応力再配分軌跡(SRL)法による環状切欠き材(S20C)の低サイクル疲労・き裂発生寿命の推定

概要

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Stress redistribution locus (SRL) method has been proposed to provide a reasonable estimate of inelastic behavior under elevated temperatures employing both the elastic Finite Element (FE) analysis and a unique hyperbolic curve: ε={1/σ+(κ-1)σ}/κ, where ε and σ show dimensionless equivalent strain and stress normalized by elastic ones obtained in the elastic FE analysis. In order to investigate applicability of the SRL method for elastic-plastic components, low cycle fatigue tests were conducted employing a smooth and four kinds of circumferentially notched bars. The number of cycles to crack initiation was compared with the one estimated by the SRL method. When an adequate elastic region remained inside the notch root, the crack initiation life could be well predicted by the SRL method. However when a ratio of the plastic area in the notch root section occupied over about 0.3, the equivalent strain range on the surface of the notch root calculated by the SRL method became to be smaller than the one by the detailed inelastic FE analysis. On this occasion the crack initiation life calculated by the SRL method would be overestimated.
2010-05-25