陶瓷材料断裂韧性与缺口半径　Ⅱ　断裂韧性估算方法

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

在陶瓷材料裂纹尖端存在一个断裂过程区，当断裂过程区内平均应力达到断裂强度时．裂纹扩展．本文由理论推导并结合实验数据．得到了断裂过程区的大小是平均晶粒直径的四倍．并由平均应力断裂模型，给出了陶瓷材料断裂韧性和缺口半径及平均晶粒直径之间的关系式，由此关系式可以用宽缺口试件测出的断裂韧性去估算陶瓷材料的本质断裂韧性．

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.