SEDL / STP / STP942-EB / STP24501S

Application of the Overstress Concept for Creep-Fatigue Evaluation

Morishita, M
Oh-arai Engineering Center, Ibaragi,

Taguchi, K
Toshiba Corporation, Nuclear Engineering Laboratories, Kawasaki,

Asayama, T
Graduate Student, Research Fellow, and Professor, University of Tokyo, Tokyo,

Ishikawa, A
Graduate Student, Research Fellow, and Professor, University of Tokyo, Tokyo,

Asada, Y
Graduate Student, Research Fellow, and Professor, University of Tokyo, Tokyo,

Pages: 13    Published: Jan 1988

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Abstract

Type 304 stainless steel was subjected to a controlled push-pull strain with a wide variety of waveforms at 650°C in 0.1 μPa vacuum. No indication of oxidation was observed in the specimens. The frequency effect on creep-fatigue behavior was diminished, but the tensile hold time and waveshape effects were still observed in this high vacuum environment. It was concluded that a reduction of fatigue life due to creep-fatigue interaction is observed when a tension going time exceeds a compression going time. A back stress was determined from the data, and an overstress was defined as the difference between an applied stress and a back stress. The overstress was related to the inelastic strain rate. It is shown that overstress can be reasonably used to describe the creep-fatigue damages for life prediction.