Dislocation based plasticity in the case of nanoindentation

Kai Zhao, A.E. Mayer, Jianying He, Zhiliang Zhang*

*Corresponding author for this work

    Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review

    30 Citations (Scopus)

    Abstract

    Understanding plasticity initiation and evolution in nanoindentation tests is a fundamental issue. In this study, a continuum model is developed to analytically predict the force-depth curve by coupling the classical Hertzian solution for elastic field and the evolution of dislocation density. By considering multiple slip systems, the present model predicts the "pop-in" event well. Large-scale molecular dynamics simulations are performed to evaluate the mechanical behavior of bcc Fe under nanoindentation of a spherical indenter and to verify the continuum model. The comparison between molecular dynamics simulations and model predictions shows that the initiation and evolution of dislocation networks is strongly dependent on the loading orientation, which is associated with different deformation patterns. Applying the transition state theory, we investigate the slip-twinning transition as a function of loading rate, which supports the basic hypothesis in the continuum model that the activation of shear loop requires lower energy compared with twin nucleation, although twins can nucleate temporally and annihilate into shear loops finally. The present model provides a general framework to evaluate and rationalize the "pop-in" behavior of any materials with elastoplastic response.

    Original languageEnglish
    JournalInternational Journal of Mechanical Sciences
    Volume148
    Pages (from-to)158-173
    Number of pages16
    ISSN0020-7403
    DOIs
    Publication statusPublished - 2018

    Keywords

    • Nanoindentation
    • Dislocations
    • Molecular dynamics
    • Shear loops
    • Twinning
    • STRAIN GRADIENT PLASTICITY
    • MOLECULAR-DYNAMICS
    • SPHERICAL NANOINDENTATION
    • INTERATOMIC POTENTIALS
    • INCIPIENT PLASTICITY
    • ATOMISTIC SIMULATION
    • COLLECTIVE BEHAVIOR
    • GRAIN-BOUNDARIES
    • BCC IRON
    • SIZE

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