Indentation precracking of Y-TZP: implications to R-curves and strength

Fracture resistance curves generated with indentation cracks and semielliptical surface cracks which are free of precracking effects are compared. The differences are related to the presence of an uncracked ligament at the center of the indent induced by the inelastic zone. The role of crack shape on the R-curve behavior is also studied experimentally with through-thickness and semielliptical surface cracks. The R-curves and crack growth thresholds obtained with semielliptical cracks are correlated with failure strength and life limits measured with smooth (uncracked) specimens.