An analysis of dislocation nucleation near a free surface

Yufu Liu, Erik Van der Giessen*, Alan Needleman

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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Molecular dynamics analyses of defect-free aluminum single crystals subject to bending are carried out to investigate dislocation nucleation from free surfaces. A principal aim of the analyses is to provide background for the development of dislocation nucleation criteria for use in discrete dislocation plasticity calculations. The molecular dynamics simulations use an embedded atom potential for aluminum. Bending is imposed on a strip by specifying a linear variation of displacement rate on opposite edges. The overall bending response is determined and the character of the dislocations nucleated is identified. It is found that the stress magnitudes at the instant of dislocation nucleation are nearly an order of magnitude smaller than for homogeneous bulk dislocation nucleation. The characterization of dislocation nucleation in terms of various phenomenological nucleation criteria is explored, in particular: (i) a critical resolved shear stress; (ii) the onset of an elastic instability; and (iii) a critical stress-gradient criterion. It is found that dislocation nucleation is not well-represented by a critical value of the resolved shear stress but is reasonably well-represented by the critical stress-gradient criterion. (c) 2006 Elsevier Ltd. All rights reserved.

Original languageEnglish
Pages (from-to)1719-1732
Number of pages14
JournalInternational Journal of Solids and Structures
Issue number6
Publication statusPublished - 15-Mar-2007
EventSymposium on Physics and Mechanics of Advanced Materials - , Singapore
Duration: 1-Jan-2007 → …


  • dislocation nucleation
  • free surface
  • plasticity
  • size effect
  • molecular dynamics
  • pure bending

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