scholarly journals Single Crystal Deformation Experiments for Validation of Dislocation Dynamics Simulations

2003 ◽  
Vol 779 ◽  
Author(s):  
David H. Lassila ◽  
Mary M. LeBlanc ◽  
Moono Rhee
Keyword(s):  
Slip System ◽  
High Purity ◽  
Axial Stress ◽  
Dislocation Dynamics ◽  
Strain Response ◽  
Hardening Behavior ◽  
Uniform State ◽  
Validation Criteria ◽  
Experimental Apparatus ◽  
Dynamics Simulations

AbstractA new experimental apparatus has been developed for performing compression deformation experiments on high-purity Mo single crystals. These experiments provide data that can validate 3-D dislocation dynamics (DD) simulations. The experiments are performed under conditions that allow unconstrained deformation; thus, a relatively uniform state of axial stress is maintained during deformation. In the following sections, we describe the new experimental apparatus and our results from experiments performed at ambient temperature at a strain rate of s–1. Validation criteria based on the Mo experiments may include comparing the stress-strain response using 3-D strain information, the predicted slip-system yield, and work-hardening behavior.

Uniaxial Stress Deformation Experiment for Validation of 3-D Dislocation Dynamics Simulations

2002 ◽  
Vol 124 (3) ◽  
pp. 290-296 ◽  
Author(s):  
David H. Lassila ◽  
Mary M. LeBlanc ◽  
Gregory J. Kay
Keyword(s):  
Experimental Data ◽  
Single Crystal ◽  
Single Crystals ◽  
High Purity ◽  
Axial Stress ◽  
Uniaxial Stress ◽  
Dislocation Dynamics ◽  
Uniform State ◽  
Dynamics Simulations ◽  
Unconstrained Motion

An apparatus has been developed for performing compression deformation experiments on oriented metallic single crystals to provide data for validation of 3-D dislocation dynamics simulations. The experiment is performed under conditions that allow unconstrained motion of the upper and lower compression platen, and thus a relatively uniform state of axial stress is maintained during the deformation. Experiments have been performed on high-purity Mo single crystal and polycrystalline Cu. Various aspects of the experimental procedures and results are presented. Possible usages of the experimental data for the validation of 3-D dislocation dynamics simulations are discussed.

Three-Dimensional Continuum Dislocation Dynamics Simulations of Dislocation Structure Evolution in Bending of a Micro-Beam

MRS Advances ◽  
2016 ◽  
Vol 1 (24) ◽  
pp. 1791-1796 ◽  
Author(s):  
Alireza Ebrahimi ◽  
Thomas Hochrainer
Keyword(s):  
Dislocation Density ◽  
Slip System ◽  
Evolution Equations ◽  
Three Dimensional ◽  
Dislocation Dynamics ◽  
Structure Evolution ◽  
Internal Variables ◽  
Plastic Shear ◽  
Continuum Dislocation Dynamics ◽  
Dynamics Simulations

ABSTRACTA persistent challenge in multi-scale modeling of materials is the prediction of plastic materials behavior based on the evolution of the dislocation state. An important step towards a dislocation based continuum description was recently achieved with the so called continuum dislocation dynamics (CDD). CDD captures the kinematics of moving curved dislocations in flux-type evolution equations for dislocation density variables, coupled to the stress field via average dislocation velocity-laws based on the Peach-Koehler force. The lowest order closure of CDD employs three internal variables per slip system, namely the total dislocation density, the classical dislocation density tensor and a so called curvature density.In the current work we present a three-dimensional implementation of the lowest order CDD theory as a materials sub-routine for Abaqus®in conjunction with the crystal plasticity framework DAMASK. We simulate bending of a micro-beam and qualitatively compare the plastic shear and the dislocation distribution on a given slip system to results from the literature. The CDD simulations reproduce a zone of reduced plastic shear close to the surfaces and dislocation pile-ups towards the center of the beam, which have been similarly observed in discrete dislocation simulations.

scholarly journals A Novel Mechanical Method to Measure Shear Strength in Specimens Under Pressure

2006 ◽  
Vol 929 ◽  
Author(s):  
Juan Pablo Escobedo ◽  
David Field ◽  
David Lassila ◽  
Mary Leblanc
Keyword(s):  
Shear Strength ◽  
Thin Foil ◽  
Testing Procedure ◽  
Dislocation Dynamics ◽  
Calibration Data ◽  
Discrete Dislocation Dynamics ◽  
Discrete Dislocation ◽  
Thin Foils ◽  
Experimental Apparatus ◽  
Dynamics Simulations

ABSTRACTA new experimental apparatus has been developed for performing shear tests on specimens held under moderately high hydrostatic pressures (on the order of 4 GPa). This testing procedure experimentally determines the pressure-dependent shear strength of thin foil specimens. The experiments provide calibration data for models of materials subjected to extreme pressures such as the Steinberg-Guinan hardening model and can assist in model validation for discrete dislocation dynamics simulations, among others. This paper reports the development of the experimental procedures and the results of initial experiments on thin foils of polycrystalline Ta performed under hydrostatic pressures ranging from 1 to 4 GPa. Both yielding and hardening behavior of Ta are observed to be sensitive to the imposed pressure.

scholarly journals Size Dependence of Dislocation-Mediated Plasticity in Ni Single Crystals: Molecular Dynamics Simulations

2009 ◽  
Vol 2009 ◽  
pp. 1-10 ◽  
Author(s):  
Xiaoyan Li ◽  
Wei Yang
Keyword(s):  
Slip System ◽  
Single Crystals ◽  
Temperature Effects ◽  
Size Dependence ◽  
Dislocation Dynamics ◽  
Deformation Mechanisms ◽  
Atomistic Simulations ◽  
Single Slip ◽  
System A ◽  
Dynamics Simulations

We investigate the compressive yielding of Ni single crystals by performing atomistic simulations with the sample diameters in the range of 5 nm ∼ 40 nm. Remarkable effects of sample sizes on the yield strength are observed in the nanopillars with two different orientations. The deformation mechanisms are characterized by massive dislocation activities within a single slip system and a nanoscale deformation twining in an octal slip system. A dislocation dynamics-based model is proposed to interpret the size and temperature effects in single slip-oriented nanopillars by considering the nucleation of incipient dislocations.

scholarly journals On the three-dimensional spatial correlations of curved dislocation systems

2021 ◽  
Vol 5 (1) ◽  
Author(s):  
Joseph Pierre Anderson ◽  
Anter El-Azab
Keyword(s):  
Correlation Function ◽  
Slip System ◽  
Correlation Functions ◽  
Mean Field ◽  
Coarse Graining ◽  
Dislocation Dynamics ◽  
Coarse Grained ◽  
Spatial Correlation Function ◽  
Line System ◽  
Dislocation Densities

AbstractCoarse-grained descriptions of dislocation motion in crystalline metals inherently represent a loss of information regarding dislocation-dislocation interactions. In the present work, we consider a coarse-graining framework capable of re-capturing these interactions by means of the dislocation-dislocation correlation functions. The framework depends on a convolution length to define slip-system-specific dislocation densities. Following a statistical definition of this coarse-graining process, we define a spatial correlation function which will allow the arrangement of the discrete line system at two points—and thus the strength of their interactions at short range—to be recaptured into a mean field description of dislocation dynamics. Through a statistical homogeneity argument, we present a method of evaluating this correlation function from discrete dislocation dynamics simulations. Finally, results of this evaluation are shown in the form of the correlation of dislocation densities on the same slip-system. These correlation functions are seen to depend weakly on plastic strain, and in turn, the dislocation density, but are seen to depend strongly on the convolution length. Implications of these correlation functions in regard to continuum dislocation dynamics as well as future directions of investigation are also discussed.

Plastic Ploughing of a Sinusoidal Asperity on a Rough Surface

2015 ◽  
Vol 82 (7) ◽  
Author(s):  
H. Song ◽  
R. J. Dikken ◽  
L. Nicola ◽  
E. Van der Giessen
Keyword(s):  
Friction Stress ◽  
Dislocation Dynamics ◽  
Two Dimensional ◽  
Unit Process ◽  
Contact Models ◽  
Self Similar ◽  
Dynamics Simulations ◽  
Micrometer Scale ◽  
Edge Dislocations ◽  
Flat Contact

Part of the friction between two rough surfaces is due to the interlocking between asperities on opposite surfaces. In order for the surfaces to slide relative to each other, these interlocking asperities have to deform plastically. Here, we study the unit process of plastic ploughing of a single micrometer-scale asperity by means of two-dimensional dislocation dynamics simulations. Plastic deformation is described through the generation, motion, and annihilation of edge dislocations inside the asperity as well as in the subsurface. We find that the force required to plough an asperity at different ploughing depths follows a Gaussian distribution. For self-similar asperities, the friction stress is found to increase with the inverse of size. Comparison of the friction stress is made with other two contact models to show that interlocking asperities that are larger than ∼2 μm are easier to shear off plastically than asperities with a flat contact.

Annealing of dislocation loops in dislocation dynamics simulations

2009 ◽  
Vol 3 ◽  
pp. 012001 ◽  
Author(s):  
Dan Mordehai ◽  
Emmanuel Clouet ◽  
Marc Fivel ◽  
Marc Verdier
Keyword(s):  
Dislocation Dynamics ◽  
Dislocation Loops ◽  
Dynamics Simulations
Sign in / Sign up

Export Citation Format

Share Document