DETERMINATION OF SHORT-CRACK TOUGHNESS CURVES

Measurements of indentation crack length vs applied bend stress mere u sed to develop a new method of analysis for determining short-crack to ughness curves. Three glass-ceramics and a polycrystalline alumina wer e used as prototype test materials. Crack-shape effects mere incorpora ted into the analysis. The magnitude of the residual-stress factor can be determined independently from the experimental data using the meth odology. In contrast to other test methods using indentation precracks , calibration constants or reference materials are not required for ob taining absolute values of the toughness, Good agreement with conventi onal toughness values reported for the long-crack limit mas obtained f or the different materials tested.