Dynamic fracture instabilities in brittle crystals generated by thermal phonon emission: Experiments and atomistic calculations

Fouad Atrash, Dov Sherman*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Dynamic cleavage fracture experiments of brittle single crystal silicon revealed several length scales of surface and path instabilities: macroscale path selection, mesoscale crack deflection, and nanoscale surface ridges. These phenomena cannot be predicted or explained by any of the continuum mechanics based equations of motion of dynamic cracks, as presumably critical energy dissipation mechanisms are not fully accounted for in the theories. Experimentally measured maximum crack speed, always lower than the theoretical limit, is another phenomenon that is as yet not well understood. We suggest that these phenomena depend on velocity dependent and anisotropic material property that resists crack propagation. The basic approach is that the bond breaking mechanisms during dynamic crack propagation vibrate the atoms at the crack front to generate thermal phonon emission, or heat, which provides additional energy dissipation mechanisms. This energy dissipation mechanism is a material property that resists crack propagation. To evaluate this property, we combined the continuum based elastodynamic Freund equation of motion with molecular dynamics atomistic computer experiments. We analyzed the above experimental dynamic fracture instabilities in silicon with the obtained velocity dependent and anisotropic material property and show its importance in cleavage of brittle crystals.

Original languageEnglish
Pages (from-to)844-856
Number of pages13
JournalJournal of the Mechanics and Physics of Solids
Volume60
Issue number5
DOIs
StatePublished - May 2012
Externally publishedYes

Funding

FundersFunder number
EU-FP-NMP

    Keywords

    • Brittle crystals
    • Crack instabilities
    • Crystal anisotropy
    • Dynamic crack propagation
    • Phonon emission

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