Densification and residual stresses induced in glass surfaces by Vickers indentations

Images and profiles of Vickers impressions produced on as-received float-gl ass were obtained using atomic force microscopy (AFM). The images show that the impression edges undergo elastic recovery parallel to surface. The pro files made it possible to measure vertical elastic recovery, e(v)(r). For a 40 g nominal load, maximum penetration depth of indenter was (2.20 +/- 0.0 3) mu m, and recovery at the impression center was e(v)(0) = (0.98 +/- 0.03 ) mu m. Vertical elastic recovery was non-uniform along profiles. Permanent impressions produced resulted from glass mass displacement downward, produ cing an increase in glass density in impression vicinity, which is discusse d in terms of changes in O-Si-O and Si-O-Si bond angles and Si-O bond lengt h. Near impression edges, pileup was observed for which a simplified model is proposed taking into account the compaction and stresses near the impres sions. (C) 2000 Elsevier Science B.V. All rights reserved.