Finite element analysis and life modeling of a notched superalloy under thermal mechanical fatigue loading

Notched thermal mechanical fatigue (TMF) of a directionally solidified (DS) superalloy applied for turbine blades has been studied experimentally and numerically. The test results, failure analysis, constitutive model and life prediction method of the notched superalloy were presented. Two types of notched specimens with the theory stress concentration (Kt) of 1.5 and 2 were designed. The temperature applied to the specimens ranged from 500 to 1000 °C. With a developed constitutive model for TMF, the cyclic stress and strain responses at the notches were analyzed. The dominated damage area which was defined as 1 mm zone was identified with the basis of the scanning electron microscope (SEM) observations as well as the finite element analysis results. Finally, an averaged stress based life model corresponding to the damage process zone was proposed with good accuracy to prediction TMF lives with or without notches.