PRCI PR-140-406

L51489e

Welding Institute of Canada

Need: Many pipeline codes have introduced, or are about to introduce, alternative acceptance criteria for defects. Most of these alternative acceptance criteria are based on a CTOD toughness approach and many have been validated using full-scale tests. These approaches have been shown to be conservative using well-aligned pipe tests. It has been shown, however, that the likelihood of producing defects in a girth weld is considerably increased when misalignment is present. In this case, it is not known whether misalignment would reduce the level of conservatism in the proposed engineering critical analyses.

Result: This present program has used finite element analyses and full-scale tests to evaluate the effect of misalignment on fracture. The finite element calculations were performed using two- and three-dimensional analyses. The elastic analysis showed that predicted J increased with increasing misalignment and crack depth. This normally would not be a problem as pipelines usually operate well above their transition temperature and do not use low toughness weldments. The elastic-plastic finite element analysis predicted little effect of misalignment on strain to initiate tearing because of the high Jll required. This result was confirmed by the three complementary full-scale fracture tests performed.

Benefit: The analysis of the fracture tests showed that the previous models proposed for fracture were valid when misalignment was present provided very low toughness weldments were not used.

Product Details

Published:

08/01/1985

Number of Pages:

114

File Size:

1 file , 1.2 MB