セラミックスの加工損傷の検出と曲げ強度

概要

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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 (3×4×36 mm) ground transversely with #600 and #140 grindstones, and round bars (φ4×36 mm) ground circumferentially with #600 and #325 grindstones. Bending strength was obtained by subjecting the specimens to a 4-point loading test (inner span 10 mm, outer span 30 mm). The examination revealed that the grinding damage to the specimens mentioned above was the creation of some cracks in the depth range of 4〜50 μm. The relation between the fracture stress σ_f and the equivalent crack length a_e is shown by an upward convex curve on logarithmic paper. The curves are expressed by eqn. Κ_<IC>=σ_f√<π(a_e+a_e0)> or eqn. Κ_<IC>=σ_f(a_e+γ)・√<π/{a_e+(γ/2)}> where Κ_<IC> is a fracture toughness value, a_<e0> is an equivalent latent crack length, and γ is a microstructure parameter. The experimental results correspond well to these equations by using 14〜15 μm as a_<e0> and 8〜9 μm as γ, which are about twice as large as the values for a natural pore defect.
社団法人日本材料学会の論文
1995-07-15