Finite element analysis of identation on glass(II)

The shapes of indentations made on Na₂O-SiO₂ glasses with differentalkali content were studied by using the finite element method to estimate the basic mechanical properties of the glasses. The yield stress Y, densification factor ¦α¦ and hardenining coefficient H′ of the glasses were successfully estimated, which cannot be determined by the usual methods. The densification factors ¦α¦ obtained for each glass at various temperatures did not change much, and it was considered that they were determined mainly by the structure of the glass. The value of ¦α¦ approached zero when the content of Na₂O exceeded 35 mol%, which corresponds to the stuffing effect of alkali ions in the glass network. The yield stress Y estimated by this method differed considerably from the tensile strength of the glass. The difference was especially large for the glass with low alkali content, i.e. the larger the value of ¦α¦ the larger the difference between Y from the hardness and the tensile strength. The reason for this could be partly attributed to the difference in the mode of deformation.