Scale-dependent pop-ins in nanoindentation and scale-free plastic fluctuations in microcompression

John Shimanek, Quentin Rizzardi, Gregory Sparks, Peter M. Derlet, Robert Maa

Research output: Contribution to journalArticlepeer-review


Nanoindentation and microcrystal deformation are two methods that allow probing size effects in crystal plasticity. In many cases of microcrystal deformation, scale-free and potentially universal intermittency of event sizes during plastic flow has been revealed, whereas nanoindentation has been mainly used to assess the stress statistics of the first pop-in. Here, we show that both methods of deformation exhibit fundamentally different event-size statistics obtained from plastic instabilities. Nanoindentation results in scale-dependent intermittent microplasticity best described by Weibull statistics (stress and magnitude of the first pop-in) and lognormal statistics (magnitude of higher-order pop-ins). In contrast, finite-volume microcrystal deformation of the same material exhibits microplastic event-size intermittency of truncated power-law type even when the same plastic volume as in nanoindentation is probed. Furthermore, we successfully test a previously proposed extreme-value statistics model that relates the average first critical stress to the shape and scale parameter of the underlying Weibull distribution.

Original languageEnglish (US)
Pages (from-to)196-205
Number of pages10
JournalJournal of Materials Research
Issue number2
StatePublished - 2020


  • crystal
  • microstructure
  • nanoindentation

ASJC Scopus subject areas

  • General Materials Science
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering


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