Abstract
To accomplish the safety analysis and to predict the lifetime of high-temperature components with flaws, several concepts have been proposed to correlate creepcrack initiation and growth with fracture mechanics parameters. The concepts of stress-intensity factor K, reference stress o sub ref, line integral C *, and others will be discussed. Among them, the C *-integral concept seems to have the widest range of applicability, if large creep zones develop and steady state creep conditions can be assumed. The numerical evaluation of C * by the virtual crack extension method is described. The methods are demonstrated by two- and three-dimensional finite element simulations including creep crack growth. As for ductile fracture experiments, plane stress and plane strain simulations are bounds to the three-dimensional simulations which agree well with corresponding experiments.