Viscoelastic behavior of a soda-lime-silica glass in the 293–833 K range by micro-indentation

The viscoelastic behavior of a soda-lime silica glass (a standard window glass) was investigated by means of Vickers indentation from room temperature to 833 K. Hardness values decrease gradually from 293 to 673 K and drop rapidly above 673 K. The flow kinetics of the glass at high temperature was analyzed in the light of atomic force microscopy observations. It was observed that densification significantly contributes to the permanent deformation at low temperatures, whereas volume conservative flow played a more and more important role as temperature was increased. Master curves of the relaxation modulus and the creep compliance were obtained from constant-rate and constant-load indentation experiments, respectively. A major finding was that the viscous flow process is nonlinear, with a sharp decrease of the apparent viscosity as the mean contact pressure increases.