检索结果-南通市图书馆

Modeling and parameter identification of linear time-varying systems based on adaptive chirplet transform under random excitation

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2021年第4期34卷 56-66页

作者： Jie ZHANG Zhiyu SHI Lirong LI State Key Laboratory of Mechanics and co.trol of Mechanical Structures Nanjing University of Aeronautics and AstronauticsNanjing 210016China shanghai aircraft customer service co. Ltd.Shanghai 200241China

In this paper,a time–frequency algorithm based on adaptive chirplet transform for parameter modeling and identification of Linear Time-Varying(LTV)systems under random excitation is *** is assumed that the solution of responses of LTV structures is expressed as the sum of multico.ponent Linear Frequency Modulated(LFM)signals in a *** the measured acceleration response is used to perform the adaptive chirplet transform,in which an integral algorithm is employed to reco.struct the velocity and displacement *** vibration differential equation with time-varying co.fficients is transformed into a simple linear ***,for systems under random excitation,the input–output relation based on co.relation function is also derived to estimate the parameters including physicals parameters and instantaneous modal *** full procedure of the method is presented and validated by using simulated *** results show that the presented method is accurate and robust for various LTV systems under random excitation.

关键词： Acceleration response Chirplet transform LTV systems Random excitation System parameter identification

Joint optimization of sampling interval and co.trol for co.dition-based maintenance using availability maximization criterion

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Electronics 2018年第1期29卷 203-215页

作者： LI Xin CAI Jing ZUO Hongfu LIU Ruochen CHEN Xi GUO Jiachen co.lege of Civil Aviation Nanjing University of Aeronautics and AstronauticsNanjing 211106China School of Automobile and Traffic Engineering Jiangsu University of TechnologyChangzhou 213001China shanghai aircraft customer service co. Ltd.Shanghai 200241China

Most of the maintenance optimization models in co.dition-based maintenance(CBM) co.sider the co.t-optimal criterion, but few papers have dealt with availability maximization for maintenance applications. A novel optimal Bayesian co.trol approach is presented for maintenance decision making. The system deterioration evolves as a three-state co.tinuous time hidden semi-Markov process. co.sidering the optimal maintenance policy, the multivariate Bayesian co.trol scheme based on the hidden semi-Markov model(HSMM) is developed, the objective is to maximize the long-run expected average availability per unit time. The proposed approach can optimize the sampling interval and co.trol limit jointly. A case study using Markov chain Monte Carlo(MCMC)simulation is provided and a co.parison with the Bayesian co.trol scheme based on hidden Markov model(HMM), the age-based replacement policy, Hotelling’s T2, multivariate exponentially weihted moving average(MEWMA) and multivariate cumulative sum(MCUSUM) co.trol charts is given, which illustrates the effectiveness of the proposed method.

关键词： co.dition-based maintenance(CBM) availability maximization Markov chain Monte Carlo(MCMC) hidden semiMarkov model(HSMM) Bayesian co.trol sampling interval

Aerodynamic/mechanism optimization of a variable camber Fowler flap for general aviation aircraft

在线全文

学校读者我要写书评

暂无评论

Science China(Technological Sciences) 2017年第8期60卷 1144-1159页

作者： TIAN Yun WANG Tao LIU PeiQing FENG PeiHua National Lab for Aeronautics and Astronautics Beijing 100191 China co.AC shanghai aircraft customer service co. Ltd Shanghai 200241 China School of Aeronautic Science and Engineering Beihang University Beijing 100191 China Beijing Machinery and Electronics Engineering Institute Beijing 100074 China

A co.ventional Fowler flap is designed to improve the take-off and landing performances of an aircraft. Because the flight states of general aviation aircraft vary significantly. A Fowler flap with a double-sliding track has been designed, which is ca- pable of changing airfoil camber while cruising and climbing as well as meeting low-speed performance requirements. The aerodynamic characteristics of the variable camber Fowler flap were studied by co.putational simulation, and cambering was found to be beneficial for improving the lift-to-drag ratio when the lift co.fficient was larger than the critical value, below which decambering was more effective; this critical value differed somewhat under different co.ditions. Taking the mecha- nism into acco.nt, the take-off and landing co.figurations were optimized on the basis of the GA （W）-1 airfoil with a 30% chord Fowler flap. co.pared with reference co.figuration, the maximum lift co.fficient of optimized take-off co.figuration was increased by 6.6% as well as the stalling angle and the lift-to-drag ratio were increased by 1.3° and 7.58%, respectively. Moreover, the maximum lift co.fficient of the optimized landing co.figuration was increased by 6.3%, and the stalling angle was increased by 1.1°; however, the nose-down pitching moment of both co.figurations increased. Similar results were at- rained on a general aviation aircraft wing/body co.bination nism was established in a co.puter-aided design system, achieved by the double-sliding track. A 3D model of the variable-camber Fowler flap driving mecha- and the results showed that all design co.figurations co.ld be

关键词： Fowler flap general aviation aircraft variable camber optimization

Research of Maintenance Task Interval Optimization of Elevator Hydraulic Actuation System

在线全文

学校读者我要写书评

暂无评论

International Journal of Plant Engineering and Management 2019年第3期24卷 169-179页

作者： CHEN Rui WANG Yiping SUN Tieyuan shanghai aircraft customer service co. Ltd.

In order to solve the best maintenance interval problem of the elevator hydraulic actuation systems on civil aircraft, a method based on reliability and co.t minimum is introduced in this paper. The estimation of system reliability is presented by using two-parameter Weibull distributions. The parameters are estimated by using Weibull probability statistical analysis and the practical operational data. Then, the maintenance optimization model isformulated where the objective function is to minimize the expected schedule maintenance co.t in a time unit. The results of numerical example show that the proposed model co.ld scheme the optimal maintenance intervals for the co.sidered system when the parameters are given. This research has certain significance in theoryand engineering practice.

关键词： elevator hydraulic actuation system maintenance interval minimum co.t Weibull

Research on the Civil aircraft customer service System Simulation Based on SD Model

在线全文

学校读者我要写书评

暂无评论

Research on the Civil Aircraft Customer Service System Simul...

Toward an understanding of dwell fatigue damage mechanism of bimodal Ti-6Al-4V alloys

2012 IEEE 19th International co.ference on Industrial Engineering and Engineering Management(IE&EM 2012)

作者： Jun Xu Cui-xia BI School of Eco.omics and Management Beihang University shanghai aircraft customer service co.LTD.

customer service ability is one of the key co.petitiveness in market co.petition for civil aircraft manufacturers who participate. To establish the mature reliable civil aircraft customer service system based on the service strategy is an important aspect to reflect the customer service skills. Based on the idea of system dynamics, this paper co.structed a system dynamics model （SD model） of the customer service system of co.AC, and through the simulation of the system, analyzed the key factors which affect the running of the customer service system, to provide the basis for decision-making and measures.

关键词： Civil aircraft customer service system simulation system dynamic model

来源： cnki会议评论

在线全文

cnki会议

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2022年第13期108卷 244-255页

作者： L.R.Zeng L.M.Lei X.M.Luo G.P.Zhang Shenyang National Laboratory for Materials Science Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China School of Mechanical Engineering Chengdu UniversityChengdu 610106China AECC shanghai co.mercial aircraft Engine Manufacturing co. Ltd.Shanghai 201306China

Dwell fatigue effect is a long-standing problem threatening the long-term service reliability for fan blades and fan disks of an aircraft *** understand the basic mechanism of dwell fatigue damage,pure fatigue and 60 s dwell fatigue properties of bimodal Ti-6Al-4V alloys with different volume fractions of the primaryα(α_(p))phase were examined *** results showed that both pure fatigue and dwell fatigue life decreased with increasing the volume fraction of theα_(p)phase and the dwell fatigue life was lower than the pure fatigue *** quasi-in-situ test results and the quantitative characterization of damage behaviors of the local microstructure units defined by theα_(p)-seco.daryα(α_(s))co.bination reveal that theα_(s)phase close to theα_(p)phase with extensively slip activities was gradually damaged under dwell fatigue loading,while that under pure fatigue loading was undamaged,demonstrating that the dwell loading induced the damage of theα_(s)phase,and further reduced the fatigue life.A stress relaxation-based model is proposed to describe the physical mechanism on dwell fatigue damage of the bimodal Ti-6Al-4V alloy,*** elastic deformation of theα_(s)phase caused by the strain inco.patibility would be gradually transformed into plastic deformation during the dwell stage,and thus promotes fatigue *** model provides new insights into the microsco.ic process of stress/strain transfer between the soft and hard microstructure units under dwell fatigue loading.

关键词： Dwell effect Fatigue damage Stress relaxation Volume fraction of primaryαphase Quasi-in-situ testing

Causes of progressive stamping die damage and retooling measures to reduce carbide punch fracture

在线全文

学校读者我要写书评

暂无评论

Baosteel Technical Research 2016年第4期10卷 30-35页

作者： LIANG Gaofei YAN Yuanyuan LUO Xiaoliang LIN Changqing FU Yan'an SHAO Zongqiang Research Institute Baoshan Iron & Steel Co. Ltd. Shanghai 201900 China Manufacturing Management Department Baoshan Iron & Steel Co. Ltd. Shanghai 201900 China customer & Product service Department Baoshan Iron & Steel Co. Ltd. Shanghai 201900 China

We investigated the reasons for frequently appearing early failure of carbide punches in a progressive stamping die when they were used to produce magnetic shielding steel parts. The failure modes of the carbide punches were statistically classified. Edge chipping and shoulder fracturing were the two types of failure modes that were found. The co.position, hardness, and microstructure of the punches were analyzed. The co.alt co.tent was found to be too low to ensure sufficient toughness. The brittle phase of tungsten carbide （WC）was prone to breaking off during the shear cutting process, and resulted in edge chipping. In addition, the material chips were easily bonded to the punch edge when there was a lack of press oil lubricity. It resulted in an uneven blanking clearance, which caused a lateral force and finally resulted in shoulder fracturing of the punches. Improvement measures were introduced to address the abovementioned issues. By using the carbide punches with greater toughness and shear cutting oil with high lubricity, the early damage problems of the punches are effectively solved, which ensures normal production of the magnetic shielding steel parts.

关键词： progressive die shear cutting failure fracture