EFFECT OF NOTCH-ROOT RADIUS ON THE FRACTURE TOUGHNESS OF A FINE-GRAINED ALUMINA

The dependence of K(IC) on the notch-root radius has been examined for a notch radius as small as a few micrometers in a dense, fine-grained, polycrystalline alumina ceramic. The notch radius can be systematically varied by using a semimanual procedure in a special jig which polishes out rather than cuts the specimen. K(IC) is independent of the notch sharpness for notch-root radii <10 MUm. The results are critically compared with those obtained by other standard techniques and discussed in terms of residual compressive stresses introduced during the notching procedure.