Grain Size Strengthening in Microcrystalline Copper: A Three-Dimensional Dislocation Dynamics Simulation

2009 ◽  
Vol 423 ◽  
pp. 25-32 ◽  
Author(s):  
Christophe de Sansal ◽  
Benoit Devincre ◽  
Ladislas P. Kubin
Keyword(s):  
Plastic Deformation ◽  
Mechanical Response ◽  
Initial Density ◽  
Three Dimensional ◽  
Dislocation Dynamics ◽  
Dynamics Simulation ◽  
Key Factors ◽  
Slip Mechanism ◽  
Dynamics Simulations ◽  
Dislocation Sources

This article reports on a study of the microstructure and mechanical response of copper polycrystals with grain sizes in the micrometer range. Three-dimensional dislocation dynamics simulations are used for the first time to investigate grain boundary strengthening and the Hall-Petch law. The methodology, which involves constructing a microcrystalline representative volume element with periodic boundary conditions, is briefly presented. Simulation results show that the initial density of dislocation sources and the cross-slip mechanism are two key factors controlling the heterogeneity of plastic deformation within the grains. At yield, the smaller the grains size, the more plastic deformation is heterogeneously distributed between grains and homogeneously distributed inside the grains. A size effect is reproduced and it is shown that the Hall-Petch exponent decreases from the very beginning of plastic flow and may reach a stable value at strains larger than the conventional proof stress.

A study of the submicron indent-induced plastic deformation

1999 ◽  
Vol 14 (6) ◽  
pp. 2251-2258 ◽  
Author(s):  
C. F. Robertson ◽  
M. C. Fivel
Keyword(s):  
Plastic Deformation ◽  
Three Dimensional ◽  
Dislocation Nucleation ◽  
Dislocation Dynamics ◽  
Dynamics Simulation ◽  
Nanoindentation Test ◽  
Experimental Conditions ◽  
Discrete Dislocation Dynamics ◽  
Discrete Dislocation ◽  
Transmission Electron

A new method has been developed to achieve a better understanding of submicron indent-induced plastic deformation. This method combines numerical modeling and various experimental data and techniques. Three-dimensional discrete dislocation dynamics simulation and the finite element method (FEM) were used to model the experimental conditions associated with nanoindentation testing in fcc crystals. Transmission electron microscopy (TEM) observations of the indent-induced plastic volume and analysis of the experimental loading curve help in defining a complete set of dislocation nucleation rules, including the shape of the nucleated loops and the corresponding macroscopic loading. A validation of the model is performed through direct comparisons between a simulation and experiments for a nanoindentation test on a [001] copper single crystal up to 50 nm deep.

scholarly journals Probing the transition from dislocation jamming to pinning by machine learning

2020 ◽  
Vol 4 (1) ◽  
Author(s):  
Henri Salmenjoki ◽  
Lasse Laurson ◽  
Mikko J. Alava
Keyword(s):  
Machine Learning ◽  
Mechanical Response ◽  
Collective Motion ◽  
Three Dimensional ◽  
Dislocation Dynamics ◽  
Form Complex ◽  
Discrete Dislocation Dynamics ◽  
Discrete Dislocation ◽  
Two Phases ◽  
Dynamics Simulations

Abstract Collective motion of dislocations is governed by the obstacles they encounter. In pure crystals, dislocations form complex structures as they become jammed by their anisotropic shear stress fields. On the other hand, introducing disorder to the crystal causes dislocations to pin to these impeding elements and, thus, leads to a competition between dislocation-dislocation and dislocation-disorder interactions. Previous studies have shown that, depending on the dominating interaction, the mechanical response and the way the crystal yields change.Here we employ three-dimensional discrete dislocation dynamics simulations with varying density of fully coherent precipitates to study this phase transition − from jamming to pinning − using unsupervised machine learning. By constructing descriptors characterizing the evolving dislocation configurations during constant loading, a confusion algorithm is shown to be able to distinguish the systems into two separate phases. These phases agree well with the observed changes in the relaxation rate during the loading. Our results also give insights on the structure of the dislocation networks in the two phases.

Construction of plastic contact deformation maps on ceramics: a case study on aluminum nitride

1996 ◽  
Vol 54 ◽  
pp. 636-637
Author(s):  
D. L. Callahan
Keyword(s):  
Plastic Deformation ◽  
Aluminum Nitride ◽  
Mechanical Response ◽  
Three Dimensional ◽  
Bright Field Image ◽  
Perfectly Plastic ◽  
Contrast Analysis ◽  
Deformation Patterns

Modern polishing, precision machining and microindentation techniques allow the processing and mechanical characterization of ceramics at nanometric scales and within entirely plastic deformation regimes. The mechanical response of most ceramics to such highly constrained contact is not predictable from macroscopic properties and the microstructural deformation patterns have proven difficult to characterize by the application of any individual technique. In this study, TEM techniques of contrast analysis and CBED are combined with stereographic analysis to construct a three-dimensional microstructure deformation map of the surface of a perfectly plastic microindentation on macroscopically brittle aluminum nitride.The bright field image in Figure 1 shows a lg Vickers microindentation contained within a single AlN grain far from any boundaries. High densities of dislocations are evident, particularly near facet edges but are not individually resolvable. The prominent bend contours also indicate the severity of plastic deformation. Figure 2 is a selected area diffraction pattern covering the entire indentation area.

Molecular Dynamics Simulations of High Energy Cascades in Iron

1994 ◽  
Vol 373 ◽  
Author(s):  
Roger E. Stoller
Keyword(s):  
Molecular Dynamics ◽  
Three Dimensional ◽  
High Energy ◽  
Dynamics Simulation ◽  
Method Of Molecular Dynamics ◽  
Energy Cascades ◽  
Iron Based ◽  
The Many ◽  
Property Changes ◽  
Dynamics Simulations

AbstractA series of high-energy, up to 20 keV, displacement cascades in iron have been investigated for times up to 200 ps at 100 K using the method of molecular dynamics simulation. Thesimulations were carried out using the MOLDY code and a modified version of the many-bodyinteratomic potential developed by Finnis and Sinclair. The paper focuses on those results obtained at the highest energies, 10 and 20 keV. The results indicate that the fraction of the Frenkel pairs surviving in-cascade recombination remains fairly high in iron and that the fraction of the surviving point defects that cluster is lower than in materials such as copper. In particular, vacancy clustering appears to be inhibited in iron. Some of the interstitial clusters were observed to exhibit an unexpectedly complex, three-dimensional morphology. The observations are discussed in terms of their relevance to microstructural evolution and mechanical property changes in irradiated iron-based alloys.

Influence of Initial Defects on the Mechanical Properties of Single Crystal Copper: Discrete Dislocation Dynamics Study

2018 ◽  
Vol 913 ◽  
pp. 627-635
Author(s):  
Ming Yi Zhang ◽  
Min Zhong ◽  
Shuai Yuan ◽  
Jing Song Bai ◽  
Ping Li
Keyword(s):  
Dislocation Density ◽  
Single Crystal ◽  
Mechanical Response ◽  
Three Dimensional ◽  
Dislocation Dynamics ◽  
Single Crystal Copper ◽  
Discrete Dislocation Dynamics ◽  
Discrete Dislocation ◽  
Stress Curve ◽  
Initial Dislocation Density

In this paper, three dimensional discrete dislocation dynamics method was used to quantitatively investigate the influence of initial defects on mechanical response of single crystal copper. Both the irradiation defects (interstitial loops) and random dislocation lines with different densities are considered. The simulation results demonstrate that the yield strength of single crystal copper is higher with higher initial dislocation density and higher interstitial loop density. Dislocation density increases quickly by nucleation and multiplication and microbands are formed during plastic deformation when only the random dislocation lines are initially considered. Characteristics of microbands show excellent agreement with experiment results. Dislocation multiplication is suppressed in the presence of interstitial loops, and junctions and locks between dislocations and interstitial loops are formed. Dislocation density evolution shows fluctuation accompanied with strain-stress curve fluctuation.

Plastic Deformation of Textured Zircaloy 2

2011 ◽  
Vol 702-703 ◽  
pp. 838-841
Author(s):  
Santosh Kumar Sahoo ◽  
V. D. Hiwarkar ◽  
Prita Pant ◽  
Indradev Samajdar ◽  
Karri V. Mani Krishna ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Residual Stresses ◽  
Room Temperature ◽  
Deformation Behaviour ◽  
Dislocation Dynamics ◽  
Dynamics Simulation ◽  
Distinct Class ◽  
Dislocation Interactions ◽  
Temperature Deformations ◽  
Grain Misorientation

The present study deals with deformation behaviour of textured Zircaloy 2 with two dominant orientations: basal and non-basal. During initial stages (20%), two distinct class of grains were observed – non-deforming/non-fragmenting grains and deforming/fragmenting grains. The so-called non- deforming/non-fragmenting grains remain equiaxed even after 50% of deformation. They also have insignificant in-grain misorientation developments and have more residual stresses. Dislocation dynamics simulation showed that the dislocation interactions/mobility is insignificant in basal orientations at room temperature deformations.

Multiscale modeling of plasticity in a copper single crystal deformed at high strain rates

2015 ◽  
Vol 1 (1) ◽  
Author(s):  
Sagar Chandra ◽  
M. K. Samal ◽  
V. M. Chavan ◽  
R. J. Patel
Keyword(s):  
Single Crystal ◽  
Multiscale Modeling ◽  
Crystal Plasticity ◽  
Mechanical Response ◽  
Md Simulations ◽  
Dislocation Dynamics ◽  
Copper Single Crystal ◽  
Deformation Response ◽  
Discrete Dislocation ◽  
Dynamics Simulations

AbstractA hierarchical multiscale modeling approach is presented to predict the mechanical response of dynamically deformed (1100 s−1−4500 s−1) copper single crystal in two different crystallographic orientations.Anattempt has been made to bridge the gap between nano-, micro- and meso- scales. In view of this, Molecular Dynamics (MD) simulations at nanoscale are performed to quantify the drag coefficient for dislocations which has been exploited in Dislocation Dynamics (DD) regime at the microscale. Discrete dislocation dynamics simulations are then performed to calculate the hardening parameters required by the physics based Crystal Plasticity (CP) model at the mesoscale. The crystal plasticity model employed is based on thermally activated theory for plastic flow. Crystal plasticity simulations are performed to quantify the mechanical response of the copper single crystal in terms of stressstrain curves and shape changes under dynamic loading. The deformation response obtained from CP simulations is in good agreement with the experimental data.

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