Combination of Continuum and Atomistic Approaches for the Study of Dislocation Nucleation from Atomic Size Surface Defects

2001 ◽  
Vol 677 ◽  
Author(s):  
Sandrine Brochard ◽  
Pierre Beauchamp ◽  
Jean Grilhé
Keyword(s):  
Stress Concentration ◽  
Surface Defects ◽  
Dislocation Nucleation ◽  
Point Force ◽  
Atomistic Simulations ◽  
Elastic Precursor ◽  
Atomic Size ◽  
Strong Localization ◽  
Elastic Shear ◽  
The Continuum

ABSTRACTAtomistic simulations realized on an f.c.c. crystal containing atomic size surface defects (step and groove) show that the defects are privileged sites for dislocation nucleation. Before nucleation, an elastic shear, precursor of the dislocation, appears in the plane in zone with the step where the dislocation will be nucleated. In order to explain the strong localization of the localized elastic precursor shear, we have analyzed the stress concentration near the surface defects using the continuum point force approach. For the step case, the origin of the localized shear is related to an increase in the interplanar separation due to the stress concentration.

scholarly journals Atomistic Simulations of Stress Concentration and Dislocation Nucleation at Grain Boundaries

2011 ◽  
Vol 2 (0) ◽  
pp. 20-23 ◽  
Author(s):  
Tomohito TSURU ◽  
Yoshiyuki KAJI ◽  
Takashi TSUKADA ◽  
Yoji SHIBUTANI
Keyword(s):  
Stress Concentration ◽  
Grain Boundaries ◽  
Dislocation Nucleation ◽  
Atomistic Simulations

Atomistic Simulations of Nanoindentation on Cu (111) with a Void

2008 ◽  
Vol 33-37 ◽  
pp. 919-924
Author(s):  
Chung Ming Tan ◽  
Yeau Ren Jeng ◽  
Yung Chuan Chiou
Keyword(s):  
Finite Element ◽  
Stress Concentration ◽  
Indentation Depth ◽  
Equilibrium Configuration ◽  
Complete System ◽  
Internal Surface ◽  
Atomistic Simulations ◽  
Element Formulation ◽  
Variable Parameters ◽  
Deformed State

This paper employs static atomistic simulations to investigate the effect of a void on the nanoindentation of Cu(111). The simulations minimize the potential energy of the complete system via finite element formulation to identify the equilibrium configuration of any deformed state. The size and depth of the void are treated as two variable parameters. The numerical results reveal that the void disappears when the indentation depth is sufficiently large. A stress concentration is observed at the internal surface of the void in all simulations cases. The results indicate that the presence of a void has a significant influence on the nanohardness extracted from the nanoindentation tests.

Length Scale Effects in Materials Deformation of Nano and Microscale Au Structures

2009 ◽  
Author(s):  
Jie Lian ◽  
Junlan Wang
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Size Effect ◽  
Sample Size ◽  
Atomistic Simulation ◽  
Scale Effects ◽  
Elastic Recovery ◽  
Boundary Effect ◽  
Dislocation Nucleation ◽  
Atomistic Simulations

In this study, intrinsic size effect — strong size dependence of mechanical properties — in materials deformation was investigated by performing atomistic simulation of compression on Au (114) pyramids. Sample boundary effect — inaccurate measurement of mechanical properties when sample size is comparable to the indent size — in nanoindentation was also investigated by performing experiments and atomistic simulations of nanoindentation into nano- and micro-scale Au pillars and bulk Au (001) surfaces. For intrinsic size effect, dislocation nucleation and motions that contribute to size effect were analyzed for studying the materials deformation mechanisms. For sample boundary effect, in both experiments and atomistic simulation, the elastic modulus decreases with increasing indent size over sample size ratio. Significantly different dislocation motions contribute to the lower value of the elastic modulus measured in the pillar indentation. The presence of the free surface would allow the dislocations to annihilate, causing a higher elastic recovery during the unloading of pillar indentation.

scholarly journals Atomistic Simulations of Dislocations in Confined Volumes

MRS Bulletin ◽  
2009 ◽  
Vol 34 (3) ◽  
pp. 184-189 ◽  
Author(s):  
P.M. Derlet ◽  
P. Gumbsch ◽  
R. Hoagland ◽  
J. Li ◽  
D.L. McDowell ◽  
...  
Keyword(s):  
Molecular Dynamics ◽  
Time Scale ◽  
Finite Temperature ◽  
Atomistic Simulation ◽  
Dislocation Nucleation ◽  
Atomic Scale ◽  
Atomistic Simulations ◽  
Complementary Role ◽  
Nanocrystalline Structures ◽  
Strength And Ductility

AbstractInternal microstructural length scales play a fundamental role in the strength and ductility of a material. Grain boundaries in nanocrystalline structures and heterointerfaces in nanolaminates can restrict dislocation propagation and also act as a source for new dislocations, thereby affecting the detailed dynamics of dislocation-mediated plasticity. Atomistic simulation has played an important and complementary role to experiment in elucidating the nature of the dislocation/interface interaction, demonstrating a diversity of atomic-scale processes covering dislocation nucleation, propagation, absorption, and transmission at interfaces. This article reviews some atomistic simulation work that has made progress in this field and discusses possible strategies in overcoming the inherent time scale challenge of finite temperature molecular dynamics.

Robustness Analysis of Algorithms to Estimate Constitutive Laws of Biological Filaments

2015 ◽  
Author(s):  
Jessica Gray ◽  
Soheil Fatehiboroujeni ◽  
Sachin Goyal
Keyword(s):  
Analysis Of Algorithms ◽  
Robustness Analysis ◽  
Dna Looping ◽  
Constitutive Law ◽  
Atomistic Simulations ◽  
Key Driver ◽  
Configuration Data ◽  
Function Relationship ◽  
Relationship Of ◽  
The Continuum

The structure-function relationship of biological filaments is greatly impacted by their mesoscale mechanics that involves twisting and bending deformations. For example, the mechanics of DNA looping is a key driver in gene regulation. The continuum-rod models have emerged as efficient tools for simulating the nonlinear dynamics of such deformations. However, there is no direct way to derive or measure the constitutive law of biological filaments for their continuum modeling. Therefore, it is an active area of research to develop inverse algorithms based on a continuum rod model that can estimate the constitutive law from the atomistic configurations of the filament. This paper presents a set of such algorithms that can use data from the dynamic states of deformation obtained from atomistic simulations or other sources. Depending on the kinematic quantities that are computed from the configuration data, the inverse algorithms differ in their steps to estimate the internal restoring moments and forces. The paper investigates and compares the robustness of these inverse algorithms accounting for the effect of noise in the data.

scholarly journals Failure Analysis of the Tree Column Structures Type AlSi10Mg Alloy Branches Manufactured by Selective Laser Melting

Materials ◽  
2020 ◽  
Vol 13 (18) ◽  
pp. 3969
Author(s):  
Peikang Bai ◽  
Pengcheng Huo ◽  
Taotao Kang ◽  
Zhanyong Zhao ◽  
Wenbo Du ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Stress Concentration ◽  
Selective Laser Melting ◽  
Fracture Morphology ◽  
Eutectic Structure ◽  
Laser Melting ◽  
Different Shapes ◽  
Si Content ◽  
Elastic Shear ◽  
Tree Type

AlSi10Mg alloy branches were fabricated by selective laser melting (SLM), and the branches were employed to evaluate their effect on the mechanical properties. When the porous branches were compressed along its building direction, the tree column structures-type AlSi10Mg alloy branches collapsed twice, which had typical elastic, shear, collapse, and densification stages. The compressive stress concentration at the interface between the support and the porous body caused the fracture of the tree column structures-type AlSi10Mg alloy branches. The fracture surface indicated that the prepared tree-type branches were distributed with different shapes of dimples, and the Si content inside the dimples was higher than that of the edge. The morphology of the Al-Si eutectic structure formed by SLM and the stress concentration at the Al/Al-Si-eutectic interface affected the fracture morphology and Si content distribution.

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