複合損傷シミュレーション解析による Co 基超合金の高温低サイクル疲労寿命評価

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A life assessment method is proposed for severely damaged components such as heavy-duty gas turbine nozzles. The method named "Multi-factor damage simulation analysis" is introduced as a sort of inverse problem analysis for actual complex damage phenomena influenced by temperature-stress distribution, microstructural inhomogeneity, environment, interaction of multiple cracks, and so on. The microstructural inhomogeneity model of Co-base nozzle superalloy FSX414 is constructed by using fractal geometry of random percolation cluster model. Multiple crack intiation and growth simulation is performed with a probabilistic damage parameter which is defined as the transition probability of crack initiation and growth in the form of monotonically increasing function of cycle. This method was applied for high temperature low cycle fatigure testing of FSX414 at 923K, 1023K, 1123K and 1223K by assigning relatively simple values for resistance R and driving force F. Arrhenius type temperature dependence was postulated for resistance R by taking account of the experimental results. The crack morphology obtained by the simulation and the crack length distribution were quite similar to the observation results of the failed low cycle fatigue specimen surface. Moreover, the temperature dependence of the rate of life expenditure (1/N_<25>) coincided with the experimental results. Therefore, it is concluded that this method is a promising way to estimate the life of severely damaged component under complex situations.
1992-12-15

複合損傷シミュレーション解析による Co 基超合金の高温低サイクル疲労寿命評価

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