Indentation Behavior of Ion-Exchanged Glasses

Indentation fracture mechanics was extended to include the effect of a thin layer of residual stress on the identation strength of brittle materials. The proposed theory was used to predict the residual stress values for an ion-exchanged glass. For flaws placed before the exchange, considerable strengthening was observed, but the value of the surface stress predicted was considerably underestimated. For flaws placed after the exchange, there was no strengthening and the value of the surface stress was predicted to be zero. The failure of the indentation analysis indicates that it has to be modified for accurate stress determination. Thin layers of residual stress were found to retard the initiation of surface damage, but their influence on the strength after damage initiation was minimal.