RESIDUAL-STRESSES IN A SODA-LIME-SILICA GLASS-CERAMIC

The present study was undertaken to test the validity of existing mode ls for: (i) the residual internal stresses which arise due to thermal and elastic mismatch in duplex systems; and (ii) the critical particle diameter for spontaneous cracking. The specimens studied were bulk nu cleated, partially crystallized 17.20Na(2)O-32.09CaO-48.12SiO(2)-2.59P (2)O(5) (mol%) glasses. The residual stress was determined by an X-ray diffraction technique for a particular set of hkl planes. The crystal diameters and volume fractions crystallized were measured by an image analyzer system. The experimental residual stress was in agreement wi th the calculated value within the measurement errors. On the other ha nd, the theoretical value of the critical particle diameter, calculate d by an energy balance approach, was more than ten times smaller than the experimental value, suggesting that the semi-spherical crack assum ed in the model does not hold for our system. A preliminary fitting wi th a fracture mechanics model was also carried out.