欠陥寸法の確率分布と微視き裂進展挙動を考慮した常圧焼結窒化ケイ素の疲労寿命シミュレーション

概要

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In this study, a computer simulation taking into account the defects size distribution and the micro-crack propagation behavior was conducted by using virtual bending specimens. The defects size distributions in the virtual specimens were estimated by using a Monte-Calro technique based on a large number of defects diameter (approximately 72000) measured on the Si3N4 specimen surface. The effects of two types of scatter－one is defects diameter, the other is micro-crack propagation rate－on fatigue lives were estimated separately. It is proved that the scatter of fatigue life mainly originated from the scatter of defect size. For the cases of the simulation using micro-crack propagation behavior, estimated fatigue lives were always shorter than that of using long-crack propagation behavior. Recognizing simulated fatigue lives Nf as crack propagation lives Np, we can define a crack initiation life Ni. As the applied stress decreases, estimated value of Ni/Nf increases. It is remarkable that this tendency shows a good agreement with the experimantal value of Ni/Nf. It is concluded a crack initiation life and its scatter are very important to discuss the fatigue lives in ceramic materials.
日本材料学会の論文