Densification dependent yield criteria for sodium silicate glasses – An atomistic simulation approach

Abstract

Silicate glasses are macroscopically brittle but ductile at the micron scale. This plastic response is complex: in open structure materials, such as amorphous silica, plastic yield results in significant densification. While, more compact structures (e.g. soda-silicate glasses) are known to suppress densification and promote shear flow. We have carried out atomic scale simulations to analyze the plastic response of a series of silicates with increasing sodium content. Quasi-static, multi-axial deformation tests were performed on large samples (≈ 10 3 nm 3 ). Their yield behavior was quantified at different stress states, by measuring permanent volume changes. Qualitative agreement was found between the response of modeled systems and experimental results. Strong coupling between plastic yield and densification was observed. Our results also suggest that sodium silicates may densify not only under hydrostatic compression but also upon shear at large strains. Based on these numerical results, we propose a general yield criterion for soda-silicate glasses in which density is an internal variable. As density increases, the elliptic yield surface (characterizing amorphous silicates with open structures) gradually

Mechanical properties of simple computer glasses

“…In [43] a value of σ ∞ /G ≈ 0.03 was observed using the Stillinger-Weber model for amorphous silicon [44]. A value of σ ∞ /G ≈ 0.11 can be estimated based on the stress-strain signals reported in [45] for computer models of sodium silicate glasses that employ the van Beest-Kramer-van Santen potential [46]. The spread in these values indicates that the simple computer models investigated in this work only represent a narrow class of amorphous solids.…”

Plastic response of amorphous silicates, from atomistic simulations to experiments – A general constitutive relation

“…A generic analytical form for the yield criteria of silicate glasses has been evaluated numerically using Molecular Dynamics (or more precisely Molecular Statics) following the methodology reported in Molnár et al (2016b) and Molnár et al (2016a). In brief, through numerical experiments, different loading combinations have been applied to various systems modeling several binary glass compositions.…”

“…We have therefore derived an analytical expression for the yield criterion as a function of pressure. The flow data obtained in the simulations have not been directly used for the constitutive relation but it was found that assuming associated plasticity we obtained a reasonable rendering of the computed irreversible strains (Molnár et al (2017b); Molnár et al (2016a)).…”

“…Due to the complexity of the topic, only a limited number of papers have appeared, for metallic glasses ; Schuh and Lund (2003); Shimizu et al (2006)), nano-crystaline metals (Lund and Schuh (2004); Salehinia et al (2014);van Swygenhoven et al (1999)), glassy polymers (Mott et al (1993); Rottler and Robbins (2001)) and other model materials (McDowell (2010); Xu et al (2014)). Recently, we have shown that yield surfaces can be calculated by atomic scale simulations for amorphous silicates (Molnár et al (2016a)). However, this approach is not widespread because of some shortcomings of these simulations.…”

Indentation densification of fused silica assessed by raman spectroscopy and constitutive finite element analysis

“…Several constitutive models 8,[26][27][28][29][30][31][32] have been developed to describe the anomalous plastic flow behavior of fused silica. First attempts considered volume-conservative plastic shear flow using von Mises plasticity.…”