EXTENDED CHARLES-HILLIG THEORY FOR STRESS-CORROSION CRACKING OF GLASS

The work originally performed by Charles and Hillig (C & H) on the chemical stress corrosion cracking of glass is based on the chemical reaction rate theory and restricts the analysis to only the kinetic change at the exact location of the crack tip. As a result, crack sharpening/blunting is predicted when the applied stress lies above/below the static fatigue limit. The present paper extends the investigation within the same physical framework to the geometric change of the entire cavity surface, particularly in the vicinity of the cavity apex region. It has been found that a physical-property-dependent parameter (m) exists which exerts a strong influence on the crack-tip morphology. In the case of m = m(th), where m(th) is a threshold m which assumes a value of almost-equal-to 45 for an elliptical cavity having a minor to major axes ratio of 0.01, the current predictions reduce to the C & H results. In general, however, m not-equal m(th), and the single-valued fatigue limit degenerates into a range of applied stresses under which either enhanced blunting (m > m(th)) or necking (m < m(th)) is predicted to take place. Evaluation of m for soda-lime glass reveals that m > 45, suggesting that enhanced blunting takes place at the crack tip when external loads are applied at a moderate level for a typical crack having an initial major to minor axes ratio > 100 in a soda-lime glass specimen.