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

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.

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.

A theoretical study of wrinkle propagation in graphene with flower-like grain boundaries

2021 ◽  
Author(s):  
Zihui Zhao ◽  
Yafei Wang ◽  
Changguo Wang
Keyword(s):  
Grain Boundaries ◽  
Theoretical Study ◽  
Atomistic Simulations ◽  
Dynamic Surface ◽  
Surface Wrinkle

This study investigated dynamic surface wrinkle propagation across a series of flower-like rotational grain boundaries (GBs) in graphene using theoretical solutions and atomistic simulations. It was found that there was...

scholarly journals CREEP RUPTURE LIFE OF PRE-STRAINED SUPERALLOY N07080

2021 ◽  
Vol 9 (10) ◽  
pp. 1167-1176
Author(s):  
Omer Beganovic ◽  
Keyword(s):  
Stress Concentration ◽  
Grain Boundaries ◽  
Rupture Life ◽  
Warm Rolling ◽  
Creep Rupture ◽  
Cavity Nucleation ◽  
Standard Heat ◽  
Creep Cavity ◽  
Heat Treated

The creep of the pre-strained superalloy N07080 is described in this work. The pre-strain was achieved by warm rolling at 1050 oC.-The warm rolling was performed due to additional strengthening, i.e increasing of the superalloy hardness.-The pre-strain drastically reduces the creep rupture life of the superalloy compared to the creep rupture life of the standard heat treated superalloy.-The drastic reductionof the creep rupture life is result of rapid creep cavity nucleation on stress concentration sites along primary grain boundaries of the pre-strained superalloy.-Recrystallization eliminates potential sites for rapid cavity nucleation and prolongates the creep rupture life.

scholarly journals Pop-in behavior and elastic-to-plastic transition of polycrystalline pure iron during sharp nanoindentation

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Fabian Pöhl
Keyword(s):  
Grain Boundaries ◽  
Strong Influence ◽  
Electron Backscatter Diffraction ◽  
Dislocation Nucleation ◽  
Stress Fields ◽  
Shear Stresses ◽  
Statistical Process ◽  
Iron Crystal ◽  
Electron Backscatter ◽  
Backscatter Diffraction

Abstract This study analyzes the elastic-to-plastic transition during nanoindentation of polycrystalline iron. We conduct nanoindentation (Berkovich indenter) experiments and electron backscatter diffraction analysis to investigate the initiation of plasticity by the appearance of the pop-in phenomenon in the loading curves. Numerous load–displacement curves are statistically analyzed to identify the occurrence of pop-ins. A first pop-in can result from plasticity initiation caused by homogeneous dislocation nucleation and requires shear stresses in the range of the theoretical strength of a defect-free iron crystal. The results also show that plasticity initiation in volumes with preexisting dislocations is significantly affected by small amounts of interstitially dissolved atoms (such as carbon) that are segregated into the stress fields of dislocations, impeding their mobility. Another strong influence on the pop-in behavior is grain boundaries, which can lead to large pop-ins at relatively high indentation loads. The pop-in behavior appears to be a statistical process affected by interstitial atoms, dislocation density, grain boundaries, and surface roughness. No effect of the crystallographic orientation on the pop-in behavior can be observed.

Nanometer Scale Mechanical Behavior of Grain Boundaries

2011 ◽  
Vol 1297 ◽  
Author(s):  
Chien-Kai Wang ◽  
Huck Beng Chew ◽  
Kyung-Suk Kim
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Virtual Work ◽  
Potential Interaction ◽  
Dislocation Nucleation ◽  
Nanometer Scale ◽  
Nonlinear Field ◽  
Boundary Slip ◽  
Nucleation Sites ◽  
Eam Potential

ABSTRACTA nonlinear field projection method has been developed to study nanometer scale mechanical properties of grain boundaries in nanocrystalline FCC metals. The nonlinear field projection is based on the principle of virtual work, for virtual variations of atomic positions in equilibrium through nonlocal interatomic interactions such as EAM potential interaction, to get field-projected subatomic-resolution traction distributions on various grain boundaries. The analyses show that the field projected traction produces periodic concentrated compression sites on the grain boundary, which act as crack trapping or dislocation nucleation sites. The field projection was also used to assess the nanometer scale failure processes of Cu Σ5 grain boundaries doped with Pb. It was revealed that the Pb dopants prevented the emission of dislocations by grain boundary slip and embrittles the grain boundary.

Interaction Between Lattice Dislocations and Grain Boundaries In Ordered Compounds

1990 ◽  
Vol 213 ◽  
Author(s):  
B.J. Pestman ◽  
J. Th. M. De Hosson ◽  
V. Vitek ◽  
F.W. Schapink
Keyword(s):  
Shear Stress ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Partial Dislocation ◽  
Atomistic Simulations ◽  
Many Body ◽  
Shockley Partial Dislocation ◽  
Screw Dislocations ◽  
Applied Shear Stress ◽  
Tilt Boundaries

ABSTRACTThe interaction of 1/2<1 1 0> screw dislocations with symmetric [1 1 0] tilt boundaries was investigated by atomistic simulations using many-body potentials representing ordered compounds. The calculations were performed with and without an applied shear stress. The observations were: absorption into the grain boundary, attraction of a lattice Shockley partial dislocation towards the grain boundary and transmission through the grain boundary under the influence of a shear stress. It was found that the interaction in ordered compounds shows similarities to the interaction in fcc.

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