On the fracture toughness of extrudates and its relationship to rates of bulk particle attrition

Abstract

In the course of systematic studies of the bulk attrition of three well-characterised cylindrical alumina extrudates of about 3 mm dia. and 3 mm length, a desirable goal was to relate the attrition to fundamental material parameters. From the standpoint of fracture mechanics, a logical basic parameter is K IC, the stress intensity factor at failure. The three grades of extrudate were also cast in the form of rectangular bars, which are particularly useful for obtaining K IC. However, the extrudates are brittle and porous, making it not possible to introduce a crack of known length into a specimen prior to testing. None the less, a recently developed method employing a chevron notch cut into the bars has been employed; three calculational techniques are deployed that yield consistent and logically related values of K IC . Utilisation of the values of K IC for unification of attrition data was not entirely successful, better correlation being achieved by use of estimates of the material tensile failure stress probably because the flaw structures of the three extrudates are not the same. It remains logical that the parameters K IC and flaw size are important variables for attrition and these can be usefully considered independently.