INDENTATION PRECRACKING OF Y-TZP - IMPLICATIONS TO R-CURVES AND STRENGTH

Fracture resistance curves generated with indentation cracks and semie lliptical surface cracks which are free of precracking effects are com pared. The differences are related to the presence of an uncracked lig ament at the center of the indent induced by the inelastic zone. The r ole of crack shape on the R-curve behavior is also studied experimenta lly with through-thickness and semielliptical surface cracks. The R-cu rves and crack growth thresholds obtained with semielliptical cracks a re correlated with failure strength and life limits measured with smoo th (uncracked) specimens. (C) 1998 Elsevier Science S.A. All rights re served.