抄録
In recent years, the problems of the dynamic creep have become of increased interest with the use of alloys at high temperature. With a view to predicting the dynamic creep from the static creep data, the analysis based upon the strain hardening theory, was reported in the previous papers by the authors. In the papers, it was found that the analysis could be applied to the materials of relatively stable structure, that is, carbon steels, some ferritic and austenitic steels and commercially pure titanium. In the case of supper alloys of precipitation hardening type, however, considerable discrepancy was observed between the theory and the experiments, and this discrepancy seemed to result from the acceleration of precipitation hardening or the strain retardation due to alternating stress.
In the present paper, the dynamic creep tests to elucidate the effects of alternating stress frequency on the strain retardation have been carried out within the frequency range from 20 to 4000cpm.
In the experiments, for the higher frequency range from 800 to 4000cpm the alternating stress has been applied to a specimen by the centrifugal force of rotating eccentric mass as reported previously, and for the lower range of 20 and 80cpm the alternating stress has been applied by an eccentric disc and lever mechanism. In both cases, the application of sinusoidally alternating stress has been accurately attained.
The tests have been carried out with a low carbon steel at the temperature of 450°C.
It is found from the test results that, taking the stress amplitude and the mean stress as the same, the creep curves for the various alternating frequencies coincided approximately with the creep curve under the corresponding equivalent static stress analytically obtained.
