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Static solution on four-region spherial cavity expansion model in a pressure sensitive medium

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Journal of Harbin Institute of Technology(New Series) 2010年第3期17卷 405-408页

作者：于雪梅唐立强杨勇 college of Aerospace and Civil Engineering Harbin Engineering University avic Harbin aircraft industry Group co.ltd. Aircraft Design Institute

Spherical cavity expansion model is often used to study the mechanic characteristics of pressure sensitive mediums. The most important one we do in the paper is that we construct a four-region model with σθ≠0 in damage region,which is different from what Satapathy did before and is more reasonable. By adopting this model,different constitutive equations were constructed by different method-elastic mechanics in elastic region,damage mechanics and fracture mechanics in damage region,and macro-micro mechanics theory in plastic region. Then using Durban's self-similarity assumption,the control differential equations with boundary conditions were established,and the static numerical solution of stress field and displacement field in the three different regions of elastic,damage and plastic area were discussed respectively. Results showed that this four-region model can describe precisely the mechanic characteristics of pressure sensitive mediums under initial pressure.

关键词： pressure-sensitive material spherical cavity expansion damage mechanics self-similarity assumption constitutive equation

Numerical study of the splashing wave induced by a seaplane using mesh-based and particle-based methods

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Theoretical & Applied Mechanics Letters 2023年第5期13卷 375-381页

作者： Yang Xu Peng-Nan Sun Xiao-Ting Huang Salvatore Marrone Lei-Ming Geng School of Ocean Engineering and Technology Sun Yat-sen UniversityZhuhai 519082China CNR-INM.Institute of Marine Engineering Rome 00128Italy avic general huanan aircraft industry co. LtdZhuhai 519080China

In recent years,forest fires and maritime accidents have occurred frequently,which have had a bad impact on human production and ***,the development of seaplanes is an increasingly urgent *** is important to study the taxiing process of seaplanes for the development of seaplanes,which is a strong nonlinear fluid-structure interaction *** this paper,the smoothed particle hydrodynamics(SPH)method based on the Lagrangian framework is utilized to simulate the taxiing process of seaplanes,and the SPH results are compared with those of the finite volume method(FVM)based on the Eulerian *** results show that the SPH method can not only give the same accuracy as the FVM but also have a strong ability to capture the splashing waves in the taxiing process,which is quite meaningful for the subsequent study of the effect of a splash on other parts of the seaplane.

关键词： Seaplane Splashing Fluid-structure interactions SPH Method

Study on compressive Properties of Z-pinned Laminates in RTD and Hygrothermal Environment

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Chinese Journal of Aeronautics 2012年第1期25卷 64-70页

作者： LI Chenghu YAN Ying WANG Ping QI Desheng WEN Yonghai School of Aeronautic Science and Engineering Beihang UniversityBeijing 100191China China Electric Power Research Institute Beijing 100192China avic Harbin aircraft industry Group co.ltd. Harbin 150066China

compressive tests of [0]t2 and [90]t2 unidirectional laminates and [45/0/-45/90] 2s quasi-isotropic laminates are accomplished in both room-temperature and dry （RTD） and hygrothermal environment. And simulation studies on the compressive strength of Z-pinned laminates of [0112 and [45/0/-45/90] 2s are conducted by using finite element analysis （FEA）. A microstructural unit cell for FEA is created to simulate a representative laminates unit with one pin. Within the unit cell, the first directions of the elements＇ material coordinate systems are changed to simulate the fibres＇ deflecting around the pin. The hygrothermal effect is simulated by the material properties＇ adjustments which are determined by the compressive tests of non-pined laminates. The experimental results indicate that the percentage of reduction in the compressive modulus of Z-pinned laminates caused by Z-pin becomes smaller with the percentage of 0° fibres decreasing in the laminates; the compressive strength of quasi-isotropic laminates reduces and the percentage of the reduction in the compressive strength declines with Z-pin volume content increasing, and the moisture absorption ratio of the Z-pinned specimens is greater than that of the non-pinned specimens, because the cracks around Z-pin increase the moisture absorption. In addition, the simulations show that the deflection of fibres around Z-pin is the main factor for the reduction in the compressive strength of Z-pinned unidirectional laminates, the dilution of fibre volume content caused by resin-rich pocket is the principal factor for the decline in the compressive strength of Z-pinned quasi-istropic laminates, and the compressive strength of Z-pinned specimens in hygrothermal environment reduces as the result of superimposition of some factors, including the changes in material properties caused by hygrothermal environment, the deflection of fibres and the resin-rich pocket caused by Z-pin.

关键词： Z-pin laminates hygrothermal environment simulation study strength

Improving strength-ductility synchronously of Electron beam welded Ti600/Ti2AlNb joint through isothermal forging

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Progress in Natural Science:Materials International 2024年第3期34卷 532-539页

作者： Yongqiang Zhang Xiangyi Xue Guoming Zheng Jingli Zhang Huiming Li Shewei Xin State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi'an Qin Ti Intelligent Manufacturing Technologies co.ltd. Northwest Institute for Nonferrous Metal Research Xi'an University of Science and Technology avic Xi'an aircraft industry Group company ltd.

Different alloys can be flexibly combined to meet the performance needs of different parts of the compressor disc by welding process. However, achieving a good combination of dissimilar alloys with different mechanical properties has always been a research difficulty. In this work, a Ti600/Ti2AlNb joint was fabricated through electron beam welding and an isothermal forging was used to optimized its microstructure and mechanical performance. The isothermal forging process increases the ultimate tensile strength（UST） and yield strength（YS）of the Ti600/Ti2AlNb joint by ～18 %, while ～2.5 times the ductility. It is indicated that before forging, the Ti600/Ti2AlNb joint exhibits a much lower strength than that of Ti600 matrix, whereas the opposite is true after isothermal forging. The isothermal forging broken the coarse columnar grains of Ti600/Ti2AlNb joint and render to an equiaxed B2 structure in which the acicular α2and O phase are precipitated, resulting a synchronous enhancement of strength and ductility. This work may pave an effective routine for improving the comprehensive mechanical properties of dissimilar metal welding joint.

关键词： Electron beam welding Ti600/Ti2AlNb joint Isothermal forging Mechanical performance

Tribological evaluation of surface modified H13 tool steel in warm forming of Ti–6Al–4V titanium alloy sheet

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Chinese Journal of Aeronautics 2014年第4期27卷 1002-1009页

作者： Wang Dan Li Heng Yang He Ma Jun Li Guangjun State Key Laboratory of Solidification Processing School of Materials Science and EngineeringNorthwestern Polytechnical University avic Cheng Du aircraft industry (Group) co. Ltd

The H13 hot-working tool steel is widely used as die material in the warm forming of Ti–6Al–4V titanium alloy sheet. However, under the heating condition, severe friction and lubricating conditions between the H13 tools and Ti–6Al–4V titanium alloy sheet would cause difficulty in guaranteeing forming quality. Surface modification may be used to control the level of friction force, reduce the friction wear and extend the service life of dies. In this paper, four surface modification methods（chromium plating, TiAlN coating, surface polishing and nitriding treatment）were applied to the H13 surfaces. Taking the coefficient of friction（coF） and the wear degree as evaluation indicators, the high-temperature tribological behavior of the surface modified H13 steel was experimentally investigated under different tribological conditions. The results of this study indicate that the tribological properties of the TiAlN coating under dry friction condition are better than the others for a wide range of temperature（from room temperature to 500 C）, while there is little difference of tribological properties between different surface modifications under graphite lubricated condition, and the variation law of coF with temperature under graphite lubricated is opposite to that under the dry friction.

关键词： coefficient of friction H13 Surface modification Ti-6Al-4V Tools Warm forming Wear

Dynamic analysis of C/C composite finger seal

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Chinese Journal of Aeronautics 2014年第3期27卷 745-758页

作者： Chen Guoding Wang Li’na Yu Qiangpeng Su Hua School of Mechanical Engineering Northwestern Polytechnical University avic commercial aircraft Engine co. Ltd

A seal device as an important component of aeroengines has decisive influence on per- formance, reliability, and working life of aeroengines. With the development of aeroengines, demands on the performance characteristics of seal devices are made strictly. Finger seal as a novel kind of sealing device, recently attracts more and more attentions in academic circles and engineer- ing fields at home and abroad. Research on finger seals has been extensively developed, especially on leakage and wear performances under dynamic conditions. However, it is a pity that the work on finger seals has been limited with a single approach that is improving the performance by structural optimization; in addition, the technology of dynamic analysis on finger seals is weak. Aiming at the problems mentioned above, a distributed mass equivalent dynamic model of finger seals considering the coupling effect of overlaid laminates is established in the present paper, the dynamic perfor- mance of 2.5 dimension C/C composite finger seal is analyzed with the model, and then the effects of fiber bundle density and fiber bundle preparation direction on finger seal＇s dynamic performance are discussed, as well as compared with those of co-based alloy finger seal. The current work is about dynamic analysis of finger seals and application of C/C composite in this paper may have much academic significance and many engineering values for improving research level of finger seal dynamics and exploring feasibility of C/C composite being used for finger seals.

关键词： Aeroengine C/C composite co-based alloy Equivalent dynamic model Finger seal

Analysis Method of Transient Temperature Field for Fuel Tank ofHigh-Altitude Large UAV

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Journal of Harbin Institute of Technology(New Series) 2016年第6期23卷 41-46页

作者： Qing Ai Liang Chen Xiaojing Xu Shiyu Liu Zhenwen Hu Xinlin Xia School of Energy Science and Engineering Harbin Institute of TechnologyHarbin 150000China avic Chengdu aircraft industry(Group)co.ltd. Chengdu 610091China

Based on the analysis of factors affecting transient temperature field of aircraft fuel tank and coupled heat transfer mechanism, a mathematical model of transient coupled heat transfer, including the dynamic- change of fuel quality, the internal heat transfer, the external aerodynamic convection and the radiation heat transfer, is established. Taking the aerodynamic convection and radiation heat transfer outside the tank as the third kinds of thermal boundary conditions for the thermal analysis of the fuel tank, calculation of internal and external coupling heat of fuel tank is decoupled. Ther^nal network method combined with hierarchical dynamic- grid is used to deal with the fuel consumption, and carry on the heat transfer analysis of the fuel tank. The numerical method for the transient temperature field of aircraft fuel tank is established. Through the simulation calculation, the transient temperature distribution of the fuel tank under different flight conditions is obtained, and the influence of the fuel mass and the external thermal environment on the temperature field is analyzed.

关键词： unmanned aerial vehicle fuel tank transient temperature field numerical simulationCLC number TK16 Document code A Article ID 1005-9113(2016)06-0041-06

Investigation of stress distribution and damage behavior caused by forced installation of a composite bolted joint with a hole-location error

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Chinese Journal of Aeronautics 2024年第1期37卷 201-217页

作者： Chinan LIU Yuan LI Yi CHENG An’an ZHAO Kunpeng DU Yue SHI Ximing LI Hui CHENG School of Mechanical Engineering Northwestern Polytechnical UniversityXi’an 710072China avic Xi’an aircraft industry Group company ltd Xi’an 710089China

In this paper,the influence of forced installation caused by a hole-location error on the 3D stress distribution and damage of a composite bolted joint is *** analytical model of stress distributed on composite holes is promoted,in view of non-uniform extrusion caused by forced *** first,non-uniform extrusion of the hole edge caused by forced installation is *** to the contact state,expression of hole deformation is ***,based on Hertz theory,the maximum extrusion load is obtained with help of deformation *** constructing an elastic foundation beam model,3D stress distributed on a hole could be analyzed according to the extrusion ***,stress distribution predicted by the above analytical method is compared with that provided by FE considering composite ***,a forced installation experiment is carried out to analyze the damage distribution of the *** show that a central-symmetrically distributed stress is introduced by the hole-location *** an increment of the error,strength of composite decreases due to extrusion ***,stress presents a concave distribution on the *** the hole-location error exceeding 3%,stress decreases gradually due to failure of *** of holes does not exhibit a centrosymmetric *** damage is mainly distributed on the entrance of the hole at the lower sheet.

关键词： Hole-location error composite joint Forced installation Stress distribution Damage

Preparation of bimodal grain size 7075 aviation aluminum alloys and their corrosion properties

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Chinese Journal of Aeronautics 2017年第5期30卷 1777-1788页

作者： Wenming TIAN Songmei LI Jianhua LIU Mei YU Yujie DU avic Changhe aircraft industry (Group) corporation ltd Jingdezhen 333002 China School of Materials Science and Engineering Beihang University Beijing 100083 China

The bimodal grain size metals show improved strength and ductility compared to traditional metals; however, their corrosion properties are unknown. In order to evaluate the corrosion properties of these metals, the bimodal grain size 7075 aviation aluminum alloys containing different ratios of coarse（100 μm in diameter） and fine（10 μm in diameter） grains were prepared by spark plasma sintering（SPS）. The effects of grain size as well as the mixture degree of coarse and fine grains on general corrosion were estimated by immersion tests, electrochemical measurements and complementary techniques such as scanning electron microscope（SEM） and transmission electron microscope-energy disperse spectroscopy（TEM-EDS）. The results show that, compared to fine grains, the coarse grains have a faster dissolution rate in acidic NaCl solution due to the bigger size,higher alloying elements content and larger area fraction of second phases in them. In coarse grains,the hydrogen ions have a faster reduction rate on cathodic second phases, therefore promoting the corrosion propagation. The mixture of coarse and fine grains also increases the electrochemical heterogeneity of alloys in micro-scale, and thus the increased mixture degree of these grains in metal matrix accelerates the corrosion rate of alloys in acidic NaCl solution.

关键词： 7075 aluminum alloy corrosion Spark plasma sintering Transmission electron microscope