FATIGUE CURVES FOR ANNEALED AND NORMALIZED AND TEMPERED 2.25CR.-1MO. STEEL

摘要

Fatigue failure data from the literature have been complied on 2.25CR.-1MO. steal in this report. The data covers the temperature range of 80F-1100℉ (26.7C-S93°C). An average failure curve was developed at temperature where data were available. The annealed and normalized and tempered fatigue failure data was reduced to a common strength base with the aid of an analytical stress versus strain equation to determine the elastic and plastic strain ranges from the average total strain ranges at each temperature. For the 2.25CR.-1MO. steal regardless of initial strength Level, very little difference was found in low cycle fatigue strength. The present practice used by the ASME Subgroup on Fatigue of the ASME Boiler and Pressure Vessel Code was used to develop Fatigue Design Curves. A reduction factor of 20 was applied to failure cycles on the plastic strain range curves to determine the plastic strain ranges and a reduction factor of 2 on the failure elastic strain range curves to determine the elastic strain ranges. At each cycle the design curve is the sum of the calculated plastic and elastic strain ranges. For this material the use of elastic stress analysis at 850℉ (454°C) is dependent on the magnitude of the primary stress (S{sub}m) used for design. At the higher allowable primary stresses there is sufficient creep strain to decrease fatigue Life.