Plastic deformation of amorphous silicates

There is only a limited number of experiments which can provide data suitable for the design of constitutive relations for amorphous silicates. However, numerical simulations can also help along the way. Within the MultiSil consortium, we have pioneered the use of molecular dynamics (MD) to emulate typical calibration experiments which cannot be performed (yet) with amorphous silicates, such as plastic deformation in pure shear [1]. The key idea is that with MD, we can obtain structure (...)

Using in situ compression in a SEM, we have directly demonstrated plastic yielding in uniaxial compression for amorphous silica. A decent pîllar is turned into a pan-cake within dozens of seconds. Of course its (original) diameter is little more than 2 microns...
Figure : three stages of the compression of a silica pillar, a few microns across. The flattening without fracture is the result of extensive plasticity.
More quantitatively, we have demonstrated that this plastic flow occurs (...)

For the plastic flow of silicate glasses, the coupling between pressure and shear is still a debated issue. The problem is especially acute for amorphous silica, which is prone to densification due to large free volume. Here we have used Molecular Dynamics simulations of a model iono-covalent amorphous solid with large free volume to investigate this coupling. Of course this model tries to emulate amorphous silica. The most interesting result is the shape of the yield surface : the MD (...)

The plasticity of amorphous silicates
People have dreamt for a perfectly plastic glass material for millennia : plastic glass is one of the many colourful inventions strewn around Petronius’ Satyricon. In chapter LI, a glassmaker proudly presents the stunned emperor with a marvelous glassware, which, when thrown to the ground, does not shatter : the resulting bumps can even be mended with a hammer.
Indeed, brittleness actually results from a competition between plastic deformation and (...)

the dream for plastic glasses dates back to to millenia...(more)