Discussion of several life prediction methods for fatigue-creep interaction

摘要

Life prediction methods for fatigue-creep interactions are briefly reviewed. In particular, the approaches based on energy exhaustion, toughness exhaustion and ductility exhaustion are discussed respectively. The merits and demerits and applicable ranges of the above three models are evaluated using the data from literatures and tests of stress controlled fatigue-creep interaction for 1.25Cr0.5Mo steel at 520°C. The prediction accuracies of these three methods are all better than those of conventional frequency separation technique and strain energy frequency separation technique. Moreover, the energy model is applicable to both stress and strain control mode, the ductility exhaustion model has the highest prediction accuracy, and the mean strain rate model has the simplest form and is applicable to various combination modes of pure creep, pure fatigue or fatigue-creep interaction under stress control, thus widens the application scope of Monkman-Grant empirical equation, and has significant engineering application value and application prospect. At the end of this paper, the application steps of mean strain rate model are described.