Continuum simulation of the evolution of dislocation densities during nanoindentation

Engels, P.; Ma, Anxin; Hartmaier, Alexander

doi:10.1016/j.ijplas.2012.05.010

Cited by 62 publications

(23 citation statements)

References 37 publications

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“…In stark contrast with these approaches which emphasize on individual atoms or dislocation segments, a number of researchers have advocated the use of a modeling strategy that focuses on dislocation density (Walgraef and Aifantis, 1985;Groma, 1997;Acharya, 2001;Arsenlis et al, 2004;Zhou and Sun, 2004;Evers et al, 2004;Yefimov and Van der Giessen, 2005;Pontes et al, 2006;Ma et al, 2006;Hochrainer et al, 2007;Lee et al, 2010;Watanabe et al, 2010;Alankar et al, 2011;Hirschberger et al, 2011;Bargmann et al, 2011;Liu et al, 2011;Shanthraj and Zikry, 2012;Engels et al, 2012;Aghababaei and Joshi, 2013;Li et al, 2014). Unlike DDD which becomes handicapped at high strains, such a strategy would be well suited for large-strain problems with high quantities of dislocations, since any amount of dislocations can still be represented a dislocation density.…”

Section: Introductionmentioning

confidence: 99%

A new dislocation-density-function dynamics scheme for computational crystal plasticity by explicit consideration of dislocation elastic interactions

Leung

Cheng

et al. 2015

International Journal of Plasticity

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a b s t r a c tCurrent strategies of computational crystal plasticity that focus on individual atoms or dislocations are impractical for real-scale, large-strain problems even with today's computing power. Dislocation-density based approaches are a way forward but a critical issue to address is a realistic description of the interactions between dislocations. In this paper, a new scheme for computational dynamics of dislocation-density functions is proposed, which takes full consideration of the mutual elastic interactions between dislocations based on the Hirth-Lothe formulation. Other features considered include (i) the continuity nature of the movements of dislocation densities, (ii) forest hardening, (iii) generation according to high spatial gradients in dislocation densities, and (iv) annihilation. Numerical implementation by the finite-volume method, which is well suited for flow problems with high gradients, is discussed. Numerical examples performed for a single-crystal aluminum model show typical strength anisotropy behavior comparable to experimental observations. Furthermore, a detailed case study on small-scale crystal plasticity successfully captures a number of key experimental features, including power-law relation between strength and size, low dislocation storage and jerky deformation.

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Section: Introductionmentioning

confidence: 99%

A new dislocation-density-function dynamics scheme for computational crystal plasticity by explicit consideration of dislocation elastic interactions

Leung

Cheng

et al. 2015

International Journal of Plasticity

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“…The Hertz lines of maximum shear stress in the compression of a flat surface by a cylindrical or spherical indenter show this clearly [14]. Zhong and Zhu [15] showed that nucleation, gliding and interaction of Shockley partial dislocations in fcc structures were involved in the early plastic stages of indentation, and recently detailed dislocation analysis was also carried out by Begau et al [16] and Engles et al [17].…”

Section: Introductionmentioning

confidence: 99%

Plastic deformation in nanoindentation of tantalum: A new mechanism for prismatic loop formation

et al. 2014

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The mechanisms of deformation under a nanoindentation in tantalum, chosen as a model body-centered cubic (bcc) metal, are identified and quantified. Molecular dynamics (MD) simulations and indentation experiments are conducted for [1 0 0], [1 1 0] and [1 1 1] normals to surface orientations. The simulated plastic deformation proceeds by the formation of nanotwins, which rapidly evolve into shear dislocation loops. It is shown through a dislocation analysis that an elementary twin (three layers) is energetically favorable for a diameter below $7 nm, at which point a shear loop comprising a perfect dislocation is formed. MD simulations show that shear loops expand into the material by the advancement of their edge components. Simultaneously with this advancement, screw components of the loop cross-slip and generate a cylindrical surface. When opposite segments approach, they eventually cancel by virtue of the attraction between them, forming a quasi-circular prismatic loop composed of edge dislocation segments. This "lasso"-like mechanism by which a shear loop transitions to a prismatic loop is identified for both [0 0 1] and [1 1 1] indentations. The prismatic loops advance into the material along h1 1 1i directions, transporting material away from the nucleation site. Analytical calculations supplement MD and experimental observations, and provide a framework for the improved understanding of the evolution of plastic deformation under a nanoindenter. Dislocation densities under the indenter are estimated experimentally ($1.2 Â 10 15 m À2 ), by MD ($7 Â 10 15 m À2 ) and through an analytical calculation (2.6-19 Â 10 15 m À2 ). Considering the assumptions and simplifications, this agreement is considered satisfactory. MD simulations also show expected changes in pile-up symmetry after unloading, compatible with crystal plasticity.

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“…Apart from transmission electron microscopy, one of the most successful recent methods delivering direct evidence for dislocation activity in the metals is nanoindentation [18][19][20][21][22][23][24][25][26][27]. During the nanoindentation of perfectly prepared samples with a very low dislocation density, it is possible to observe a homogeneous dislocation nucleation (HDN) below the surface in the volume.…”

Section: Introductionmentioning

confidence: 99%

Correlation between the hydrogen chemical potential and pop-in load during in situ electrochemical nanoindentation

Barnoush¹,

Kheradmand²,

Hajilou³

2015

Scripta Materialia

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Continuum simulation of the evolution of dislocation densities during nanoindentation

Cited by 62 publications

References 37 publications

A new dislocation-density-function dynamics scheme for computational crystal plasticity by explicit consideration of dislocation elastic interactions

A new dislocation-density-function dynamics scheme for computational crystal plasticity by explicit consideration of dislocation elastic interactions

Plastic deformation in nanoindentation of tantalum: A new mechanism for prismatic loop formation

Correlation between the hydrogen chemical potential and pop-in load during in situ electrochemical nanoindentation

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