DYNAMICS OF A DISLOCATION SET IN MOTION BY AN EXTERNAL STRESS

2002 ◽  
Vol 13 (01) ◽  
pp. 97-105 ◽  
Author(s):  
M. ROBLES ◽  
L. PERONDI ◽  
K. KASKI
Keyword(s):  
Shear Stress ◽  
Dislocation Motion ◽  
External Stress ◽  
Atomic Scale ◽  
Dislocation Velocity ◽  
Two Dimensional ◽  
Tracking Method ◽  
Stress Pulse ◽  
Lennard Jones ◽  
Dynamics Simulations

The relation between dislocation velocity and resolved shear stress is studied computationally at the atomic scale using Molecular Dynamics simulations in a two-dimensional Lennard–Jones system. Mimicking a well known experimental technique, we apply a calibrated stress pulse to a system with a single dislocation and follow with a run-time graphics tool and displacement-field based tracking method, the dislocation motion caused by momentum transfer from an externally generated stress pulse. The empirically suggested power law relation between dislocation velocity and resolved shear stress seems to hold also in the atomic scale.

scholarly journals Shear-rate dependence of thermodynamic properties of the Lennard-Jones truncated and shifted fluid by molecular dynamics simulations

2021 ◽  
Author(s):  
Martin P. Lautenschlaeger ◽  
Hans Hasse
Keyword(s):  
Molecular Dynamics ◽  
Shear Stress ◽  
Shear Rate ◽  
Molecular Dynamics Simulations ◽  
Local Structure ◽  
Rate Dependence ◽  
Lennard Jones ◽  
Fluid Properties ◽  
Dynamics Simulations ◽  
Shear Rate Dependence

It was shown recently that using the two-gradient method, thermal, caloric, and transport properties of fluids under quasi-equilibrium conditions can be determined simultaneously from nonequilibrium molecular dynamics simulations. It is shown here that the influence of shear stresses on these properties can also be studied using the same method. The studied fluid is described by the Lennard-Jones truncated and shifted potential with the cut-off radius r*c = 2.5σ. For a given temperature T and density ρ, the influence of the shear rate on the following fluid properties is determined: pressure p, internal energy u, enthalpy h, isobaric heat capacity cp, thermal expansion coefficient αp, shear viscosity η, and self-diffusion coefficient D. Data for 27 state points in the range of T ∈ [0.7, 8.0] and ρ ∈ [0.3, 1.0] are reported for five different shear rates (γ ̇ ∈ [0.1,1.0]). Correlations for all properties are provided and compared with literature data. An influence of the shear stress on the fluid properties was found only for states with low temperature and high density. The shear-rate dependence is caused by changes in the local structure of the fluid which were also investigated in the present work. A criterion for identifying the regions in which a given shear stress has an influence on the fluid properties was developed. It is based on information on the local structure of the fluid. For the self-diffusivity, shear-induced anisotropic effects were observed and are discussed.

Interaction Between Dislocations and Misfit Interface

2000 ◽  
Vol 634 ◽  
Author(s):  
A. Kuronen ◽  
K. Kaski ◽  
L. F. Perondi ◽  
J. Rintala
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Misfit Dislocation ◽  
Driving Force ◽  
Two Dimensional ◽  
Lennard Jones ◽  
Dynamics Simulations ◽  
Nucleation Of Dislocations

ABSTRACTMechanisms responsible for the formation of a misfit dislocation in a lattice-mismatched system have been studied using Molecular Dynamics simulations of a two-dimensional Lennard-Jones system. Results show clearly how the strain due to the lattice-mismatched interface acts as a driving force for migration of dislocations in the substrate and the overlayer and nucleation of dislocations in the overlayer edges. Moreover, we observe dislocation reactions in which the gliding planes of dislocations change such that they can migrate to the interface.

MOLECULAR DYNAMIC STUDY OF A SINGLE DISLOCATION IN A TWO-DIMENSIONAL LENNARD–JONES SYSTEM

2003 ◽  
Vol 14 (04) ◽  
pp. 407-421 ◽  
Author(s):  
MIGUEL ROBLES ◽  
VILLE MUSTONEN ◽  
KIMMO KASKI
Keyword(s):  
Constant Strain Rate ◽  
Equation Of Motion ◽  
Dislocation Motion ◽  
Strain Rates ◽  
Interactive Simulation ◽  
Two Dimensional ◽  
Single Dislocation ◽  
Lennard Jones ◽  
Quasi Static Process ◽  
Dynamics Method

In this work the motion of a single dislocation in a two-dimensional triangular lattice is studied by using classical Molecular Dynamics method with the Lennard–Jones inter-atomic potential. The dislocation motion is investigated with an interactive simulation program developed to track automatically the movement of lattice defects. Constant strain and constant strain-rate deformations were applied to the system. From constant strain simulations a curve of shear stress versus dislocation velocity is obtained, showing a nonlinear power law relation. An equation of motion for the dislocation is proposed and found to be applicable when the movement of dislocation follows a quasi-static process. Numerical simulations at different strain rates show an elastic-to-plastic transition that modifies the dynamics of the dislocation motion.

MASS DISTRIBUTION OF A TWO-DIMENSIONAL FRAGMENTATION PROCESS

2005 ◽  
Vol 16 (02) ◽  
pp. 253-258 ◽  
Author(s):  
L. E. ARARIPE ◽  
A. DIEHL ◽  
J. S. ANDRADE ◽  
R. N. COSTA FILHO
Keyword(s):  
Mass Distribution ◽  
Radial Component ◽  
Fragmentation Process ◽  
Lennard Jones Potential ◽  
Two Dimensional ◽  
Jones Potential ◽  
Lennard Jones ◽  
Mass Size ◽  
Dynamics Simulations ◽  
Number Of Particles

We perform extensive molecular dynamics simulations to study the mass size distribution of a two-dimensional fragmentation process. Our model consists of a large number of particles interacting through the Lennard–Jones potential. The fragmentation is induced by suddenly imposing a radial component on the particles' velocities, in order to mimic an explosion phenomenon. We then investigate the effect of the input energy on the resulting mass distribution of fragments.

The Vibrational Modes of Model Bulk Metallic Glasses

2009 ◽  
Vol 1224 ◽  
Author(s):  
Peter M. Derlet ◽  
Robert Maaß ◽  
Jörg F. Löffler
Keyword(s):  
Metallic Glasses ◽  
High Frequency ◽  
Bulk Metallic Glasses ◽  
Pair Potential ◽  
Low Frequency ◽  
Atomic Scale ◽  
Vibrational Modes ◽  
Lennard Jones ◽  
Dynamics Simulations ◽  
Topological Disorder

AbstractBulk metallic glasses exhibit confined low and high frequency vibrational properties resulting from the significant bon and topological disorder occuring at the atomic scale. The precise nature of the low frequency modes and how they are influenced by local atomic structure remains unclear. Using standard harmonic analysis, the current work investigates various aspects of the problem by diagonalizing the Hessian of atomistic samples derived from molecular dynamics simulations via a model binary Lennard Jones pair potential.

Hydrogen-enhanced dislocation velocities in Ni3Al single crystals

2000 ◽  
Vol 15 (1) ◽  
pp. 7-9 ◽  
Author(s):  
C. B. Jiang ◽  
S. Patu ◽  
Q. Z. Lei ◽  
C. X. Shi
Keyword(s):  
Activation Energy ◽  
Shear Stress ◽  
Single Crystals ◽  
Room Temperature ◽  
Dislocation Motion ◽  
Dislocation Velocity ◽  
Dislocation Mobility ◽  
Preliminary Results ◽  
Etch Pit

The average dislocation velocity in hydrogenated Ni3Al single crystals was directly measured as a function of resolved shear stress (RSS) at room temperature (293 K) by the etch-pit technique. It was found that the dislocation velocity with hydrogen is about 5–25 times faster than that without hydrogen for the same RSS, and hydrogen decreases activation energy for dislocation motion in Ni3Al single crystals. The reason hydrogen can enhance dislocation velocity in this compound is briefly discussed. These preliminary results quantitatively provide the first evidence of hydrogen-enhancing dislocation mobility in Ni3Al material.

Molecular Dynamics Investigation of Two-Dimensional Atomic-Scale Friction

1994 ◽  
Vol 116 (2) ◽  
pp. 225-231 ◽  
Author(s):  
D. E. Kim ◽  
N. P. Suh
Keyword(s):  
Molecular Dynamics ◽  
Frictional Force ◽  
Md Simulation ◽  
Atomic Scale ◽  
Two Dimensional ◽  
Simulation Studies ◽  
Adhesive Interaction ◽  
Lennard Jones ◽  
Type Crystal ◽  
Insight Into

Molecular dynamics (MD) simulation studies of two-dimensional atomic-scale frictional force are presented. The motivation for this work is to gain insight into the effects of interatomic forces on the frictional phenomena. Instantaneous friction coefficients are calculated for an atom scanning across the surface of a two-dimensional Lennard-Jones type crystal in both static and dynamic modes. It is found that net frictional force can arise even in the absence of adhesive interaction between the scanning atom and the substrate. Furthermore, in the case of nondestructive sliding the frictional interaction leads to increase in the substrate temperature which can be calculated.

scholarly journals Effect of Impurities on a Two-Dimensional Dodecagonal Quasicrystal

2021 ◽  
Author(s):  
Masahiro Fuwa ◽  
Masahide Sato
Keyword(s):  
Interaction Potential ◽  
Rotational Symmetry ◽  
Lennard Jones Potential ◽  
Two Dimensional ◽  
Jones Potential ◽  
Lennard Jones ◽  
Impurity Density ◽  
Effect Of Impurities ◽  
Potential Matrix ◽  
Dynamics Simulations

Abstract Langevin dynamics simulations are performed to examine how impurities affect two-dimensional dodecagonal quasicrystals. We assumed that the interaction potential between two particles is the Lennard-Jones-Gauss potential if at least one of these particles is a matrix particle and that the interaction potential between two impurities is the Lennard-Jones potential. Matrix particles and impurities impinge with constant rates on the substrate created by a part of a dodecagonal quasicrystal consisting of square and triangular tiles. The dependences of the twelve-fold rotational order and the number of shield-like tiles on the impurity density are examined after sufficient solid layers are grown. While the change in the twelve-fold rotational symmetry is small, the number of shield-like tiles in the solid increases greatly with increasing impurity density.

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