The First Aircraft Institute of AVIC
The First Aircraft Institute of AVIC
Zhan Z.,Beihang University |
Hu W.,Beihang University |
Li B.,Beihang University |
Zhang Y.,The First Aircraft Institute of AVIC |
And 2 more authors.
International Journal of Mechanical Sciences | Year: 2017
Fatigue is a major reason for the failure of components subjected to cyclic loadings, and the fatigue failure of components can be divided into two phases: crack initiation and crack propagation. In this study, continuum damage mechanics (CDM) combined with the extended finite element method (XFEM) is proposed to predict the total fatigue life of components, that is, the crack initiation life and propagation life. First, the damage-coupled elastic-plastic constitutive equations and fatigue damage evolution equations are derived to calculate the fatigue damage and to predict the crack initiation life of a material under cyclic loads. Second, according to the distribution of the damage field and trend of fatigue damage evolution, the criterion to judge the formation of crack initiation is proposed. Third, based on linear elastic fracture mechanics (LEFM) with XFEM, the crack propagation life is predicted. Then, fatigue crack initiation and propagation analysis for a specimen with a preset pit and for a fuselage structure with opening are conducted using the method described above. Finally, fatigue experiments are conducted to verify the proposed method, and the predicted total fatigue life and crack propagation path are in accordance with the experimental results. © 2017 Elsevier Ltd
Zhan Z.,Beihang University |
Meng Q.,Beihang University |
Hu W.,Beihang University |
Sun Y.,Beihang University |
And 2 more authors.
International Journal of Fatigue | Year: 2017
In this study, an approach based on continuum damage mechanics is applied to the fatigue life prediction and to analysing the influence of various factor on scarf bolted joints used in an aircraft fuselage. First, the damage-coupled elastic-plastic constitutive equations and fatigue damage evolution equations are presented, and the corresponding numerical calculation algorithm is established using the ABAQUS platform. Then, the proposed fatigue damage model is validated by a group of fatigue tests on scarf joints. Subsequently, the aforementioned approach is applied to the influencing factor analysis of scarf bolted joints. The effects of the scarf angle, the surface friction and the clamping force are investigated in detail. In addition, the sensitivity of the fatigue life with respect to the scarf angle, surface friction and clamping force is evaluated. The effect mechanisms of these factors are revealed clearly, and the influencing trends are presented quantitatively, which has important practical significance for the design of scarf joints. © 2017 Elsevier Ltd
Yue T.,Beihang University |
Zhang X.,Beihang University |
Wang L.,Beihang University |
Ai J.,the First Aircraft Institute of AVIC
Aerospace Science and Technology | Year: 2017
In this paper, a sliding mode flight controller is formulated in order to enhance the lateral maneuverability for a tailless telescopic wing morphing aircraft by using additional asymmetric wing telescoping. Based on the nonlinear time-varying equations of motion and the approximate aerodynamic model obtained by wind tunnel tests, a nonlinear time-varying model with coupling between aerodynamic parameters and control inputs is established and the open-loop dynamic response characteristics are analyzed. According to the difficulty of precise aerodynamic modeling during both sides of wing telescoping, the sliding mode control approach is used to design the control law to track maneuver reference command, which has a low requirement for modeling precision and is suitable for the nonlinear time-varying system. In addition, the control inputs are allocated to asymmetric wing telescoping and aerodynamic control surfaces based on the minimum energy method. The closed-loop simulation results of a roll agility maneuvering called “T90 maneuvering” are presented. The results show that a larger roll angular velocity is produced and the control surfaces in the maneuvering flight can maintain a large control margin, which means the maneuverability is significantly improved and the control burden of the aerodynamic control surfaces has been reduced compared with the aircraft without use of telescopic wings; moreover, the robustness of the sliding mode controller is verified by simulation of aerodynamic perturbations. © 2017 Elsevier Masson SAS
Zhang D.,The First Aircraft Institute of AVIC |
Zhang J.,The First Aircraft Institute of AVIC |
Li J.,The First Aircraft Institute of AVIC
Hangkong Xuebao/Acta Aeronautica et Astronautica Sinica | Year: 2016
Energy balance is the core factor and also one of the most difficult points of the design of solar powered aircrafts. Based on solar radiation model, energy principle and typical flight profile of solar powered aircrafts, this paper conducts research on energy balance modeling for solar powered aircrafts. Both takeoff-climb-cruise energy balance model and the whole day duration flight energy balance model are constructed based on the flight profile and energy requirement. Energy calculating formula for each time phase is presented, and multiple cases of glide are discussed. The energy balance models are validated through an analysis example. © 2016, Press of Chinese Journal of Aeronautics. All right reserved.
Wang Y.,Northwestern Polytechnical University |
Zhang B.,Northwestern Polytechnical University |
Guo Z.,The First Aircraft Institute of AVIC |
Dong Q.,The First Aircraft Institute of AVIC
Hangkong Xuebao/Acta Aeronautica et Astronautica Sinica | Year: 2013
A free-form deformation parameterization (FFD) method is established based on non-uniform rational B-spline (NURBS) basis function. Furthermore, by coupling the transfinite interpolation (TFI) grid deformation technology and computational fluid dynamics (CFD) method with improved particle swarm optimization (PSO) arithmetic, a general aerodynamic optimization design system is constructed. Then, the aerodynamic optimization design system is applied to designing a large upswept afterbody of transport aircraft C17 on the restrictions of nondecreasing maximum structure height, width and upswept angle. The optimized afterbody decreases the total drag by 2.6% and pressure drag by 19.8% respectively. A comparison analysis of the aerodynamic shape and flow pattern reveals that the key factors for the optimized afterbody to decrease the pressure drag greatly are the increased near-roundness of the afterbody cross-section and decreased near-roundness change ratio along the fuselage axis. The two factors enable the adverse pressure gradient along the circumferential direction to become smaller, which can suspend aferbody separation and weaken afterbody vortex strength. The aerodynamic optimization design system constructed in this paper has good practicability and engineering application prospect.
Wang L.-S.,Tsinghua University |
Wang L.-S.,The First Aircraft Institute of AVIC |
Cen S.,Tsinghua University |
Xie L.-L.,Tsinghua University |
Lu X.-Z.,Tsinghua University
Gongcheng Lixue/Engineering Mechanics | Year: 2016
Numerical simulation is an effective method for investigating the earthquake-induced collapse mechanism of super-tall buildings. As one of the most important lateral-force resistant components, the shear walls usually exhibit complex mechanical behaviors and even fail with large deformation induced by structural collapse. Hence, a reliable numerical model which can consider large deformation is critical for the earthquake-induced collapse simulation. A high-performance quadrilateral shell element based on the theory of generalized conforming element, accounting for the geometric nonlinearity of large deformation using the updated Lagrangian formula, is herein proposed and implemented in an open-source software (i.e. OpenSees). The reliability of the element and associated algorithm for large deformation is initially validated through classic examples. Subsequently, simulation of various shear walls is conducted using the multi-layer section and the proposed shell element. Through a comparison with the experimental data, the reliability of the element is further validated in representing the complex mechanical behavior of shear walls, and the element is capable of capturing the key collapse characteristics of reinforced concrete components. The research outcome will assist in providing an effective tool for further investigation on the collapse mechanism of super-tall buildings using OpenSees. © 2016, Engineering Mechanics Press. All right reserved.
Yang J.,The First Aircraft Institute of AVIC |
Chen J.,Northwestern Polytechnical University |
Zhang Q.,Northwestern Polytechnical University
Jinshu Rechuli/Heat Treatment of Metals | Year: 2015
TC21 titanium alloy sample was prepared by laser near net forming, and microstructure and properties of deposited and double annealed specimens were investigated by OM, SEM and tensile properties test. The results show that the microstructure of laser near net formed specimen has a epitaxial growth characteristics that the β columnar crystal grows along the height direction of deposition. The microstructure of β columnar crystal appear as basket-weave and smaller than forging matrix. The tensile strength of the alloy is equal to strength of forging actual measurement at room temperature, the plasticity is lower than that of the forging, but all over the forging standard. There are a lot of dimples with different shape and size distributed on tensile fracture, thus is ductile fracture. ©, 2015, Chinese Mechanical Engineering Society of Heat Treatment. All right reserved.
Wei F.,Huazhong University of Science and Technology |
Pan X.,Huazhong University of Science and Technology |
Zeng Y.,Huazhong University of Science and Technology |
Ding H.,The First Aircraft Institute of AVIC
Yi Qi Yi Biao Xue Bao/Chinese Journal of Scientific Instrument | Year: 2011
At present, no standard is defined for the fiber-optical transmissions of CAN signals. A fiber-optic CAN hub and the scheme of constructing CAN network based on the hub (patent pending) are proposed in this paper. After a summarization of the three features of the physical layer of twisted-pair CAN bus, the working principle and the design method of the hub are discussed in detail. Through replacing the "Wire-AND" in twisted-pair CAN with CPLD "AND" logic and enabling the bus monitoring function of the nodes by sending the "ANDed" signal back to them, the fiber-optic CAN bus is completely compatible with the existing CAN standard above the physical layer. Two methods of expanding the fiber-optic CAN bus are also described. An eight-port prototype hub was implemented and test result proves the correctness and feasibility of the proposed scheme. The research work is very important to the promotion of new physical layer standard of CAN bus.
Liu Z.-H.,Beihang University |
Wu Z.,Beihang University |
Gao X.,The First Aircraft Institute of AVIC
Xi Tong Gong Cheng Yu Dian Zi Ji Shu/Systems Engineering and Electronics | Year: 2010
The relation between memory and variable numbers is found, and the effects of the ratio of grid partition dimensions to incident wavelength and the truncation number to memory are presented based on multilevel fast multipole algorithm (MLFMA) and memory which is the primary part of the storage matrix. When incident frequency is invariable and grid partition dimensions decrease, the memory of radiating pattern and receiving pattern is directly proportional to total unknown numbers, and the sparse matrix memory increases by a square ratio to unknown numbers. The whole memory mushrooms under the influence of them as an affirmative result. When grid data are invariable and incident frequency reduces, the sparse matrix memory does not change and the memory of radiating pattern and receiving pattern would decrease with a reduction in frequency, at the same delamination number, while the sparse matrix memory increases by a square ratio with a reduction in delamination numbers. The memory of radiating pattern and receiving pattern does not change and the oscillation of the whole memory is enhanced when the frequency changes by even number times. After improving the precision control of truncation numbers, the calculating precision is enhanced notably, but the memory of radiating pattern and receiving pattern and the whole memory increase correspondingly.
Kong M.,The First Aircraft Institute of AVIC |
Duan Z.,The First Aircraft Institute of AVIC |
Ma Y.,The First Aircraft Institute of AVIC
Shiyan Liuti Lixue/Journal of Experiments in Fluid Mechanics | Year: 2016
Aerodynamic characteristics of icing on different wing sections are one of the most important factors to be considered for designing anti/de-icing system. Wind tunnel routine force measure tests were carried out to obtain aerodynamic characteristics using simulation ice model on different wing sections of an airplane. Wing leading icing on different wing span sections would lead to different aerodynamic performance losses. Cruise and landing configurations were involved to study the lift, drag and pitch characteristics of the airplane. The results of the research showed that icing in the middle part of the wing lead to the greatest aerodynamic performance losses, and icing at the root and the tip of the wing leads to less aerodynamic performance losses which could be propitious to establish effective and efficient anti/de-icing system. © 2016, Editorial Department of JOURNAL OF EXPERIMENTS IN FLUID MECHANICS. All right reserved.