FRACTURE TOUGHNESS, SURFACE FLAW SIZES AND FLAW DENSITIES IN Al_2O_3

摘要

Surface flaw sizes and flaw densities on polished dense polycrystalline alumina specimens with grain sizes G = 1.2,3.8 and 14.1 μm were measured using Hertzian indentation. Two surface finishes were studied: well-polished (Syton) and coarse-polished (45μm diamond paste). Flaw sizes and densities a high density of small flaws while coarse grained specimens exhibited a higher density of larger flaws. Fracture toughness (K_IC) for each material (relating to the propagation of flaws of a few μm depth) was Determined from the minimum fracture load in a series of Hertzian tests.