窒化ケイ素系セラミックスのR曲線及び疲労き裂成長挙動

概要

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The R-curve and fatigue behavior were investigated for two kinds of silicon nitride with different microstructures. In these materials the toughening exponents determined by the indentation-strength-in-bending method are almost zero. Moreover, the values of fracture toughness obtained by the indentation crack size measurement and the single-edge-precracked-beam method are the same. Therefore, it is concluded that these materials show flat R-curves. On the other hand, it is found that a considerable cyclic-fatigue effect, distinct from static fatigue, exists in these materials. Cyclic-fatigue crack growth rates are higher in small grained silicon nitride than in large grained one. When the crack growth behavior is represented by a power law relationship including two terms of the stress intensity range ⊿K and the maximum stress intensity K_max ; i. e. da/dN=C(K_max)^p(⊿K)^q, significant differences in the values of the exponent p and q between these materials are not recognized. On the basis of the above results and other data available, the factors affecting the cyclic-fatigue behavior and cyclic fatigue mechanisms are discussed.
社団法人日本セラミックス協会の論文
1995-07-01