Static fatigue in glass — A reappraisal

The delayed failure of soda-lime glass was tested after different surface and heat treatments and at different humidities. It was found that the treatment history of the glass strongly influenced the characteristics times of failure and the effect of humidity on these times. However, the functional dependence of log failure time on relative stress was similar for most treatments. Analysis of the distributions of failure times at particular stresses showed that the log failure time was not linear with applied stress, as often assumed. The experimental data fit better inverse proportionality between log time and relative stress. Analysis of previous data on crack propagation (‘K - ν curves’) in glass also showed this proportionality. Some theoretical reasons for these results are examined.