1991 Volume 31 Issue 9 Pages 1001-1006
Isothermal long term creep-fatigue tests and combined temperature-strain cycling tests were conducted with the newly developed testing machines suitable for long term running. The aim of these tests was to establish a more reliable method for the life prediction of structural components subjected to complex stress-strain histories due to load-temperature variations. Three heats of 1Cr-Mo-V forged steels widely adapted for steam turbine rotors were sampled and the differences of creep-fatigue properties due to technological evolution of steel making were examined. The two heats were produced in the 1960s and the one in the 1980s. The results were analyzed by the life prediction method proposed by the present authors, which was characterized by a quantitative description of the materials degradation with time based on the creep rupture ductility.