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Molecular dynamics simulations of the shape memory effect in a chain of Lennard‐Jones crystals

Molecular dynamics simulations of the shape memory effect in a chain of Lennard‐Jones crystals Purpose – Shape memory alloys are a fascinating class of materials because they combine both structural and functional properties. These properties strongly depend on temperature. One consequence of this dependency yields the characteristic shape‐memory effect: shape memory alloys can recover processed reference configurations after significant plastic deformations simply upon a change of temperature. For real materials, such processes incorporate characteristic hysteresis. This paper aims at an understanding of these materials from an atomistic point of view. Design/methodology/approach – 2D molecular‐dynamics (MD) simulations describing a chain consisting of 32 linked Lennard‐Jones crystals are presented. The crystals consist of nested lattices of two atom species. Distinct lattice structures can be identified, interpreted as austenite and (variants of) martensite. Temperature and/or load‐induced phase transitions between these configurations are observed in MD simulations. Previously, the thermal equation of state of one isolated crystal was investigated and its phase stability was discussed in detail. In the multi‐crystal chain considered in the present paper, individual crystals contribute collectively to the thermo‐mechanical behavior of the assembly. Findings – The paper presents the results of numerical experiments with this polycrystalline chain under strain‐, load‐ and/or temperature‐control. The results show that with the assumption of simple Lennard‐Jones potentials of interaction between atoms in individual crystals and linking these crystals allows to reproduce the features associated with the fascinating behavior of shape memory alloys, including pseudo‐plasticity, pseudo‐elasticity and the shape memory effect. Originality/value – Owing to the special setup chosen, interfaces are missing between adjacent crystals in the chain assembly. The paper shows that in this situation load‐induced austenite/martensite transitions do not exhibit hysteresis in tension/compression cycles. This observation indirectly supports mesoscopic‐level work in the literature which explicitly introduces interface energy to model such hysteresis. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Multidiscipline Modeling in Materials and Structures Emerald Publishing

Molecular dynamics simulations of the shape memory effect in a chain of Lennard‐Jones crystals

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Publisher
Emerald Publishing
Copyright
Copyright © 2010 Emerald Group Publishing Limited. All rights reserved.
ISSN
1573-6105
DOI
10.1108/15736101011055275
Publisher site
See Article on Publisher Site

Abstract

Purpose – Shape memory alloys are a fascinating class of materials because they combine both structural and functional properties. These properties strongly depend on temperature. One consequence of this dependency yields the characteristic shape‐memory effect: shape memory alloys can recover processed reference configurations after significant plastic deformations simply upon a change of temperature. For real materials, such processes incorporate characteristic hysteresis. This paper aims at an understanding of these materials from an atomistic point of view. Design/methodology/approach – 2D molecular‐dynamics (MD) simulations describing a chain consisting of 32 linked Lennard‐Jones crystals are presented. The crystals consist of nested lattices of two atom species. Distinct lattice structures can be identified, interpreted as austenite and (variants of) martensite. Temperature and/or load‐induced phase transitions between these configurations are observed in MD simulations. Previously, the thermal equation of state of one isolated crystal was investigated and its phase stability was discussed in detail. In the multi‐crystal chain considered in the present paper, individual crystals contribute collectively to the thermo‐mechanical behavior of the assembly. Findings – The paper presents the results of numerical experiments with this polycrystalline chain under strain‐, load‐ and/or temperature‐control. The results show that with the assumption of simple Lennard‐Jones potentials of interaction between atoms in individual crystals and linking these crystals allows to reproduce the features associated with the fascinating behavior of shape memory alloys, including pseudo‐plasticity, pseudo‐elasticity and the shape memory effect. Originality/value – Owing to the special setup chosen, interfaces are missing between adjacent crystals in the chain assembly. The paper shows that in this situation load‐induced austenite/martensite transitions do not exhibit hysteresis in tension/compression cycles. This observation indirectly supports mesoscopic‐level work in the literature which explicitly introduces interface energy to model such hysteresis.

Journal

Multidiscipline Modeling in Materials and StructuresEmerald Publishing

Published: Jun 16, 2010

Keywords: Materials management; Modelling; Phase transformations; Crystals; Alloys; Solids

References

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