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Please use this identifier to cite or link to this item: http://hdl.handle.net/1860/2721

Title: Sapphire: a kinking nonlinear elastic solid
Authors: Basu, S.
Barsoum, Michel W.
Kalidindi, Surya R.
Issue Date: 16-Mar-2006
Publisher: American Institute of Physics
Citation: Journal of Applied Physics 99: pp. 063501-7.
Abstract: Kinking nonlinear elastic (KNE) solids are a recently identified large class of solids that deform fully reversibly by the formation of dislocation-based kink bands [Barsoum et al. Phys. Rev. Lett. 92, 255508 2004 .] We further conjectured that a high c/a ratio—that ensures that only basal slip is operative—is a sufficient condition for a solid to be KNE. The c/a ratio of sapphire is 2.73 and thus, if our conjecture is correct, it should be a KNE solid. Herein by repeatedly loading—up to 30 times—the same location of sapphire single crystals of two orientations—A and C—with a 1 m radius spherical nanoindenter, followed by atomic force microscopy, we showed that sapphire is indeed a KNE solid. After pop-ins of the order of 100 nm, the repeated loadings give rise to fully reversible, reproducible hysteresis loops wherein the energy dissipated per unit volume per cycle Wd is of the order of 0.5 GJ/m3. Wd is due to the back and fro motion of the dislocations making up the incipient kink bands that are fully reversible. The results presented here strongly suggest that—like in graphite and mica—kink bands play a more critical role in the room temperature constrained deformation of sapphire than had hitherto been appreciated. Our interpretation is also in agreement with, and can explain most, recent nanoindentation results on sapphire.
URI: http://dx.doi.org/10.1063/1.2179974
Appears in Collections:Faculty Research and Publications (MSE)

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