RELATIONSHIP BETWEEN TEMPERATURE PROPERTY AND LOADING FREQUENCY OF ROTATING BENDING FATIGUE TESTING MACHINE OF CANTILEVER TYPE

摘要

Fatigue property in gigacycle regime is focused as an important subject in recent years. In such a long-life region, a tremendous long period is required to perform the tests. To overcome this difficulty, a part of authors has been developing the new rotating bending fatigue testing machine, which enables to reduce the test period and cost drastically. It was confirmed that the fatigue test dates are consistent with many experimental results obtained by hydraulic tension and compression fatigue testing machines and the rotating bending fatigue test machines of both-handed type known as Ono type. Although it prefers to reduce the fatigue test period as short as possible, the maximum frequency of a rotating bending fatigue test is limited by the standards because of the possibility of local temperature rise in specimen caused by the cyclic plastic work and the heat transfer from fatigue testing machine. Such local temperature rise might affect the fatigue property. However, the appropriate loading frequency limit is unclear because of the difficulty of the temperature measurement in the fracture portion of a specimen precisely during the rotating bending fatigue test. An in-situ temperature measuring technique is proposed to measure the temperature at the fracture portion of the specimen in real time during the fatigue testing, and the validity to determine the loading frequency of a rotating bending fatigue testing machine is discussed in this study.