Microstructural Characterization of Shape Memory Alloys on the Atomic Scale

Begau, Christoph; Hartmaier, Alexander

doi:10.1002/9781118889879.ch33

Cited by 2 publications

(2 citation statements)

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“…Since the focus is placed on the energy densities of dislocation networks, these grainboundaries are identified in a post-processing step that constructs a surface mesh as a representation of grain-or phase boundaries as described in [30]. In order to ignore the energy contribution in these defects, any atom within a distance of 1.2 nm (about three times the lattice constant) is marked as being biased by a grain-boundary and is not considered in the subsequent analysis steps.…”

Section: Methodsmentioning

confidence: 99%

Free energy function of dislocation densities by large scale atomistic simulation

Begau,

Sutmann,

Hartmaier

2015

Preprint

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This paper discusses the free energy of complex dislocation microstructures, which is a fundamental property of continuum plasticity. In the past, multiple models of the self energy of dislocations have been proposed in the literature that partially contradict each other. In order to gain insight into the relationship between dislocation microstructures and the free energy associated with them, instead of deriving a model based on theoretical or phenomenological arguments, here, these quantities are directly measured using large scale molecular dynamics simulations. Plasticity is induced using nanoindentation that creates an inhomogeneous distribution of dislocations as the result of dislocation nucleation and multiplication caused by the local deformation. Using this approach, the measurements of dislocation densities and free energies are ab-initio, because only the interatomic potential is defining the reaction of the system to the applied deformation. The simulation results support strongly a linear relation between the scalar dislocation density and the free energy, which can be related very well to the classical model of mechanical energy of straight dislocations, even for the complex dislocation networks considered here.

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Section: Methodsmentioning

confidence: 99%

Free energy function of dislocation densities by large scale atomistic simulation

Begau,

Sutmann,

Hartmaier

2015

Preprint

Self Cite

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show abstract

“…Within 200,000 time-steps the pillar is compressed by 10%. This simulation is a realistic use-case, as it is a shortened re-run of a simulation published in [34]. In this test, each domain is handling a fairly large number of atoms and the load is changing slowly but steadily due to two mechanisms: First of all, atoms are forced to move downwards, causing the upper part of the simulation box becoming void of atoms over time.…”

Section: Nanopillar Compressionmentioning

confidence: 99%