常圧焼結窒化ケイ素の高温繰返し荷重下におけるき裂進展挙動 : 応力比の影響

概要

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Crack propagation tests of sintered silicon nitrode were carried out under sinusoidal cyclic load at elevated temperatures. The stress ratios used were 0.5 and 0.1, while the test temperature ranged from 1073K to 1273K. The main results obtained are as follows : (1) Although the crack propagation rate with R=0.1 was higher than that with R=0.5 at 1073K, this tendency faded out at 1223K. (2) The crack propagation rate at R=0.5 increased with temperature, while that at R=0.1 did not change with temperature. (3) When the maximum stress intensity factor K_<I max> decreased stepwise with R=0.1, the crack propagation rate decreased gradually, although K_<I max> increased with crack length at each K_<I max> revel. (4) Slight oxidation started at 1073K. The grain boundary glassy phase softened at 1173K and Si_3N_4 crystal was attacked severely by oxygen in the atmosphere at 1273K.
社団法人日本材料学会の論文
1992-12-15