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dislocation mechanics

sairajatm's picture

Finite Element Approximation of Finite Deformation Dislocation Mechanics

We develop and demonstrate the first general computational tool for finite deformation static and dynamic dislocation mechanics. A finite element formulation of finite deformation (Mesoscale) Field Dislocation Mechanics theory is presented. The model is a minimal enhancement of classical crystal/J_2 plasticity that fundamentally accounts for polar/excess dislocations at the mesoscale. It has the ability to compute the static and dynamic finite deformation stress fields of arbitrary (evolving) dislocation distributions in finite bodies of arbitrary shape and elastic anisotropy under general boundary conditions. This capability is used to present a comparison of the static stress fields, at finite and small deformations, for screw and edge dislocations, revealing heretofore unexpected differences. The computational framework is verified against the sharply contrasting predictions of geometrically linear and nonlinear theories for the stress field of a spatially homogeneous dislocation distribution in the body, as well as against other exact results of the theory. Verification tests of the time-dependent numerics are also presented. Size effects in crystal and isotropic versions of the theory are shown to be a natural consequence of the model and are validated against available experimental data. With inertial effects incorporated, the development of an (asymmetric) propagating Mach cone is demonstrated in the finite deformation theory when a dislocation moves at speeds greater than the linear elastic shear wave speed of the material.

 

Paper can be found at link Finite_Deformation_Dislocation_Mechanics.

 

 

 

Tuncay Yalcinkaya's picture

Full scholarships available at European Commission funded workshop on physics based material models in Izmir / Turkey

European Commission' s JRC (Joint Research Centre) is organizing the 3rd workshop on physics based material models and experimental observations (http://iwpmeo.org/) in collaboration with University of Oxford, Max-Planck-Institut für Eisenforschung and Middle East Technical University. The workshop will be held in Izmir/Turkey on 2-4 June 2014.

Amit Acharya's picture

Dislocation motion and instability

Yichao Zhu       Stephen J. Chapman       Amit Acharya

(to appear in Journal of the Mechanics and Physics of Solids)

Arash_Yavari's picture

Affine Development of Closed Curves in Weitzenbock Manifolds and the Burgers Vector of Dislocation Mechanics

In the theory of dislocations, the Burgers vector is usually defined by referring to a crystal structure. Using the notion of affine development of curves on a differential manifold with a connection, we give a differential geometric definition of the Burgers vector directly in the continuum setting, without making use of an underlying crystal structure.

Amit Acharya's picture

Anisotropic yield, plastic spin, and dislocation mechanics

(This paper is to appear in the IUTAM Procedia on "Linking scales  in computations: from microstructure to macro-scale properties," edited by Oana Cazacu)

Amit Acharya, S. Jonathan Chapman

Amit Acharya's picture

New perspectives in plasticity theory

 

A field theory of dislocation mechanics and plasticity is illustrated through new results at the nano, meso, and macro scales. Specifically, dislocation nucleation, the occurrence of wave-type response in quasi-static plasticity, and a jump condition at material interfaces and its implications for analysis of deformation localization are discussed.

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