An Analysis of a Crack in Weld by Using Near-Field as Well as Far-Field Crack Parameters

Abstract

A study of ductile crack growth characteristics in stainless steel welds is reported in this paper. A hybrid-type analysis of combined experimental, analytical, and predictive procedures on the subject is addressed. The study focuses on the effects of a stress/strain interaction phenomenon occurring between the crack tip and the weld-base material interface. Clear dependence of the crack initiation fracture characteristics on the weld size relative to the specimen size was found. Also, fracture toughness of a tungsten inert gas weld is shown to be comparable to that for the base stainless steel metal, whereas that of a submerged arc weld is shown to be significantly lower than the base metal. Because of the stress/strain nonproportionality associated with a local unloading due to crack growth in a ductile material, the use of a crack-tip parameter such as ΔTP* or Jˆ-integral was emphasized. On the other hand, prediction of a crack instability was attempted using a less rigorous J-estimation scheme procedure.