Ductile fracture mechanical analyses of large scale thermal shock experiments

Abstract

Large scale thermal shock tests of Oak Ridge National Laboratory (ORNL), Staatliche Materialprüfungsanstalt Stuttgart (MPA) and Heissdampfreaktor (HDR) have been analysed by pre- and postcalculations with the finite element program ADINA extended by fracture mechanical options based on the J- integral . The results show that temperatures, displacements, strains and stresses can be approximated well. Due to the well-known geometry dependence of specimens' crack resistance in some cases a satisfactory assessment of the crack behaviour can only be obtained by extension of the one-parametric J- integral concept, e.g. with determination of the stress triaxiality in a region in front of the crack tip. Furthermore the influence of residual stresses due to repeated loading of a cracked vessel with plastification at the crack tip seems to be important in fracture assessment.