Effects of indenter geometry on indentation-induced densification of soda-lime glass

Hardness of glass is known to be related to the resistance to permanent deformation. However, the mechanism of permanent deformation of glass under a sharp diamond indenter is not clear yet. One of the deformation modes of oxide glass at room temperature is permanent densification. In this study, the indentation-induced densification of soda-lime glass under diamond indenters was evaluated from the volume recovery of indentation imprint by thermal annealing. The volume change of the indentation imprint by annealing corresponds to the densified volume under the indenter. Using some kinds of diamond indenters, which have different inclined face angles, the ratios of densified volume to the total “lost” volume under the indenters were determined. With an increase in the inclined face angle, the densification contribution decreased and the shear-flow contribution increased. This indenter-shape dependence of densification in glass is discussed in terms of the stress dependence of the deformation mechanisms in glass.