Micropillar compression

Accurate assessment of the constitutive law of amorphous silica can be brought by an experiment generating a quasi-homogeneous stress state in the sample. We use uniaxial compression for that reason, which has to be performed at the microns scale in order to make the plastic deformation more energetically favorable than fracture.

Micro-pillars of 5 µm in height and 3 µm in diameter have been manufactured by Reactive Ion Etching by the FEMTO-ST Institute within the MIMENTO technologic platform [1].

Instrumented compression by a diamond flat punch [2] are reversible below a threshold load. However above that threshold, evidences of a permanent plastic flow can be seen both on the load-displacement curves and on SEM observations of the micro-pillar.

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Computing the applied stress as the applied load divided by the pillar’s section, the threshold stress appears to be close to 7GPa. The permanent radial expansion of the upper section of the micro-pillars clearly state that an important contribution of the plastic flow is volume-conservative

The observed deformed profile and crack pattern give important insights on the occuring plastic flow and the resulting stress inhomogeneities.

==Publications==
*[http://hal.archives-ouvertes.fr/hal-00677258 Micro-pillar testing of amorphous silica] : Micro-pillar testing of amorphous silica, R. Lacroix, V. Chomienne, G. Kermouche, J. Teisseire, S. Queste, E. Barthel, Int J App Glass Sci 3, 1 (2012) 36-43.

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