Accuracy of the predicting for creep-fatigue cyclic life based on parameters in a characteristic cycle

Abstract The purposes of the present work are to evaluate the prediction accuracy of characteristic cycle on creep-fatigue life prediction and to analyze the advantages and disadvantages of various models in tensile strain-dwell tests. The parameters of the first cycle, the 10% life, the half-life, and the characteristic cycle that we proposed (a turning point between the initial rapid softening and subsequent slight softening/hardening) are employed to linear-damage-summation (LDS) and energy-life prediction models based on the creep-fatigue data of directionally-solidified Nickel-based superalloy, DZ445, at 900 °C. It is found that the characteristic cycle parameters with clear physical significance have the highest life prediction accuracy. Moreover, the optimal critical value of fatigue and creep damage (the coordinate of the creep-fatigue envelope intersection) in the LDS is also determined. The prediction accuracy of creep damage based on the time-fraction, the simple ductility-exhaustion, and the strain-energy- density-exhaustion models is sequentially improved in the LDS rule. In the energy-life model, the life prediction accuracy based on damage mechanism and frequency correction is higher than the value without any correction. This investigation provides a new method of the parameter-selection for the creep-fatigue life prediction, which is accurate and convenient. It provides the theoretical-guidance for creep-fatigue life prediction in both laboratory experiment and actual components.