Abstract
Strain-controlled creep-fatigue tests were carried out on smooth specimens of austenitic stainless steel SUS 316 L with the strain rate of ε=2×10-5/s in tension and ε=2×10-3/s in compression at 650°C in air. Replicas of the specimen surface were taken at a constant interval of strain cycles, and the lengths of all the cracks on the entire specimen surface (=628 mm2) were measured by means of image processing through the life. Based on statistics of extremes, the maximum crack length was estimated using the crack length data taken from the sample area of 16 mm2, and the estimated maximum length was compared with the measured maximum length. It was found that before initiation of crack coalescence, the estimated value was in good agreement with the measured value. Thus, the limit and usefulness of statistics of extremes in the estimation of the maximum fatigue crack length were shown.
