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
Deng Y.,The First Aircraft Institute of AVIC |
Liao Z.,The First Aircraft Institute of AVIC |
Duan Z.,The First Aircraft Institute of AVIC
Kongqi Donglixue Xuebao/Acta Aerodynamica Sinica | Year: 2014
Five different three-elements airfoils which contain slat, fix foil and flap were analyzed. The only difference of those three-elements airfoils is the shape of the slat coves, which are faired to five shape, and the cusps are changed with the fairing accordingly. Using the RANS simulation of the in house CFD tool "CCFD-MB", the relative aerodynamic characters of the coves, such as the Reynolds effects, the stall behaviors, the lift and the drag coefficients, were analyzed. Some of the similar researches done by Boeing and DLR were also mentioned in the document as reference work. The paper indicates some beneficial results: some kinds of the slat coves may lead to negative Reynolds effects; some kinds of cove fairings provide better aero efficiency and potential noise reduction tendency; the normal slat coves wildly adopted in industry design are not the best choices from the point of aerodynamic, yet the aerodynamic characteristic are acceptable. Some suggestions on the choice of slat coves were given according to the consideration of aerodynamic and structure.
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.
Chai J.,The First Aircraft Institute of AVIC |
Gao X.,The First Aircraft Institute of AVIC |
Li Q.,The First Aircraft Institute of AVIC
27th Congress of the International Council of the Aeronautical Sciences 2010, ICAS 2010 | Year: 2010
A numerical method which is based on unstructured grids to compute high-temperature ionized air radiation is described. The multispecies N-S equations are used and the chemical model includes 11 species (O2,N2,O,N,NO, NO+ , N+,O+,N+ 2 , O+ 2 , e-) and 20 reactions. For simulating thermal nonequilibrium effect, the two-temperature model is considered. The finite volume method (FVM) is used for spatial and directional discretization for the RTE on unstructured grids. The code can deal with different kinds of species and radiative bands. Particularly, the Delta, Epsilon, Beta prime and Gamma prime bands of NO are considered in this paper. The numerical results of MUSES-C for hypersonic flow with hightemperature ionized radiation are shown, and compared well with the reference data and experimental data.
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.
Zhang Y.,Northwestern Polytechnical University |
Zheng X.T.,Northwestern Polytechnical University |
Yang J.,The First Aircraft Institute of AVIC |
Wang B.T.,The First Aircraft Institute of AVIC
Applied Mechanics and Materials | Year: 2014
The wide range of applications of fiber-reinforced composites in numbers of engineering fields is demanding better understanding on its hydrothermal properties. Especially for those are applied under complex hydrothermal environment such as aircraft industry. However, most methods we used at the present are either complicated or demand high-cost. In this paper, a novel approach based on finite element method (FEM) is proposed to calculate the hydrothermal factor by supposing an original decrease in the laminates stiffness. The integrated strains, consisting of Room Temperature Dry (RTD) strain and FEM simulated strain with the Elevated Temperature Wet (ETW) strain, are used to make an estimate for the hydrothermal factor. Hence, this FEM approach with low cost can be used to calculate the hydrothermal factor without doing full-scale structural ETW experiments. Compared with experimental results of the notched compression and single-bolted joints, it can be concluded that the approach introduced in the present paper can predict excellently the determination scope of the hydrothermal factor reasonably even in structural scale. © (2014) Trans Tech Publications, Switzerland.