Crack growth, including fatigue limit and crack arrest, have been investigated for glasses of the systems xNa20-11AI203-(89-x)SiO 2, xNa20-(100-x)Si02 and xNa20-7CaO-(93-x)Si02 in water as well as in acid and alkaline solutions. From studies of the dependence of the crack arrest on the alkali content of the glass, the kind of alkali (K § Na § Li § the pH of the corrosive medium, the ageing time and ageing loading in conjunction with measuring the alkali leaching behaviour, the basic mechanism of crack arrest and fatigue limit can be concluded. Owing to load-and medium-dependent diffusion processes, a crackgrowth retarding leached layer at the crack is generated with modified strength and crack growth properties compared to the bulk properties. In high alkali-containing glasses the process is additionally stimulated by stresses produced in the leached layer at the crack tip and at the crack surfaces.

No abstract

No abstract

No abstract

No abstract