Avalanches in 2D Dislocation Systems: Plastic Yielding Is Not Depinning

Ispánovity, Péter Dusán; Laurson, Lasse; Zaiser, Michael; Groma, István; Zapperi, Stefano; Alava, Mikko J.

doi:10.1103/physrevlett.112.235501

Cited by 136 publications

(206 citation statements)

References 41 publications

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“…For slow deformation, we find that the avalanche distribution decays as a power law, PðsÞ ∼ s −τ , with an exponent close to τ = 2. This value is different from the one measured in flat geometry through 2D dislocation dynamics (33) and colloidal crystal simulations (34), which yield τ ' 1. This finding suggests that the shell curvature introduces peculiar properties to the dynamics of plastic avalanches.…”

Section: Resultsmentioning

confidence: 67%

Deformation and failure of curved colloidal crystal shells

Negri

Sellerio

Zapperi

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Designing and controlling particle self-assembly into robust and reliable high-performance smart materials often involves crystalline ordering in curved spaces. Examples include carbon allotropes like graphene, synthetic materials such as colloidosomes, or biological systems like lipid membranes, solid domains on vesicles, or viral capsids. Despite the relevance of these structures, the irreversible deformation and failure of curved crystals is still mostly unexplored. Here, we report simulation results of the mechanical deformation of colloidal crystalline shells that illustrate the subtle role played by geometrically necessary topological defects in controlling plastic yielding and failure. We observe plastic deformation attributable to the migration and reorientation of grain boundary scars, a collective process assisted by the intermittent proliferation of disclination pairs or abrupt structural failure induced by crack nucleating at defects. Our results provide general guiding principles to optimize the structural and mechanical stability of curved colloidal crystals.T he morphology of crystals becomes peculiar when selfassembled on curved shells. For example, the Gaussian curvature of a sphere demands the presence of geometrically necessary rotational defects (disclinations) such as the 12 pentagons in a soccer ball. Disclinations can be found in thin shell structures at different length scales: from the world of carbon allotropes (1) [as in fullerenes, nanotubes, and graphene (2)] to biological systems [such as in lipid membranes (3), solid domains on vesicles (4, 5), or in viral capsids (6-8)], and in synthetic structures such as colloidosomes, colloidal particle shells lying at the interface between two fluids (9-12). Thin-shell structures are often conceived for encapsulation purposes at various scales (i.e., as delivery vehicles of different kinds of cargo, from drugs to flavors and cosmetics) and arise naturally in biological systems. Examples include crystalline and glassy colloidosomes, capsules of Janus and patchy particles, nematic vesicles, and viral capsids.Theoretical considerations indicate that arranging a colloidal crystal into a curved geometry involves elastic deformation and the presence of geometrically necessary disclinations showed by simulations to be attached to extended grain boundary scars (13-15), as also confirmed in several experiments (5,9,16,17). Thus, grain boundary scars are different from standard grain boundaries in that they have a nonzero disclination charge, which makes them more costly. Such a complex topological structure is bound to interfere with the mechanical response of the shell in a way that is still unclear. Understanding this point, however, is of utmost importance to control the deformation of many functionalized self-assembled materials (9,18,19). Numerical and theoretical approaches to date are typically based on solving the elasticity field between grain-boundary scars and deriving equilibrium particle configurations from the effective free energy of the...

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Section: Resultsmentioning

confidence: 67%

Deformation and failure of curved colloidal crystal shells

Negri

Sellerio

Zapperi

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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“…Such a definition leads to an avalanche size distribution which is, in the regime of large avalanches, completely equivalent to that of the TCDDD model [28]. However, in the regime of small avalanches problems arise since the CADDD dynamics by its structure does not allow us to impose a strain rate threshold that would allow us to separate quasireversible dislocation motions in between avalanches from the strongly irreversible motions occurring, subsequent to some local stress threshold being crossed, during the avalanches themselves.…”

Section: Cellular Automaton Representation (Caddd)mentioning

confidence: 99%

“…As the underlying lower-scale model we use conventional 2D discrete dislocation dynamics (DDD) models that have been studied extensively in the literature [23][24][25][26][27]. We consider load-controlled quasistatic plastic deformation where individual avalanches can be readily identified [28]. We focus on early stages of deformation (the microplastic regime before system-scale yielding occurs).…”

Section: Introductionmentioning

confidence: 99%

Role of weakest links and system-size scaling in multiscale modeling of stochastic plasticity

et al. 2017

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Plastic deformation of crystalline and amorphous matter often involves intermittent local strain burst events. To understand the physical background of the phenomenon a minimal stochastic mesoscopic model was introduced, where details of the microstructure evolution are statistically represented in terms of a fluctuating local yield threshold. In the present paper we propose a method for determining the corresponding yield stress distribution for the case of crystal plasticity from lower scale discrete dislocation dynamics simulations which we combine with weakest link arguments. The success of scale linking is demonstrated by comparing stress-strain curves obtained from the resulting mesoscopic and the underlying discrete dislocation models in the microplastic regime. As shown by various scaling relations they are statistically equivalent and behave identically in the thermodynamic limit. The proposed technique is expected to be applicable to different microstructures and also to amorphous materials.

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“…By contrast with the depinning transition, our arguments predict that crackling occurs within the hysteresis loop, with avalanches of mean size M a ∼ N δσ min ∼ N θ/(1+θ) . Numerical observations of such crackling in models of plasticity in solids below the yield stress were reported very recently [100].…”

Section: Depinning Of An Elastic Interfacementioning

confidence: 99%

Marginal Stability in Structural, Spin, and Electron Glasses

Müller

Wyart

2015

Annu. Rev. Condens. Matter Phys.

183

264

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We revisit the concept of marginal stability in glasses, and determine its range of applicability in the context of avalanche-type response to slow external driving. We argue that there is an intimate connection between a pseudo-gap in the distribution of local fields and crackling in systems with long-range interactions. We show how the principle of marginal stability offers a unifying perspective on the phenomenology of systems as diverse as spin and electron glasses, hard spheres, pinned elastic interfaces and the plasticity of soft amorphous solids.

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Avalanches in 2D Dislocation Systems: Plastic Yielding Is Not Depinning

Cited by 136 publications

References 41 publications

Deformation and failure of curved colloidal crystal shells

Deformation and failure of curved colloidal crystal shells

Role of weakest links and system-size scaling in multiscale modeling of stochastic plasticity

Marginal Stability in Structural, Spin, and Electron Glasses

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