構造用セラミックスの強度および破壊じん性評価モデルについて(<小特集>セラミック材料小特集)

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In order to elucidate the notch width or notch root radius dependence of the critical stress intensity factor evaluated by SENB (Single Edge Notched Beam) specimens, 4-point bending tests were carried out on hot-pressed SiC (with 2wt% AlN) and sintered Si_3N_4. The Experimental results showed that the critical stress intensity factor K_c determined with SENB specimens coincides with a valid fracture toughness K_<Ic>, value only when notch root radius ρ is smaller than about 10μm. For larger root radii, the variation of K_c with ρ was observed, and this can not be attributed only to the stress concentration effect of notch. In the present study, by introducing a micro-damage concept a method was proposed for evaluating K_<Ic> from K_c values given by SENB specimens having rather blunt notch. On the basis of the published strength data for SiC, the relation between strength and microstructure was examined. It was assumed that a micro-damage existed at the machine finished surface, and its size should be the sum of the machined damage depth h_<max>, and the maximum grain diameter d_<max>. Here, h_<max> can be estimated from the average grit size of the diamond disk used. Ananalysis was made of the dependence of K_c on ρ by considering the micro-damage at the notch root, and a theoretical expression was formulated. The experimentally observed K_c-ρ relation agreed quite well with the theoretical prediction.
社団法人日本材料学会の論文
1986-01-15

構造用セラミックスの強度および破壊じん性評価モデルについて(<小特集>セラミック材料小特集)

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