Recent Progress in Discrete Dislocation Dynamics and Its Applications to Micro Plasticity

Po, Giacomo; Mohamed, Manal G.; Crosby, Tamer; Erel, Can; El–Azab, Anter; Ghoniem, Nasr M.

doi:10.1007/s11837-014-1153-2

Cited by 109 publications

(81 citation statements)

References 105 publications

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“…Besides the experimental observations, computer simulations have greatly contributed to the investigation of the response of materials during nanoindentation. The common modeling methods are finite element [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41], crystal plasticity [42][43][44][45][46][47][48][49][50], discrete dislocation dynamics [51][52][53][54][55][56][57][58][59][60][61][62], the quasicontinuum method [63][64][65][66][67][68][69][70][71][72][73]…”

Section: Introductionmentioning

confidence: 99%

Review of Nanoindentation Size Effect: Experiments and Atomistic Simulation

2017

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Nanoindentation is a well-stablished experiment to study the mechanical properties of materials at the small length scales of micro and nano. Unlike the conventional indentation experiments, the nanoindentation response of the material depends on the corresponding length scales, such as indentation depth, which is commonly termed the size effect. In the current work, first, the conventional experimental observations and theoretical models of the size effect during nanoindentation are reviewed in the case of crystalline metals, which are the focus of the current work. Next, the recent advancements in the visualization of the dislocation structure during the nanoindentation experiment is discussed, and the observed underlying mechanisms of the size effect are addressed. Finally, the recent computer simulations using molecular dynamics are reviewed as a powerful tool to investigate the nanoindentation experiment and its governing mechanisms of the size effect.

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Section: Introductionmentioning

confidence: 99%

Review of Nanoindentation Size Effect: Experiments and Atomistic Simulation

2017

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“…The 'parametric' DD approach is ideal for 3D modeling of multi-defect dynamics to achieve efficient modeling of curved dislocations of arbitrary shape, orientation and length. Although DD remains a 'stateof-the-art' method due to the nature of its ongoing development [Po et al, 2014b], there is a long history of development since the 1990's [Amodeo and Ghoniem, 1990a;Canova et al, 1993;Van der Giessen and Needleman, 1995;Zbib et al, 2000;Zbib, 2009;Po and Ghoniem, 2014;Po et al, 2014a,b;Beneš et al, 2009]. At its core, the procedure of evaluating the Peach-Koehler force interactions, discretizing the motion, network configuration and shape is well-established [Po et al, 2014b;Zbib, 2012].…”

Section: Framework Of Conventional Mesoscale Dd Simulationsmentioning

confidence: 99%

“…In this implementation, DD simulations are coded with object-oriented C++ programming to model the discretized motion of dislocation loops and FR sources [Po et al, 2014b]. In its most fundamental form, DD is a meshless-continuum method with 'infinite' dimensions; however, a mesh can be utilized for the implementation of fixed surface boundary conditions.…”

Section: Framework Of Conventional Mesoscale Dd Simulationsmentioning

confidence: 99%

“…Modeling the mesoscale microstructure-property relationship observed in real materials would be very useful to guide future developments in the field of GB engineering. Dislocation dynamics (DD) simulations are widely acknowledged as a breakthrough mesoscale technique, with the capacity to establish a phenomenological link between fundamental atomistic studies and macroscale continuum models useful for real-world material design [Mcdowell, 2001[Mcdowell, , 2010Zbib and Diaz de La Rubia, 2002;Po et al, 2014b].…”

Section: Introductionmentioning

confidence: 99%

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Dislocation dynamics in polycrystals with atomistic-informed mechanisms of dislocation - grain boundary interactions

Burbery

Das

et al. 2017

J. Micromech. Mol. Phys.

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In polycrystalline materials, dislocations can interact with grain boundaries (GBS) through a number of mechanisms including dislocation absorption, pile-up formation, dissociation reactions within the GB plane and (possibly) dislocation nucleation from the interface itself. The effects of dislocation pile-ups contribute significantly to the mechanical behavior of polycrystalline materials by creating back-stresses that inactivate the primary slip systems in the vicinity of the interface, corresponding with the celebrated Hall-Petch relationship between size and strength. However, dislocation pile-ups cannot be contained within the small grain sizes that can be accommodated by molecular dynamics simulations, which to-date remain the primary computational method used to study the discrete structure of GBs.Dislocation dynamics (DD) simulations are a promising framework for computational modeling that are used to provide insights about phenomena that can only be explained from the intermediate scale between atomistic and macro scales. However, a robust framework for modeling dislocation interactions with internal microstructure such as grain boundaries (GBs) has yet to be achieved for 3D models of DD. Furthermore, this is the first implementation which explicitly includes the dislocation content of the interface. The framework described in this paper is effective for studying GBdislocation interactions (including inter-granular effects) and the approach for partitioning the DD simulation domain. To achieve a robust method to differentiate between crystal regions, the present framework utilizes a mesh-based partitioning system. Within each grain, slip systems are determined by the grain orientation. The versatile construction described, allows modeling of an arbitrary crystallography, size and grain geometry. Extrinsic dislocations that intersect the interface are constrained to glide on the line of intersection between the glide plane and GB plane. Atomistically informed criteria for § Corresponding author. N. B. Burbery et al.slip transmission are implemented, based on the geometrically optimal outgoing glide plane which shares a common line of intersection on the GB plane. Slip transmission is only initiated when the resolved shear stress in one of the compatible outgoing slip directions exceeds an approximate threshold resolved shear stress, which is based on observations made with molecular dynamics studies. The primary aim of the present study was to establish a sufficiently 'generic' framework to enable the modelling of various GB structures, polycrystal geometries and crystallographic orientations. The framework described in the present work provides a means to study multi-grain deformation processes governed by dislocations pile-ups at GBs, in detail beyond feasible limits of experiments or atomistic simulation approaches.

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“…Dislocation climb is inhibited, while cross-slip is modeled as a thermally activated process with an activation enthalpy dependent on the Escaig stress [26]. Boundary conditions for the simulation domain are imposed by utilizing the superposition principle of the elastic field of dislocations in an infinite medium with an elastic boundary value solver implemented through the finite element method (FEM), as described in [27]. A compressive load is applied, imposing a prescribed rate of vertical displacement on the top surface of the pillar corresponding to a strain rate of 10 4 -10 5 s À1 .…”

Section: Discrete Dislocation Dynamics Simulationsmentioning

confidence: 99%

The origin of strain avalanches in sub-micron plasticity of fcc metals

Crosby

Erel

et al. 2015

Acta Materialia

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Numerous experimental observations have recently demonstrated two aspects of sub-micron plasticity in nano pillars: (1) the statistical nature of the yield strength, and (2) the existence of dynamic temporal oscillations in the hardening regime. The present work is focused on the second aspect, where we study strain avalanches in nickel nano pillars via a series of 3-D dislocation dynamics (DD) simulations. The computer simulations reveal the existence of a key mechanism that explains the origin of oscillations in post-yield plastic flow in fcc metals. Small dipolar-loops easily form through several cross-slip mechanisms, and then act as internal glide dislocation sources. When dislocations exit pillar boundaries, they leave many dipolar-loops behind. At this stage, the pillar is starved from dislocations and an increase in stress is necessary to keep up with the applied strain rate (hardening stage). At some critical stress level, dipolar-loops become effective Frank-Read sources of new glide dislocations that collectively move in a burst mode, producing strain avalanches (softening stage). The time delay between these two states, which is determined by the average dislocation velocity and pillar diameter, leads to plastic strain oscillations and intermittent dislocation avalanches, consistent with experimental observations.

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Recent Progress in Discrete Dislocation Dynamics and Its Applications to Micro Plasticity

Cited by 109 publications

References 105 publications

Review of Nanoindentation Size Effect: Experiments and Atomistic Simulation

Review of Nanoindentation Size Effect: Experiments and Atomistic Simulation

Dislocation dynamics in polycrystals with atomistic-informed mechanisms of dislocation - grain boundary interactions

The origin of strain avalanches in sub-micron plasticity of fcc metals

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