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This report is the result of a research program on creep-fatigue damage conducted under a Grant from PVRC on engineering materials such as 316 stainless steel. The main objective of the program is to analyze, evaluate and develop a model for creep-fatigue interaction under uniaxial and biaxial stress/strain cycling at elevated temperature. The biaxial loading was torsion coupled with axial loading with 30 minutes hold-time to generate the creep effect. Data was obtained from fatigue-creep tests conducted at 1150F (620C). Based on test data and in-depth macro-micro analysis, a model which accounts for uniaxial creep damage is developed on the basis of ductility-exhaustion concept. A comparison is made between the proposed ductility-exhaustion model and the time fraction rule. The proposed model shows a better and more comprehensive prediction capability than the time fraction rule and was able to distinguish whether the failure is by creep or by low cycle fatigue.

For creep-fatigue damage under biaxial state of strain/stress cycling, the uniaxial proposed ductility damage concept was modified to account for the biaxial strain/stress effect.

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Published: 1995 Number of Pages: 43 File Size: 1 file , 2.9 MB