Thermal Healing of Realistic Flaws in Glass.

For any given environmental conditions the tensile strength of glass is a function of the geometry of the critical flaw and the residual stresses in the vicinity of the flaw. The strength of heat treated glass is conventionally considered to be equal to the sum total of the residual stress and the extrinsic strength of annealed glass. Recent experiments suggest that there is an additional contribution to strength attributable to crack healing. To quantify it, uniaxial and equibiaxial strength tests on both as-received and carefully annealed glass specimens were performed for different edge geometries and edge finishes. The results show that strength recovery attributable to healing is significant, and this strength gain appears to correlate with the quality of the edge finish. Possible explanations of this phenomenon are provided. Independently of healing effects, it was also found that the edge quality has a marginal effect on the mean strength but has a significant positive effect at low fractile values often used in design applications. [ABSTRACT FROM AUTHOR]