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Investigations on the Corrosion Behaviour and Structural Characteristics of Low Temperature Nitrided and Carburised Austenitic Stainless Steel

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材料热处理学报 2004年第5期25卷 311-315页

作者： d. Mnter h.-J. Spies h. Biermann Chr. Eckstein department of Materials Engineering Technische Universitat Bergakademie Freiberg 09599 Freiberg/ GermanyDepartment of Materials Engineering Technische Universitat Bergakademie Freiberg 09599 Freiberg/ GermanyDepartment of Materials Engineering Technische Universitat Bergakademie Freiberg 09599 Freiberg/ GermanyCorrosion laboratory Steel-Centre-Freiberg (SZF) Research centre of the Technische Universitat Bergakademie Freiberg 09599 Freiberg/ Germany

The wear resistance of austenitic stainless steels can be improved by thermo-chemical surface treatment with nitrogen and carbon. however, it is possible that the corrosion resistance will be impaired by the precipitation of chromiumnitrid or -carbide. The present contribution deals with investigations of the corrosion behaviour and structural characteristics of a low temperature nitrided and carburised austenitic stainless steel. The material investigated was AISI 316L (X2CrNiMol7-12-2) austenitic stainless steel. A commercial plasma-nitriding unit (pulsed dc) was used for the nitriding and carburising process. Additional samples were treated by the gasoxinitriding process for a comparison between plasma- and gasoxinitriding. The nitrided and carburised layer of austenitic stainless steel consists of the nitrogen or carbon S-phase (expanded austenite), respectively. X-ray diffraction investigations show the typical shift of the peaks to lower angles, indicating expansion of the fee lattice. Also the X-ray diffraction technique was employed to study the residual stresses in the nitrogen and carbon S-phase. The corrosion behaviour of surface engineered samples was investigated with electrochemical methods. Anodic potentiodynamic polarisation curves were recorded for testing the resistance against general corrosion (in h2SO4) and pitting corrosion (in NaCl).

关键词：奥氏体不锈钢腐蚀低温渗氮低温渗碳残留应力

Structure and Magnetic Properties of S-doped Mn_3O_4/S Composited Nanoparticles and Mn_3O_4 Nanoparticles

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Journal of Materials Science & Technology 2011年第6期27卷 503-506页

作者： X. he Z.h. Wang d.Y. Geng Z.d. Zhang Shenyang National Laboratory for Materials Science Institute of Metal Research and International Centre for Materials Physics Chinese Academy of Sciences Shenyang 110016 China

Composited nanoparticles,consisting of Mn3O4,S-doped Mn3O4 and S,were synthesized by co-precipitation reaction and Mn3O4 nanoparticles were then obtained after removing the pure S from the composited *** Mn3O4-type phase with larger lattice constant a was formed by doping *** fixed temperatures below Curie temperature（TC）,the magnetization of the S-doped Mn3O4/S composited nanoparticles was smaller than that of the Mn3O4 *** blocking temperature was 36.3 and 34.8 K for Sdoped Mn3O4/S composite and Mn3O4 nanoparticles,*** anisotropy field of S-doped Mn3O4/S composite was determined to be about 55.3 kOe.

关键词： Nanostructured materials Chemical synthesis X-ray diffraction Magnetic measurements

Review of deployment technology for tethered satellite systems

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Acta Mechanica Sinica 2018年第4期34卷 754-768页

作者： B.S.Yu h.Wen d.P.Jin State Key Laboratory of Mechanics and Control of Mechanical Structures Nanjing University of Aeronautics and Astronautics

Tethered satellite systems（TSSs） have attracted significant attention due to their potential and valuable applications for scientific research. With the development of various launched on-orbit missions, the deployment of tethers is considered a crucial technology for operation of a TSS. Both past orbiting experiments and numerical results have shown that oscillations of the deployed tether due to the Coriolis force and environmental perturbations are inevitable and that the impact between the space tether and end-body at the end of the deployment process leads to complicated nonlinear phenomena. hence, a set of suitable control methods plays a fundamental role in tether deployment. This review article summarizes previous work on aspects of the dynamics, control, and ground-based experiments of tether deployment. The relevant basic principles, analytical expressions, simulation cases, and experimental results are presented as well.

关键词： Tethered satellite deployment dynamics Control Experiment

Numerical Simulation of Vortex Engine Flow Field:One Phase and Two Phases

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Journal of Thermal Science 2009年第3期18卷 226-234页

作者： A.F.Najafi S.d.Saemi M.h.Saidi department of Energy Engineering Power and Water University of Technology department of Mechanical Engineering Sharif University of Technology

Aiming at improving efficiency in combustion systems, the study on droplet behavior and its trajectory is of crucialimportance. Vortex engine is a kind of internal combustion engine which uses swirl flow to achieve highercombustion efficiency. One of the important advantages of designing vortex engine is to reduce the temperatureof walls by confining the combustion products in the inner vortex. The scopes of this investigation are to studyvortex engine flow field as well as effective parameters on fuel droplet behavior such as droplet diameter, dropletinitial velocity and inlet velocity of the flow field. The flow field is simulated using Reynolds Stress TransportModel (RSM). The Eulerian-Lagrangian method and the one-way coupling approach are employed to simulatetwo phase flow and dispersed phase in the chamber, respectively. A new method, based on computing pressureforce exerted on the droplet surface, is introduced to determine the distinction between using one-way andtwo-way coupling approaches. The results showed that the droplets with smaller diameter are more likely to followthe flow stream lines than bigger droplets, thus evaporate completely in the chamber. Moreover, droplets withgreater initial velocity have higher evaporation rate, yielding the existence of evaporation and combustion in theinner vortex. Additionally, the higher inlet velocity of continuous phase results in higher centrifugal force, leadsdroplets in question to deviate towards the wall faster.

关键词： Vortex Engine Swirl Flow Lagrangian Approach Fuel droplet

Implementation aspects of a phase-field approach for brittle fracture

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Frontiers of Structural and Civil Engineering 2019年第2期13卷 417-428页

作者： G.d.hUYNh X.,ZhUANG h.NGUYEN-XUAN Institute of Continuum Mechanics Leibniz-Universitat Hannover30167 HannoverGermany Center for Interdisciplinary Research in Technology Ho Chi Minh CityUniversity of Technology (HUTEH)Ho Chi Minh City Vietnam

This paper provides a comprehensive overview of a phase-field model of fracture in solid mechanics setting. We start reviewing the potential energy governing the whole process of fracture including crack initiation, branching or merging. Then, a discretization of system of equation is derived, in which the key aspect is that for the correctness of fracture phenomena, a split into tensile and compressive terms of the strain energy is performed, which allows crack to occur in tension, not in compression. For numerical analysis, standard finite element shape functions are used for both primary fields including displacements and phase field. A staggered scheme which solves the two fields of the problem separately is utilized for solution step and illustrated with a segment of Python code.

关键词： phase-field modeling FEM staggered scheme fracture

Study of Thermal and hydraulic Performances of Circular and Square Ribbed Rough Microchannels Using LBM

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Journal of Thermal Science 2015年第6期24卷 549-556页

作者： M.A.Taher h.d.Kim Y.W Lee department of Mechanical and Automotive Engineering Pukyong National University department of Mechanical Engineering Andong National University

The effects of roughness geometries and relative roughness height at the slip flow regime to investigate the thermal and hydraulic performances of microchannel have been considered in the present article using a thermal Lattice Boltzmann Method(TLBM).A two dimensional 9-bit(d2Q9)single relaxation time(SRT)model is used to simulate this *** micro-flows,the local density variation is still relatively small,but the total density changes,therefore,in order to account this density variation and its effect on the kinematic viscosityν,a new relaxation time proposed by Niu et al.[13]is *** roughness geometry is modeled as a series of square and circular riblets with a relative roughness height from 0%to 10%of the channel *** friction coefficients in terms of Poiseuille number(Pn)and the dimensionless heat transfer rate in terms of Nusselt number(Nu)have been discussed in order to analyze the roughness *** thermal-hydraulic performance(η)is calculated considering the simultaneous effects of thermal and fluid friction(pressure drop)at the slip flow regime at Knudsen number,Kn,ranging from 0.01 to 0.10 with other controlling parameters for both kind of *** results have been compared with previous published works and it is found to be in very good agreement.

关键词： Lattice-Boltzmann Friction factor Knudsen number Surface Roughness

Unsteady time-dependent incompressible Newtonian fluid flow between two parallel plates by homotopy analysis method(hAM),homotopy perturbation method(hPM)and collocation method(CM)

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Propulsion and Power Research 2018年第3期7卷 247-256页

作者： M.R.Shirkhani h.A.hoshyar I.Rahimipetroudi h.Akhavan d.d.Ganji department of Mechanical Engineering Sari BranchIslamic Azad UniversitySariIran Young Researchers Club Sari BranchIslamic Azad UniversitySariIran department of Mechanical Engineering Ghaemshahr BranchIslamic Azad UniversityGhaemshahrIran

Analytical and numerical analyses have performed to study the problem of the flow of incompressible Newtonian fluid between two parallel plates approaching or receding from each other *** Navier–Stokes equations have been transformed into an ordinary differential equation using a similarity *** powerful analytical methods called collocation method(CM),the homotopy perturbation method(hPM),and the homotopy analysis method(hAM)have been used to solve nonlinear differential *** has been attempted to show the capabilities and wide-range applications of the proposed methods in comparison with a type of numerical analysis as fourth-order Runge–Kutta numerical method in solving this ***,velocity fields have been computed and shown graphically for various values of physical *** objective of the present work is to investigate the effect of Reynolds number and suction or injection characteristic parameter on the velocity field.

关键词： homotopy analysis method(hAM) Collocation method(CM) homotopy perturbation method(hPM) Parallel porous plates Unsteady flow

MOLECULAR dYNAMICAL STUdY OF ThE ENERGY RELAXATION PROCESSES AFTER hEATING ThE VIBRATIONAL dEGREE OF FREEdOM IN A dIATOMIC MOLECULAR CRYSTAL

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Acta Mechanica Sinica 1988年第4期4卷 372-377页

作者： d.h.Tsai USA 10100 Lloyd Road.Potomac.Md 20854

Energy relaxation processes initiated by sndden heating of the vibrational degree of freedomwere studied with molecular dynamical method.A unit cell of bee structure containing 128 diatomicmolecules with periodic boundary conditions was *** Morse potential was assumed as theatom atom *** was found that the logarith of the equilibration time depends linearly upon afactor f21which is proportional to the frequency ra of the intra-and inter-molecular vibrations.

关键词： molecular dynamics relaxation mol(?)ular erystal

Fabrication and characteristics of nitrogen-doped nanocrystalline diamond/p-type silicon heterojunction

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Nano-Micro Letters 2010年第1期2卷 56-59页

作者： d.Lu h.d.Li S.h.Cheng J.J.Yuan X.Y.Lv State Key Laboratory of Superhard Materials Jilin University

Nitrogen-doped nanocrystalline diamond films(N-NdFs)have been deposited on p-type silicon(Si)by microwave plasma chemical vapor *** reaction gases are methane,hydrogen,and nitrogen without the conventional argon(Ar).The N-NdFs were characterized by X-ray diffraction,Raman spectroscopy,and scanning electron *** grain sizes are of 8~10 nm in *** N-NdF shows n-type behavior and the corresponding N-NdF/p-Si heterojunction diodes are realized with a high rectification ratio of 102 at^7.8 V,and the current density reaches to1.35 A/cm2 at forward voltage of 8.5 *** findings suggest that fabricated by Ch_4/h_2/N_2 without Ar,the N-NdFs and the related rectifying diodes are favorable for achieving high performance diamond-based optoelectronic devices.

关键词： Nanocrystalline diamond film Chemical vapor deposition Nitrogen doped heterojunction diodes Current-voltage characteristics