Understanding the response of glasses to sharp contact loading via classical molecular dynamics simulation

Abstract

Glass materials have enabled many products for a wide range of applications. One downside of oxide glasses is that they are very susceptible to crack under sharp contact loading. There have been extensive studies in experiments to understand the deformation mechanisms and to improve crack resistance of glass. However, conducting in-situ characterizations in real-time experimentally is challenging, which has mostly limited our understanding of glass deformation and cracking behaviors under sharp contact loading. This study conducted nanoindentation tests using classical molecular dynamics simulation to understand how the stress/strain fields and the structure of glass evolve under sharp contact loading from an atomistic perspective. First, we used the 2.5D nanoindentation method in sodium aluminosilicate and sodium aluminoborate systems to illustrate the structural origin of the improved crack resistance of boron-containing glass. To generate stress/strain fields and deformation patterns in glass that can be directly compared with instrumented experimental studies, we developed a 3-D nanoindentation protocol to mimic real-life loading conditions, and applied it in a model metallic glass favoring shear flow to understand the shear band activation/interaction mechanism. After validating our results with multiple experimental studies, we conducted more 3-D nanoindentation simulations in metallic and silica glasses with different densification abilities. The comparisons between silica and metallic glasses suggest that balancing shear deformation with a combination of instantaneous and permanent densification can provide multiple pathways to dissipate energy under indentation, thus increasing the load to initiate cracks and improving the damage resistance of glass.