Abstract:Military aircraft is characterized by outstanding comprehensive performance, considerable technical difficulties and high demand for precision and quality. With the ever-increasing requirements of military aircraft development, digital technologies have become an important means of improving the comprehensive performance, enhancing the manufacturing quality, shortening the test cycle and reducing the development cost by virtue of openness, agility and collaboration. This paper reviews the digital development history of military aircraft both at home and abroad and summarizes the digital collaborative development system features taking shape in the development of China"s military aircraft represented by J-20 fighter jet. Based on the challenges presented by the future development trend of military aircraft to the existing digital technologies as well as the requirements for innovation and progress, this paper proposes a transformation from "digital" development to "agile" development and puts forward the key technologies and outlook for digital agile development of future military aircraft from the aspects of performance, manufacturing and testing.

Abstract:Aerodynamic stealth design is a key technology for aircraft to realize efficient combat in high-risk environments, and it has been a hot technology researched by aviation powers for a long time. This paper combines the group"s many years of experience in aerodynamic stealth design and the demand for aerodynamic stealth design in recent years, summarizes and analyzes the development history and current research status of the aerodynamic stealth design of overall aerodynamic layout, the aerodynamic stealth design of wing and the aerodynamic stealth design of air intake and exhaust system. According to the current research status, three key technologies for comprehensive and optimal aerodynamic stealth design are sorted out: efficient parameterization technology for complex shape, aerodynamic stealth refinement design technology, and integrated aerodynamic stealth design technology for internal and external flow. Finally, combined with the design requirements of aerodynamic stealth for future aircraft, four key research directions are proposed: aerodynamic electromagnetic infrared integrated stealth design, aerodynamic stealth design considering coating, aerodynamic/stealth structure integrated design, and active flow control stealth integrated design.

Abstract:Bionics is a systematic science that imitates or characterizes natural systems. The application of bionic technology to aircraft design provides a new principle and technical support for the improvement of aerodynamic performance, reduction of structural weight, which has a broad application prospect. In this paper, firstly, based on the demand for improving aircraft performance, the application of bionic technology in aviation engineering is classified, and the bionic biological prototypes, typical features, and bionic functions of bionic technology in aerodynamic morphology, aerodynamic drag reduction and noise reduction, bionic structural layout, and bionic lightweight structures of aircraft are summarized. Then application of aero-bionics and structure bionics of aircraft is overviewed. Finally, the potential application direction of bionic technology in aircraft is prospected, including comprehensive design of bionic lift and drag reduction, multi-scale and multi-level bionic lightweight design, integrated design of bionic structure and function, etc., which provides reference for the application of bionic technology in aeronautical engineering.

Abstract:Radar and communication are the "clairwise eyes" and "wind ears" on the battlefield, which play a very important role in modern information war. Anti-radiation unmanned aerial vehicle(UAV)is a weapon system that can suppress and destroy radar and communication targets for a long time, and is an indispensable electronic warfare "hard kill In this paper, the general situation, key technology and development prospect of anti-radiation UAV are discussed. Firstly, the definition, characteristics and advantages of anti-radiation UAV are given, and the differences between anti-radiation UAV and anti-radiation missile in design concept, operational use and tactical purpose are analyzed. Then the development of anti-radiation UAV and its development in the world"s major military powers are introduced. The main key technologies to be solved in the development of anti-radiation UAV equipment are analyzed and summarized. Finally, the future development trend of anti-radiation UAV is prospected. With the development and application of autonomous technology, intelligent technology and swarm technology, the new generation of anti-radiation UAV will be a new combat equipment with new quality combat effectiveness on the battlefield.

Abstract:The high-frequency vibration problem of structures seriously affects the service safety, reliability and comfort of the aircraft. It is of great academic value and engineering significance to predict the high-frequency vibration response of structures efficiently and accurately. The energy finite element method (EFEM) is a new method developed in recent years to predict high-frequency vibration response. It overcomes the shortcomings of traditional methods such as the finite element method (FEM) and the statistical energy analysis (SEA) in predicting high-frequency vibration response. In this paper, the research progress of the energy finite element method in recent years are reviewed. The basic theory of the energy finite element method and its extension and application in engineering are elaborated. Studies of the energy finite element method in predicting the high-frequency vibration response of aircraft structures is introduced. In addition, the future directions of the energy finite element method are prospected.

Abstract:Aircraft panel flutter is a typical aeroelastic stability problem that typically occurs during supersonic flight, characterized by aerodynamic unilateral effects and significant structural and aerodynamic nonlinearity. This article reviews the current research status of panel flutter issues both domestically and internationally from the perspectives of flutter analysis methods and experimental techniques. It summarizes the commonly used technical means for panel flutter analysis and testing in the engineering community: structural nonlinear models such as geometric nonlinear model and material nonlinear model; aerodynamic nonlinear modeling methods such as piston theoretical model, CFD aerodynamic model, reduced order model of aerodynamic nonlinear model, and local flow piston theory; flutter equation solving methods such as spatial discretization method and reduced order model technology; and two test methods such as wind tunnel test and ground flutter test. This article also analyses the advantages and disadvantages of these research methods and recommends to the future research directions of panel flutter technology.

Abstract:Hydrogen power is one of the important forms to promote the realization of the "double caibon" goal in aviation field. The manufacturing ,testing and qualification of hydrogen power will provide important support for the realization of the "double caibon" goal in aviation field. In this paper, the development background of hydrogen energy power at home and abroad is analyzed in combination with the "double caibon" goal in aviation field,and the forward planning of hydrogen energy power and the latest progress of the overall flight test of hydrogen energy power are systematically reviewed. The key technologies of hydrogen power flight test are analyzed in detail, and the technology of adapting to aeroengine flight platform is analyzed emphatically. It covers hydrogen storage and transportation, adaptation of hydrogen powered flight platforms, special measurement technologies, safety protection and control technologies, flight test supporting facilities, flight test verification and evaluation technologies, and airworthiness compliance studies. The aim is to provide reference for the research on hydrogen power demonstration, hydrogen power product evaluation, safe operation of hydrogen power, aviation technology innovation, low carbon and high quality development of aviation.

Abstract:High-speed rolling bearings are critical components of aircraft engines, requiring efficient lubrication and cooling technologies to ensure stable operation under the harsh conditions of high speed, high temperature, and heavy load. Compared to traditional jet lubrication, under-race lubrication offers numerous advantages and has become the mainstream lubrication method for modern engine main shaft bearings. This paper focuses on the efficient lubrication and cooling technology for aircraft engine main shaft bearings, comparing typical lubrication methods. It systematically reviews and summarizes the current development status of under-race lubrication technology, discusses the lubrication and cooling effects of under-race lubricated bearings, and explores future development trends in lubrication and cooling technology for high-speed bearings in aircraft engines. This provides a reference for efficient lubrication, cooling, and refined thermal management of aviation bearings.

Abstract:Cold spray additive manufacturing technology, with its unique "solid-state deposition" process characteristics, has shown great application potential in the repair and remanufacturing of damaged aerospace structures. For components remanufactured using cold spray, the manufacturing quality depends on the bonding strength at the substrate interface, the structural integrity within the deposition body and the final processed surface quality. This article focuses on the entire cold spray remanufacturing process, aiming to introduce more universal high-performance cold spray remanufacturing methods from three aspects: substrate surface pretreatment, strengthening techniques for the cold spray deposit, and post-treatment of the cold spray deposit. In addition, this article presents existing cases of cold spray additive repair and remanufacturing in the aerospace sector both domestically and internationally, and provides an outlook on the remaining issues and future development directions in the field of aerospace remanufacturing.

Abstract:After several generations of development iterations, following four to five ages of progress, civil aircraft has entered a breakthrough and subversive era, the complete aircraft, including the research and development of airborne equipment, manufacture have broken the traditional aviation concept and pattern. On the basis of reviewing the development and evolution of airborne equipment materials, processes, functions and performance, this paper analyzes the impact of airborne equipment on the reliability, operational performance and special operation requirements of modern civil aircraft systems, summarizes the application trend of emerging technologies in the aviation industry, and points out that electric drive, digitalization, networking and intelligence will become the beacon of the technological upgrading and development of airborne equipment. Looking forward to the development strategy and trend of civil aircraft localization, Only by conforming to the trend of contemporary era and seizing the opportunity of technological change, the localization of civil aircraft equipment may make breakthroughs and advances in the increasingly fierce market competition and in the great transforming unseen in a century.

Abstract:Through the introduction of 5000 series Defense Acquisition Management Procedures and evolution and development process of the U.S. Department of Defense, combined with the review of typical major aviation weapon system program development process，the causes and trends of evolution of defense weapon system research and development management procedures are analyzed according to The Qian Xuesen School of Systems Engineering, Philosophy of Engineering, Theory of Engineering Knowledge and other viewpoints. This paper discusses the basic attributes of the research and development of national defense weapon system such as complexity, knowledge, systematicness and integration, call for the implementation of the strategy of reducing risks by knowledge accumulation in the research and development of major weapon system, and promote the in-depth application of knowledge-based equipment development acquisition methods.

Abstract:This paper proposes a landing control system based on incremental dynamic inverse control . The control system consists of an angle of attack maintenance loop and a trajectory rate control loop based on incremental dynamic inversion, which achieve decoupling of angle of attack and trajectory, as well as direct control of trajectory by direct lift. A differential tracker is introduced to estimate the track angular acceleration signal required in the incremental dynamic inverse control law. The simulation results show that the designed landing control system based on incremental dynamic inversion has excellent control accuracy, speed, and robustness. It can achieve accurate tracking of the trajectory under different sea conditions interference, and the landing points can meet the quality requirements for the distribution of carrier based aircraft landing points.

Abstract:Forward swept wing is one of the forms of aircraft layout. Regarding the aerodynamic characteristics of induced drag of forward swept wings, existing papers have provided confusing understandings. In order to clarify the concept of induced drag of forward swept wings, this paper calculates and analyzes the induced drag characteristics of forward swept wings using nonlinear lift surface, lift line, and high-precision Euler equation solving methods, and compares them with corresponding aft-swept wings and straight wings. The research results indicate that there is a problem with the perception that the induced drag of forward swept wings is smaller than that of aft-swept wings. Even within the framework of potential flow theory, the induced drag of forward swept wings is greater than that of aft-swept wings. This paper also briefly summarizes the advantages of forward swept wings.

Abstract:Hypersonic vehicles encounter challenges in adapting to complex external environments during missions. Conventional fixed-wing aircraft have limited optimal aerodynamic performance under specific conditions. In contrast, morphing aircraft can adapt to various mission environments by altering their aerodynamic shape to control their flight characteristics. Based on numerical simulations, this paper analyzes the changes in aerodynamic characteristics of a hypersonic folding-wing aircraft before and after wing folding, revealing the effects of wing folding on aerodynamic performance. Meanwhile, the influence of aeroelasticity in the wing on the aerodynamic characteristics of the aircraft during the wing folding process is discussed. The outcomes show that the wing folding process has a minimal effect on the drag coefficient but significantly affects the lift coefficient and lift-to-drag ratio. Moreover, due to the presence of shock waves at the wingtips, stress is mainly concentrated in these areas, resulting in a relatively small impact of aeroelasticity on the aircraft’s aerodynamic behavior.

Abstract:The precise and efficient simulation of static and dynamic performance of lattice structure has emerged as a focal area of research. This paper proposes a simulation analysis method for the modification of additive manufacturing lattice structures with variable cross-section beams. Leveraging the dynamic response of 3D-printed lattice structures, we establish and solve an inverse problem model for the geometric parameters of variable cross-section beam elements. We conduct inverse problem calibration of variable cross-section beam parameters for lattice structures with different diameters and establish interpolation models for the geometric parameters of variable cross-section beams with varying diameters. Finally, we validate the effectiveness of the interpolation models for the geometric parameters of variable cross-section beams on lattice structures of different diameters and gradient lattice structures. The simulation analysis model of variable cross-section beams established in this study demonstrates comparable accuracy in dynamic performance simulation to solid element model, also significantly improves analysis efficiency. This study is expected to provide an efficient and accurate modeling foundation for the dynamic optimization design of complex gradient lattice structures.

Abstract:The frequency response functions, and modal parameters are the premise for analyzing robot vibrations during robotic milling process, and modal parameters have strong posture-dependence. The finite element method and dynamic model often lose accuracy due to the difficulty in exactly modeling the stiffness and damping properties of robots. To predict the modal parameters quickly and accurately in all robot postures within the machining space, this paper proposes a modal parameter prediction method based on Gaussian process regression. The influence of joint angles and Euler angles of a six degree-of-freedom serial robot on the modal parameters of the robotic milling system is investigated. Based on this, a posture-related modal parameters prediction model is established to characterize the relationship between modal parameters and robot postures through 245 sets of modal testing experiments in the machining plane. The model can predict the posture-related modal parameters for all robot postures by a limited number of modal testing experiments. The proposed method is validated by experiments.

Abstract:The performance verification and evaluation of stealth materials is a crucial part in the R&D and application cycle of high-performance stealth materials. In order to solve the problems such as single content and incomplete evaluation method of stealth materials, a new evaluation method for application-oriented stealth materials was proposed. The method improves the shape of the test specimen to weaken the interference of the non-examination scattering source on the test results as much as possible. In addition, the area integration method is further utilized to weight the area integration of the test data in multiple bands, and a comprehensive quantitative evaluation is made on the key performance of stealth materials, which is characterized by comprehensive and accurate evaluation. The method is oriented to practical engineering needs, fully characterizes the key stealth performance of stealth materials in practical application scenarios, provides a new way for comprehensive evaluation of the key wave-absorbing performance of stealth materials in all frequency bands, and has completed its application in the stealth material selection process of typical stealth combat aircraft.

Abstract:Aerial recovery, dense flight and aerial refueling of unmanned aerial vehicles (UAVs) all involve flight stability and position control of the vehicle in a close-range interference flow field. In view of the background of UAV lateral recovery and release, adopting interference aerodynamic derivative model, the research work has established the longitudinal small disturbance equation of motion of the vehicle in the close interference flow field, and has proposed using the rudder deflection to simulate the restoring force to achieve the longitudinal positional stability of the UAV. Using typical vehicle data, adopting the state space analysis method, establishing the cost function, the research work has completed the optimal control design of pitch rudder deflection and variable thrust , simulated and verified the method of achieving the UAV longitudinal close-range-flight stability control, and has preliminarily verified the feasibility of close-range-flight stability.

Abstract:The distributed system architecture with openness and comprehensive control features has been successfully applied in the development of flight control systems for advanced fighter jets. However, current fault-tolerant control for flight control systems mainly targets centralized flight control systems in third-generation aircraft and cannot be directly applied to flight control systems with a distributed architecture. Therefore, this paper will study fault-tolerant design for flight control systems based on distributed system architecture. Firstly, this paper introduces the typical system architecture of distributed flight control systems and the objectives of their fault-tolerant design. Secondly, based on the operational timing and working mode characteristics of the distributed system, a time-based fault-tolerant design is conducted. Finally, based on the composition and system architecture characteristics of the distributed system, a system architecture-based fault-tolerant design is carried out. Through the analysis of the operational timing, working modes, composition, and system architecture characteristics of the distributed system, this paper identifies the key entry points and design principles for fault-tolerant design of distributed systems, and explains the solutions, methods, and engineering practice effects of the fault-tolerant design scheme.

Abstract:Wing spar structures in aviation aircraft can cause thermal deformation and vibration of flexible members during service due to alternating heat flux caused by solar thermal radiation. The deformation of the rod will further affect the magnitude and distribution of heat flux, making it a typical force shape coupling system. The stiffness, mass, or load matrix of a coupled system usually has time-varying characteristics, and the modal and response of the system can only be obtained by solving the characteristic equations multiple times and gradually integrating them. How to ensure the computational accuracy and efficiency of the solving process is a major challenge. Based on the dynamic stiffness method and the Wittrick Williams algorithm, the accurate solution of the system"s natural frequency and mode has been achieved; Further combining with the precise integration method, the structural response was obtained. The results show that the deviation between the 1st -4th natural frequencies and the finite element solution is within 1 ‰, and the maximum relative deviation of the response is 1%. When the variable thermal axial force approaches the critical load for structural instability, the vibration frequency of the structure rapidly decreases and tends towards 0, and the thermally induced vibration will exhibit divergence.

Abstract:Composite sandwich panels possess the characterizations of lightweight and high load-bearing capacity. They also face diverse failure modes, and an in-depth study of their mechanical performance and failure mechanisms is essential to ensure structural safety and applicability. In this paper, three-point bending static and fatigue tests were carried out for the sandwich panels consist of plain weave glass fiber/cyanate fabric laminate and Nomex honeycomb by using a specially designed test fixture to investigate the bending-shear load capacity and fatigue performance of the panel, and observe the fatigue damage and failure phenomena. According to the internal stress states of the sandwich panel, fatigue damage models were established for the face panels subjected to in-plane stresses and the sandwich core subjected to out-of-plane shear. Substituting the honeycomb core by an equivalent solid, the bending panel was discretized by using the solid finite elements. Then the bending fatigue lives of the sandwich panel were predicted by means of finite element analysis and cumulative fatigue damage analysis. The simulated bending fatigue performance of the sandwich panel correlate well with the experimental results. The predicted fatigue lives are a little conservative and acceptable.

Abstract:A large number of mechanical connection structures in aircraft face vibration fatigue problems, and the evaluation of vibration fatigue performance is the key to determining the service life, safety design and evaluation of the structure. In order to study the vibration fatigue performance of typical titanium alloy connection structures, this paper designs typical connection structures with different support shapes and rivet spacing using TC4 titanium alloy thin plates, builds a vibration fatigue test system, and compaers the vibration fatigue performance of different connection structures under narrowband random loads through experiments; a method for predicting the vibration fatigue life of connection structures based on random vibration Srms-N curves was proposed by introducing stress severity coefficients. The results show that under similar vibration stress levels, the vibration fatigue performance of the T-shaped support connection structure is better than that of U-shaped support structure; on the premise of ensuring the strength of the connection, increasing the spacing between rivets appropriately can improve the vibration fatigue resistance of the connection structure; after introducing the stress severity factor, the vibration fatigue life of the connection structure is significantly improved, and the difference between the predicted life and the test results is within 30%.

Abstract:In scramjet, the isolator plays a crucial role as a transitional component between the combustor and the inlet.SWithin the isolator, complex flow phenomena such as shock wave/boundary layer interactions, flow separation, and shock trains are observed under the influence of high backpressure from the combustor.SIn this study, the Self-Adaptive Turbulence Eddy Simulation (SATES) is used to numerically study the shock train characteristics in a cylindrical isolator. The primary focus is to analyze the potential challenges faced when the isolator is coupled with the combustor, including the effects of constant or pulsating backpressure at the isolator exit and wall temperature on the shock train characteristics within the isolator. The results indicate that an increase in the exit backpressure of the isolator, a decrease in the frequency of pulsating backpressure, and an elevation in wall temperature can all cause the shock train to move towards the inlet, leading to potential unstart risks. Therefore, in practical engineering applications, particular attention should be paid to the high backpressure and low-frequency oscillations induced during the combustor combustion process, as well as the wall heat conduction effects, to prevent the shock train from being expelled from the isolator, which could result in the shutdown of not only the isolator but also the entire engine.

Abstract:In the hose-drogue aerial refueling, because the hose is a flexible body, there is a floating phenomenon under the disturbance of complex wind fields such as tanker wake, gust and atmospheric, which seriously affects the success rate of docking. In view of the high accuracy and real-time requirements in the process of modeling the wake flow field of tanker and studying the influence of wake wind field disturbance, the method of combining neural network and CFD is adopted. Based on high-precision CFD method to generate flow field data, BP neural network is used to train the mapping between wind field coordinate parameters and velocity parameters, so as to establish the tanker wake wind field model. Aiming at the problems of poor anti-interference ability, strong dependence on model and difficulty in engineering realization, fuzzy PD control method is adopted to realize the swing suppression of wing-rudder active stabilization drogue under complex wind field interference. The simulation results show that the average floating amplitude in Y and Z directions is reduced by 86.49% and 79.04% respectively, and the flight test results show that the average speed intensity in Y and Z directions is reduced 72.98% and 65.29% respectively, which effectively restrains the floating amplitude of drogue.

Abstract:The real-life disaster simulation training based on virtual simulation technology for the participants plays an important role in the optimization of aviation rescue command structure, staff training, and the practical applications of tactical methods. In this paper, we propose MPSS model based on the discrete event modeling for setting up the collaboration training points in the aviation emergency management. The virtual simulation of aviation emergency management is conducted based on the VOS and the performance of the crews in the collaborative training is assessed comprehensively by using READ method, forming a complete process of “mission modeling-mission training- training assessment”. A helicopter forest fire fighting mission was built based on the aviation emergency management virtual simulation collaboration training system verified the feasibility of the methods. It is proved that the collaboration training techniques can assist in rescuer training and improving the capability of participants in aviation emergency management.