FRACTURE OF ALUMINA WITH CONTROLLED PORES

Fracture from artificial spherical pores, as well as natural defects, in alumina in a grain-size range of 0.8-9.2 mu m has been studied expe rimentally and compared with a fracture-mechanics model, Results from fracture-strength measurements have been combined with detailed fracto graphic analysis to elucidate the ensuing crack instability. Two exist ing models of possible crack configurations have been extended and con trasted. The semicircular crack as well as the circumferential crack b oth are described as flaws in the stress-concentrating field of a sphe rical pore. Surface correction terms afforded by the presence of the p ore have been incorporated. A comparative computation shows that fract ure occurs more likely from the semicircular crack configuration than the circumferential crack configuration.