J-integral and local damage fracture analyses for a pump casing containinglarge weld repairs

Three-dimensional J-integral and two-dimensional Local Approach finite elem ent studies are described for postulated crack-like defects in a large repa ir weld to the casing of a light water reactor circulation pump. The repair weld residual stress field is simulated and plant operating pressure and t hermal transient loads are applied. Crack tip constraint effects are quanti fied through detailed analysis of the cracked structure and compact tension fracture toughness specimens. Fracture initiation crack sizes are shown to be larger than conceivable fabrication defects that are detectable using m odern ultrasonic inspection techniques. The Local Approach study demonstrat es the benefits of quantifying crack tip constraint conditions, compared wi th conventional J-estimation schemes and cracked body J-integral analysis. The method of introducing the crack into the finite element model is shown to have a large effect on calculated crack tip fracture parameters; a slowl y developing crack in the residual stress field being more benign. (C) 2001 Elsevier Science Ltd. All rights reserved.