Subcritical Crack Growth Characteristics of Soda-Lime Glass Evaluated from CT Specimen and Bend Specimen with Small Indented Crack

Abstract

For comparing crack growth characteristics, subcritical crack growth data for soda-lime glass subjected to sustained load in water were obtained using conventional CT specimens with long crack and bend specimens with small Knoop indented crack. The relation between crack velocity V and stress intensity factor KI obtained from as-indented specimens containing indentation crack shows that there is residual stress effect which increases crack growth in the region of lower KI values. In addition, the slopes of the V-KI curves for the as-indented specimens are much less than those for the CT specimens. However, the V-KI curve for the indented and subsequently annealed specimen shows almost the same trend as that for the CT specimens. Thus, the effective stress intensity factor KIeff including the residual stress effect can be used to explain the anomalous growth of the indentation crack in its as-indented state.