210 高温下における窒化けい素のき裂進展抵抗上昇に及ぼす負の応力比の影響

概要

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The stress shielding effect in silicon nitride plays an important role on the improvement of crack growth resistance. In this study, the effect of compressive loading on stress shielding and cyclic fatigue crack growth behavior at elevated temperature was investigated. In order to clarify the crack growth mechanism at the vicinity of a crack tip, cyclic fatigue tests of silicon nitride at elevated temperature (1273K) under various stress ratios including negative stress part were conducted. As a result, crack growth rate at elevated temperature was found to be lower than that at room temperature. Especially under high compressive loading, crack growth rate was extremely lower than the crack growth rate under the positive stress ratio. It may be caused by the healing of process zone under the negative stress ratio at elevated temperature.
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