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Study on the Mechanical Properties of Ni-Ti-Cu Shape Memory Alloy Considering Different Cu Contents

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Computer Modeling in Engineering & Sciences 2022年第6期131卷 1601-1613页

作者： Bingfei Liu Yangjie Hao Transportation Science and Engineering college Civil Aviation University of ChinaTianjin300300China Aeronautical Engineering college Civil Aviation University of ChinaTianjin300300China

By adding copper to increase the performance,the Ni-Ti-Cu Shape Memory Alloy(SMA),has been widely used in the field of engineering in recent years.A thermodynamic constitutive model for Ni-Ti-Cu SMA considering different copper contents is established in this work.Numerical results for two different copper contents,as examples,are compared with the experimental results to verify the accuracy of the theoretical work.Based on the verified constitutive model,the effects of different copper content on the mechanical properties of Ni-Ti-Cu SMA and the tensile and compressive asymmetric properties of Ni-Ti-Cu SMA are finally discussed,respectively.

关键词： Shape memory alloy copper contents constitutive model tension and compression asymmetric

Improved adaptive genetic algorithm based RFID positioning

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Journal of Systems Engineering and Electronics 2022年第2期33卷 305-311页

作者： LI Yu WU Honglan SUN Youchao civil aviation college Nanjing University of Aeronautics and AstronauticsNanjing 211100China

The existing active tag-based radio frequency identi-fication(RFID)localization techniques show low accuracy in practical applications.To address such problems,we propose a chaotic adaptive genetic algorithm to align the passive tag ar-rays.We use chaotic sequences to generate the intersection points,the weakest single point intersection is used to ensure the convergence accuracy of the algorithm while avoiding the optimization jitter problem.Meanwhile,to avoid the problem of slow convergence and immature convergence of the algorithm caused by the weakening of individual competition at a later stage,we use adaptive rate of change to improve the optimiza-tion efficiency.In addition,to remove signal noise and outliers,we preprocess the data using Gaussian filtering.Experimental results demonstrate that the proposed algorithm achieves high-er localization accuracy and improves the convergence speed.

关键词： radio frequency identification(RFID)positioning im-proved genetic algorithm Gaussian filter passive tags

Study on the resolution of multi-aircraft flight conflicts based on an IDQN

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Chinese Journal of Aeronautics 2022年第2期35卷 195-213页

作者： Dong SUI Weiping XU Kai ZHANG College of Civil Aviation Nanjing University of Aeronautics and AstronauticsNanjing 211106China

With the rapid growth of flight flow,the workload of controllers is increasing daily,and handling flight conflicts is the main workload.Therefore,it is necessary to provide more efficient conflict resolution decision-making support for controllers.Due to the limitations of existing methods,they have not been widely used.In this paper,a Deep Reinforcement Learning(DRL)algorithm is proposed to resolve multi-aircraft flight conflict with high solving efficiency.First,the characteristics of multi-aircraft flight conflict problem are analyzed and the problem is modeled based on Markov decision process.Thus,the Independent Deep Q Network(IDQN)algorithm is used to solve the model.Simultaneously,a’downward-compatible’framework that supports dynamic expansion of the number of conflicting aircraft is designed.The model ultimately shows convergence through adequate training.Finally,the test conflict scenarios and indicators were used to verify the validity.In 700 scenarios,85.71%of conflicts were successfully resolved,and 71.51%of aircraft can reach destinations within 150 s around original arrival times.By contrast,conflict resolution algorithm based on DRL has great advantages in solution speed.The method proposed offers the possibility of decision-making support for controllers and reduce workload of controllers in future high-density airspace environment.

关键词： Air traffic control Conflict resolution Multi-agent system Multi-aircraft flight conflict Reinforcement learning

Evaluation of the performance of GNSS-based velocity estimation algorithms

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Satellite Navigation 2022年第3期3卷 162-177,I0004页

作者： Li Ji Rui Sun Qi Cheng Junhui Wang College of Civil Aviation Nanjing University of Aeronautics and AstronauticsNanjing211106China

Global Navigation Satellite System(GNSS)based velocity estimation is one of the most cost-effective and widely used methods in determining velocity in geodesy and transport applications.Highly accurate and reliable velocity measurements can be obtained by exploiting the raw Doppler,carrier phase,and pseudorange measurements with a GNSS receiver.There are several approaches to GNSS-based velocity determination.This paper investigates the characteristics of the approaches which are currently popular and applicable to the observations of Global Positioning System(GPS),BeiDou Navigation Satellite System(BDS),and their combination(GPS/BDS).Specifically,it evaluates the performance of the velocity estimated based on the Raw Doppler method,the Time-Differenced Pseudorange method,the Time-Differenced Carrier Phase method,and the Double-Differenced Carrier Phase method,in both static and dynamic modes and in open and urban scenarios.The experiments show that BDS has the advantages in delivering accurate velocity determinations over GPS in the Asia–Pacific region,and the effectiveness of the GPS/BDS in improving the overall accuracy of velocity determination in complex urban scenarios.

关键词： GNSS BDS GPS Vehicle velocity determination

Modal analysis strategy and nonlinear dynamic characteristics of complicated aero-engine dual-rotor system with rub-impact

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Chinese Journal of Aeronautics 2022年第1期35卷 184-203页

作者： Pingchao YU Guo CHEN Lunxu LI College of Civil Aviation Nanjing University of Aeronautics and AstronauticsNanjing 211106China

This paper aims to gain insight into the nonlinear modal characteristics and the possible influence of the modes on the responses for the practical dual-rotor system with rub-impact in aero-engine.The finite solid element method combined with a constraint stiffness model produced by rub-impact is introduced to build the governing equation of the complicated nonlinear dual-rotor system.In order to deal with the efficiency and numerical divergence in the process of solving the nonlinear modes of this large-scale nonlinear system,an analysis strategy is proposed by integrating a two-layer reduction technique into the harmonic balance method.The effectiveness of the analysis strategy is validated by applying to a simple rotor system,which can easily obtain the theoretical result.Based on the modeling method and analysis strategy,the modal characteristics of an aero-engine dual-rotor system with rub-impact are revealed.The results show that the modal frequency of the dual-rotor system increases when rub-impact occurs and has the feature of interval,which allows us to obtain the critical speeds of the rubbing system by traditional Campbell diagram.The rotation direction is an important factor since it can not only affect the gyroscopic effect but also change the friction effect of the rub-impact.It is found that the modal frequencies of the counter-rotation dual-rotor are less than those of co-rotation condition.More importantly,the forward modes of the counter-rotation dual-rotor may be instable when rub-impact occurs at a certain rotor,while the corresponding modes under the co-rotation condition are always stable.Furthermore,by analyzing the rubbing response of the dual-rotor,it is found that the modal characteristics have an important influence on rotor’s response.The instable forward modes existing in the counter-rotation dual-rotor may lead to the divergence of the response when passing the corresponding critical speed.

关键词： Dual-rotor system Instability Modal characteristics Rub-impact Vibration response

Time Sequence Change-Point Model of Electrostatic State Parameters of Aircraft Engine

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Transactions of Nanjing University of Aeronautics and Astronautics 2018年第1期35卷 126-134页

作者： Fu Yu Wei Dongdong Zuo Hongfu Feng Zhengxing college of Aeronautical Engineering Civil Aviation University of China College of Civil Aviation Nanjing University of Aeronautics and Astronautics

Electrostatic monitoring technology of particle charging information can facilitate online monitoring of aero-engine,which effectively enhances engine fault diagnosis and health managements.Unlike traditional engine state monitoring technologies,aircraft engine monitoring by gas path electrostatic monitoring not only covers the predicted information source itself,but also detects the information that can provide an early warnings for initial fault states through gas path charging levels.This paper establishes a non-stationary time sequence change-point model for anomaly recognition of electrostatic signals based on change-point theory combined with difference method of non-stationary time series.Finally,electrostatic induction data were utilized by the engine life test for a particular aircraft to validate the proposed algorithm.The results indicate that the activity level and the event rate were0.5—0.8(nc)and 50%,respectively,which were far greater than 4—12(pc)and 0—4% under normal working conditions of the engine.

关键词： aero-engine state identification electrostatic monitoring technology time series change-point statistics

Removal of Chromium(Ⅲ) from Monoammonium Phosphate Solutions by a Porous Adsorbent of Fluor(calcium silicate) Composites

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Journal of Wuhan University of Technology(Materials Science) 2020年第2期35卷 384-392页

作者： ZHU Xinhua JIA Xuhong College of Civil Aviation Safety Engineering Civil Aviation Flight University of ChinaGuanghan 618307China

The products of monoammonium phosphate containing Cr^3+resulted in disqualification,and further posed a serious threat to ecological environment and human beings.Herein,the porous adsorbent of fluor(calcium silicate)composites(FCSc)was prepared by hydrothermal method using diatomaceous earth,hydrated lime and additive(NaF)as raw materials,which was characterized and used for the removal of Cr^3+from monoammonium phosphate solutions.The effects of different parameters,such as solution pH,initial Cr^3+concentration,temperature and contact time on the adsorption of Cr^3+onto FCSc were investigated in details.The results indicated that the adsorption process was in agreement with the pseudo-second-order kinetic model and Freundlich isotherm.The spontaneous and endothermic nature of the adsorption process was obtained by analyzing various thermodynamic parameters(△G0,△H0,and△S0).In addition,computational monte carlo simulations between Cr3+ions and FCSc were conducted to elucidate the adsorption mechanism.Such kind of porous adsorbent provided a potential application in the removal of impurities from monoammonium phosphate industry.

关键词： fluor(calcium silicate)composites monoammonium phosphate solutions chromium(Ⅲ) removal monte carlo simulations

On Behaviors of Functionally Graded SMAs under Thermo-Mechanical Coupling

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Acta Mechanica Solida Sinica 2016年第1期29卷 46-58页

作者： Bingfei Liu Pengcheng Ni Wei Zhang Airport college Civil Aviation University of China Sino-European Institute of aviation Engineering Civil Aviation University of China

An analytical solution is obtained for the Functionally Graded Shape Memory Alloy （FG-SMA） composites subjected to thermo-mechanical coupling. Young＇s modulus and thermal expansion coefficient of the material are assumed to vary in different forms of power function through the thickness, with the Poisson＇s ratio being constant. An SMA constitutive model is combined with the averaging techniques of composite to determine the mechanical properties of the FG-SMA composites. Different phase transformation steps and the corresponding stress distributions through the thickness direction are given. The results show that the average stresses decrease as the transformations proceed.

关键词： functionally graded SMAs phase transformation constitutive model

Brownian Dynamics Simulations of Rigid Polyelectrolyte Chains Grafting to Spherical Colloid

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Chinese Journal of Polymer Science 2018年第6期36卷 791-798页

作者： Qing-Hai Hao Zhen Zheng Gang Xia Hong-Ge Tan college of Science Civil Aviation University of China

Brownian dynamics simulations are employed to explore the effects of chain stiffness and trivalent salt concentration on the conformational behavior of spherical polyelectrolyte brush. The rigid brush adopts bundle-like morphology at a wide range of trivalent salt concentration. The number variation of bundles pinned on the colloid surface shows a non-monotonic profile as a function of the chain stiffness. The radial distributions of monomers and ions and the charge ratio between condensed ions and monomers are calculated. The charge inversion is observed for the high salt concentration regardless of chain rigidity. Furthermore, the pair correlation functions of monomer-monomer and monomer-salt cation are used to elucidate the aggregated mechanism of the bundle-like structure.

关键词： Brownian dynamics simulation Spherical polyelectrolyte brush Chain stiffness Trivalent salt concentration Pinned bundle morphology