Abstract
Creep rupture tests under interrupted loading were carried out with a low carbon steel at a temperature of 450°C. The load was applied once a day for the period of one tenth of rupture under continuous loading. Transient increase of creep rate was observed at the beginning of every loading interval through all stages (the 1st, 2nd and 3rd stages) of creep. As the results of this increase of strain rate, the rupture life under the interrupted loading was somewhat less than under the continuous loading, although the difference is practically negligible except when it is under high stress level. The increase of creep rate seems to result from the softening of the material during the unloading interval rather than recovery.
