Paper Title
Determination of True Fracture Toughness of Polycrystalline Advanced Ceramics at a Range of Loading Rates
Abstract
Polycrystalline advanced ceramics represent synthetic product constituted of hard carbide or other tough material
particles bonded together by a metallic binder. Superior wear and corrosion resistance, high temperature stability, low thermal
expansion and many more extreme properties give significance to these materials for their use in ferrous materials machining
and industrial applications such as construction and mining, automotive and agriculture, oil and gas drilling etc. Behaviour of
these materials is of extreme importance considering the nature and costs of these materials, in order to be able to prevent their
fracture in operation. At present, their fracture properties data are quite scarce in the literature. Fracture of polycrystalline
advanced ceramics in mode I loading across the range of loading rates was studied using notched three point bending
specimens with two different average grain size and the predictions of the linear elastic fracture mechanics theory. Dependency
on the notch root radius was analysed experimentally obtaining apparent and true fracture toughness as well as their
interdependence. This dependency was confirmed analytically using predictions by the theory of critical distances. The
resulting true fracture toughness showed certain deviation to apparent fracture toughness, which is more pronounced for
smaller grain size compacts.
Index Terms - Fracture toughness, Notch root radius dependency, Polycrystalline advanced ceramics, Theory of critical
distances