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.

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.

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.

scholarly journals Gradient Crystal Plasticity: A Grain Boundary Model for Slip Transmission

Materials ◽  
2019 ◽  
Vol 12 (22) ◽  
pp. 3761
Author(s):  
Xiang-Long Peng ◽  
Gan-Yun Huang ◽  
Swantje Bargmann
Keyword(s):  
Dislocation Dynamics ◽  
Fine Grained ◽  
Discrete Dislocation ◽  
Geometric Factors ◽  
Polycrystal Plasticity ◽  
Boundary Model ◽  
Dynamics Simulations ◽  
Grain Misorientation ◽  
Gb Model ◽  
Slip Transmission

Interaction between dislocations and grain boundaries (GBs) in the forms of dislocation absorption, emission, and slip transmission at GBs significantly affects size-dependent plasticity in fine-grained polycrystals. Thus, it is vital to consider those GB mechanisms in continuum plasticity theories. In the present paper, a new GB model is proposed by considering slip transmission at GBs within the framework of gradient polycrystal plasticity. The GB model consists of the GB kinematic relations and governing equations for slip transmission, by which the influence of geometric factors including the misorientation between the incoming and outgoing slip systems and GB orientation, GB defects, and stress state at GBs are captured. The model is numerically implemented to study a benchmark problem of a bicrystal thin film under plane constrained shear. It is found that GB parameters, grain size, grain misorientation, and GB orientation significantly affect slip transmission and plastic behaviors in fine-grained polycrystals. Model prediction qualitatively agrees with experimental observations and results of discrete dislocation dynamics simulations.

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