Читать книгу Encyclopedia of Glass Science, Technology, History, and Culture - Группа авторов - Страница 50

Incremental oxide factors for the calculation of the elastic properties from the composition compiled in the right‐hand part of Table 3 are taken from a widely accepted earlier publication [21]; for the sake of clarity, they have been adjusted with respect to the units used, i.e. to cm³/mol for volume, and to GPa for modulus increments. Young's modulus E is then calculated with

Figure 8 Change of Young's modulus E in the base glass composition 74 SiO₂ 10 CaO 16 Na₂O upon the replacement of x wt % silica by another oxide.

(4)

where x(j) and M(j) are the mole fraction and molar mass of oxide j, respectively, and ρ the density of the glass.

As for Poisson's ratio μ, it is calculated as

(5)

The manner in which Young's modulus varies when a glass composition of (74 − x)SiO₂, 10 CO, 16 Na₂O (by wt) is modified by an addition of x wt % of another oxide is illustrated in Figure 8. Young's modulus can be raised by the addition of P, Li, B, Zr, Mg, and Al oxides, and in contrast lowered by oxides of heavy mono‐ and divalent ion oxides. True, such small additions do not yield major overall effects but the tendency is clearly shown.