Fatigue and Fracture-Toughness Characterization of SAW and SMA A537 Class I Ship-Steel Weldments

摘要

A study was conducted to assess the use of various toughness tests and criteria to predict the fracture behavior of weldments containing a low-toughness heat affected zone. Natural fatigue cracks were initiated and propagated to various sizes in 1-inch A537 Class I steel submerged-arc-welded (SAW) and shielded-metal-arc (SMA) butt-welded Tee joints having various weld reinforcement heights (surface cracked specimens). The most severe service temperature and loading rate of secondary containment shells for LNG ships was duplicated by testing the surface cracked specimens at -60 deg F at loading times of about a second. Fracture mechanics procedures and existing empirical correlations among tests were used to interpret the data. The fatigue crack initiation and propagation behavior observed during preparation of these specimens was consistent with published data. Fatigue crack initiation data were obtained at -60 def F. Elastic plastic behavior was observed in 15 out of 16 tests of the surface cracked weldments. The brittle fracture observed in the one test was analyzed and predicted from the lowest values of all the fracture toughness tests except for the KIc (3 point bend) test. Discussions and recommendations are given for assessing toughness results of weldments having a low-toughness zone 'masked' by adjacent high-toughness regions. (Author)