Transition from ductile to brittle failure of sodium silicate glasses: a numerical study
- PDF / 332,748 Bytes
- 6 Pages / 432 x 648 pts Page_size
- 103 Downloads / 204 Views
Transition from ductile to brittle failure of sodium silicate glasses: a numerical study Gergely Molnár1, Patrick Ganster1, Anne Tanguy2, János Török3, Guillaume Kermouche1 1
École de Mines de Saint-Étienne, Centre SMS, Laboratoire Georges Friedel, CNRS-UMR5307, 158 Cours Fauriel, 42023, Saint- Étienne, France. 2 Laboratoire de Mécanique des Contacts et des Structures, Institut National des Sciences Appliquées de Lyon 18-20, rue des Sciences, 69621, Villeurbanne Cedex, France. 3 Department of Theoretical Physics, Budapest University of Technology and Economics, Budapest H-1111, Hungary. ABSTRACT
Using molecular statics calculations, sodium silicate glasses are expanded in an isotropic manner to analyze the composition dependence of the mechanical response. Increasing the amount of sodium makes the systems more ductile. The tensile strength is reduced and the final load bearing strain limit is increased. Hydrostatic strain hardening appears in the ductile samples. To explain this phenomena, the density is coarse-grained to identify microscopic defects. In samples containing a significant amount of sodium, a large amount of nano-voids appear before reaching the maximum load bearing capacity. In high sodium content silicates these cracks may cause the hardening observed in the pressure results. In samples with low sodium content, the failure is abrupt and only a large crack is observed. Increasing the amount of long term but weaker Na-O interactions, instead of the short range Si-O ones could explain the observed transition. INTRODUCTION Silicate glasses are widely used for their ease in forming and recycling, among other interesting physical and mechanical properties. Sodium silicates have a complex mechanical behavior resulting from the mixing of two different materials: silica as network former, and sodium oxide, where sodium acts as a network modifier. Sodium-silicate glasses are known as "normal", while pure silica glasses have an anomalous mechanical behavior characterized by their densification upon compression at small scales [1]. Understanding small-scale plastic behavior of silicate glasses is crucial to understand crack initiation processes and the brittle behavior of glasses at large scales [2]. Dynamic crack formation was widely investigated in the literature for pure silica [3-6]. Rountree et al. [5] showed that even for brittle materials, the material near the crack tip becomes ductile. A good qualitative agreement was found between their results and experimental observations. Experiments showed [7] that the network modifier ion (e.g. sodium) has a significant effect on the ductility of the material. Sodium makes the original silica network to yield at an early stage, consequently creates a higher plastic strain resistance. To investigate this topic, atomistic simulations were performed using hydrostatic tension tests. We use a static calculation scheme [10], which can establish the connection between time-less particle and static continuum methods. Contrary to molecular dynamics, in molecular statics
Data Loading...
