Fracture Toughness of Ceramics and Notch Radius II Fracture Toughness Predicting Method

Because of the technical diffculty to create an ideal plannar crack with zcro root radius, macronotchedspecimen are of ten prepared for testing the fracture toughness of ceramics. In this paper, the quantitativeexpression of fracture toughness of ceramics and notch radius was investigated. Based on the theory thatthere exists a fracturc proccss zone in front of crack tip and average stress fracture model, a relationbetween fracture toughness and notch radius was derived, with this relation, the fracture toughness ofceramics can be predicted from tested value of macronotched specimens. Combined the fracture processzone with the experiment results from the available literature, it is showed that the scale of fracture processzone is four times of average grain diameter. Compared with the experimental results, we have a conclusionthat when the notch radius reach to the average grain diametcr, the tested results can yield the true valueKIc under 6% deviation.