Deviations from Newtonian rheological behavior in alkali borate glasses

Deviations from Newtonian viscous flow behavior in glasses have been measured with a special viscosimeter, with which very low values of the shear velocity can be measured interferometrically. Measuring the viscosities of B2O3 glass and alkali borate glasses, the former was found to behave as a Maxwellian liquid, the latter as a Bingham liquid, showing a yield value for the shearing stress. To eliminate the elastic behavior difference between B2O3 glass and alkali borate glasses the flow behavior of alkali borate glasses was measured under conditions of an alternating load, whereas the flow behavior of B2O3 glass was measured under condition of continuous and alternating load. In the latter case no mutual differences were found. The difference in flow behavior is explained on the basis of the structures of these glasses.