Chapter 30. Machining Damage and Slow Crack Growth/Reliability Analysis of Glass Specimens

Summary

The slow crack growth behavior of soda-lime rectangular beam specimens was determined in flexure as a function of grinding orientation by using constant stress-rate testing in distilled water. Four different grinding orientations of 0, 30, 60 and 90° relative to the principal stress direction, were introduced to produce one possible flaw population (surface flaws) onto the uniaxial flexure beam specimens. The slow crack growth parameter, n=13, was found to be independent of grinding orientation. The dependency of inert strength on grinding orientations was consistent with that of fatigue strength for a given stress rate, indicating that a consistent rate of strength degradation from inert strength occurred at each orientation via slow crack growth occurred. The consistent SCG parameter n occurring in mixed mode conditions of 30 and 60° grinding orientations implies that the contribution of mixed-mode slow crack growth was minimal and that most of the major crack growth would take place under mode I condition. The CARES/Life reliability analysis indicated that best correlation to experimental data was achieved for highly aligned and highly shear sensitive flaws.