Abstract
In order to find the mechanism of fatigue, it is very important to investigate the change of stress-strain relation during the fatigue process. During the past several years, the author performed a series of studies on the fatigue under the low-cycle rotating-beam bending and summarized their results. In the present report, the results of the studies are given in outlines concerning the effects of various tests conditions on the stress-strain relation and the criterion of fatigue failure. From the measurements of strain amplitude in their change in several kinds of metallic materials during the fatigue tests of the constant stress amplitude, the difference is indicated in fatigue hardening (or fatigue softening) among the materials, and the dependency of fatigue hardening (or fatigue softening) on the time rate is evaluated. Its relation to strain hardening is also discussed.
