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Linking discrete particle simulation to continuum process modelling for granular matter: Theory and application

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Particuology 2011年第4期9卷 342-357页

作者： H.P. Zhu Z.Y. Zhou q.f. Hou A.B. Yu School of Engineering University of Western Sydney Locked Bag 1797 Penrith NSW 2751 Australia Laboratory for Simulation and Mo-delling of Particulate Systems School of Materials Science and Engineering The University of New South Wales Sydney NSW 2052 Australia

Two approaches are widely used to describe particle systems： the continuum approach at macroscopic scale and the discrete approach at particle scale. Each has its own advantages and disadvantages in the modelling of particle systems. It is of paramount significance to develop a theory to overcome the disadvantages of the two approaches. Averaging method to link the discrete to continuum approach is a potential technique to develop such a theory. This paper introduces an averaging method, including the theory and its application to the particle flow in a hopper and the particle-fluid flow in an ironmaking blast furnace.

关键词： Particle flow Gas-solid flow Discrete approach Averaging method Hopper flow Blast furnace

EffECT Of LOW-fREqUENCY ELECTROMAGNETIC fIELD ON THE AS-CASTING MICROSTRUCTURES AND MECHANICAL PROPERTIES Of HDC 2024 ALUMINUM ALLOY

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Acta Metallurgica Sinica(English Letters) 2008年第3期21卷 205-210页

作者： q.f. Zhu Z.H. Zhao J.Z. Cui Y.B. Zuo f. qu Key Laboratory of Electromagnetic Processing of Materials Ministry of Education Northeastern Univer- sity Shenyang 110004 China

The influences of the low frequency electromagnetic field on the horizontal direct chill casting process were investigated experimentally. Ingots of 2024 aluminum alloy with a cross size of 40 mm× 200 mm were produced by the conventional horizontal chill casting process and low frequency electromagnetic horizontal chill casting processre- spectively. The as-cast structures and the mechanical property of the ingots were examined. The results showed that the low frequency electromagnetic field could sub- stantially refine the microstructures and pronouncedly reduce the macrosegregation in the horizontal direct chill casting process. Moreover, the surface quality of the ingot was prominently improved by the low frequency electromagnetic field. The fracture strength and elongation percentage of the ingot was increased with the low frequency electromagnetic field.

关键词： Horizontal direct chill casting Low frequency electromagnetic field 2024 aluminum alloy Microstructures Macrosegregation

EffECTS Of DIffERENT fUNCTIONAL GROUP-CONTAINING ORGANICS ON MORPHOLOGY-CONTROLLED SYNTHESIS Of SILVER NANOPARTICLES AT ROOM TEMPERATURE

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Acta Metallurgica Sinica(English Letters) 2006年第5期19卷 362-370页

作者： A.L. Wang H.B. Yin M. Ren X.N. Cheng q.f. Zhou X.f. Zhang faculty of Chemistry and Chemical Engineering Jiangsu University Zhenjiang 212013 China Department of Chemical Engineering Jiangsu Teachers University of Technology Changzhou 213001China

Silver nanoparticles with average particles sizes ranging from 2 to 131nm were manipulatively synthesized starting from silver nitrate using different functional group-containing organic modifiers at room temperature. The effects of the organic modifiers on the morphology of the resulting silver nanoparticles were strongly dependent on the intrinsic properties of the functional groups and the reducibility of the reductant. Numerous ether bonds （-0-）present in polyethylene glycol and Tween-80 were beneficial to the formation of silver nanoparticles with particle sizes of several nanometers in a narrow size distribution in both weak and strong reducing environments. Cetyltrimethylammonium bromide induced the formation of nanosized silver triangle plates in a weak reducing environment. The crystal growth of the silver nanoparticles with particle sizes of more than lOnm was postulated through an adhesion process of small-sized particles followed by a subsequent coalescence process under the present reaction conditions.

关键词： silver nanoparticle nanostructure crystal growth TEM (transmissionelectron microscopy)

STUDY ON THE PROBLEMS Of CONTACT IN THE NUMERICAL SIMULATION Of SHEET fORMING

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Acta Metallurgica Sinica(English Letters) 2000年第2期13卷 459-464页

作者： K.f. Zhang, f.X. Diao, q.f. Song, W. Wu, K.B. Chen and T.Xie Harbin Institute of Technology, Harbin 150001, China

This study is concerned with the problems of contact in the process of numerical simulation of sheet metal forming in rigid visco-plastic shell fEM. In respect of analysis of sheet deep drawing process,for the tool model described by triangular elements, a kind of contact judging algorithm about the correlation between the node of deformed mesh and the triangular element of a tool is presented. In SPf/DB Lagrangian multiplier method is adopted to solve the contact problem between deformed meshes, and a new reliable practical dynamic contact checking algorithm is presented. As computation examples, the simulation results of metal sheet deep drawing and SPf/DB are introduced in this paper.

关键词： kcontact search algorithm rigid visco-plastic shell fEM Lagrangian multiplier method sheet metal forming

Irradiation-induced homogeneous plasticity in amorphous/amorphous nanolaminates

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Journal of Materials Science & Technology 2020年第22期54卷 70-77页

作者： L.Huang Z.q.Chen P.Huang X.K.meng f.Wang State Key Laboratory for Mechanical Behavior of Material School of Materials Science and EngineeringXi'an Jiaotong UniversityXi'an710049China Institute of Materials Engineering National Laboratory of Solid State MicrostructuresCollaborative Innovation Center of Advanced MicrostructuresNanjing UniversityNanjing 210023China State Key Laboratory for Strength and Vibration of Mechanical Structures School of Aerospace EngineeringXi'an Jiaotong UniversityXi'an710049China

Achieving homogeneous plastic deformation in metallic glasses is a long-standing goal yet to be solved in materials science. Here we investigate the effect of ion irradiation on the plastic deformation behavior of ZrCu/ZrCuNiAlSi amorphous/amorphous nanolaminates(A/ANLs) via nanoindentation testing. The experimental results indicate a dramatic change in deformation mode from multiple shear banding events to homogeneous compressive deformation before and after ion irradiation on the A/ANLs in the areas underneath the indenter. Ion irradiation-induced changes of both fraction and distribution of free volume inside each constituent layer and interfacial state in the A/ANLs may be responsible for the unusual homogeneous deformation behavior. Our results suggest that the mechanical property of A/ANLs could be modified by tuning both the inner and interfacial structure via ion irradiation.

关键词： Metallic glasses Ion irradiation Plastic deformation Nanolaminates Interface

Projective representation of D_(6)group in twisted bilayer graphene

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Chinese Physics B 2021年第7期30卷 1-4页

作者： Noah f.q.Yuan Department of Physics Massachusetts Institute of TechnologyCambridgeMassachusetts 02139USA

Within the framework of continuum model,we study the projective representation of emergent D_(6)point group in twisted bilayer *** then construct tight-binding models of the lowest bands without and with external elec... 详细信息

关键词： twisted bilayer graphene tight-binding model projective representation

Molecular Dynamics Simulation of Porous Layer-enhanced Dislocation Emission and Crack Propagation in Iron Crystal

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Journal of Materials Science & Technology 2011年第11期27卷 1025-1028页

作者： D. Li f.Y. meng X.q. Ma L.J. qiao W.Y. Chu Department of Physics University of Science and Technology Beijing Beijing 100083 China Corrosion and Protection Center Key Lab of Environmental Fracture （Ministry of Education） University of Science and Technology Beijing Beijing 100083 China

The internal stress induced by a porous layer or passive layer can assist the applied stress to promote dislocation emission and crack propagation, e.9. when the pipeline steel is buried in the soil containing water, resulting in stress corrosion cracking （SCC）. Molecular dynamics （MD） simulation is performed to study the process of dislocation emission and crack propagation in a slab of fe crystal with and without a porous layer on the surface of the crack. The results show that when there is a porous layer on the surface of the crack, the tensile stress induced by the porous layer can superimpose on the external applied stress and then assist the applied stress to initiate crack tip dislocation emission under lowered stress intensity KI, or stress. To respond to the corrosion accelerated dislocation emission and motion, the crack begins to propagate under lowered stress intensity KI, resulting in SCC.

关键词： Molecular dynamics simulation Dislocation emission Crack propagation Porouslayer Stress intensity

Reliability of quasi integrable and non-resonant Hamiltonian systems under fractional Gaussian noise excitation

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Acta Mechanica Sinica 2020年第4期36卷 902-909页

作者： q.f.Lu W.q.Zhu M.L.Deng Department of Mechanics State-Key Laboratory of Fluid Power and Mechatronic SystemsZhejiang UniversityHangzhou 310027China

The reliability of quasi integrable and non-resonant Hamiltonian system under fractional Gaussian noise(fGn)excitation is *** rather flat fGn power spectral density(PSD)in most part of frequency band,the fGn is innovatively regarded as a wide-band ***,the stochastic averaging method for quasi integrable Hamiltonian systems under wide-band noise excitation is applied to reduce 2n-dimensional original system into n-dimensional averaged ltd stochastic differential equations(SDEs).Reliability function and mean first passage time are obtained by solving the associated backward Kolmogorov equation and Pontryagin *** validity of the proposed procedure is tested by applying it to an example and comparing the numerical results with those from Monte Carlo simulation.

关键词： Reliability fkst passage time quasi integrable and non-resonant Hamiltonian systems fractional Gauss noise

Stochastic averaging of quasi integrable and resonant Hamiltonian systems excited by fractional Gaussian noise with Hurst index 1/2

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Acta Mechanica Solida Sinica 2017年第1期30卷 11-19页

作者： q.f.Lü M.L.Deng W.q.Zhu Department of Mechanics State Key Laboratory of Fluid Power and Mechatronic SystemsKey Laboratory of Soft Machines and Smart Devices of Zhejiang ProvinceZhejiang University

A stochastic averaging method of quasi integrable and resonant Hamiltonian systems under excitation of fractional Gaussian noise （fGn） with the Hurst index 1/2 〈 H 〈 1 is proposed. first, the definition and the basic property of fGn and related fractional Brownian motion （iBm） are briefly introduced. Then, the averaged fractional stochastic differential equations （SDEs） for the first integrals and combinations of angle variables of the associated Hamiltonian systems are derived. The stationary probability density and statistics of the original systems are then obtained approximately by simulating the averaged SDEs numerically. An example is worked out to illustrate the proposed stochastic averaging method. It is shown that the results obtained by using the proposed stochastic averaging method and those from digital simulation of original system agree well.

关键词： quasi integrable and resonant Hamiltonian system fractional Brownian motion fractional Gaussian noise Stochastic averaging method Internal resonant