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molecular dynamics simulation of cylindrical Richtmyer-Meshkov instability

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Science China(Physics,Mechanics & Astronomy) 2018年第11期61卷 61-71页

作者： Zhenhong Wu Shenghong Huang Juchun Ding Weirong Wang Xisheng Luo Department of Modern Mechanics University of Science and Technology of China

The microscopic-scale Richtmyer-Meshkov(RM) instability of a single-mode Cu-He interface subjected to a cylindrically converging shock is studied through the classical molecular dynamics simulation. An unperturbed interface is first considered to examine the flow features in the convergent geometry, and notable distortions at the circular inhomogeneity are observed due to the atomic fluctuation. Detailed processes of the shock propagation and interface deformation for the single-mode interface impacted by a converging shock are clearly captured. Different from the macroscopic-scale situation, the intense molecular thermal motions in the present microscale flow introduce massive small wavelength perturbations at the single-mode interface, which later significantly impede the formation of the roll-up structure. Influences of the initial conditions including the initial amplitude,wave number and density ratio on the instability growth are carefully analyzed. It is found that the late-stage instability development for interfaces with a large perturbation does not depend on its initial amplitude any more. Surprisingly, as the wave number increases from 8 to 12, the growth rate after the reshock drops gradually. The distinct behaviors induced by the amplitude and wave number increments indicate that the present microscopic RM instability cannot be simply characterized by the amplitude over wavelength ratio(η). The pressure history at the convergence center shows that the first pressure peak caused by the shock focusing is insensitive to η, while the second one depends heavily on it.

关键词： molecular dynamics simulation Richtmyer-Meshkov instability converging shock

molecular dynamics simulation of the flow mechanism of shear-thinning fluids in a microchannel

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Chinese Physics B 2024年第4期33卷 516-525页

作者：杨刚郑庭程启昊张会臣 Naval Architecture and Ocean Engineering College Dalian Maritime UniversityDalian 116026China

Shear-thinning fluids have been widely used in microfluidic systems,but their internal flow mechanism is still ***,in this paper,molecular dynamics simulations are used to study the laminar flow of shear-thinning fluid in a *** validated the feasibility of our simulation method by evaluating the mean square displacement and Reynolds number of the solution *** results show that the change rule of the fluid system's velocity profile and interaction energy can reflect the shear-thinning characteristics of the *** velocity profile resembles a top-hat shape,intensifying as the fluid's power law index *** interaction energy between the wall and the fluid decreases gradually with increasing velocity,and a high concentration of non-Newtonian fluid reaches a plateau ***,the velocity profile of the fluid is related to the molecule number density distribution and their values are inversely *** analyzing the radial distribution function,we found that the hydrogen bonds between solute and water molecules weaken with the increase in *** observation offers an explanation for the shear-thinning phenomenon of the non-Newtonian flow from a micro perspective.

关键词： molecular dynamics simulation non-Newtonian fluid microchannel shear-thinning

molecular dynamics simulation OF THE ROLE OF DISLOCATIONS IN MICROCRACK HEALING

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Acta Mechanica Sinica 2000年第4期16卷 366-373页

作者：李深高克玮乔利杰褚武扬周富信 Dept.of Mater.Phys. Univ.of Sci.Tech.BeijingBeijing 100083China LNM Inst.of Mech. CASBeijing 100080China

The molecular dynamics method is used to simulate microcrack healing during heating or/and under compressive stress.A centre microcrack in Cu crystal would be sealed under compressive stress or by *** role of com- pressive stress and heating in crack healing was *** microcrack healing, dislocation generation and motion *** there were pre-existing disloca- tions around the microcrack,the critical temperature or compressive stress necessary for microcrack healing would decrease,and,the higher the number of dislocations, the lower the critical temperature or compressive *** critical temperature necessary for microcrack healing depended upon the orientation of the crack plane. For example,the critical temperature for the crack along the(001)plane was the lowest,i.e.770K.

关键词： microcrack healing molecular dynamics simulation dislocation

molecular dynamics simulation of Shock Response of CL-20 Co-crystals Containing Void Defects

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Defence Technology（防务技术） 2024年第1期31卷 364-374页

作者： Changlin Li Wei Yang Qiang Gan Yajun Wang Lin Liang Wenbo Zhang Shuangfei Zhu Changgen Feng State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing 100081China School of Materials Science&Engineering Beijing Institute of TechnologyBeijing 100081China

To investigate the effect of void defects on the shock response of hexanitrohexaazaisowurtzitane(CL-20)co-crystals,shock responses of CL-20 co-crystals with energetic materials ligands trinitrotoluene(TNT),1,3-dinitrobenzene(DNB),solvents ligands dimethyl carbonate(DMC) and gamma-butyrolactone(GBL)with void were simulated,using molecular dynamics method and reactive force *** is found that the CL-20 co-crystals with void defects will form hot spots when impacted,significantly affecting the decomposition of molecules around the *** degree of molecular fragmentation is relatively low under the reflection velocity of 2 km/s,and the main reactions are the formation of dimer and the shedding of nitro *** existence of voids reduces the safety of CL-20 co-crystals,which induced the sensitivity of energetic co-crystals CL-20/TNT and CL-20/DNB to increase more *** has occurred under the reflection velocity of 4 km/s,energetic co-crystals are easier to polymerize than solvent co-crystals,and are not obviously affected by *** results show that the energy of the wave decreases after sweeping over the void,which reduces the chemical reaction frequency downstream of the void and affects the detonation performance,especially the solvent co-crystals.

关键词： CL-20 co-crystals molecular dynamics simulation Reactive forcefield Impact response Hot spot Void defect

molecular dynamics simulation Studies on the Micromorphology and Proton Transport of Nafion/Ti_(3)C_(2)T_(x) Composite Membrane

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Chinese Journal of Polymer Science 2024年第3期42卷 373-387,I0009页

作者： Zhi-Yue Han Su-Peng Pei Chun-Yang Yu Yong-Feng Zhou School of Chemical and Environmental Engineering Shanghai Institute of TechnologyShanghai 201418China School of Chemistry&Chemical Engineering Frontiers Science Center for Transformative MoleculesShanghai Key Laboratory of Electrical Insulation and Thermal AgingShanghai Jiao Tong UniversityShanghai 200240China Key Laboratory of Green and High-end Utilization of Salt Lake Resources Chinese Academy of SciencesXining 810008China

The perfluorosulfonic acid(PFSA) membrane doped with two-dimensional conductive filler Ti_(3)C_(2)T_(x) is a fuel cell proton exchange membrane with high application potential. Experimental studies showed that the proton conductivity of Nafion/Ti_(3)C_(2)T_(x) composite membrane is improved significantly compared with that in pure Nafion. However, the microscopic mechanism of doping on the enhancement of membrane performance is remain unclear now. In this work, molecular dynamics simulation was used to investigate the microscopic morphology and proton transport behaviors of Nafion/Ti_(3)C_(2)T_(x) composite membrane at the molecular level. The results shown that there were significant differences about the diffusion kinetics of water molecules and hydroxium ions in Nafion/Ti_(3)C_(2)T_(x) at low and high hydration levels in the nanoscale *** the increase of water content, Ti_(3)C_(2)T_(x) in membrane was gradually surrounded by ambient water molecules to form a hydration layer, and forming a relatively continuous proton transport channel between Nafion polymer and Ti_(3)C_(2)T_(x) monomer. The continuous proton transport channel could increase the number of binding sites of proton and thus achieving high proton conductivity and high mobility of water molecules at higher hydration level. The current work can provide a theoretical guidance for designing new type of Nafion composite membranes.

关键词： Nafion/Ti_(3)C_(2)T_(x)composite membrane Proton transport molecular dynamics simulation

molecular dynamics simulation and Experimental Proof of Hydrogen-enhanced Dislocation Emission in Nickel

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Journal of University of Science and Technology Beijing 2002年第1期9卷 59-64页

作者： Zhongji Li, Jinxu Li, Wuyang Chu, Hui Liu, Lyie Qiao, Materials Science and Engineering School, University of Science and Technology Beijing. Beijing 100083, China E-mail: lqiao@*** Mat. Sci. and Eng. Sch. Univ. of Sci. and Technol. Beijing Beijing 100083 China

A quasi three dimensions molecular dynamic method was used to simulate the effect of hydrogen on dislocation emission and crack propagation in nickel. In situ observation in a transmission electron microscope (TEM) was used to confirm the simulation results. The simulation result indicated that hydrogen solubilized in nickel decreased the critical stress intensity for the dislocation emission, i.e., hydrogen enhanced dislocation emission. In situ observation in TEM showed that hydrogen enhanced dislocation emission and motion before the initiation of hydrogen-induced crack.

关键词： nickel molecular dynamics simulation hydrogen dislocation emission TEM

molecular dynamics simulation of the Evolution of Interfacial Dislocation Network and Stress Distribution of a Ni-Based SingleCrystal Superalloy

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Acta Metallurgica Sinica(English Letters) 2016年第7期29卷 689-696页

作者： Yun-Li Li Wen-Ping Wu Zhi-Gang Ruan Key Laboratory of Geotechnical and Structural Engineering Safety of Hubei Province School of Civil EngineeringWuhan University State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan University

The evolution of misfit dislocation network at γ/γ＇ phase interfaces and the stress distribution characteristics of Ni-based single-crystal superalloys under different temperatures of 0, 100 and 300 K are studied by molecular dynamics （MD） simulation. It was found that a closed three-dimensional misfit dislocation network appears on the γ/γ＇ phase interfaces, and the shape of the dislocation network is independent of the lattice mismatch. Under the influence of the temperature, the dislocation network gradually becomes irregular, a/2 [110] dislocations in the γ matrix phase emit and partly cut into the γ＇ phase with the increase in temperature. The dislocation evolution is related to the local stress field, a peak stress occurs at γ/γ＇ phase interface, and with the increase in temperature and relaxation times, the stress in the γ phase gradually increases, the number of dislocations in the γ phase increases and cuts into γ＇ phase from the interfaces where dislocation network is damaged. The results provide important information for understanding the temperature dependence of the dislocation evolution and mechanical properties of Ni-based single-crystal superalloys.

关键词： Ni-based single-crystal superalloy molecular dynamics simulation Dislocation network Stress distribution

molecular dynamics simulation of the tribological performance of amorphous/amorphous nano-laminates

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Journal of Materials Science & Technology 2022年第10期105卷 226-236页

作者： Dongpeng Hua Wan Wang Dawei Luo Qing Zhou Shuo Li Junqin Shi Maosen Fu Haifeng Wang State Key Laboratory of Solidification Processing Center of Advanced Lubrication and Seal MaterialsNorthwestern Polytechnical UniversityXi’anShaanxi 710072PR China

Because the amorphous/amorphous nano-laminates could enhance signifcantly the mechanical properties of the amorphous materials,they have been widely studied as a new group of structural *** this study,the nano-scratch performance of the Cu_(80)Zr_(20)/Cu_(20)Zr_(80)(A/B-type)and the Cu_(20)Zr_(80)/Cu_(80)Zr_(20)(B/A-type)amorphous/amorphous nano-laminates was evaluated by molecular dynamics *** dependences on the type of indenter,layer thickness,stacking mode and scratch depth were systematically *** is a signifcant size effect for the tribological properties of amorphous/amorphous nanolaminates that the friction force of the A/B-type increases with the increase of layer thickness,but the friction force of the B/A-type decreases as the layer thickness *** interface has an obvious obstruction effect on the shear deformation and reduces the plastic affected region below the scratched ***,the contact environment of the indenter bottom has an important influence on the normal force,so it’s not that the deeper the depth,the greater the normal *** it should not be ignored when evaluating the tribological properties of the amorphous/amorphous *** work can deepen the understanding of hetero-interface on the deformation mechanism during nano-scratch,and help to design amorphous nano-laminates with tailored tribological performance for practical applications.

关键词： Amorphous/amorphous nano-laminates Nano-scratch molecular dynamics simulation Tribology

molecular dynamics simulation of Behaviours of Non-Polar Droplets Merging and Interactions with Hydrophobic Surfaces

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Journal of Bionic Engineering 2008年第4期5卷 271-281页

作者： Y.Y. Yan C.Y. Ji School of the Built Environment University of Nottingham Nottingham NG7 2RD UK

This paper presents a molecular dynamics simulation of the behaviours of non-polar droplets merging and also the fluid molecules interacting with a hydrophobic surface. Such behaviours and transport phenomena are popular in general microchannel flow boiling and two-phase flow. The droplets are assumed to be composed of Lennards-Jones type molecules. Periodic boundary conditions are applied in three coordinate directions of a 3-D system, where there exist two liquid droplets and their vapour. The two droplets merge when they come within the prescribed small distance. The merging of two droplets apart from each other at different initial distances is tested and the possible larger （or critical） non-dimensional distance, in which droplets merging can occur, is discussed. The evolution of the merging process is simulated numerically by employing the molecular dynamics （MD） method. For interactions with hydrophobic solid wall, a system with fluid confined between two walls is used to study the wetting phenomena of fluid and solid wall. The results are compared with those of hydrophilic wall to show the unique characteristics of hydrophobic interactions by microscopic methods.

关键词： molecular dynamics simulation mist flow droplets merging hydrophobic wetting