窒化けい素の高温静疲労強度に及ぼす欠陥寸法の影響

概要

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Static-fatigue crack behavior for different sizes of artificial flaws in sintered silicon nitride was measured at elevated temperatures. The growth process of cracks consists of three stages. In the first stage, the crack shows a rapid growth, but the growth rate decreases in the second stage. In the third stage, the growth rate increases again and the material begins to fracture under high applied stresses, otherwise, the growth rate continues to decrease under low stresses. Consequently, a static-fatigue limit, below which cracks are arrested, exists for each condition. The effect of crack size on the static fatigue limit show a similar tendency as that for short time strength. That is, the threshold stress intensity for cracks smaller than 200μm becomes lower than that for large cracks. Furthermore, interpretation using the Larson-Miller parameter can be applied to the results with fractured specimens, but it does not hold for the results with specimens reaching the static-fatigue limit.
社団法人日本機械学会の論文
1987-08-25