常圧焼結窒化ケイ素の引張試験と強度に及ぼす空孔等製造欠陥の影響(<小特集>セラミック材料小特集)

概要

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Tensile tests were carried out on sintered Si_3N_4 at room temperature under the ambient condition, and the influence of defects upon the fracture stress was discussed. As the surface of specimens was prepared carefully, fracture of 57 specimens out of 60 originated from the defects such as voids or inclusions which resulted from the sintering process. As a parameter to describe the size of the defect, √<area> was used which is the square root of the area of a 3-dimensional defect projected to the direction of the maximum principal stress. The results obtained are as follows. (1) √<area> of defects which caused fracture nearly conforms to the first asymptotic distribution of the largest value and the fracture strength conforms to Weibull distribution. (2) √<area> is a good parameter to describe the size of the defect from the standpoint of fracture. (3) Defects such as voids and inclusions act exactly as cracks of the same size. (4) The fracture strength can be estimated by using the distribution of √<area>, the fracture toughness and the mean grain size of Si_3N_4.
社団法人日本材料学会の論文
1989-01-15