Densification and residual stresses induced in glass surfaces by Vickers indentations

Images and profiles of Vickers impressions produced on as-received float-glass were obtained using atomic force microscopy (AFM). The images show that the impression edges undergo elastic recovery parallel to surface. The profiles made it possible to measure vertical elastic recovery, ev(r). For a 40 g nominal load, maximum penetration depth of indenter was (2.20±0.03) μm, and recovery at the impression center was ev(0)=(0.98±0.03) μm. Vertical elastic recovery was non-uniform along profiles. Permanent impressions produced resulted from glass mass displacement downward, producing an increase in glass density in impression vicinity, which is discussed in terms of changes in O−Si−O and Si−O−Si bond angles and Si−O bond length. Near impression edges, pileup was observed for which a simplified model is proposed taking into account the compaction and stresses near the impressions.