Scratch‐induced yielding and ductile fracture in silicate glasses probed by nanoindentation

Abstract

Lateral nanoindentation provides access to the scratch hardness of glass surfaces. The specific sensitivity of the scratching experiment to surface mechanical properties can be enhanced when the local load at the tip apex is reduced. Here, we report on ramp‐load scratch tests on a range of silicate glasses using a sphero‐conical tip shape. Similar as with regular scratching experiments using sharp indenters, such tests create a sequence of micro‐ductile, micro‐cracking, and micro‐abrasive regimes. Detailed investigation of the indenter displacement h and of the lateral force FL as recorded in situ, however, reveals pronounced deviations in comparison to Vickers or Berkovich scratching experiments. Most notably, this includes an abrupt increase in both h and FL at moderate normal load, marking the onset of ductile fracture, and a yield point at the transition from fully elastic deformation to the elastic‐plastic regime at low load. For the range of examined silicate glasses, we find that structural cohesion controls yielding, whereas scratch‐induced fracture and micro‐abrasion are dominated by the volume density of bond energy.

Effect of humidity on friction, wear, and plastic deformation during nanoscratch of soda lime silica glass

“…Similar load‐dependent surface damage modes can be found for silica glass when scratched with a Berkovich indenter tip with a normal load up to 300 mN 13 . When the surface of silica‐based glass (such as fused silica and SLS) is scratched with a much sharper cono‐spherical indenter tip, chipping can readily occur, with an apparent friction coefficient much higher than that in the elastic and plastic regimes 14,15 …”

“…13 When the surface of silica-based glass (such as fused silica and SLS) is scratched with a much sharper cono-spherical indenter tip, chipping can readily occur, with an apparent friction coefficient much higher than that in the elastic and plastic regimes. 14,15 Apart from the applied load, the environmental conditions, such as the presence of water vapor, are known to alter the surface chemistry of silicate glass. Without a physical contact, water molecules can react with silicate glass surface via diffusion and hydration as well as hydrolysis of Si-O-Si network, 16,17 and these chemical reactions can finally alter the glass topography, 18 network connectivity, 19 and nanomechanical properties.…”

Effect of Al2O3 addition on the thermal expansion of sodium alkaline‐earth silicate glasses: A molecular dynamics study

“…In this table, the density, $$E_y$$, and G of a (SiO 2 ) 50 (CaO) 50 glass constructed by the MD simulations are compared with experimental data 39,40 . The experimental moduli were assumed to be the averaged values of those of (SiO 2 ) 40 (CaO) 55 and (SiO 2 ) 55 (CaO) 45 glasses 40 . Consequently, the density estimated agreed well with experimental data, while the moduli were evidently underestimated.…”

“…Ca-1st was optimized using only DFT data, whereas Ca-BO9 was obtained by considering both DFT and experimental data. 39,40 Numbers in the parentheses are absolute errors from comparison with the experimental values. temperature range from 300 to 700 K, because the MD cell size linearly changes in this temperature range, as shown in Figure S1 of the SI.…”

Advancing the Mechanical Performance of Glasses: Perspectives and Challenges

“…[37] Evaluating the surface sink-in during lateral indentation with a blunt indenter was demonstrated as a means to evaluate the yielding of glass surfaces. [38,39] A major advantage of such methods lies in their applicability to realscale samples, i.e., specimens that do not require microfabrication or further processing, affecting subsequent data evaluation and interpretability. Despite such advances, the availability of intrinsic data is still limited to only a small number of glass compositions, which presents a serious obstacle in the elucidation of the effect of glass chemistry and atomic structure on glass mechanics versus the role of extrinsic factors.…”