GIGA-CYCLE FATIGUE STRENGTH OF TYPE STBA 24 STEEL USING AN ULTRASONIC FATIGUE TESTING MACHINE

摘要

This study carried out very high cycle fatigue tests using type STBA 24, the steel for tube in boiler and heat exchanger, at room and elevated (673K) temperatures by a developed ultrasonic fatigue testing and conventional hydraulic testing machines, and obtained the fatigue lives. This paper also described the cracks observed on specimen surface of fatigued specimen and discussed the very high cycle fatigue strength properties. It was confirmed that the fatigue data in the test by the ultrasonic fatigue testing machine are continuous and compatible with the results obtained by the hydraulic tension-compression testing machine. Fatigue lives more than 10~6 cycles at room and high temperatures can be predicted conservatively by the best fit fatigue design curve currently employed in the nuclear power plant design.