Fractographic Investigation of Subcritical Crack Growth at Inherent Flaws in Polycrystalline Ceramics.

摘要

Variations in intergranular and transgranular fracture along radii extending from fracture origins in hot pressed (H.P.) alumina, 96% alumina and H.P. silicon nitride were studied. The percent intergranular fracture (PIF) was plotted versus stress intensity factor (K sub I) for various distances from the fracture origins assuming smooth crack fronts and the absence of localized stresses. The observed variations were analyzed in relation to single crystal and polycrystal K sub IC values. The results were used to suggest fractographic criteria for subcritical crack growth boundaries in these materials. (Author)