Fracture mechanics characterization of crack growth under creep and fatigue conditions
Final Report. COST 501-Project D 10.
Safety analysis and the lifetime prediction of high-temperature components with defects have to take creep crack growth into account. The unavoidable stress concentrations and large stress gradients in real structures cause a highly localized accumulation of damage. Macroscopic crack growth takes place with damage almost absent elsewhere in the structure. Based on theoretical considerations and experimental evidence, several concepts have been investigated to correlate crack growth under high-temperature conditions with material parameters of fracture mechanics, e.g., stress-intensity factor K, and, line integrals J and C. It could be shown for different materials that these parameters describe the behavior of cracks independent of geometry and loading conditions within certain limits of validity. The laboratory results then can be transferred to real structures for (residual) lifetime predictions or safety analyses. Numerical simulations of experiments and, in particular, of structura l parts are essential for the understanding of crack-tip deformation behavior. Theoretical and numerical tools can be used to derive approximate and simple formulae which, in turn, then can be used to calculate loading parameters.