Inconel 718 superalloy has extensive applications in a variety of industries such as the moulding,aerospace and medical due to its excellent mechanical features such as poor thermal conductivity,high strength at high ...Inconel 718 superalloy has extensive applications in a variety of industries such as the moulding,aerospace and medical due to its excellent mechanical features such as poor thermal conductivity,high strength at high temperatures and corrosion resistance.However,it is very difficult to process by traditional machining and finishing methods.Abrasive based finishing process is one of non-traditional finishing method applied to complex surfaces.Shot peening process is one of the surface treatment processes mostly applied to improve the surface strength.The superior advantages of these two processes are combined into one process.This newly developed and patented process is called as GOV process.In this study,the effects of GOV process parameters(number of cycles,steel ball size,media concentration)on the surface quality of Inconel 718 already pre-processed by wire electric discharge machining are investigated.The performance parameters are identified as surface roughness,material removal and white layer thickness.Surface finishing with the GOV process improves the surface roughness,Ra value by decreasing from 2.63μm to 0.46μm by removing micro-level chips up to 10.7 mg which is supported by SEM images.White layer formed due to nature of EDM process is completely removed from specimen surface.展开更多
Lattice structures are three-dimensional structures composed of repeated geometrical shapes with multiple interconnected nodes,providing high strength-to-weight ratios,customizable properties,and efficient use of mate...Lattice structures are three-dimensional structures composed of repeated geometrical shapes with multiple interconnected nodes,providing high strength-to-weight ratios,customizable properties,and efficient use of materials.A smart use of materials leads to reduced fuel consumption and lower operating costs,making them highly desirable for aircraft manufacturers.Furthermore,the customizable properties of lattice structures allow for tailoring to specific design requirements,leading to improved performance and safety for aircraft.These advantages make lattice structures an important focus for research and development in the aviation industry.This paper presents an experimental evaluation of the mechanical compression properties of lattice trusses made with Ti6Al4V,designed for use in an anti-ice system.The truss structures were manufactured using additive manufacturing techniques and tested under compressive loads to determine mechanical properties.Results showed that lattice trusses exhibited high levels of compressive strength,making them suitable for use in applications where mechanical resistance and durability are critical,such as in anti-ice systems.We also highlight the potential of additive manufacturing techniques for the fabrication of lattice trusses with tailored mechanical properties.The study provides valuable insights into the mechanical behavior of Ti6Al4V lattice trusses and their potential applications in anti-ice systems,as well as other areas where high strength-to-weight ratios are required.The results of this research contribute to the development of lightweight,efficient,and durable anti-ice systems for use in aviation and other industries.展开更多
Good distribution of samples and weights can improve the computational accuracy and efficiency in the stochastic response analyses of aerospace problems with uncertain parameters.This work proposes a new Generalized L...Good distribution of samples and weights can improve the computational accuracy and efficiency in the stochastic response analyses of aerospace problems with uncertain parameters.This work proposes a new Generalized L2 Discrepancy based on a General Point(GL2D-GP)for generating samples and their corresponding weights.The proposed GL2D-GP is an extension of the existing discrepancy by introducing the non-same weights and a smaller box to measure probability errors.Minimizing the GL2D-GP can yield a weight optimization formula that generates a set of optimal non-identical weights for a given sample set.Through minimizing the GL2D-GP assigned to the set of optimal non-same weights,a new sample and weight generation method is developed.In the proposed method,the samples can be easily generated in terms of the generalized Halton formula with a series of optimal permutation vectors which are found by the intelligent evolutionary algorithm.Once the sample set is obtained,the optimal weights can be generated in terms of the weight optimization formula.Five numerical examples are presented to verify the high accuracy,efficiency,and strong robustness of the proposed sample generation method based on GL2D-GP.展开更多
Aerospace optical cables and fiber-optic connectors have numerous advantages(e.g.,low loss,wide transmission frequency band,large capacity,light weight,and excellent resistance to electromagnetic interference).They ca...Aerospace optical cables and fiber-optic connectors have numerous advantages(e.g.,low loss,wide transmission frequency band,large capacity,light weight,and excellent resistance to electromagnetic interference).They can achieve optical communication interconnections and high-speed bidirectional data transmission between optical terminals and photodetectors in space,ensuring the stability and reliability of data transmission during spacecraft operations in orbit.They have become essential components in high-speed networking and optically interconnected communications for spacecrafts.Thermal stress simulation analysis is important for evaluating the temperature stress concentration phenomenon resulting from temperature fluctuations,temperature gradients,and other factors in aerospace optical cables and connectors under the combined effects of extreme temperatures and vacuum environments.Considering this,advanced optical communication technology has been widely used in high-speed railway communication networks to transmit safe,stable and reliable signals,as high-speed railway optical communication in special areas with extreme climates,such as cold and high-temperature regions,requires high-reliability optical cables and connectors.Therefore,based on the finite element method,comprehensive comparisons were made between the thermal distributions of aerospace optical cables and J599III fiber optic connectors under different conditions,providing a theoretical basis for evaluating the performance of aerospace optical cables and connectors in space environments and meanwhile building a technical foundation for potential optical communication applications in the field of high-speed railways.展开更多
In this paper, the operating conditions, technical requirements, performance characteristics, design ideas, application experiences and development trends of aerospace engine bearings, including material technology, i...In this paper, the operating conditions, technical requirements, performance characteristics, design ideas, application experiences and development trends of aerospace engine bearings, including material technology, integration design and reliability, are reviewed. The development history of aerospace engine bearing is recalled briefly at first. Then today＇s material technologies and the high bearing performances of the bearings obtained through the new materials are introduced, which play important roils in the aeroengine bearing developments. The integration design ideas and practices are explained to indicate its significant advantages and importance to the aerospace engine bearings. And the reliability of the shaft-bearing system is pointed out and treated as the key requirement with goals for both engine and bearing. Finally, as it is believed that the correct design comes from practice, the pre-qualification rig testing conducted by FAG Aerospace GmbH ＆ Co. KG is briefly illustrated as an example. All these lead to the development trends of aerospace engine bearings from different aspects.展开更多
Combination of topology optimization and additive manufacturing technologies provides an effective approach for the development of light-weight and high-performance structures.A heavy-loaded aerospace bracket is desig...Combination of topology optimization and additive manufacturing technologies provides an effective approach for the development of light-weight and high-performance structures.A heavy-loaded aerospace bracket is designed by topology optimization and manufactured by additive manufacturing technology in this work.Considering both mechanical forces and temperature loads,a formulation of thermo-elastic topology optimization is firstly proposed and the sensitivity analysis is derived in detail.Then the procedure of numerical optimization design is presented and the final design is additively manufactured using Selective Laser Melting(SLM).The mass of the aerospace bracket is reduced by over 18%,benefiting from topology and size optimization,and the three constraints are satisfied as well in the final design.This work indicates that the integration of thermo-elastic topology optimization and additive manufacturing technologies can be a rather powerful tool kit for the design of structures under thermal-mechanical loading.展开更多
As few or no failures occur during accelerated life test,it is difficult to assess reliability for long-life products with traditional life tests.Reliability assessment using degradation data of product performance ov...As few or no failures occur during accelerated life test,it is difficult to assess reliability for long-life products with traditional life tests.Reliability assessment using degradation data of product performance over time becomes a significant approach.Aerospace electrical connector is researched in this paper.Through the analysis of failure mechanism,the performance degradation law is obtained and the statistical model for degradation failure is set up; according to the research on statistical analysis methods for degradation data,accelerated life test theory and method for aerospace electrical connector based on performance degradation is proposed by improving time series analysis method,and the storage reliability is assessed for Y11X series of aerospace electrical connector with degradation data from accelerated degradation test.The result obtained is basically consistent with that obtained from accelerated life test based on failure data,and the two estimates of product＇s characteristic life only have a difference of 8.7%,but the test time shortens about a half.As a result,a systemic approach is proposed for reliability assessment of highly reliable and long-life aerospace product.展开更多
Control of uncertain dynamical systems has been an area of active research for the past several decades and to this end, various robust control approaches have been proposed in the literature. The active disturbance r...Control of uncertain dynamical systems has been an area of active research for the past several decades and to this end, various robust control approaches have been proposed in the literature. The active disturbance rejection control （ADRC） represents one prominent approach that has been widely studied and applied for designing robust controllers in diverse areas of engineering applications. In this work, a brief review of the approach and some of its applications in aerospace are discussed. The results show that the approach possesses immense potential to offer viable solution to real-life aerospace problems.展开更多
By integrating topology optimization and lattice-based optimization,a novel multi-scale design method is proposed to create solid-lattice hybrid structures and thus to improve the mechanical performance as well as red...By integrating topology optimization and lattice-based optimization,a novel multi-scale design method is proposed to create solid-lattice hybrid structures and thus to improve the mechanical performance as well as reduce the structural weight.To achieve this purpose,a two-step procedure is developed to design and optimize the innovative structures.Initially,the classical topology optimization is utilized to find the optimal material layout and primary load carrying paths.Afterwards,the solid-lattice hybrid structures are reconstructed using the finite element mesh based modeling method.And lattice-based optimization is performed to obtain the optimal crosssection area of the lattice structures.Finally,two typical aerospace structures are optimized to demonstrate the effectiveness of the proposed optimization framework.The numerical results are quite encouraging since the solid-lattice hybrid structures obtained by the presented approach show remarkably improved performance when compared with traditional designs.展开更多
Friction stir welding （FSW） has been widely adopted in aerospace industry for fabricating high-strength aluminum alloy structures, such as large volume fuel tanks, due to its exceptional advantages includ- ing low d...Friction stir welding （FSW） has been widely adopted in aerospace industry for fabricating high-strength aluminum alloy structures, such as large volume fuel tanks, due to its exceptional advantages includ- ing low distortion, less defects and high mechanical properties of the joint. This article systematically reviews the key technical issues in producing large capacity aluminum alloy fuel tanks by using FSW, including tool design. FSW process optimization, nondestructive testing （NDT） techniques and defect repairing techniques, etc. To fulfill the requirements of Chinese aerospace industry, constant-force FSW, retractable tool FSW, lock joint FSW, on-line NDT and solid-state equal-strength FSW techniques, as well as a complete set of aerospace aluminum FSW equipment, have been successfully developed. All these techniques have been engineered and validated in rocket tanks, which enormously improved the fabrication ability of Chinese aerospace industry.展开更多
Efficient bolted joint design is an essential part of designing the minimum weight aerospace structures, since structural failures usually occur at connections and interface. A comprehensive numerical study of three-d...Efficient bolted joint design is an essential part of designing the minimum weight aerospace structures, since structural failures usually occur at connections and interface. A comprehensive numerical study of three-dimensional(3D) stress variations is prohibitively expensive for a large-scale structure where hundreds of bolts can be present. In this work, the hybrid composite-to-metal bolted connections used in the upper stage of European Ariane 5ME rocket are analyzed using the global-local finite element(FE) approach which involves an approximate analysis of the whole structure followed by a detailed analysis of a significantly smaller region of interest. We calculate the Tsai-Wu failure index and the margin of safety using the stresses obtained from ABAQUS. We find that the composite part of a hybrid bolted connection is prone to failure compared to the metal part. We determine the bolt preload based on the clamp-up load calculated using a maximum preload to make the composite part safe. We conclude that the unsuitable bolt preload may cause the failure of the composite part due to the high stress concentration in the vicinity of the bolt. The global-local analysis provides an efficient computational tool for enhancing 3D stress analysis in the highly loaded region.展开更多
In the present study,an efficient overset grid method by means of parallel implicit hole-cutting is proposed for the sake of simulating unsteady flows in aerospace engineering involving multiple bodies in relative mov...In the present study,an efficient overset grid method by means of parallel implicit hole-cutting is proposed for the sake of simulating unsteady flows in aerospace engineering involving multiple bodies in relative movement.In view of the degraded computational efficiency and robustness for conventional overset grid assembly,several innovative techniques are developed within the overset grid assembly process,viz.,a bookkeeping alternative digital tree method to speed up the donor-cell searching,a fast parallel advancing front algorithm to accelerate the wall-distance calculation and a message-passing strategy with efficient information communication and lower storage expenditure within distributed computational architecture.The contribution of the developed techniques is evidenced by comparison with the existing alternative ways in terms of computing efficiency.Subsequently,the overset grid method is embedded into an inhouse programed URANS solver to examine its capability in predicting the flow field of complex applications such as helicopter,store separation and component deploying.Results show that the developed overset grid methodology is,in practice,able to resolve the aerodynamic characteristics of complex aerospace engineering with a high-fidelity flow topology and accuracy.展开更多
The decomposition and combustion characteristics of ammonium dinitramide (ADN) based non-toxic aerospace propellant are analytically studied to determine the effects of catalytic bed structure (slenderness ratio) and ...The decomposition and combustion characteristics of ammonium dinitramide (ADN) based non-toxic aerospace propellant are analytically studied to determine the effects of catalytic bed structure (slenderness ratio) and operation parameters (mass fraction ratio of ADN/CH3OH) on the general performance within the ADN-based thruster. In the present research, the non-equilibrium temperature model is utilized to describe the heat transfer characteristics between the fluid phase and solid phase in the fixed bed. We determined the fluid resistance characteristics in the catalytic bed by experiments involving the method of pressure-mass. We have done the simulation study based on the available results in the literature and found the complex physical and chemical processes within the ADN thruster. Furthermore, an optimized catalytic bed slenderness ratio was observed w让h a value of 1.75 and the mass fraction ratio of 5.73 significantly influenced the propellant performance. These results could serve as a reference to explore the combustion characteristics within the thruster and the preparation of future propellants.展开更多
The influence of varying shim layers on the progressive damage/failure of a composite component in a bolted composite-aluminum aerospace structural assembly was investigated using a non-linear three-dimensional(3 D)st...The influence of varying shim layers on the progressive damage/failure of a composite component in a bolted composite-aluminum aerospace structural assembly was investigated using a non-linear three-dimensional(3 D)structural solid elements assembled model of a carbon fiber-reinforced polymer(CFRP)-aluminum single-lap joint with a titanium(Ti-6 Al-4 V)fastener and a washer generated with the commercial finite element(FE)software package,ABAQUS/Standard.A progressive failure algorithm written in Fortran code with a set of appropriate degradation rules was incorporated as a user subroutine in ABAQUS to simulate the non-linear damage behavior of the composite component in the composite-aluminum bolted aerospace structure.The assembled 3 DFE model simulated,as well as the specimen for the experimental testing consisted of a carbon-epoxy IMS-977-2 substrate,aluminum alloy 7075-T651 substrate,liquid shim(Hysol EA 9394),solid peelable fiberglass shim,a titanium fastener,and a washer.In distinction to previous investigations,the influence of shim layers(liquid shim and solid peelable fiberglass shim)inserted in-between the faying surfaces(CFRP and aluminum alloy substrates)were investigated by both numerical simulations and experimental work.The simulated model and test specimens conformed to the standard test configurations for both civil and military standards.The numerical simulations correlated well with the experimental results and it has been found that:(1)The shimming procedure as agreed upon by the aerospace industry for the resolution of assembly gaps in bolted joints for composite materials is the same for a composite-aluminum structure;liquid shim series(0.3,0.5 and 0.7 mm thicknesses)prolonged the service life of the composite component whereas a solid peelable fiberglass shim most definitely had a better influence on the 0.9 assembly gap compared with the liquid shim;(2)The shim layers considerably influenced the structural strength of the composite component by delaying its ultimate failure thereby increasing its service life;and(3)Increasing the shim layer′s thickness led to a significant corresponding effect on the stiffness but with minimal effect on the ultimate load.展开更多
Motor-pump assembly is the core component of the Aerospace Electro-hydrostatic Actuator(EHA).Thus,the design of the motor pump can be very challenging under conditions of high speed and wide pressure range,especially ...Motor-pump assembly is the core component of the Aerospace Electro-hydrostatic Actuator(EHA).Thus,the design of the motor pump can be very challenging under conditions of high speed and wide pressure range,especially in particular working mediums.Our ultimate goal is to pursue better flow characteristics under a wide range of working conditions.In this paper,we built a sub-model of the main friction interfaces and a model of single-shaft coaxial motor-pump assembly adopting the method of hierarchical modeling.The experimental investigation of the output characteristics was mainly carried out in a phosphate ester medium environment.Then,the flow characteristics were compared and analyzed with the simulation results.Results indicated that the flow characteristics of the motor-pump assembly could be accurately simulated by the model and quite severe in a low speed and high-pressure environment.展开更多
Thermal energy storage(TES)is a key technology for renewable energy utilization and the improvement of the energy efficiency of heat processes.Sectors include industrial process heat and conventional and renewable pow...Thermal energy storage(TES)is a key technology for renewable energy utilization and the improvement of the energy efficiency of heat processes.Sectors include industrial process heat and conventional and renewable power generation.TES systems correct the mismatch between supply and demand of thermal energy.In the medium to high temperature range(100~1000℃),only limited storage technology is commercially available and a strong effort is needed to develop a range of storage technologies which are efficient and economical for the very specific requirements of the different application sectors.At the DLR's Institute of Technical Thermodynamics,the complete spectrum of high temperature storage technologies,from various types of sensible over latent heat to thermochemical heat storages are being developed.Different concepts are proposed depending on the heat transfer fluid(synthetic oil,water/steam,molten salt,air)and the required temperature range.The aim is the development of cost effective,efficient and reliable thermal storage systems.Research focuses on characterization of storage materials,enhancement of internal heat transfer,design of innovative storage concepts and modelling of storage components and systems.Demonstration of the storage technology takes place from laboratory scale to field testing(5 kW^1 MW).The paper gives an overview on DLR's current developments.展开更多
The worldwide air traffic underwent a rapid development in recent decades.?Between the early 70s and the late 90s of the last century civil air traffic?doubled every 15 years. The civil aviation market will continue t...The worldwide air traffic underwent a rapid development in recent decades.?Between the early 70s and the late 90s of the last century civil air traffic?doubled every 15 years. The civil aviation market will continue to grow with 4% - 5%?each year within the next 20 years. This enormous growth represents major?challenges for airframers, engine makers, suppliers, airlines, air traffic management?and ground infrastructure. In addition, the public debate on the worldwide?civil air traffic is dominated by environmental and climate issues, even though only 2% of the man-made carbon dioxide (CO2) emissions are due to air transportation. Therefore the aerospace industry will have to focus on a low-emission and quite air traffic, and on the conservation of natural resources and our environment. The end-use consumer and environmental policy requirements?for aircrafts of the next generation translate into components with improved efficiency and reliability. Rolling bearings are one of these components which?significantly determine the reliability and mechanical efficiency of aerospace applications such as aircraft and rotorcraft engines and transmission systems.?They have to withstand very demanding operating conditions. Especially main shaft?bearings in modern aircraft engines experience high rotational speeds andtemperatures. Furthermore aerospace bearings have to meet the highest reliability?standards and require low-weight design solutions. These operating conditions?and requirements present a continuous challenge for improvements in all?fields of bearing technology. This article presents solutions in aspects of materials, design, analysis, and surface technologies in order to meet the environmental, reliability, and economical requirements of advanced aerospace bearing systems. State of the art bearing analysis and advanced bearing design solutions?contributing to lower friction power losses and increased systems efficiency?are discussed. Weight, functional, and maintenance benefits are presented with the example of highly integrated aircraft engine main shaft bearings. It is also shown that the progress in bearing materials and surface technology development is the basis for weight and friction energy reduction in aerospace?bearing systems.展开更多
Various micro-mechanical and micro-structural influences on fatigue crack growth resistance of the material have been investigated over the years. It is widely recognized that resistance to fatigue crack growth can be...Various micro-mechanical and micro-structural influences on fatigue crack growth resistance of the material have been investigated over the years. It is widely recognized that resistance to fatigue crack growth can be differentiated into ‘intrinsic＇ and ‘extrinsic＇. The separation of intrinsic and extrinsic crack growth resistance has constituted a major theme of fatigue research in the last 30 years, with the concept of crack closure or crack tip shielding being used to rationalize a wide range of micro-structural and mechanical influences on fatigue crack growth behavior. An accurately quantitative understanding of intrinsic and extrinsic effects on crack growth is essential to directed alloy design for improved fatigue resistance, and/or improved structural service life. This paper presents a compliance-based crack closure measurement method and a multi-mechanism based analytical model for the separation of intrinsic and extrinsic material fatigue resistance, with application in characterizing the fatigue performance of two high strength damage tolerant airframe AI alloys.展开更多
Commercial space activities are closely related to national politics,economy,and military. Due to the factors such as national security and economic benefits,most countries are actively developing commercial aerospace...Commercial space activities are closely related to national politics,economy,and military. Due to the factors such as national security and economic benefits,most countries are actively developing commercial aerospace.In recent years,with the rapid development of private space companies such as SpaceX Corporation and Blue Origin Company,the cost of commercial space launch has been greatly reduced,which has had a huge effect on the existed international commercial market. Patent is the product of market competition. It is an effective means for international first-class companies to gain a competitive initiative and occupy the market superiority through protecting their intellectual property rights by patents during commercial space cooperation. At present,most of China aerospace enterprises are derived from national defense military units. Patents of national defense military units are the results of intellectual labor,which are characterized by their proprietary,temporal,and regional characteristics. However,due to the characteristics of national defense services,military monopoly,and group nature of property rights,the patent protection of defense units is different from that of ordinary enterprises. The problem of intellectual property protection in commercial space cooperation is more complicated. Therefore,in the fierce competition of international commercial aerospace,how China space companies can use patents to enhance their international competitiveness in commercial space cooperation is worthy of thinking and planning in advance. By analyzing the patent protection strategies and typical cases adopted by domestic and foreign aerospace companies in commercial space cooperation,it is expected to provide a reference for China space enterprises to effectively use patent strategies in commercial and space cooperation and to enhance China commercial aerospace competitiveness.展开更多
This article provides a brief overview of the teaching and research at the School of Aerospace Engineering(SAE) to celebrate the 80 th anniversary of the establishment of aeronautics as a discipline at Tsinghua Univer...This article provides a brief overview of the teaching and research at the School of Aerospace Engineering(SAE) to celebrate the 80 th anniversary of the establishment of aeronautics as a discipline at Tsinghua University. The evolution of the school, undergraduate/graduate students and faculty members, and research activities and achievements have been described. The research input including research funding and research projects are summarized, showing a diversity of funding sources and a significant growth in either sum total or spending per researcher. The achievements including publications and inter/national academic awards are also introduced. It can be seen that the level of academic publications has been growing over the past decades. In addition,four representative research achievements have been briefly described to show the scientific contributions of the school.展开更多
文摘Inconel 718 superalloy has extensive applications in a variety of industries such as the moulding,aerospace and medical due to its excellent mechanical features such as poor thermal conductivity,high strength at high temperatures and corrosion resistance.However,it is very difficult to process by traditional machining and finishing methods.Abrasive based finishing process is one of non-traditional finishing method applied to complex surfaces.Shot peening process is one of the surface treatment processes mostly applied to improve the surface strength.The superior advantages of these two processes are combined into one process.This newly developed and patented process is called as GOV process.In this study,the effects of GOV process parameters(number of cycles,steel ball size,media concentration)on the surface quality of Inconel 718 already pre-processed by wire electric discharge machining are investigated.The performance parameters are identified as surface roughness,material removal and white layer thickness.Surface finishing with the GOV process improves the surface roughness,Ra value by decreasing from 2.63μm to 0.46μm by removing micro-level chips up to 10.7 mg which is supported by SEM images.White layer formed due to nature of EDM process is completely removed from specimen surface.
文摘Lattice structures are three-dimensional structures composed of repeated geometrical shapes with multiple interconnected nodes,providing high strength-to-weight ratios,customizable properties,and efficient use of materials.A smart use of materials leads to reduced fuel consumption and lower operating costs,making them highly desirable for aircraft manufacturers.Furthermore,the customizable properties of lattice structures allow for tailoring to specific design requirements,leading to improved performance and safety for aircraft.These advantages make lattice structures an important focus for research and development in the aviation industry.This paper presents an experimental evaluation of the mechanical compression properties of lattice trusses made with Ti6Al4V,designed for use in an anti-ice system.The truss structures were manufactured using additive manufacturing techniques and tested under compressive loads to determine mechanical properties.Results showed that lattice trusses exhibited high levels of compressive strength,making them suitable for use in applications where mechanical resistance and durability are critical,such as in anti-ice systems.We also highlight the potential of additive manufacturing techniques for the fabrication of lattice trusses with tailored mechanical properties.The study provides valuable insights into the mechanical behavior of Ti6Al4V lattice trusses and their potential applications in anti-ice systems,as well as other areas where high strength-to-weight ratios are required.The results of this research contribute to the development of lightweight,efficient,and durable anti-ice systems for use in aviation and other industries.
基金the support of the National Natural Science Foundation of China(Nos.12372190,12272077)the Fundamental Research Funds for the Central Universities,China(Nos.DUT20RC(5)009,DUT20GJ216).
文摘Good distribution of samples and weights can improve the computational accuracy and efficiency in the stochastic response analyses of aerospace problems with uncertain parameters.This work proposes a new Generalized L2 Discrepancy based on a General Point(GL2D-GP)for generating samples and their corresponding weights.The proposed GL2D-GP is an extension of the existing discrepancy by introducing the non-same weights and a smaller box to measure probability errors.Minimizing the GL2D-GP can yield a weight optimization formula that generates a set of optimal non-identical weights for a given sample set.Through minimizing the GL2D-GP assigned to the set of optimal non-same weights,a new sample and weight generation method is developed.In the proposed method,the samples can be easily generated in terms of the generalized Halton formula with a series of optimal permutation vectors which are found by the intelligent evolutionary algorithm.Once the sample set is obtained,the optimal weights can be generated in terms of the weight optimization formula.Five numerical examples are presented to verify the high accuracy,efficiency,and strong robustness of the proposed sample generation method based on GL2D-GP.
基金supported by the National Natural Science Foundation of China(U23A20336).
文摘Aerospace optical cables and fiber-optic connectors have numerous advantages(e.g.,low loss,wide transmission frequency band,large capacity,light weight,and excellent resistance to electromagnetic interference).They can achieve optical communication interconnections and high-speed bidirectional data transmission between optical terminals and photodetectors in space,ensuring the stability and reliability of data transmission during spacecraft operations in orbit.They have become essential components in high-speed networking and optically interconnected communications for spacecrafts.Thermal stress simulation analysis is important for evaluating the temperature stress concentration phenomenon resulting from temperature fluctuations,temperature gradients,and other factors in aerospace optical cables and connectors under the combined effects of extreme temperatures and vacuum environments.Considering this,advanced optical communication technology has been widely used in high-speed railway communication networks to transmit safe,stable and reliable signals,as high-speed railway optical communication in special areas with extreme climates,such as cold and high-temperature regions,requires high-reliability optical cables and connectors.Therefore,based on the finite element method,comprehensive comparisons were made between the thermal distributions of aerospace optical cables and J599III fiber optic connectors under different conditions,providing a theoretical basis for evaluating the performance of aerospace optical cables and connectors in space environments and meanwhile building a technical foundation for potential optical communication applications in the field of high-speed railways.
文摘In this paper, the operating conditions, technical requirements, performance characteristics, design ideas, application experiences and development trends of aerospace engine bearings, including material technology, integration design and reliability, are reviewed. The development history of aerospace engine bearing is recalled briefly at first. Then today＇s material technologies and the high bearing performances of the bearings obtained through the new materials are introduced, which play important roils in the aeroengine bearing developments. The integration design ideas and practices are explained to indicate its significant advantages and importance to the aerospace engine bearings. And the reliability of the shaft-bearing system is pointed out and treated as the key requirement with goals for both engine and bearing. Finally, as it is believed that the correct design comes from practice, the pre-qualification rig testing conducted by FAG Aerospace GmbH ＆ Co. KG is briefly illustrated as an example. All these lead to the development trends of aerospace engine bearings from different aspects.
基金supported by the National Key Research and Development Program of China(Nos.2017YFB1102800,2016YFB0201600)the National Natural Science Foundation of China(Nos.11672239,51735005)。
文摘Combination of topology optimization and additive manufacturing technologies provides an effective approach for the development of light-weight and high-performance structures.A heavy-loaded aerospace bracket is designed by topology optimization and manufactured by additive manufacturing technology in this work.Considering both mechanical forces and temperature loads,a formulation of thermo-elastic topology optimization is firstly proposed and the sensitivity analysis is derived in detail.Then the procedure of numerical optimization design is presented and the final design is additively manufactured using Selective Laser Melting(SLM).The mass of the aerospace bracket is reduced by over 18%,benefiting from topology and size optimization,and the three constraints are satisfied as well in the final design.This work indicates that the integration of thermo-elastic topology optimization and additive manufacturing technologies can be a rather powerful tool kit for the design of structures under thermal-mechanical loading.
基金supported by National Natural Science Foundation of China (Grant No. 50935002,Grant No. 51075370,Grant No. 51105341)National Hi-tech Research and Development Program of China (863 Program,Grant No. 2007AA04Z409)Civil Aerospace Science and Technology Pre-research Project of China (Grant No. B122006 2302)
文摘As few or no failures occur during accelerated life test,it is difficult to assess reliability for long-life products with traditional life tests.Reliability assessment using degradation data of product performance over time becomes a significant approach.Aerospace electrical connector is researched in this paper.Through the analysis of failure mechanism,the performance degradation law is obtained and the statistical model for degradation failure is set up; according to the research on statistical analysis methods for degradation data,accelerated life test theory and method for aerospace electrical connector based on performance degradation is proposed by improving time series analysis method,and the storage reliability is assessed for Y11X series of aerospace electrical connector with degradation data from accelerated degradation test.The result obtained is basically consistent with that obtained from accelerated life test based on failure data,and the two estimates of product＇s characteristic life only have a difference of 8.7%,but the test time shortens about a half.As a result,a systemic approach is proposed for reliability assessment of highly reliable and long-life aerospace product.
文摘Control of uncertain dynamical systems has been an area of active research for the past several decades and to this end, various robust control approaches have been proposed in the literature. The active disturbance rejection control （ADRC） represents one prominent approach that has been widely studied and applied for designing robust controllers in diverse areas of engineering applications. In this work, a brief review of the approach and some of its applications in aerospace are discussed. The results show that the approach possesses immense potential to offer viable solution to real-life aerospace problems.
基金supported by National Key Research and Development Program(No.2017YFB1102800)Key Project of NSFC(Nos.51790171 and 51761145111)NSFC for Excellent Young Scholars(No.11722219)。
文摘By integrating topology optimization and lattice-based optimization,a novel multi-scale design method is proposed to create solid-lattice hybrid structures and thus to improve the mechanical performance as well as reduce the structural weight.To achieve this purpose,a two-step procedure is developed to design and optimize the innovative structures.Initially,the classical topology optimization is utilized to find the optimal material layout and primary load carrying paths.Afterwards,the solid-lattice hybrid structures are reconstructed using the finite element mesh based modeling method.And lattice-based optimization is performed to obtain the optimal crosssection area of the lattice structures.Finally,two typical aerospace structures are optimized to demonstrate the effectiveness of the proposed optimization framework.The numerical results are quite encouraging since the solid-lattice hybrid structures obtained by the presented approach show remarkably improved performance when compared with traditional designs.
文摘Friction stir welding （FSW） has been widely adopted in aerospace industry for fabricating high-strength aluminum alloy structures, such as large volume fuel tanks, due to its exceptional advantages includ- ing low distortion, less defects and high mechanical properties of the joint. This article systematically reviews the key technical issues in producing large capacity aluminum alloy fuel tanks by using FSW, including tool design. FSW process optimization, nondestructive testing （NDT） techniques and defect repairing techniques, etc. To fulfill the requirements of Chinese aerospace industry, constant-force FSW, retractable tool FSW, lock joint FSW, on-line NDT and solid-state equal-strength FSW techniques, as well as a complete set of aerospace aluminum FSW equipment, have been successfully developed. All these techniques have been engineered and validated in rocket tanks, which enormously improved the fabrication ability of Chinese aerospace industry.
基金Project(282522)supported by the European Union's Research and Innovation Funding Programme
文摘Efficient bolted joint design is an essential part of designing the minimum weight aerospace structures, since structural failures usually occur at connections and interface. A comprehensive numerical study of three-dimensional(3D) stress variations is prohibitively expensive for a large-scale structure where hundreds of bolts can be present. In this work, the hybrid composite-to-metal bolted connections used in the upper stage of European Ariane 5ME rocket are analyzed using the global-local finite element(FE) approach which involves an approximate analysis of the whole structure followed by a detailed analysis of a significantly smaller region of interest. We calculate the Tsai-Wu failure index and the margin of safety using the stresses obtained from ABAQUS. We find that the composite part of a hybrid bolted connection is prone to failure compared to the metal part. We determine the bolt preload based on the clamp-up load calculated using a maximum preload to make the composite part safe. We conclude that the unsuitable bolt preload may cause the failure of the composite part due to the high stress concentration in the vicinity of the bolt. The global-local analysis provides an efficient computational tool for enhancing 3D stress analysis in the highly loaded region.
基金supported by the National Natural Science Foundation of China(Nos.11672133,12002161)Open Foundations of EDL Laboratory,China(No.EDL19092111)+2 种基金supports from National Science Foundation of Shaanxi Province,China(No.2021JQ-078)Fundamental Research Fund of Zhuhai,China(No.ZH22017003210011PWC)Aeronautical Science Foundation of China(No.F2021110)are acknowledged as well。
文摘In the present study,an efficient overset grid method by means of parallel implicit hole-cutting is proposed for the sake of simulating unsteady flows in aerospace engineering involving multiple bodies in relative movement.In view of the degraded computational efficiency and robustness for conventional overset grid assembly,several innovative techniques are developed within the overset grid assembly process,viz.,a bookkeeping alternative digital tree method to speed up the donor-cell searching,a fast parallel advancing front algorithm to accelerate the wall-distance calculation and a message-passing strategy with efficient information communication and lower storage expenditure within distributed computational architecture.The contribution of the developed techniques is evidenced by comparison with the existing alternative ways in terms of computing efficiency.Subsequently,the overset grid method is embedded into an inhouse programed URANS solver to examine its capability in predicting the flow field of complex applications such as helicopter,store separation and component deploying.Results show that the developed overset grid methodology is,in practice,able to resolve the aerodynamic characteristics of complex aerospace engineering with a high-fidelity flow topology and accuracy.
文摘The decomposition and combustion characteristics of ammonium dinitramide (ADN) based non-toxic aerospace propellant are analytically studied to determine the effects of catalytic bed structure (slenderness ratio) and operation parameters (mass fraction ratio of ADN/CH3OH) on the general performance within the ADN-based thruster. In the present research, the non-equilibrium temperature model is utilized to describe the heat transfer characteristics between the fluid phase and solid phase in the fixed bed. We determined the fluid resistance characteristics in the catalytic bed by experiments involving the method of pressure-mass. We have done the simulation study based on the available results in the literature and found the complex physical and chemical processes within the ADN thruster. Furthermore, an optimized catalytic bed slenderness ratio was observed w让h a value of 1.75 and the mass fraction ratio of 5.73 significantly influenced the propellant performance. These results could serve as a reference to explore the combustion characteristics within the thruster and the preparation of future propellants.
基金the Innovation Foundation of National Research Center for Commercial Aircraft Manufacturing Engineering Technology in China (No. SAMC13-JS-13-021)Jiangsu Key Laboratory of Precision and Micro-Manufacturing Technology for the provision of financial support
文摘The influence of varying shim layers on the progressive damage/failure of a composite component in a bolted composite-aluminum aerospace structural assembly was investigated using a non-linear three-dimensional(3 D)structural solid elements assembled model of a carbon fiber-reinforced polymer(CFRP)-aluminum single-lap joint with a titanium(Ti-6 Al-4 V)fastener and a washer generated with the commercial finite element(FE)software package,ABAQUS/Standard.A progressive failure algorithm written in Fortran code with a set of appropriate degradation rules was incorporated as a user subroutine in ABAQUS to simulate the non-linear damage behavior of the composite component in the composite-aluminum bolted aerospace structure.The assembled 3 DFE model simulated,as well as the specimen for the experimental testing consisted of a carbon-epoxy IMS-977-2 substrate,aluminum alloy 7075-T651 substrate,liquid shim(Hysol EA 9394),solid peelable fiberglass shim,a titanium fastener,and a washer.In distinction to previous investigations,the influence of shim layers(liquid shim and solid peelable fiberglass shim)inserted in-between the faying surfaces(CFRP and aluminum alloy substrates)were investigated by both numerical simulations and experimental work.The simulated model and test specimens conformed to the standard test configurations for both civil and military standards.The numerical simulations correlated well with the experimental results and it has been found that:(1)The shimming procedure as agreed upon by the aerospace industry for the resolution of assembly gaps in bolted joints for composite materials is the same for a composite-aluminum structure;liquid shim series(0.3,0.5 and 0.7 mm thicknesses)prolonged the service life of the composite component whereas a solid peelable fiberglass shim most definitely had a better influence on the 0.9 assembly gap compared with the liquid shim;(2)The shim layers considerably influenced the structural strength of the composite component by delaying its ultimate failure thereby increasing its service life;and(3)Increasing the shim layer′s thickness led to a significant corresponding effect on the stiffness but with minimal effect on the ultimate load.
基金This study was co-supported by the Chinese Civil Aircraft Project(No.MJ-2017-S49)China Postdoctoral Science Foundation(No.2021M700331).
文摘Motor-pump assembly is the core component of the Aerospace Electro-hydrostatic Actuator(EHA).Thus,the design of the motor pump can be very challenging under conditions of high speed and wide pressure range,especially in particular working mediums.Our ultimate goal is to pursue better flow characteristics under a wide range of working conditions.In this paper,we built a sub-model of the main friction interfaces and a model of single-shaft coaxial motor-pump assembly adopting the method of hierarchical modeling.The experimental investigation of the output characteristics was mainly carried out in a phosphate ester medium environment.Then,the flow characteristics were compared and analyzed with the simulation results.Results indicated that the flow characteristics of the motor-pump assembly could be accurately simulated by the model and quite severe in a low speed and high-pressure environment.
基金funded through the basic DLR funding of the Helmholtz AssociationSpecific support for several projects was given by the German Federal Ministry of Economics and Technology and the German Federal Ministry for the Environment,Nature Conservation and Nuclear SafetyThe CellFlux project is funded by E.ON AG as part of the International Research Initiative.Responsibility for the content of this publication lieswith the authors
文摘Thermal energy storage(TES)is a key technology for renewable energy utilization and the improvement of the energy efficiency of heat processes.Sectors include industrial process heat and conventional and renewable power generation.TES systems correct the mismatch between supply and demand of thermal energy.In the medium to high temperature range(100~1000℃),only limited storage technology is commercially available and a strong effort is needed to develop a range of storage technologies which are efficient and economical for the very specific requirements of the different application sectors.At the DLR's Institute of Technical Thermodynamics,the complete spectrum of high temperature storage technologies,from various types of sensible over latent heat to thermochemical heat storages are being developed.Different concepts are proposed depending on the heat transfer fluid(synthetic oil,water/steam,molten salt,air)and the required temperature range.The aim is the development of cost effective,efficient and reliable thermal storage systems.Research focuses on characterization of storage materials,enhancement of internal heat transfer,design of innovative storage concepts and modelling of storage components and systems.Demonstration of the storage technology takes place from laboratory scale to field testing(5 kW^1 MW).The paper gives an overview on DLR's current developments.
文摘The worldwide air traffic underwent a rapid development in recent decades.?Between the early 70s and the late 90s of the last century civil air traffic?doubled every 15 years. The civil aviation market will continue to grow with 4% - 5%?each year within the next 20 years. This enormous growth represents major?challenges for airframers, engine makers, suppliers, airlines, air traffic management?and ground infrastructure. In addition, the public debate on the worldwide?civil air traffic is dominated by environmental and climate issues, even though only 2% of the man-made carbon dioxide (CO2) emissions are due to air transportation. Therefore the aerospace industry will have to focus on a low-emission and quite air traffic, and on the conservation of natural resources and our environment. The end-use consumer and environmental policy requirements?for aircrafts of the next generation translate into components with improved efficiency and reliability. Rolling bearings are one of these components which?significantly determine the reliability and mechanical efficiency of aerospace applications such as aircraft and rotorcraft engines and transmission systems.?They have to withstand very demanding operating conditions. Especially main shaft?bearings in modern aircraft engines experience high rotational speeds andtemperatures. Furthermore aerospace bearings have to meet the highest reliability?standards and require low-weight design solutions. These operating conditions?and requirements present a continuous challenge for improvements in all?fields of bearing technology. This article presents solutions in aspects of materials, design, analysis, and surface technologies in order to meet the environmental, reliability, and economical requirements of advanced aerospace bearing systems. State of the art bearing analysis and advanced bearing design solutions?contributing to lower friction power losses and increased systems efficiency?are discussed. Weight, functional, and maintenance benefits are presented with the example of highly integrated aircraft engine main shaft bearings. It is also shown that the progress in bearing materials and surface technology development is the basis for weight and friction energy reduction in aerospace?bearing systems.
文摘Various micro-mechanical and micro-structural influences on fatigue crack growth resistance of the material have been investigated over the years. It is widely recognized that resistance to fatigue crack growth can be differentiated into ‘intrinsic＇ and ‘extrinsic＇. The separation of intrinsic and extrinsic crack growth resistance has constituted a major theme of fatigue research in the last 30 years, with the concept of crack closure or crack tip shielding being used to rationalize a wide range of micro-structural and mechanical influences on fatigue crack growth behavior. An accurately quantitative understanding of intrinsic and extrinsic effects on crack growth is essential to directed alloy design for improved fatigue resistance, and/or improved structural service life. This paper presents a compliance-based crack closure measurement method and a multi-mechanism based analytical model for the separation of intrinsic and extrinsic material fatigue resistance, with application in characterizing the fatigue performance of two high strength damage tolerant airframe AI alloys.
文摘Commercial space activities are closely related to national politics,economy,and military. Due to the factors such as national security and economic benefits,most countries are actively developing commercial aerospace.In recent years,with the rapid development of private space companies such as SpaceX Corporation and Blue Origin Company,the cost of commercial space launch has been greatly reduced,which has had a huge effect on the existed international commercial market. Patent is the product of market competition. It is an effective means for international first-class companies to gain a competitive initiative and occupy the market superiority through protecting their intellectual property rights by patents during commercial space cooperation. At present,most of China aerospace enterprises are derived from national defense military units. Patents of national defense military units are the results of intellectual labor,which are characterized by their proprietary,temporal,and regional characteristics. However,due to the characteristics of national defense services,military monopoly,and group nature of property rights,the patent protection of defense units is different from that of ordinary enterprises. The problem of intellectual property protection in commercial space cooperation is more complicated. Therefore,in the fierce competition of international commercial aerospace,how China space companies can use patents to enhance their international competitiveness in commercial space cooperation is worthy of thinking and planning in advance. By analyzing the patent protection strategies and typical cases adopted by domestic and foreign aerospace companies in commercial space cooperation,it is expected to provide a reference for China space enterprises to effectively use patent strategies in commercial and space cooperation and to enhance China commercial aerospace competitiveness.
文摘This article provides a brief overview of the teaching and research at the School of Aerospace Engineering(SAE) to celebrate the 80 th anniversary of the establishment of aeronautics as a discipline at Tsinghua University. The evolution of the school, undergraduate/graduate students and faculty members, and research activities and achievements have been described. The research input including research funding and research projects are summarized, showing a diversity of funding sources and a significant growth in either sum total or spending per researcher. The achievements including publications and inter/national academic awards are also introduced. It can be seen that the level of academic publications has been growing over the past decades. In addition,four representative research achievements have been briefly described to show the scientific contributions of the school.
