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INVESTIGATION ON APPLICABILITY OF VARIOUS STRESS DEFINITIONS IN Atomistic simulation

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Acta Mechanica Solida Sinica 2009年第6期22卷 644-649页

作者： Ran Xu Bin Liu AML Department of Engineering Mechanics Tsinghua University Beijing 100084 China

How to correctly extract Cauchy stress from the Atomistic simulations is a crucial issue in studying the mechanical behaviours of atomic systems, but is still in controversy. In this paper, three typical Atomistic simulation examples are used to validate various existing stress definitions. It is found that the classical virial stress fails in predicting the stresses in these examples, because the velocity depends on the choice of the local average volume or the reference frame velocity and other factors. In contrast, the Lagrangian cross-section stress and Lagrangian virial stress are validated by these examples, and the instantaneous Lagrangian atomic stress definition is also proposed for dynamical problems.

关键词： atomic stress virial stress Atomistic simulation

Atomistic simulation of helium bubble nucleation in palladium

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Atomistic simulation of helium bubble nucleation in palladiu...

Atomistic simulation of Interaction between Grain Boundary and Dislocations in Ni_3Al

9th International Conference on Computer simulation of Radiation Effects in Solids

作者： Liang Wang~1 Wangyu Hu~(1*) Shifang Xiao~1 Jianyu Yang~2 Huiqiu Deng 1 Department of Applied Physics Hunan University Changsha 410082 China 2 Department of Maths and Physics Hunan Institute of Engineering Xiangtan 411104 China

＜正＞A palladium crystal including two surfaces has been constructed with 11808 atoms. 55 helium atoms occupied the octahedral position of palladium crystal are introduced and restricted in a spherical region.MD simu... 详细信息

关键词： Helium bubble Nucleation Atomistic simulation Cluster Molecular dynamics

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Journal of Materials Science & Technology 1993年第5期9卷 327-337页

作者： Dongliang LIN(T.L.Lin) Da CHEN Min LU Department of Materials Science,Shanghai Jiaotong University,Shanghai,200030,China Shanghai Jiaotong Univ Shanghai China

The embedded atom type potentials and static relaxation method combined with a steepest decent computational technique have been used to simulate the interaction between the grain boundary (GB) and dislocations in Ni_3Al alloys.The focus has been placed on the energy feature of the interaction,the distortion of GB structural units,and the dislocation core structure near the GB.Im- plication has also been made on the results for the understanding of the mechanism responsible for B-enhanced ductility.

关键词： Atomistic simulation grain boundary dislocation Ni_3Al

The physical origin of observed repulsive forces between general dislocations and twin boundaries in FCC metals:An atom-continuum coupling study

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Journal of Materials Science & Technology 2022年第14期109卷 221-227页

作者： Jiayong Zhang Hongwu Zhang Qian Li Lizi Cheng Hongfei Ye Yonggang Zheng Jian Lu Department of Engineering Mechanics State Key Laboratory of Structural Analysis for Industrial EquipmentFaculty of Vehicle Engineering and MechanicsDalian University of TechnologyDalian 116024China Department of Mechanical Engineering Shenyang National Laboratory for Materials ScienceGreater Bay Joint DivisionCity University of Hong KongTat Chee AvenueKowloonHong KongChina CityU-Shenzhen Futian Research Institute Shenzhen 518045China

The combination of ultrahigh strength and excellent ductility of nanotwinned materials is rooted in the interaction between dislocations and twin boundaries(TBs).Quantifying the interaction between TBs and dislocations not only offers fresh perspectives of designing materials with high strength and ductility,but also becomes the cornerstone of multiscale modeling of materials with TBs.In this work,an atomcontinuum coupling model was adopted to quantitatively investigate the interaction between dislocations and TBs.The simulation shows that the dislocation-TB interaction is much weaker than the interaction between dislocations at the same distance.simulation of the early stage of dislocation pileups further verifies that the experimentally observed repulsive forces are essentially from the dislocations or kink-like steps on TBs.The interaction between TBs and dislocations with different Burgers vectors was demonstrated referring to the elastic theory of dislocations.With the intrinsic interaction between dislocations and TBs being clarified,this work will promote further development of the multiscale simulation methods,such as discrete dislocation dynamics or phase-field method,of materials with TBs by providing a quantitative description of the interactions between TBs and dislocations.

关键词： Twin boundary Intrinsic interaction Repulsive force Dislocation pileup Atomistic simulation Anisotropic elasticity

atomistic/CONTINUUM simulation OF INTERFACIAL FRACTURE——PART Ⅰ: Atomistic simulation

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Acta Mechanica Sinica 1994年第3期10卷 150-161页

作者：谭鸿来杨卫 Department of Engineering Mechanics Tsinghua University Beijing China 100084

The phenomenon of interfacial fracture, as manifested by atom- istic cleavage, debonding and dislocation emission, provides a challenge for combined atomistic-continuum analysis. As a precursor for fully coupled atomistic-continuum simulation of interfacial fracture, we focus here on the atomistic behavior within a nanoscopic core surrounding the crack tip. The inter-atomic potential under Em- bedded Atom Method is recapitulated to form an essential framework of Atomistic simulation. The calculations are performed for a side-cracked disc configuration un- der a remote K field loading. It is revealed that a critical loading rate defines the brittle-to-ductile transition of homogeneous materials. We further observe that the near tip mode mixity dictates the nanoscopic profile near an interfacial crack tip. A zigzag interface structure is simulated which plays a significant role in the dislocation emission from an interfacial crack tip, as will be explored in the second part of this investigation.

关键词： interfacial fracture Atomistic simulation mode mixity loading rate zigzag interface

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Transfer or blockage:Unraveling the interaction between deformation twinning and grain boundary in tantalum under shock loading with molecular dynamics

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Journal of Materials Science & Technology 2023年第25期156卷 118-128页

作者： Z.C.Meng M.M.Yang A.H.Feng S.J.Qu F.Zhao L.Yang J.H.Yao Y.Yang Q.B.Fan H.Wang Interdisciplinary Centre for Additive Manufacturing (ICAM) School of Materials and ChemistryUniversity of Shanghai for Science and TechnologyShanghai 200093China Institute of Metal Research Chinese Academy of SciencesShenyang 110016China School of Materials Science and Engineering University of Science and Technology of ChinaShenyang 110016China School of Materials Science and Engineering Tongji UniversityShanghai 201804China Academy for Advanced Interdisciplinary Studies Southern University of Science and TechnologyShenzhen 518055China National Key Laboratory of Science and Technology on Materials Under Shock and Impact School of Materials Science and EngineeringBeijing Institute of TechnologyBeijing 100081China Beijing Institute of Technology Chongqing Innovation Center Chongqing 401135China

The interaction between{112}deformation twinning and grain boundary in coaxial polycrystalline tantalum under shock compression was studied with molecular dynamics simulation under different grain pair misorientation angles(MA)and geometric compatibility factor(m’).Generally,in the coaxial polycrystal,the value of MA determines the occurrence of twin transfer(TT)or twin blockage(TB),i.e.,twin transfer occurs at MA≤29°with twin blockage otherwise.Under TT,the value of m’affects the selection of twin variants.,i.e.,the twin system with a larger m’is easier to active.The morphology of twin pairs is ruler-shaped and lenticular under TT and TB,respectively,with different thickening mechanisms,including grain boundary dislocation emission.

关键词： Plasticity Grain boundary Twin Atomistic simulation Tantalum

Molecular simulation of Cement-Based Materials and Their Properties

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维普期刊数据库

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Engineering 2022年第8期8卷 165-178页

作者： Ashraf A.Bahraq Mohammed A.Al-Osta Omar S.Baghabra Al-Amoudi I.B.Obot Mohammed Maslehuddin Habib-ur-Rehman Ahmed Tawfik A.Saleh Department of Civil and Environmental Engineering King Fahd University of Petroleum and MineralsDhahran 31261Saudi Arabia Interdisciplinary Research Center for Construction and Building Materials King Fahd University of Petroleum and MineralsDhahran 31261Saudi Arabia Interdisciplinary Research Center for Advanced Materials King Fahd University of Petroleum and MineralsDhahran 31261Saudi Arabia Department of Chemistry King Fahd University of Petroleum and MineralsDhahran 31261Saudi Arabia

Hydrated cement is one of the complex composite systems due to the presence of multi-scale phases with varying morphologies.Calcium silicate hydrate,which is the principal binder phase in the hydrated cement,is responsible for the stiffness,strength,and durability of Portland cement concrete.To understand the mechanical and durability behavior of concrete,it is important to investigate the interactions of hydrated cement phases with other materials at the nanoscale.In this regard,the molecular simulation of cement-based materials is an effective approach to study the properties and interactions of the cement system at the fundamental scale.Recently,many studies have been published regarding Atomistic simulations to investigate the cement phases to define/explain the microscopic physical and chemical properties,thereby improving the macroscopic performance of hardened binders.The research in molecular simulation of cementitious systems involves researchers with multidisciplinary backgrounds,mainly in two areas:(1)cement chemistry,where the hydration reactions govern most of the chemical and physical properties at the atomic scale;and(2)computational materials science and engineering,where the bottom-up approach is required.The latter approach is still in its infancy,and as such,a study of the prevailing knowledge is useful,namely through an exhaustive literature review.This state-of-theart report provides a comprehensive survey on studies that were conducted in this area and cites the important findings.

关键词： Atomistic simulation Molecular dynamics Cement phases Hydration products Nanoengineering

Modes of grain growth and mechanism of dislocation reaction under applied biaxial strain:atomistic and continuum modeling

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Journal of Materials Science & Technology 2020年第14期47卷 236-250页

作者： Ying-Jun Gao Qian-Qian Deng Zhe-yuan Liu Zong-Ji Huang Yi-Xuan Li Zhi-Rong Luo Guangxi Advanced Key Laboratory of Novel Energy Materials Guangxi Key Laboratory for the Relativistic AstrophysicsSchool of Physics Science and EngineeringGuangxi UniversityNanning530004China Institute of Physics Science and Engineering Technology Yulin Normal UniversityYulin537000China

The phase field crystal method and Continuum Modeling are applied to study the cooperative dislocation motion of the grain boundary(GB)migration,the manner of the nucleation of the grain and of the grain growth in two dimensions(2 D)under the deviatoric deformation at high temperature.Three types of the nucleation modes of new finding are observed by the phase field crystal simulation:The first mode of the nucleation is generated by the GB splitting into two sub-GBs;the second mode is of the reaction of the sub-GB dislocations,such as,the generation and annihilation of a pair of partial Frank sessile dislocation in 2 D.The process can be considered as the nucleation of dynamic recrystallization;the third mode is caused by two oncoming rows of the dislocations of these sub-GBs,crossing and passing each other to form new gap which is the nucleation place of the new deformed grain.The research is shown that due to the nucleation of different modes the mechanism of the grain growth by means of the sub-GB migration is different,and therefore,the grain growth rates are also different.Under the deviatoric deformation of the applied biaxial strain,the grain growth is faster than that of the grain growth without external applied stress.It is observed that the cooperative dislocation motion of the GB migration under the deviatoric deformation accompanies with local plastic flow and the state of the stress of the system changes sharply.When the system is in the process of recrystallized grain growth,the system energy is in an unstable state due to the release of the strain energy to cause that the reverse movement of the plastic flow occurs.The area growth of the deformed grain is approximately proportional to the strain square and also to the time square.The rule of the time square of the deformed grain growth can also be deduced by establishing the continuum dynamic equation of the biaxial strain-driven migration of the GB.The copper metal is taken as an example of the calculation,and the obtained result is a good agreeme

关键词： Grain boundary splitting Grain growth Dislocation reaction Atomistic simulation Continuum modeling

Atomistic simulations on adhesive contact of single crystal Cu and wear behavior of Cu-Zn alloy

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Chinese Physics B 2021年第2期30卷 442-448页

作者：叶有俊秦乐李京刘麟吴凌康 National Quality Supervision and Inspection Center of Pressure Pipe Components Special Equipment Safety Supervision Inspection Institute of Jiangsu ProvinceNanjing 210036China School of Mechanical Engineering Changzhou UniversityChangzhou 213164China Jiangsu Power Equipment Co. LtdChangzhou 213000China School of Material Science and Engineering Georgia Institute of TechnologyAtlantaGeorgia 30332-0245USA

Atomistic simulations are carried out to investigate the nano-indentation of single crystal Cu and the sliding of the Cu-Zn alloy.As the contact zone is extended due to adhesive interaction between the contact atoms,the contact area on a nanoscale is redefined.A comparison of contact area and contact force between molecular dynamics(MD)and contact theory based on Greenwood-Williamson(GW)model is made.Lower roughness causes the adhesive interaction to weaken,showing the better consistency between the calculated results by MD and those from the theoretical model.The simulations of the sliding show that the substrate wear decreases with the mol%of Zn increasing,due to the fact that the diffusion movements of Zn atoms in substrate are blocked during the sliding because of the hexagonal close packed(hcp)structure of Zn.

关键词： Atomistic simulation nano-indentation wear behavior