Residual stresses in strength-mismatched welds and implications on fracture behavior

The effects of weld strength mismatch on welding residual stresses were discussed based on a series of recent comprehensive studies. Two typical joint configurations were analyzed in detail: a butt-welded plate and a multi-pass girth weld. The butt-welded plate represents a severely under-matched weld, in which repair welding effects were also analyzed. For the girth weld, three weld strength levels were considered to investigate the weld strength mismatch effects on weld residual stress distributions. Fracture mechanics analysis was then performed for the multi-pass girth weld for a surface crack situated along the weld centerline. Welding-induced residual stress fields were assumed to be the dominant loading mode in all cases. With the dominance of welding-induced residual stress field, such as in some of the stress corrosion cracking cases experienced in the utility industry, stress intensity factors are shown to be an appropriate and convenient fracture mechanics parameter. The implications on ductile fracture behavior were also discussed in light of the results from this study. (C) 1999 Elsevier Science Ltd. All rights reserved.