Characterization of creep fracture for weld fusion line cracks

Abstract

Long-term service cracking problems of the most high temperature components occur mainly at welded locations. These cracks are formed due to accumulated creep damage near fusion lines or at heat affected zones(HAZ) of the weld. In this study, creep crack growth test conditions with a crack along the weld fusion line are simulated by the finite element method. Since a new C-t-estimation scheme for a weld fusion line crack is required for characterizing the experimental creep crack growth data, computational studies on the C-t parameter for the fusion line crack are carried out. In performing the finite element analysis, crack tip plasticity as well as secondary creep behavior of the materials are considered. The obtained C-t versus elapsed time curves for various material property combinations are normalized by a steady state C-t value, (C* for homogeneous specimen) and a transition time tr, respectively. After normalization a unique C-t versus time curve was obtained. Using this curve, a new C-t-estimation scheme for the weld fusion line crack is proposed.