Indentation Behavior of Soda‐Lime Silica Glass, Fused Silica, and Single‐Crystal Quartz at Liquid Nitrogen Temperature

Abstract

In an attempt to elucidate the processes involved in the formation of indentation impressions, Vickers hardness measurements have been made on soda‐lime silica glass, fused silica, and crystalline quartz indented at room temperature and 77 K. The hardness of all three materials increases by a factor of ∼2.5 on cooling to liquid nitrogen temperature. High‐magnification SEM photographs revealed that the deformation and cracking patterns of the glasses changed strikingly: no shear lines were observed within the indentations, and ring cracking occurred instead of radial/median cracking. In addition, cracking occurs at much higher loads than at room temperature. The hardness results have been explained in terms of volume flow (densification) rather than shear flow (viscous or plastic) for the glasses at low temperature. The quartz crystal, on the other hand, deformed plastically at both room temperature and 77 K. Cracking differences result from changes in both flow and water activity

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

“…We eventually examine the possibility that densification is the only mechanism at stake during indentation, which is consistent with the experimental observations of Kurkjian et al [18]. Yet, in contrast to PID, we assume that shear plays a role in triggering the densification process, which is in agreement with recent molecular dynamics studies [22].…”

“…This pressure-induced densification (PID) is an improvement of previous modellings [11,12] with considerable impact on the description of the pressure-volume changes of fused silica for pressures lower than 25 GPa, taken from very recent experimental data [16,17]. In this paper, we examine the possibility that densification could be the only dissipative mechanism responsible for the creation of an imprint during the indentation process in silica glass, which is consistent with the experimental observations of Kurkjian et al [18]. This work is done at room temperature, far from the glass transition, for which shear plasticity is known to be the mechanism at stake, for instance during indentation creep [19].…”

Driving force for indentation cracking in glass: composition, pressure and temperature dependence

“…As temperature increases from ambient to 673 K, the ring/cone cracks observed in a-SiO 2 disappear to the benefit of the radial/median pattern ( figure 14a,b). Conversely, as temperature decreases, E/H as well as ν decrease and shear flow becomes less and less significant and eventually disappears at 77 K as observed by Kurkjian et al [5] in the case of a-SiO 2 and a soda-limesilica glass, for which the E/H ratio decreases from 8 and 10 to 3 and 6.3, respectively, as T decreases from room temperature to 77 K. Interestingly, as will be discussed in §3f , there seems to be also a correlation between the cone crack angle and ν. The concomitant increase of the E/H ratio results in radial/median cracks to grow on heating in a window glass (figure 14c-e).…”

Vickers Indentation Cracking of Ion-Exchanged Glasses: Quasi-Static vs. Dynamic Contact

“…They proposed a shear fault model where decohesion distance of the faults depended on time-dependent water diffusion into the shear fault interfaces (Lawn et al, 1983). Kurkjian et al (1995) on normal glasses resulted in less shear deformation, and this observation was attributed to the reduction in water activity. All of these studies suggest that the minimization of water interaction would greatly improve crack resistance and the dynamic indentation results presented in this study appear to be another example of this.…”