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Ablative behavior and mechanism of SiC_(f) /SiBCZr composites prepared by PIP process

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Journal of Advanced Ceramics 2024年第1期13卷 124-134页

作者： Mingwei Chen Yuliang Zhao Haipeng Qiu Shijian Liu Weijie Xie Yi Chen Qiyue Zhang avic Manufacturing Technology institute Beijing 100130China

SiC_(f)/SiBCZr composites were prepared by polymer precursor impregnation and pyrolysis process with near stoichiometric ratio SiC fiber preform as reinforcement phase and SiBCZr multiphase ceramic precursor as impregnating *** results highlighted that the SiC_(f)/SiBCZr composites exhibited excellent ablative properties after ablative tests at 1200℃/3600 s and 1400℃/3600 s,and the strength retention rates of the composites reached 90%and 85%,*** was mainly due to the liquid sealing effect of the ablative products represented by B2O_(3) and SiO_(2)∙B_(2)O_(3),which inhibited the ablative reaction by reducing the diffusion rate of the oxidation medium,and the solid pinning effect of the substances represented by SiO_(2),ZrO_(2),and ZrSiO_(4),which could play high viscosity and high strength characteristics to improve anti-erosion *** above-mentioned SiC_(f)/SiBCZr composites with corrosion resistance,oxidation resistance,and ablative resistance provided a solid material foundation and technical support for the development of reusable spacecraft hot-end components.

关键词： near stoichiometric ratio SiC fiber SiC_(f)/SiBCZr composite liquid sealing effect solid pinning effect

Adaptive PI Control Based Stability Margin Configuration of aircraft Control Systems with Unknown System Parameters and Time Delay

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Journal of Systems Science & Complexity 2024年第4期37卷 1507-1525页

作者： ZHANG Zhibing ZHOU Dapeng WANG Yeguang GAO Wanxin ZHANG Yanjun avic Shenyang aircraft Design and Research institute Shenyang 110035China School of Automation Beijing Institute of TechnologyBeijing 100081China State Key Lab of Autonomous Intelligent Unmanned Systems Beijing Institute of TechnologyBeijing 100081China

The stability margin is a vital indicator for assessing the safety level of aircraft control *** should maintain sufficient stability margin to ensure safety during flight,especially in the process of large maneuver *** stability margin is generally quantified by the Bode diagram,which strictly depends on the system parameters and the open-loop transfer ***,due to the uncertain flight environments,transmission delays of sensors and mode switchings,etc.,there exist large parameter and structure uncertainties in the aircraft control systems,which make it difficult to precisely configure the stability margin to the desired value by the usual control *** address this problem,an indirect adaptive control strategy is proposed in this paper,where an adaptive PI control law with the capability of self-configuration of stability margin is *** developed control law not only achieves stable time-varying command tracking in the time domain,but also is able to automatically configure the phase margin and gain margin in the frequency ***,the simulation of the one-degree-of-freedom roll rate control model of the air vehicle verifies the validity of the proposed control method.

关键词： Adaptive control aircraft control parameter uncertainty stability margin configuration

Superplastic Tension Behavior of Dissimilar TC4/SP700 Laminate through Diffusion Bonding

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Acta Metallurgica Sinica(English Letters) 2024年第2期37卷 353-363页

作者： Qianwen Zhang Tianle Li Yanbin Han Wei Zheng Xifeng Li Jianjun Wu School of Mechanical Engineering Northwestern Polytechnical UniversityXi’an710072China avic Xi’an aircraft Industry Group Company Ltd Xi’an710089China institute of Forming Technology and Equipment School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai200030China

Superplastic forming is a practical method to manufacture complex-shaped parts of titanium alloys with large *** parts of dissimilar titanium alloys fabricated by superplastic forming can achieve excellent performance by combining the advantages of *** work displays the superplastic tension behavior and microstructural evolution of dissimilar TC4/SP700 laminate prepared by the diffusion bonding *** titanium alloys can achieve metallurgical bonding at parameters of 800℃/1 h/5 *** for dynamic recrystallization and grain growth behaviors upon superplastic tension,stress-induced phase transformation plays an important role inαtoβphase transformation apart from the elevated *** superplastic deformation can be attributed to the grain boundary sliding accommodated multiplex motion of *** addition,the retained strengths of all dissimilar TC4/SP700 laminates after superplastic deformation with different strain rates and temperatures range from 807 to 890 MPa.

关键词： TC4/SP700 laminate Diffusion bonding Microstructure Superplastic tension Strength

Improving strength-ductility synchronously of Electron beam welded Ti600/Ti2AlNb joint through isothermal forging

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Progress in Natural Science:Materials International 2024年第3期34卷 532-539页

作者： Yongqiang Zhang Xiangyi Xue Guoming Zheng Jingli Zhang Huiming Li Shewei Xin State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi'an Qin Ti Intelligent Manufacturing Technologies Co.Ltd. Northwest institute for Nonferrous Metal Research Xi'an University of Science and Technology avic Xi'an aircraft Industry Group Company Ltd.

Different alloys can be flexibly combined to meet the performance needs of different parts of the compressor disc by welding process. However, achieving a good combination of dissimilar alloys with different mechanical properties has always been a research difficulty. In this work, a Ti600/Ti2AlNb joint was fabricated through electron beam welding and an isothermal forging was used to optimized its microstructure and mechanical performance. The isothermal forging process increases the ultimate tensile strength（UST） and yield strength（YS）of the Ti600/Ti2AlNb joint by ～18 %, while ～2.5 times the ductility. It is indicated that before forging, the Ti600/Ti2AlNb joint exhibits a much lower strength than that of Ti600 matrix, whereas the opposite is true after isothermal forging. The isothermal forging broken the coarse columnar grains of Ti600/Ti2AlNb joint and render to an equiaxed B2 structure in which the acicular α2and O phase are precipitated, resulting a synchronous enhancement of strength and ductility. This work may pave an effective routine for improving the comprehensive mechanical properties of dissimilar metal welding joint.

关键词： Electron beam welding Isothermal forging Mechanical performance Ti600/Ti2AlNb joint

Drogue detection for autonomous aerial refueling via hybrid pigeon-inspired optimized color opponent and saliency aggregation

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Chinese Journal of Aeronautics 2024年第5期37卷 27-38页

作者： Tongyan WU Haibin DUAN Yanming FAN State Key Laboratory of Virtual Reality Technology and Systems School of Automation Science and Electrical EngineeringBeihang UniversityBeijing 100083China Virtual Reality Fundamental Research Laboratory Department of Mathematics and TheoriesPeng Cheng LaboratoryShenzhen 518000China avic Shenyang aircraft Design and Research institute Shenyang 110035China

Drogue detection is one of the challenging tasks in autonomous aerial refueling due to the requirement for accuracy and *** detection based on image intrinsic cues can achieve fast detection,but with poor *** studies reveal that optimization-based methods provide accurate and quick solutions for saliency *** paper presents a hybrid pigeon-inspired optimization method,the optimized color opponent,that aims to adjust the weight of color opponent channels to detect the drogue *** can optimize the weights in the selected aerial refueling scene offline,and the results are applied for drogue detection in the scene.A novel algorithm aggregated by the optimized color opponent and robust background detection is presented to provide better precision and *** results on benchmark datasets and aerial refueling images show that the proposed method successfully extracts the saliency region or drogue and exhibits superior performance against the other saliency detection methods with intrinsic *** algorithm designed in this paper is competent for the drogue detection task of autonomous aerial refueling.

关键词： Autonomous aerial refueling Drones Hybrid pigeon-inspired optimization Color opponent Saliency detection Saliency aggregation

Study of Flow and Heat Transfer in an Ejector-Driven Swirl Anti-Icing Chamber

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Fluid Dynamics & Materials Processing 2024年第5期20卷 989-1014页

作者： Yi Tu Yuan Wu Yu Zeng Hunan University of Arts and Sciences Hunan Key Laboratory of Distributed Electric Propulsion Vehicle Control TechnologyChangde415000China Liaoning Provincial Key Laboratory of aircraft Ice Protection AVIC Aerodynamics Research InstituteShenyang110034China School of Aeronautic Science and Engineering Beihang UniversityBeijing100191China

The formation of ice on the leading edge of aircraft engines is a serious issue,as it can have catastrophic *** Swirl Anti-Icing(SAI)system,driven by ejection,circulates hot fluid within a 360°annular chamber to heat the engine inlet lip surface and prevent *** study employs a validated Computational Fluid Dynamics(CFD)approach to study the impact of key geometric parameters of this system on flow and heat transfer characteristics within the anti-icing ***,the entropy generation rate and exergy efficiency are analyzed to assess the energy utilization in the *** research findings indicate that,within the considered flow range,reducing the nozzle specific areaφfrom 0.03061 to 0.01083 can enhance the ejection coefficient by over 60.7%.This enhancement increases the air circulating rate,thereby intensifying convective heat transfer within the SAI ***,the reduction inφalso leads to a significant increase in the required bleed air pressure and a higher entropy generation rate,indicating lower exergy *** nozzle angleθnotably affects the distribution of hot and cold spots on the lip surface of the SAI ***θfrom 0°to 20°reduces the maximum temperature difference on the anti-icing chamber surface by 60 K.

关键词： Swirl anti-icing heat transfer exergy efficiency hot and cold spot aircraft engine

Real-time UAV path planning based on LSTM network

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Journal of Systems Engineering and Electronics 2024年第2期35卷 374-385页

作者： ZHANG Jiandong GUO Yukun ZHENG Lihui YANG Qiming SHI Guoqing WU Yong School of Electronics and Information Northwestern Polytechnical UniversityXi’an 710129China The Flight Automatic Control Research institute of avic Xi’an 710065China Military Representative Office of Marine Wuhan Bureau in Luoyang Area Luoyang 471000China

To address the shortcomings of single-step decision making in the existing deep reinforcement learning based unmanned aerial vehicle(UAV)real-time path planning problem,a real-time UAV path planning algorithm based on long shortterm memory(RPP-LSTM)network is proposed,which combines the memory characteristics of recurrent neural network(RNN)and the deep reinforcement learning *** networks are used in this algorithm as Q-value networks for the deep Q network(DQN)algorithm,which makes the decision of the Q-value network has some *** to LSTM network,the Q-value network can use the previous environmental information and action information which effectively avoids the problem of single-step decision considering only the current ***,the algorithm proposes a hierarchical reward and punishment function for the specific problem of UAV real-time path planning,so that the UAV can more reasonably perform path *** verification shows that compared with the traditional feed-forward neural network(FNN)based UAV autonomous path planning algorithm,the RPP-LSTM proposed in this paper can adapt to more complex environments and has significantly improved robustness and accuracy when performing UAV real-time path planning.

关键词： deep Q network path planning neural network unmanned aerial vehicle(UAV) long short-term memory(LSTM)

Investigation on Temperature Field Calibration and Analysis of Wind Tunnel

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Journal of Harbin institute of Technology(New Series) 2024年第3期31卷 63-79页

作者： Zhaokun Ren Zhanyuan Ma Yue Zhang Hongda Xu Yunxiang Wang Hui Xu avic Aerodynamic Research institute Harbin 150001China

For wind tunnels,it is essential to conduct temperature and flow field calibration on their test section,which is an important indicator for evaluating the quality of wind tunnel flow *** the paper,a truss composed of temperature sensors was used to calibrate the temperature field of a completed wind tunnel *** adjusting the distance between the temperature measurement truss and the nozzle,as well as the wind speed,the temperature field distribution data at different positions could be *** these data to identify important factors that affect the distribution of temperature ***,the temperature field of the wind tunnel was simulated *** purpose is to further analyze the fluid heat transfer between air and wind tunnel walls through numerical *** the above analysis methods,the quality of the temperature field in the wind tunnel has been further verified,providing reference for future wind tunnel tests of relevant models.

关键词： wind tunnel temperature field numerical simulation fluid heat transfer

Optimal confrontation position selecting games model and its application to one-on-one air combat

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Defence Technology（防务技术） 2024年第1期31卷 417-428页

作者： Zekun Duan Genjiu Xu Xin Liu Jiayuan Ma Liying Wang School of Mathematics and Statistics Northwestern Polytechnical UniversityXi'an 710072China International Joint Research Center on Operations Research Optimization and Artificial IntelligenceXi'an 710129China avic Xi’an Aeronautics Computing Technique Research institute Xi'an 710065China Unmanned System Research institute Northwestern Polytechnical UniversityXi'an 710072China

In the air combat process,confrontation position is the critical factor to determine the confrontation situation,attack effect and escape probability of ***,selecting the optimal confrontation position becomes the primary goal of maneuver *** taking the position as the UAV’s maneuver strategy,this paper constructs the optimal confrontation position selecting games(OCPSGs)*** the OCPSGs model,the payoff function of each UAV is defined by the difference between the comprehensive advantages of both sides,and the strategy space of each UAV at every step is defined by its accessible space determined by the *** we design the limit approximation of mixed strategy Nash equilibrium(LAMSNQ)algorithm,which provides a method to determine the optimal probability distribution of positions in the strategy *** the simulation phase,we assume the motions on three directions are independent and the strategy space is a cuboid to simplify the *** simulations are performed to verify the feasibility,effectiveness and stability of the algorithm.

关键词： Unmanned aerial vehicles(UAVs) Air combat Continuous strategy space Mixed strategy Nash equilibrium