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PRCI PR-15-819
- Effect of Weldment Property Variations on the Behavior of Line Pipe
- Report / Survey by Pipeline Research Council International, 01/01/1993
- Publisher: PRCI
$98.00$195.00
L51675e
Southwest Research Institute
Need: A steel weldment is a composite of zones or layers of different microstructures that possess different material properties. The zones include the base metal (or the sections of pipe), the weld metal, and a complex heat-affected zone (HAZ) of base metal that has been exposed to a variety of thermal cycles resulting in varying microstructures. The material properties of primary concern with respect to the mechanical behavior of the pipe are the stress-strain response (the constitutive properties) and the resistance to initiation and propagation of cracks or tears in the presence of a crack, notch, or other stress concentrator (the fracture toughness properties).
Result: Most of the experimental data on the behavior of welds with significant discontinuities were obtained from test specimens with surface or through-thickness notches or cracks. These data typically show an increase in load or nominal ductility for overmatched welds and a decrease in load or nominal ductility for undermatched welds. However, there are cases where the presence of a soft zone may enhance the nominal ductility and cases where overmatched welds will decrease the nominal ductility. The latter is especially likely in a girth weld with a circumferential crack in the HAZ.
Benefit: Finite element models of a section of line pipe, including different regions of the HAZ and weld metal of various strength (relative to base metal strength), were subjected to combinations of axial extension, pressure, bending and cyclic load. In addition, full-scale pipe sections with various strength welds were plastically deformed in axial tension.
Southwest Research Institute
Need: A steel weldment is a composite of zones or layers of different microstructures that possess different material properties. The zones include the base metal (or the sections of pipe), the weld metal, and a complex heat-affected zone (HAZ) of base metal that has been exposed to a variety of thermal cycles resulting in varying microstructures. The material properties of primary concern with respect to the mechanical behavior of the pipe are the stress-strain response (the constitutive properties) and the resistance to initiation and propagation of cracks or tears in the presence of a crack, notch, or other stress concentrator (the fracture toughness properties).
Result: Most of the experimental data on the behavior of welds with significant discontinuities were obtained from test specimens with surface or through-thickness notches or cracks. These data typically show an increase in load or nominal ductility for overmatched welds and a decrease in load or nominal ductility for undermatched welds. However, there are cases where the presence of a soft zone may enhance the nominal ductility and cases where overmatched welds will decrease the nominal ductility. The latter is especially likely in a girth weld with a circumferential crack in the HAZ.
Benefit: Finite element models of a section of line pipe, including different regions of the HAZ and weld metal of various strength (relative to base metal strength), were subjected to combinations of axial extension, pressure, bending and cyclic load. In addition, full-scale pipe sections with various strength welds were plastically deformed in axial tension.
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