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    Effect of Mistuned Parameters on Mode Localization of T-tail Structure
    Yang Zhichun;Yang Fei
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2009, 30 (12): 2328-2334.  
    Abstract30722)      PDF(pc) (904KB)(683)       Save
    Mode localization is often an unexpected dynamic phenomenon in weakly-coupled symmetric structures, and it arises from small imperfections (less than 5%) which perturb the symmetry of a structure. Such imperfections typically result from random manufacturing or assembly imprecision. Mode localization prediction is an important issue in T-tail structure design because drastic localized vibration phenomena may occur during the ground vibration test of a T-tail aircraft. Mode localization is dependent not only on parameter mistuning, but also on coupling degree. In this article the definition of mode localization is improved according to the peak amplitude ratio. The coupling degree is defined according to the effect of the stiffness of the horizontal stabilizer and fin on the modal frequencies of the T-tail structure. The mode localization and frequency loci veering phenomena for a T-tail structure is then studied and the effects of mistuned mass, mistuned stiffness and the location of mistuning on the mode localization of the horizontal stabilizer are investigated. Numerical simulation results for a T-tail structure model indicate that mode localization is most likely to occur in a T-tail structure consisting of weakly coupled substructures—a horizontal stabilizer and a fin. Moreover, when mode localization occurs, the first two bending vibration modes in the T-tail structure are prone to localization, and only one of the two modal frequencies is changed by parameter mistuning to induce frequency loci veering. The simulation also demonstrates that if mass or stiffness mistuning occurs to a horizontal stabilizer, the amplitude of the bigger mass side or smaller stiffness side is greater than that of the peer side. The study suggests that mode localization design is easy to achieve in T-tail structures by introducing mass mistuning on the tip of the horizontal stabilizer or stiffness mistuning on the root of the horizontal stabilizer.
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    Real-time Parameters Estimation of Inertial Platform’s HealthCondition Based on Belief Rule Base
    Hu Changhua;Si Xiaosheng
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2010, 31 (7): 1454-1465.  
    Abstract13642)      PDF(pc) (2000KB)(1006)       Save
    A real-time and accurate health condition prediction for an inertial platform is essential for cost-effective and timely maintenance planning and scheduling. Due to the fact that the true health condition of the inertial platform cannot be observed directly, it is assumed that the observations of characteristic parameters are available from monitoring, and the characteristic parameters correlate with health condition of the inertial platform. In this article, a health condition prediction system for the inertial platform is established based on belief rule base (BRB), where the characteristic parameters of the inertial platform are used as the inputs of BRB system and the health condition of platform as the output consequence. To overcome the drawbacks of current parameter optimization algorithms for BRB and satisfy real-time prediction, a parameter estimation algorithm is investigated for online updating BRB prediction system based on the expectation maximization (EM) algorithm. When the new input-output information of system operation is available, the model parameter can be updated online. Real-time health condition prediction for the inertial platform system is validated using the established model and the algorithm under investigation. The experimental results show that the proposed method can implement online parameter estimation of health condition prediction for the inertial platform effectively. In addition, compared with offline parameter optimization method, the proposed method can generate better results in terms of prediction accuracy and operating time, and thus has great potential in engineering practice.
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    Genetic collision avoidance planning algorithm for irregular shaped object with kinematics constraint
    ZHANG Zhi, LIN Shenglin, ZHU Qidan, WANG Kaiyu
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (4): 1348-1358.   DOI: 10.7527/S1000-6893.2014.0130
    Abstract12449)      PDF(pc) (7869KB)(524)       Save

    To deal with the path planning problems of irregularly shaped objects in complex environment, a genetic collision avoidance algorithm with kinematics constraint is developed. This algorithm is then applied to the path planning operations on carrier-based aircraft scheduling on carrier flight deck. Moreover, it can be extended to solve other path planning cases under such constraints. For the problems resulting from these objects, which are characterized by complex shape and the bending radius constraint while moving in complicated obstacle situations, the technique proposed is proved to be effective. Based on the traditional genetic path planning algorithm, a three-dimensional position and orientation coding method, a three-stage path decoding method and an approach specific to the collision detection and distance calculation of a track bounding box are presented. Also, a penalty term and a gene repairing strategy are brought into the genetic process to seek the optimum. Finally, simulated verifications are conducted using VC++ platform to obtain the optimal paths. The results show that the optimal collision avoidance paths in complex obstacle environment are achieved utilizing the proposed algorithm, with the pre-set bending radius constraints satisfied. It is indicated that the design yields effective solutions to the collision avoidance path planning problems correlated with this kind of objects.

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    Symmetry FrFT Used to Suppress the Fixed Background Clutter to Detect Moving Target in a SAR Image
    CHEN Guang-dong;ZHU Zhao-da;ZHU Dai-yin
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2005, 26 (6): 748-753.  
    Abstract10549)      PDF(pc) (784KB)(1113)       Save
    In single channel SAR, the echo from a slow moving target is confused with ground clutter in time、space and frequency domains. If the information about fixed clutter in SAR image can be used to suppress the background clutter, the detection of moving target will be easy. The fractional Fourier transform is a linear operator, and will not be influenced by cross terms. The FrFT is a way to concentrate the energy of the echo from a ground moving target. In two symmetry fractional Fourier domains with two inverse rotation angles of every SAR image tangential line, the static clutter’s spectrums are same, while the moving target’s are different. The absolute value subtracting of the two signals can be expected to have superior moving target detection performance. The experiment result proveds the validity of this method.
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    Development of future fighters
    YANG Wei
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2020, 41 (6): 524377-524377.   DOI: 10.7527/S1000-6893.2020.24377
    Abstract10256)      PDF(pc) (4047KB)(12594)       Save
    Recent years have witnessed extensive discussions on the change of warfare forms and the development of post-4th generation fighters against the background of great power competition and batches of 4th generation fighters entering service. This paper reviews the origin of fighter generation classification and the driving elements behind each generational leap, outlining the evolution of Observe, Orient, Decision, Act (OODA) loops for air combat and proposing the essence of OODA 3.0. After a summary of the supportive and progressive relations among mechanization, informatization and intelligentization, it explores the dialectical relationship among autonomy and manned/unmanned, as well as that among platform, system of systems, and distributed operation, followed finally by a discussion of an agile and efficient development approach of future fighters.
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    Numerical Study on Turbulent Convective Heat Transfer with n-heptane Under Supercritical Pressures
    Hua Yixin;Wang Yazhou;Meng Hua
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2010, 31 (7): 1324-1330.  
    Abstract9606)      PDF(pc) (1517KB)(1023)       Save
    This article establishes a general numerical scheme which incorporates the accurate transport and thermodynamic property calculations of a fluid under supercritical pressures based on a modified corresponding-state method and the fundamental thermodynamic relationships with the Soave-Redlich-Kwong (SRK) equation of state. A comprehensive numerical investigation of the turbulent convective heat transfer with n-heptane, a typical hydrocarbon fuel, under supercritical pressures is systematically conducted. This heat transfer phenomenon is closely related to engine cooling technique in rocket and hypersonic propulsion systems. The effect of the supercritical pressure on fluid flows and heat transfer phenomena is examined in detail. Variations of the Nusselt number are elucidated and compared with those obtained from the available empirical formulae. Numerical results indicate that under supercritical pressures, the Nusselt number decreases with decreasing pressure, and that turbulent heat transfer becomes weakened and slightly oscillated near the critical region.
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    Real-time residual life prediction based on semi-stochastic filter and expectation maximization algorithm
    FENG Lei, WANG Hongli, SI Xiaosheng, YANG Xiaojun, WANG Biaobiao
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (2): 555-563.   DOI: 10.7527/S1000-6893.2014.0257
    Abstract9490)      PDF(pc) (2024KB)(450)       Save

    The prediction of residual life (RL) is the key of the predictive maintenance for engineering equipment. Accurate and real-time prediction can provide more effective decision support to the subsequent maintenance schedule and avoid the failure effectively. In engineering practice, the performance index reflecting the degradation process of the equipment is generally not observed directly. To tackle the residual life problem under hidden degradation, a prediction method based on semi-stochastic and expectation maximization (EM) algorithm is proposed in this paper. First, the residual life is taken as the hidden state and the prediction model is constructed by building the stochastic relationship between the residual life and monitoring data. Secondly, based on the monitoring data up to the current time, a collaborative method by the extended Kalman filter (EKF) and expectation maximization algorithm is presented to achieve a real-time estimation and updating of the residual life distribution and unknown model parameters. Finally, the proposed method is validated by the application to the inertial measurement unit (IMU) and the results indicate that the method can improve the accuracy and reduce the uncertainty of the estimated residual life.

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    Application of Gauss-Hermite Filter in SINS Alignment
    XIE Yangguang, YI Guoxing, WANG Changhong, QU Yaobin
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2012, (3): 554-560.   DOI: CNKI:11-1929/V.20110726.1650.006
    Abstract9381)      PDF(pc) (1152KB)(621)       Save
    In this paper investigate the alignment problem of a stationary based strapdown inertial navigation system . In order to improve the aligning accuracy and shorten the aligning time, a Gauss-Hermite filter (GHF) is adopted in the alignment model based on large azimuth misalignment angles. The nonlinear Gauss integration of multi-variables to the mean and covariance computation in the GHF is addressed. Since large azimuth misalignment angles will introduce the nonlinearity in the alignment error equations, this paper employs linear state transformation approach to obtain the analytic solution of the linear state vector in the underlying equations. The integration of multi-variables is thus converted to the integration of a single-variable. Hence the so called "dimension problem" in the application of GHF to alignment is solved without loss of accuracy. The proposed method is applied to a SINS, and it shows that the aligning accuracy of path angle is improved by 16% and the aligning time is reduced by 75% compared with extended Kalman filter (EKF) and unscented Kalman filter (UKF).
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    High-Precision Estimation of 2D Angle for Signals with UCAs
    TAO Jian-wu;SHI Yao-wu;CHANG Wen-xiu
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2006, 27 (4): 687-691.  
    Abstract8868)      PDF(pc) (383KB)(1117)       Save
    Based on uniform circular arrays (UCAs), a high-precision estimation of 2D direction angle for multiple sources is proposed. First, exploiting information of source in 2D space-time domain forms the space-time rotational matrix, so that the multiple sources are separated. Second, based on a direct array manifold in UCA, the azimuth and elevation are estimated by Least Squares (LS). Finally, the removal method of cyclic ambiguity is presented. Numerical results show that the advantages of estimator are high precision and robustness to amplitude and phase error of sensor gain.
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    Achievements and predicaments of CFD in aeronautics in past forty years
    YAN Chao
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2022, 43 (10): 526490-526490.   DOI: 10.7527/S1000-6893.2021.26490
    Abstract8825)   HTML42)    PDF(pc) (26853KB)(5703)       Save
    Euler/RANS-based CFD methods have been rapidly developed and widely used in aeronautics since the 1980s, making remarkable achievements and playing an important role in aircraft development and aerodynamic research. This article reviews the achievements of CFD in military and civil aeronautics in the past four decades and analyzes its shortcomings, particularly the problem in separation flow simulation due to the turbulence modeling. The development of aeronautics CFD is discussed from the perspectives of turbulence models and numerical schemes. Finally, a brief conclusion and suggestions on future development are presented.
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    Kriging surrogate model and its application to design optimization: A review of recent progress
    HAN Zhonghua
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2016, 37 (11): 3197-3225.   DOI: 10.7527/S1000-6893.2016.0083
    Abstract8820)      PDF(pc) (9181KB)(5026)       Save

    Over the past two decades, surrogate modeling has received much attention from the researchers in the area of aerospace science and engineering due to its capability of greatly improving the efficiency of design optimization when high-fidelity numerical analysis is employed. Design optimization via surrogate models is intensively researched and eventually leads to a new type of optimization algorithm which is called surrogate-based optimization (SBO). Among the available surrogate models, such as polynomial response surface model, radial-basis functions, artificial neutral network, support-vector regression, multivariate interpolation or regression, and polynomial chaos expansion, Kriging model is the most representative surrogate model which has great potential in engineering design and optimization. In the context of aircraft design, this paper reviews the theory, algorithm and recent progress for researches on the Kriging surrogate model. First, the fundamental theory and algorithm of Kriging model are briefly reviewed and the experience about how to improve the robustness and efficiency is presented. Second, three major breakthroughs of Kriging model in recent years are reviewed, including gradient-enhanced Kriging, CoKriging and hierarchical Kriging. Third, the optimization mechanism and framework of surrogate-based optimization using Kriging model are discussed. In the meanwhile, the concept of infill-sampling criterion and sub optimization is presented. Five infill-sampling criteria as well as the dedicated constraint handling methods are described. Furthermore, the newly developed local EI (expected improvement) method and termination criteria for SBO are introduced. Fourth, a number of test cases including benchmark optimization problems as well as aerodynamic and multidisciplinary design optimization problems are given to demonstrate the excellent performance and great potential of the surrogate-based optimization using Kriging model. At last, the key challenges as well as future directions about the theory, algorithm and applications are discussed.

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    Influencing factors of combustion characteristics of boron particle in forced convective flow
    FANG Chuanbo, XIA Zhixun, HU Jianxin, WANG Dequan
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2015, 36 (2): 492-500.   DOI: 10.7527/S1000-6893.2014.0115
    Abstract8163)      PDF(pc) (4169KB)(340)       Save

    The combustion characteristics of single boron particle in forced convective flow in ramjet engines are investigated systemically. A physical and mathematical model is proposed taking into consideration the gas flow around the particle, the gas diffusion and the surface finite reaction dynamics. The two-dimensional axi-symmetric Navier-Stokes equations with species reactions are solved using the finite volume technique. And the numerical simulation method is validated. Then influencing factors such as the free stream velocity, particle radius, the ambient oxygen mass fraction and the ambient pressure on the combustion characteristics of single boron particle are studied by numerical simulations. And the effect mechanism for each factor is analyzed in detail. The numerical prediction results show that in forced convective flow, both the mass rate and the mass flux of the buring boron particle increase with the increase in the free stream velocity, the particle radius, the ambient oxygen mass fraction and the ambient pressure. A comprehensive analysis of the results is conducted and it is found that the mass flux of the buring boron increases with the stream Reynolds number. Then the mass flux of the buring boron particle in the static atmosphere is modified based on abundant numerical results to describe the combustion characteristics of the boron particle in forced convective flow.

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    EROSION WEAR BEHAVIOUR AND MODEL OF ABRADABLE SEAL COATING
    Yi Maozhong;Huang Baiyun;He Jiawen;Zhou Huijiu
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    1998, 19 (5): 546-552.  
    Abstract8103)      PDF(pc) (847KB)(836)       Save

    The erosion wear resistance is one of the most important properties of abradable seal coating. The erosion wear behaviour and mechanism of several kinds of middle temperature abradable seal coatings were investigated by a CMS 100 self made vacuum sand erosion machine. The results show that the relationship between the erosion weight loss and the erosion time is linear, the coatings hold a maximum erosion rate at 60° impact angle, and the relation between the erosion rate and the impact speed is an exponential function. The speed exponent increases with the increase of the impact angle. At 90° impact, the abrasive particles impinging on the coating surface produce indents and extrude lips, then the lips are work hardened and fall off; and flattened metal phase grains are impinged repeatedly, loosen and exfoliate. At 30° impact, the micro cutting, plowing and tunneling via pores and non metal phase are involved. The model of the erosion mechanism is advanced on the basis of the above mentioned erosion behaviour.

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    Laminar Flow Control Technology and Application
    ZHU Ziqiang, WU Zongcheng, DING Juchun
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2011, 32 (5): 765-784.  
    Abstract7737)      PDF(pc) (3625KB)(4903)       Save
    Friction drag is the major part of the total drag of a transport, so reducing it is essential for improving the performance and reducing the cost of a transport. Since laminar friction drag is much less than the turbulent one, one of the important measures for reducing it is to increase the laminar flow extent, and if possible, to realize a fully laminar flow. For that, three types of laminar flow control technology, i.e., natural laminar flow, fully laminar flow and hybrid laminar flow controls, are formed. In the present paper, drag reducing analysis, the concepts, methods, potential benefits and design methods of laminar flow control technology, and operational maintenance of a laminar flow aircraft (including protection of insect contamination and ice accumulation) are systematically described; Summary of researches of laminar flow control technology during 1930-2000 is briefly introduced and the progress in this field is shown by using examples of X-21A slotted suction flight tests, simulated airlines flight tests of Jetstar HLFC leading edge systems and Boeing 757 HLFC flight tests, and future research is also pointed out.
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    Influence of Opposing Jet on Flow Field and Aerodynamic Heating at Nose of a Reentry Vehicle
    Rong Yisheng;Liu Weiqiang
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2010, 31 (8): 1552-1557.  
    Abstract7299)      PDF(pc) (26444KB)(799)       Save
    A CFD study on the reduction of aerodynamic heating on the nose of a reentry vehicle by an opposing jet thermal protection system is conducted, by means of which the flow field parameters, reattachment point position, surface pressure distribution and heat flux distribution are obtained. The physical mechanism of the reduction of heat flux is analyzed. The opposing jet interacts with the freestream to form a Mach disk which enables the freestream to flow to the edges rather than interact with the surface to produce aerodynamic heating. In addition, the jet flows back to form a cool recirculation region, which reduces the difference in temperature between the surface and the nearby gas, and thus reduces the heat flux. The larger the total pressure ratio, the lower is the aerodynamic heating. To study the effect of the intensity of the opposing jet more appropriately, a new parameter RPA is defined by combining the flux and the total pressure ratio. The study shows that the same shock wave position, reattachment point position, peak heat flux position and total heat load can be obtained with the same RPA with different fluxes and total pressure ratios, which means the new ratio parameter may account for the intensity of the opposing jet and be used to analyze its influence on the flow field and total heat load at the nose of a reentry vehicle.
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    Application of Hierarchical Partial Least Squares Regression to Development Cost Prediction of Aircraft
    Wang Liyuan;Guo Jilian;Zhang Hengxi
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2009, 30 (8): 1380-1384.  
    Abstract7144)      PDF(pc) (623KB)(756)       Save
    In the analysis of the development cost of an aircraft there are usually only small samples with a large number of cost drive factors. In view of this fact and considering the advantages of hierarchical partial least squares regression (Hi-PLS) in building a regressive model in the condition of a large number of variables, an application of Hi-PLS to aircraft development cost prediction is proposed using the development cost prediction of a fighter plane fuselage as an example. After the cost drive factors of the fighter plane fuselage development cost are grouped, Hi-PLS is applied to the regress of the grouped cost drive factors, and a fuselage development cost prediction model is established. The calculated results in the example show that Hi-PLS model can reflect satisfactorily the correlation between fuselage development cost and performance parameters of a military aircraft.
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    TYPES OF FLOW OVER LEESIDE OF A CLIPPED DELTA WING AT SUPERSONIC SPEEDS
    Hong Jinsen
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    1996, 17 (5): 90-95.  
    Abstract7122)      PDF(pc) (288KB)(599)       Save
    This paper describes a flow visualization experiment over the leeside of a slender tapered wing with a leading edge sweepback angle of 65° and a biconvex section. By using laser vapor screen, schlieren and oil flow techniques, the test was carried out at Mach numbers of 1.10, 1.53, 2.53, 3.01 and 4.01 for angles of attack from 5° through 25°. And photos of flow off body and on lee surface have been taken. The vapor screen photos show seven distinct types of flow developed over the delta region of the wing. These types of flow are displayed in a plane of Mach number and angle of attack normal to the leading edge. In the region of the side edge there are side vortices formed and in the region of the trailing edge trailing vortices shed. The variations of both the bow shock positions at different Mach numbers and the positions of separating lines induced by shock waves with Mach numbers and angles of attack are obtained based upon the schlieren plus the vapor screen photos in the sections. The oil flow visualization shows clearly primary reattachment, secondary separation, secondary reattachment lines and side edge vortices on the lee surface. The results of this test are in good agreement with experiments and numerical simulations of others.
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    MULTIPLE INPUT-OUTPUT FREQUENCY RESPONSE FUNCTIONS ESTIMATION
    Li Yuefeng;Lu Minfu
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    1986, 7 (6): 596-603.  
    Abstract6797)      PDF(pc) (517KB)(1689)       Save
    The theory of multiple input-output frequency response functions estimation is studied based on the finite Fourier transform. Several possible input signal types are discussed. Of them, the deterministic signal excitation is a new technique which is adrantageous over the currently prevailing random exci tation in test time, the amount of data required to be sampled and reduced and the estimation accuracy. Moreover, the hardware requirement is simpler and it is possible to run with a dual-channel FFT analyser only.In light of the theory, a software package for 6 input-multiple output FRF estimation has been developed, running in the PDP11/23 mini computer system with 64K bytes memory. The operator is prompted to select one from 4 excitation types, ( 1 ). deterministic, ( 2 ). periodic random, ( 3 ). burst random, and( 4 ). continuous random excitation. The package was used for real structures such as a free-free beam and a helecopter tail rotor. The results show that the deterministic excitation technique was the best.
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    COMPARATIVE TEST STUDY FOR THE MAXIMUM LIKELIHOOD PRINCIPLE AND THE TREATMENT OF ITS FATIGUE TEST DATA
    Xiong Junjiang;Huang Xinyu;Gao Zhentong Xia Qianyou;Gan Weimin;Zeng Benyin;Sun Rulin
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    1996, 17 (5): 28-31.  
    Abstract6503)      PDF(pc) (228KB)(526)       Save
    On the basis of N(S-S 0) m=C , according to the maximum likelihood principle, the formulas of P S N curves are presented which were determined by the single spot method, the single spot group method and the group method.The comparative test was made, and the test data are analyzed and treated. It was found that the P S N curves determined by these three methods were approximate.By means of the single spot method,many specimens may be saved, so the single spot method may be used to determine the P S N curves of the structure components.
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    Evaluation of Equipment System Availability for Multi-echelon Maintenance Supply with Cannibalization
    RUAN Minzhi, LI Qingmin, PENG Yingwu, HUANG Aolin, WANG Shen
    ACTA AERONAUTICAET ASTRONAUTICA SINICA    2012, (4): 658-665.   DOI: CNKI:11-1929/V.20111223.1225.001
    Abstract6400)      PDF(pc) (1472KB)(617)       Save
    Cannibalization policy is an effective approach to improve support effectiveness. Under the current support condition, it can make equipment availability reach the upper limit. This paper establishs respectively availability models of a non-cannibalization system, a cannibalization system and a partial cannibalization system under the mode of multi-echelon maintenance supply in accordance with the characteristics of cannibalization combined with multi-echelon technique for recoverable item control(METRIC) theory. The analysis flow and method of support effectiveness are studied. In a given example, The initial spare parts inventory project is obtained under which the equipment availability is analyzed with different cannibalization policies. VMETRIC simulation is used to test the results, and the verification shows that there is high consistency between the two results, which proves the validity of the model.
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