Effects of Notch Root Radius on Both Crack Initiation Sites and Fracture Toughness of Al₂O₃

Abstract

Fracture toughness of fine ceramics depends on notch root radius, crack length and grain size. In this study, fracture toughness tests using three-point bend specimens of HP sintered alumina with a notch were carried out to studied the effects of notch root radius on fracture toughness and crack initiaiton sites. The notch root radius was varied in size ranging from 0.02mm to 1.0mm. The tests were also conducted at room temperature and high temperature (1000°C) to examined the influence of temperature. The results were discussed based on the process zone size fracture criterion. The relationships between notch root radius and fracture toughness measured at both room temperature and high temperature were in good agreement with the theoretical relations deduced from the criterion. Most of crack initiation sites were observed in the vicinity of the notch front.