightly inferior to the partial modular design case. Based on the above data, it can be concluded that the first and second stages of modular rockets offer the best performance and the lowest cost. © Published under licence by IOP Publishing Ltd.

关键词： Multiobjective optimization

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The azimuthal currents in the ion-driven magnetic nozzle

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Propulsion and Power Research 2022年第4期11卷 457-472页

作者： Zhiyuan Chen Yibai Wang Haibin Tang Junxue Ren Min Li Peng Wu Jinbin Cao School of Astronautics Beihang UniversityBeijing102206China Key Laboratory of Spacecraft Design Optimization and Dynamic Simulation Technologies Ministry of EducationBeijing102206China Laboratory of Space Environment Monitoring and Information Processing Ministry of Industry and Information TechnologyBeijing102206China Innovation Academy of Microsatellites Chinese Academy of SciencesShanghai201203China School of Space and Environment Beihang UniversityBeijing102206China

Ion-driven magnetic nozzles(Ti>Te)are designed as intrinsic parts of cutting-edge propulsive technologies such as variable specific impulse magnetoplasma rockets(VASIMRs)and applied-field magnetoplasmadynamic *** a two-dimensional axisymmetric particle-in-cell(PIC)code,in the ion-driven magnetic nozzle,the compositions and distributions of azimuthal currents in different axial regions are investigated under various inlet ion temperatures Ti0 and found to differ dramatically from that in the electron-driven magnetic *** reported to be all paramagnetic and vanishing under a high magnetic field,the azimuthal currents resulting from the E 3 B drift are shown to turn diamagnetic and sustain a considerable magnitude when Ti0 is *** previously reported profile of diamagnetic drift current is altered by the introduction of inlet ion temperature,and the paramagnetic part is significantly ***,a wide range of paramagnetic currents appear downstream due to the inward detachment of ions,which can also be reduced by increasing inlet ion *** considered in this paper,the azimuthal currents resulting from grad-B and curvature drift are still negligible in all cases of *** magnitude of diamagnetic azimuthal currents increases with amplifying Ti0,indicating a clear physical image of energy transformation from ion thermal energy to the directed kinetic energy through electromagnetic processes in the magnetic ***,the magnetic inductive strength also has noticeable impacts on the azimuthal currents,the current magnitude tends to decrease as the magnetic field increases,and over-increment of it may result in larger divergence angles and lower nozzle efficiency.

关键词： Magnetic nozzle Azimuthal current Ion temperature Electric propulsion

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A plasma equilibrium model for rapid estimation of SF-MPDT performance

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Plasma Science and technology 2021年第10期23卷 40-48页

作者： Yifeng Fu Cheng Zhou Peng Wu Zhongkai Zhang Zun Zhang Haibin Tang School of Space and Environment Beihang UniversityBeijing 100191People's Republic of China Beijing Institute of Control Engineering Beijing 100094People’s Republic of China School of Astronautics Beihang UniversityBeijing 100191People’s Republic of China Key Laboratory of Spacecraft Design Optimization&Dynamic Simulation Technologies Ministry of EducationBeijing 100083People’s Republic of China Laboratory of Space Environment Monitoring and Information Processing Ministry of Industry and Information TechnologyBeijing 100083People's Republic of China

In this work, a zero-dimensional plasma model for self-field magnetoplasmadynamic thrusters(SF-MPDTs) is proposed, which is based on the ion-number balance equation and energy balance equation, and can calculate the average electron temperature and the average ion temperature inside the discharge chamber conveniently. At the same time, the model can also predict the thruster performance, and the thruster performance predicted by the model is compared with experimental results, which proved the reliability of the model.

关键词： SF-MPDT plasma equilibrium diffusion equation thruster parameters

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Cathode erosion site distributions in an applied-field magnetoplasmadynamic thruster

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Plasma Science and technology 2020年第9期22卷 59-65页

作者： Peng WU Yibai WANG Yong LI Baojun WANG Kaiyu ZHANG Haibin TANG Jinbin CAO School of Astronautics Beihang UniversityBeijing 100191People's Republic of China Beijng Institute of Control Engineering Beijing 100190People’s Republic of China School of Space and Environment Beihang UniversityBeijing 100191People's Republic of China Key Laboratory of Spacecraft Design Optimization&Dynamic Simulation Technologies Ministry of EducationBeijing 100083People’s Republic of China Laboratory of Space Environment Monitoring and Information Processing Ministry of Industry and Information TechnologyBeijing 100083People's Republic of China

Erosion can influence cathode life,and is thus considered to be one of the main factors limiting the application of applied-field magnetoplasmadynamic *** this paper,erosion sites on graphite cathodes are studied so as to identify the influence of applied magnetic field and the ratio of propellant mass flow rate supplied from cathode and *** experiment results show that the application of applied magnetic field can significantly reduce the erosion rate of the cathode compared to that without magnetic *** erosion sites on the cathode vary with the relative position of the convergent-divergent magnetic field,and are mainly distributed in the divergent part of the *** erosion sites on the cathodes are found to be related to the propellant *** decreasing anode mass flow rate enlarges the range of *** results are much helpful for the analysis of cathode erosion site location since they provide evidences of erosion mechanisms and point out the directions for further research.

关键词： electric propulsion applied-field magnetoplasmadynamic thruster cathode erosion magnetic field propellant mass flow rate

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A Ply-By-Ply Discretized 2D FEA Approach with the Integrated XFEM-CE Strategy for Predicting Multiple Failures in Laminated Composite Structures

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Computer Modeling in Engineering & Sciences 2019年第7期120卷 215-234页

作者： Yana Wang Ruodi Jia Fengrui Liu School of Astronautics Beihang UniversityBeijing100191China Aeronautical Material Testing Research Center AECC Beijing Institute of Aeronautical MaterialsBeijing100095China Beijing Key Laboratory of Aeronautical Material Testing and Evaluation Beijing100095China Key Laboratory of Aeronautical Material Testing and Evaluation Aero Engine Corporation of ChinaBeijing100095China Key Laboratory of Spacecraft Design Optimization and Dynamic Simulation Technologies Minisitry of EducationBeihang UniversityBeijing100191China State Key Laboratory for Strength and Vibration of Mechanical Structures Xi’an Jiaotong UniversityXi’an710049China.

Delamination and matrix cracking are two common failure mechanisms in composite structures,and are usually coupled with each other,leading to multiple failures *** paper proposed a fast damage prediction methodology for composite laminated structures based on the ply-by-ply 2D(two dimensional)FE model of composite laminates in the transverse *** layer-wise 2D FE model was firstly used in conjunction with the integrated XFEM/CE strategy,which simulated the interface delamination with cohesive elements and the intra-ply matrix crack with XFEM(extended finite element method).To realize ply-by-ply 2D FE(finite element)modeling of composite laminates,two 2D material models were developed based on the plane stress assumption and plane strain assumption,respectively.A general crack propagation scheme was developed in the framework of the integrated XFEM-CE *** the 2D material model based on the plane strain assumption,a ply-by-ply discretized 2D FEA procedure was conducted for an out-of-plane composite Pi joint under the static tensile *** predicted load-displacement response and damage evolution process showed good agreement with the experimental results,which verified the proposed approach.

关键词： Composites laminate strength finite element analysis

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On the Effect of Cavity Shape and Size on Rarefied Hypersonic Flows

SSRN

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SSRN 2022年

作者： Jiang, Qihan Cai, Guobiao Chen, Yatao Yuan, Junya He, Bijiao Liu, Lihui School of Astronautics Beihang University Beijing100191 China Key Laboratory of Spacecraft Design Optimization and Dynamic Simulation Technologies Ministry of Education Beijing100191 China

Cavity structures are frequently encountered on hypersonic vehicle surfaces, which change the aerodynamic heat flux and force (pressure) compared with flat vehicle surfaces. The effects of the cavity lengthto-depth ratio, cavity rounded corners, Maxwellian accommodation coefficient, and free-stream Knudsen number on the heat flux and pressure loaded on the vehicle surface with rectangular cavities have been studied extensively. Still, the influence of the cavity shape and size remains. In this study, the effects of cavity shape and size on the flow field characteristics, aerodynamic surface quantities, as well as overall aerodynamic heat flux and force loaded on the surface are analyzed using the direct simulation Monte Carlo method. The rectangular cavities with sidewall angles (α) of 0◦, 15◦, 30◦, and 45◦ are selected to investigate the shape influence, and the semicircular cavities with radii (R) of 3, 6, 9, and 12 mm are chosen for size effect. The results indicate that the gas flows over the cavity configurations specified in our study hold the "open-cavity" characteristics. The vortexes formed inside the cavity are shrunk as α increases from 0◦ and 45◦, but they are similar under the R-range explored. The pressure, skin friction, and heat transfer coefficients over the surface display complex trends as varying α and R. In addition, the results reveal that the overall aerodynamic heat flux is dramatically influenced by α and R, while the aerodynamic force is mildly affected. Overall, the larger the α and R, the greater the effect of the cavity on the rarefied hypersonic flows. Our research is beneficial to the protection and optimal design of hypersonic vehicles. © 2022, The Authors. All rights reserved.

关键词： Hypersonic flow

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Modular design of A Radial Scalled Hall Thruster for Different Magnetic Configurations

Modular Design of A Radial Scalled Hall Thruster for Differe...

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International Conference on Pulsed Power

作者： A. Olano H. Tang J. Ren G. Zhang J. Li Key Laboratory of Spacecraft Design Optimization & Dynamic Simulation Technologies of Ministry of Education School of Astronautics Beihang University Beijing People's Republic of China Key Laboratory of Spacecraft Design Optimization & Dynamic Simulation Technologies of Ministry of Education School of Space and Environment Beihang University Beijing People's Republic of China Science and Technology on Vacuum Technology and Physics Laboratory Lanzhou Institute of Physics Lanzhou People's Republic of China

ISBN: (数字)9781538679692

ISBN: (纸本)9781538679708

A 100 W radial scaled Hall Thruster has been designed and manufactured using as reference design the D-55 thruster with anode layer (TAL). The magnetic field required is provided by permanent magnets following a modular design in order to compare three different magnetic field configurations: A) nominal, B) orthogonal magnetic field and C) high magnetic field. In Hall Thrusters the magnetic field is used to confine the electrons and create highly ionized plasma. Configuration A and configuration B were chosen to compare two different topographies of the magnetic field with two different magnetic field gradients and to study their influence in the plasma discharge and thruster performance. Both configurations where derived assuming Bohm diffusion as the dominant process in the plasma discharge. If instead of Bohm diffusion it is considered electron-wall collisions as main mechanism in the electron transport then a higher magnetic field is required and in consequence configuration C was designed. These three configurations are intended to provide a better understanding of the influence of the magnetic field in the thruster discharge.

关键词： Magnetic fields Discharges (electric) Plasmas Anodes Surfaces Permanent magnets Propulsion

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design and fabrication of a full elastic sub-micron-Newton scale thrust measurement system for plasma micro thrusters

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Plasma Science and technology 2021年第10期23卷 29-39页

作者： Zhongkai Zhang Guanrong Hang Jiayun Qi Zun Zhang Zhe Zhang Jiubin Liu Wenjiang Yang Haibin Tang School of Space and Environment Beihang UniversityBeijing 100191People's Republic of China Shanghai Institute of Space Propulsion Shanghai Engineering Research Center of Space EngineShanghai 201112People's Republic of China School of Astronautics Beihang UniversityBeijing 100191People's Republic of China The Institute of Space Systems University of StuttgartStuttgart D-70569GermanyBeijing 100083People's Republic of China Key Laboratory of Spacecraft Design Optimization&Dynamic Simulation Technologies Ministry of EducationBeijing 100083People's Republic of China Laboratory of Space Environment Monitoring and Information Processing Ministry of Industry and Information TechnologyBeijing 100083People’s Republic of China

In this work,a force measurement system is proposed to measure the thrust of plasma microthruster with thrust magnitude ranging from sub-micro-Newtons to hundreds *** thrust measurement system uses an elastic torsional pendulum structure with a capacitance sensor to measure the displacement,which can reflect the position change caused by the applied force perpendicular to the pendulum *** the open-loop mode,the steady-state thrust or the impulse of the plasma micro-thruster can be obtained from the swing of the pendulum,and in the closed-loop mode the steady-state thrust can be obtained from the feedback force that keeps the pendulum at a specific *** thrust respond of the system was calibrated using an electrostatic weak force generation *** results show that the system can measure a thrust range from 0 to 200μN in both open-loop mode and closed-loop mode with a thrust resolution of 0.1μN,and the system can response to a pulse bit at the magnitude of 0.1 m N s generated by a micro cathode arc *** background noise of the closed-loop mode is lower than that of the open-loop mode,both less than 0.1 m N/Hz in the range of 10 mHz to 5 Hz.

关键词： plasma thruster micro-thrust measurement torsional pendulum

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