Nanomechanics of slip avalanches in amorphous plasticity

Penghui Cao, Karin A. Dahmen, Akihiro Kushima, Wendelin J. Wright, Harold S. Park, Michael P. Short, Sidney Yip

Research output: Contribution to journalArticlepeer-review

Abstract

Discrete stress relaxations (slip avalanches) in a model metallic glass under uniaxial compression are studied using a metadynamics algorithm for molecular simulation at experimental strain rates. The onset of yielding is observed at the first major stress drop, accompanied, upon analysis, by the formation of a single localized shear band region spanning the entire system. During the elastic response prior to yielding, low concentrations of shear transformation deformation events appear intermittently and spatially uncorrelated. During serrated flow following yielding, small stress drops occur interspersed between large drops. The simulation results point to a threshold value of stress dissipation as a characteristic feature separating major and minor avalanches consistent with mean-field modeling analysis and mechanical testing experiments. We further interpret this behavior to be a consequence of a nonlinear interplay of two prevailing mechanisms of amorphous plasticity, thermally activated atomic diffusion and stress-induced shear transformations, originally proposed by Spaepen and Argon, respectively. Probing the atomistic processes at widely separate strain rates gives insight to different modes of shear band formation: percolation of shear transformations versus crack-like propagation. Additionally a focus on crossover avalanche size has implications for nanomechanical modeling of spatially and temporally heterogeneous dynamics.

Original languageEnglish (US)
Pages (from-to)158-171
Number of pages14
JournalJournal of the Mechanics and Physics of Solids
Volume114
DOIs
StatePublished - May 2018

Keywords

  • Metallic glasses
  • Serrated flow
  • Shear band
  • Slip avalanches
  • Strain-rate effects

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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