The C-H delayed failure mechanism revisited

The often cited “Charles–Hillig” model of delayed failure assumes that corrosive attack on existing flaws in glass is controlled by interactions involving the moisture in the environment, which leads to time and stress dependent failure. The analysis by Inglis of the stress multiplication at a rounded end of a flaw is combined with stress-dependent chemical kinetics and thermodynamics. Failure occurs when the tip stress reaches the ultimate strength of the glass. The model provides a physical interpretation of the empirical “Universal Fatigue Law.” When sufficient data is available, it also provides an algorithm that allows a precise determination of the minimum stress needed to induce time-dependent failure. This model is compared with the competing LEFM model.