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molecular dynamics simulation on generalized stacking fault energies of FCC metals under preloading stress

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Chinese Physics B 2015年第8期24卷 586-593页

作者：张亮吕程 Tieu Kiet 赵星裴林清 Michal Guillaume School of Mechanical Materials and Mechatronic Engineering University of Wollongong

molecular dynamics(MD) simulations are performed to investigate the effects of stress on generalized stacking fault(GSF) energy of three fcc metals(Cu, Al, and Ni). The simulation model is deformed by uniaxial tension or compression in each of [111], [11-2], and [1-10] directions, respectively, before shifting the lattice to calculate the GSF curve. Simulation results show that the values of unstable stacking fault energy(γusf), stable stacking fault energy(γsf), and unstable twin fault energy(γutf) of the three elements can change with the preloaded tensile or compressive stress in different *** ratio of γsf/γusf, which is related to the energy barrier for full dislocation nucleation, and the ratio of γutf/γusf, which is related to the energy barrier for twinning formation are plotted each as a function of the preloading stress. The results of this study reveal that the stress state can change the energy barrier of defect nucleation in the crystal lattice, and thereby can play an important role in the deformation mechanism of nanocrystalline material.

关键词： molecular dynamics embeded atom method generalized stacking fault

molecular dynamics simulations of point defects in plutonium grain boundaries

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Chinese Physics B 2012年第2期21卷 398-406页

作者：敖冰云夏吉星陈丕恒胡望宇汪小琳 National Key Laboratory for Surface Physics and Chemistry P.O.Box 718-35Mianyang 621907China Department of Applied Physics Hunan UniversityChangsha 410082China

A modified analytic embedded atom method （MAEAM） potential is constructed for fcc 5-Pu. molecular dynamics （MD） simulations with the potential are performed to investigate the interactions between two symmetrical tilt grain boundaries （GBs） and point defects such as He atom, vacancy and self-interstitial atom （SIA） in Pu. The calculated results show that point defect formation energies are on average lower than those in the lattice but variations from site to site along the GBs are very remarkable. Both substitutional and interstitial He atoms are trapped at GBs. Interstitial He atom is more strongly bound at the GB core than the substitutional He atom. The binding energy of SIA at GB core is higher than those of He atom and vacancy. GB core can bind many He atoms and SIAs due mainly to the fact that it contains many vacancies. Compared with He atom and SIA, the vacancy far from GB core is difficult to diffuse into the core. The GBs can act as sinks and sources of He atoms and SIAs, which may be a reason for the swelling of Pu after a period of self-irradiation because of the higher concentration of vacancy in the bulk.

关键词： plutonium molecular dynamics crystal defect radiation damage

molecular dynamics STUDIES ON THE DISLOCATION GLIDING NEAR A TILT BOUNDARY

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Acta Mechanica Sinica 1996年第1期12卷 73-84页

作者：陈致英 Institute of Mechanics Academia Sinica Beijing 100080 China

The gliding behavior of edge dislocation near a grain boundary(QB) in copper under pure shear stresses is simulated by using molecular dynamics(MD) method. Many-body potential incorporating the embedded atom method (EAM) is used. The critical shear stresses for a single disocation to pass across GB surface are obtained at values of sigma(c)=23MPa similar to 68 MPa and 137 MPa similar to 274 MPa for Sigma=165 small angle tilt GB at 300 K and 20 K, respectively. The first result agrees with the experimental yield stress sigma(y)(=42 MPa) quite well. It suggests that there might be one of the reasons of initial plastic yielding caused by single dislocation gliding across GB. In addition, there might be possibility to obtain yield strength from microscopic analysis. Moreover, the experimental value of sigma(y) at low temperature is generally higher than that at room temperature. So, these results are in conformity qualitatively with experimental fact. On the other hand, the Sigma=25 GB is too strong an obstacle to the dislocation. In this case, a dislocation is able to pass across GB under relatively low stress only when it is driven by other dislocations. This is taken to mean that dislocation pile-up must be built up in front of this kind of GB, if this GB may take effect on the process of plastic deformation.

关键词： molecular dynamics grain boundary dislocation copper yielding

molecular dynamics study of the mechanical characteristics of Ni/Cu bilayer using nanoindentation

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Chinese Physics B 2012年第12期21卷 389-395页

作者： Muhammad Imran Fayyaz Hussain Muhammad Rashid S.A.Ahmad Department of Physics Simulation LaboratoryThe Islamia University of Bahawalpur Department of Physics National University of Singapore

In the present work, a three-dimensional molecular dynamics simulation is carried out to perform the nanoindentation experiment on Ni single crystal. The substrate indenter system is modeled using hybrid interatomic potentials including the many-body potential embedded atom method （EAM）, and two-body morse potential. To simulate the in- dentation process, a spherical indenter （diameter = 80A, 1A=0.1 nm） is chosen. The results show that the mechanical behaviour of a monolithic Ni is not affected by crystalline orientation. To elucidate the effect of a heterogeneous interface, three bilayer interface systems are constructed, namely Ni（100）/Cu（111）, Ni（110）/Cu（111）, and Ni（111）/Cu（111）. The simulations along these systems clearly describe that mechanical behaviour directly depends on the lattice mismatch. The interface with the smaller mismatch between the specified crystal planes is proved to be harder and vice versa. To describe the relationship between film thickness and interface effect, we choose various values of film thickness ranging from 20 A to 50 A to perform the nanoindentation experiment. It is observed that the interface is significant only for the relatively small thickness of film and the separation between interface and the indenter tip. It is shown that with the increase in film thickness, the mechanical behaviour of the film shifts more toward that of monolithic material.

关键词： nanoindentation bilayer molecular dynamics thin film

molecular dynamics Study of Tension Process of Ni-Based Superalloy

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Acta Metallurgica Sinica(English Letters) 2020年第5期33卷 741-750页

作者： Hui Li Wan Du Yi Liu Materials Genome Institute Shanghai UniversityShanghai 200444China

To understand the atomistic mechanisms of tension failure of Ni-based superalloy,in this study,the classical molecular dynamics(MD)simulations were used to study the uniaxial tension processes of both the Ni/Ni3 Al interface systems and the pure Ni and Ni3 Al *** examine the effects of interatomic potentials,we adopted embedded atom method(EAM)and reactive force field(ReaxFF)in the MD *** results of EAM simulations showed that the amorphous structures and voids formed near the interface,facilitating further crack propagation within Ni *** EAM potentials also predicted that dislocations were generated and annihilated alternatively,leading to the oscillation of yielding stress during the tension *** ReaxFF simulations predicted more amorphous formation and larger tensile *** atomistic understanding of the defect initiation and propagation during tension process may help to develop the strengthening strategy for controlling the defect evolution under loading.

关键词： Ni-based superalloy molecular dynamics Embedded atom method(EAM) Reactive force field(ReaxFF) Uniaxial tension

molecular dynamics of Structural Organization in Binary Fluids with Fixed Particles

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Chinese Physics Letters 2002年第6期19卷 835-838页

作者：唐彦立马余强 NationalLaboratoryofSolidStateMicrostructures NanjingUniversityNanjing210093

We have numerically studied the structural organization in binary immiscible fluids with fixed particles. The particles that have a finite excluded volume and a selective affinity for one fluid component have a significant influence on the organization process, where the hydrodynamic flows induced by the interface motion are suppressed and the domain growth is slowed down at late stages. Two different cases with weak and strong preferential interactions are considered, and the results show that the particles in the former can be left in the unfavourable phase during the process but are permanently surrounded by the favourable phase in the latter. The study indicates that the system would develop into a dynamical steady state and the final domain size might be dependent not only on the number of particles but also on the preferential interaction strength.

关键词： molecular dynamics

molecular dynamics simulations of jet breakup and ejecta production from a grooved Cu surface under shock loading

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Chinese Physics B 2014年第4期23卷 504-507页

作者：何安民王裴邵建立段素青 Institute of Applied Physics and Computational Mathematics

Large-scale non-equilibrium molecular dynamics simulations are performed to explore the jet breakup and ejecta production of single crystal Cu with a triangular grooved surface defect under shock loading. The morphology of the jet breakup and ejecta formation is obtained where the ejecta clusters remain spherical after a long simulation time. The effects of shock strength as well as groove size on the steady size distribution of ejecta clusters are investigated. It is shown that the size distribution of ejecta exhibits a scaling power law independent of the simulated shock strengths and groove sizes. This distribution, which has been observed in many fragmentation processes, can be well described by percolation theory.

关键词： molecular dynamics ejection

molecular dynamics Simulations of Deposition and Damage on Tungsten Plasma-Facing Materials by Tungsten Dust

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Plasma Science and Technology 2014年第8期16卷 805-808页

作者：牛国鉴李小椿丁锐徐倩罗广南 Institute of Plasma Physics Chinese Academy of Sciences University of Science and Technology of China

Classical molecular dynamics has been used to study the interactions between tung- sten （W） plasma-facing materials （PFMs） and dust grains. The impact velocity of dust grains is in the range from 324 m/s to 3240 m/s. The main effect of dust grains with low impact velocity is deposition. However, a material surface can be damaged by high velocity dust grains. The cumulative damage of impacting dust grains has also been take into account. When the impact velocity is low, no significant damage is detected but a porous firm forms on the surface. Serious damage can be produced on PFMs if the impact velocity is high.

关键词： molecular dynamics dust plasma-facing materials

molecular dynamics Simulation of Microstructure Transitions in a Large-Scale Liquid Metal Al System During Rapid Cooling Processes

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Chinese Physics Letters 2002年第8期19卷 1144-1147页

作者： Liu Rang-Su Dong Ke-Jun Li Ji-Yong Yu Ai-Bing Zou Rui-Ping Department of Physics Hu'nan University Changsha 410082 School of Materials Science and Engineering The University of New South Wales Sydney New South Wales 2052 Australia Department of Chemistry Hu'nan University Changsha 410082

We perform a molecular dynamics simulation of microstructure transitions in a large-scale system consisting of 400000 atoms of liquid metal Al by the Clare supercomputer. A cluster-type index method is proposed to describe the structures of various short-range-order clusters in the liquid system. It is demonstrated that the icosahedron cluster (12 0 12 0) plays the most important role in the microstructure transition and that some larger clusters (containing more than 130 atoms) are formed in the system during the rapid cooling processes. It is obvious that the larger clusters are formed by means of combining some middle clusters, and that the middle clusters are formed with several smaller clusters. However, the larger clusters are not formed to be the multi-shell configuration as shown in the mass spectrum analysis of the cluster configurations of Al obtained by gaseous deposition, ionic spray methods and so on. This result can be used to explain the essential distinction between the cluster configurations of Al formed in two different ways.

关键词： molecular dynamics