高温純水中における炭素鋼の疲労寿命評価手法

概要

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It is well known that the fatigue life of carbon steel in oxygenated high-temperature pure water is much less than the fatigue life of carbon steel at room temperature in air when the applied strain rate is very low. The fatigue life of carbon steel was examined in order to develop an evaluation method. Cracks were found to initiate immediately after the fatigue test started in high-temperature pure water. The fatigue life was regarded to be the crack propagation life. The crack propagation rate was found to be constant against the fatigue life ratio, N/N_f. A time-domain evaluation method for fatigue crack growth rate was applied to evaluate the corrosion fatigue life. A time-based nominal crack growth rate was assumed as the reciprocal of time to failure by fatigue. The relationship between time-based nominal crack growth rates in high-temperature water and room temperature air was linear on a diagram of logarithms even when strain amplitudes and rates were changed. An environmental effect index, which was defined as the slope of this line, seemed to be influenced only by the environmental conditions. The newly developed evaluation method could successfully estimate the corrosion fatigue life of carbon steel in a high-temperature pure water environment.
社団法人日本機械学会の論文
1999-06-25