抄録
Grinding damage of ceramics was observed on sialon by the Pd pregnation method. The procedure of the method is spreading of Pd solution, loading up to 1/3 of fracture load, drying, fracturing and analyzing of the fracture surface by EPMA. The specimens mainly used were rectangular bars (3×4×36mm) ground transversely with #600 and #140 grindstones, and round bars (φ4×36mm) ground circumferentially with #600 and #325 grindstones. Bending strength was obtained by subjecting the specimens to a 4-point loading test (inner span 10mm, outer span 30mm). The examination revealed that the grinding damage to the specimens mentioned above was the creation of some cracks in the depth range of 4-50μm. The relation between the fracture stress σf and the equivalent crack length ae is shown by an upward convex curve on logarithmic paper. The curves are expressed by eqn. KIC=σf√π(ae+ae0) or eqn. KIC=σf(ae+r)·√π/{ae+(r/2)}, where KIC is a fracture toughness value, ae0 is an equivalent latent crack length, and r is a microstructure parameter. The experimental results correspond well to these equations by using 14-15μm as ae0 and 8-9μm as r, which are about twice as large as the values for a natural pore defect.
