Abstract
We have carried out uniaxial compression of micron-scale amorphous silica pillars. We have measured load–displacement curves and observed the morphology of the pillars after unloading, providing strong evidence for large plastic deformations. Minor cracking is also observed, with a well-defined pattern. We find that the van Mises stress in compression is comparable to the intrinsic tensile strength of silica. Precise analysis of the deformation of the pillars has been carried out by finite element modeling (FEM) using the constitutive equation determined previously (G. Kermouche et al., Acta Materialia, 56 (2008) 3222), which quantitatively takes into account densification, shear flow and strain hardening. The residual stress distribution we predict by FEM matches the observed crack pattern well. Finally the calculated stress fields in pillar compression and cone indentation are compared. We propose an interpretation of the contrasts in terms of confinement.
Highlights
Silicate glasses are brittle – a claim substantiated by our daily experience
The second question is methodological: experimentally, how can we investigate the plastic deformation of silicates since the typical length scales involved are so small? As a rule of thumb, the brittle to ductile transition occurs around the micron scale for amorphous silicates
We have demonstrated stable plastic flow in micronsized silica pillars
Summary
Silicate glasses are brittle – a claim substantiated by our daily experience. It has been known for years that they are ductile at small scales [1]. We believe that progress in our understanding of this ductility of silicate glasses is one of the main avenues towards the reduction of their fragility. There may be two distinct relations between fragility and ductility in silicate glasses. Practical strength is limited by surface flaws [3]. Many of these flaws are generated by contact loading of the surface, in which
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