Densification as the Only Mechanism at Stake during Indentation of Silica Glass?

Abstract

Abstract. Silica glass is known to exhibit permanent changes in density under very high pressures. These changes may reach 21%. The sharp indentation test develops pressures underneath the indenter that trigger densification. Recently, we have proposed a constitutive modeling of the pressure-induced process accounting for its salient features: densification threshold, hardening, saturation of densification and permanent increase in elastic moduli. We examine in this paper the possibility that densification could be the only mechanism for creating an imprint by indentation. We consider different models with growing complexity that we implement in a finite element software. Results indicate that the combination of shear and pressure as a driving force to densification may account for the mechanical response of the indentation test as well as the presence of densified zone underneath the imprint.

Densification contribution as a function of strain rate under indentation of terbium-doped aluminophosphate glass

“…This somewhat surprising result can be explained basing of the results obtained by Keryvin et al [33] using finite element modeling of the indentation process of silica glass. They suggest that the driving force for a , mN: a 20, b 100, c 500, d 900 Fig.…”

Impact of pressure on plastic yield in amorphous solids with open structure

“…An additional observation is that shear lowers the densification threshold [14]. Recently, there have been attempts to derive constitutive equations to account for this unconventional plastic response [15][16][17], but the respective roles of densification and shear flow remain controversial [18]. To better understand the plastic behavior of amorphous materials with an open structure and its implications in terms of plastic rearrangement mechanisms, we have carried out a numerical investigation of yield in a model system emulating amorphous silica.…”

Perfectly plastic flow in silica glass

“…In indentation experiments [23,24,22], the stress state is a complex spatial distribution of combinations of high hydrostatic pressure and shear present in roughly equal proportions [25,26]. It appears that indentation experiments can be reproduced using either yield rules coupling shear flow and densification [27,24,28], or a yield rule that only accounts for densification [29]. More data is needed beyond the indentation force-displacement curves to conclude which rule is more applicable.…”