Abstract
Dynamic creep and rupture tests were carried out with annealed specimens of a 0.15 percent carbon steel under the combined static and alternating stress with stress ratios (alternating stress/mean stress) of more than unity. The test temperature was 450°C. The results of the present study together with those obtained in the previous study for the stress ratios less than unity were analysed in the light of the authors'theory, which aims to relate the strength under dynamic stress to the static creep strength. The conclusion obtained is summarized as follows : 1. The forms of the dynamic creep curves are similar to those of the static creep curves even for the case of the stress ratio of more than unity. 2. The prediction of dynamic creep rupture strength from the static creep rupture data together with the fatigue data under reversed stress is established over the entire range of stress ratios from zero (static stress) to infinity (reversed stress). This is based on the idea that the damages of material under varying stress are composed both of the creep damage previously discussed and the fatigue damage caused by the dislocation oscillation under alternating stress. 3. The equivalent static stress, which was defined previously to predict the dynamic creep strength from the static creep data in the stage of transient creep, is applicable to the case of creep including the steady state component in addition to the transient component and also to the case of rupture. 4. The influence of the dislocation oscillation due to alternating stress on the dynamic creep was also discussed.
