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Séminaire de la Fédération

le 17 octobre 2013

Intervention de Sisina Mesarovic ( Washington State University)



Size-dependent plasticity of crystals and interfaces

Sinisa Dj. Mesarovic
School of Mechanical and Materials Engineering, Washington State University, Pullman, WA, USA

Plasticity in heterogeneous materials with small domains (e.g., polycrystals) is governed by the interactions of dislocations at interfaces. These include reactions of existing dislocations, as well as the nucleation of dislocations at an interface. The rational for interface dominated plasticity is simple: dislocations glide through the single crystal domain with relative ease, but pile up at interfaces, so that interface reactions become a critical step in continuing plastic deformation. While the details of dislocation reactions at interfaces take place at the atomic scale, the behavior of dislocations in bulk is best modeled by discrete dislocation dynamics. Both of these models are much too expensive and impractical for analyzing the resulting bulk behavior. The need for a continuum framework for describing the plasticity across crystal interfaces, including the ubiquitous size effects, is acute.
Recently developed size-dependent crystal plasticity theory [1, 2] employs the representation of the singular part of dislocation pile-up boundary layers as superdislocation boundary layers, or equivalently, as jumps in slip at the boundary, but internal to the crystal. These boundary superdislocations exist on two sides of an interface and react or combine to lower the total energy under certain conditions. In this presentation, we first develop the continuum framework for relaxation of dislocations at interfaces, including kinematic description of dislocation reactions across an interface, geometrical and thermodynamic conditions for reactions, energy dissipation in interface reactions, as well as the kinetic barriers thresholds for the reactions. We analyze the problem of single and double-slip shear of a thin film, and compare the results of continuum model with dislocation dynamics simulations [3].

[1] Mesarovic, S.Dj., Baskaran, R. & Panchenko, A. 2010 Thermodynamic coarse-graining of dislocation mechanics and the size-dependent continuum crystal plasticity. J. Mech. Phys. Solids 58 (3), 311-329.
[2] Mesarovic, S.Dj. 2010 Plasticity of crystals and interfaces: From discrete dislocations to size-dependent continuum theory. Theor. Appl. Mechanics 37(4), 289-332.
[3] Mesarovic, S. Dj., Baskaran, R. 2011 Interfaces in Size-Dependent Crystal Plasticity, Proc. 3rd Int. Conf. on Heterogeneous Material Mechanics (ICHMM-2011) May 22-26, 2011, Shanghai (ChongMing Island), China

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Type :
Séminaires - conférences
Lieu(x) :
Campus de Cachan
Amphi L108
École des Mines de Paris 
60, Boulevard Saint-Michel, Paris 6ème
Métro : Luxembourg

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