<p>The girth-weld pipes with unequal wall thickness transition joints result in the misalignment of geometry, the mismatched welding and heat-affected zone (HAZ) softening prompt inhomogeneity of material in the local area of girth weld. The misalignment of geometry and inhomogeneity of material are the main causes of local strain concentration in the girth weld, which greatly increases the possibility of crack initiation and propagation. In this paper, the finite element models of the girth-welded pipe with cracks on the fusion line have been accurately constructed, referring to the crack size and location of the actual accident pipe. The influences such as the ratio of unequal wall thicknesses, mismatched of welding, softening of HAZ and size of crack on the local strain concentrations and the driving force curves under combined load conditions such as tensile load, bending load and internal pressure have been studied. The strain responses under three matching modes of under-match, even match and over-match have been analyzed, and the effects of the ratio of unequal wall thicknesses, HAZ softening and crack size on strain capacity have been quantitatively discussed. The results show that the effect of the ratio of unequal wall thicknesses and mismatched of welding on the strain capacity of girth-weld pipes cannot be ignored. The application of unequal wall thicknesses and low matching welding in the girth-weld pipes in engineering should be avoided or reduced.</p>

Numerical Study on the Strain Capacity of Girth-Weld Pipes With Unequal Wall Thickness Transition Joints

Paper Proceedings: https://asmedigitalcollection.asme.org/PVP/PVP2021/volume/85314

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