Tensile Properties of Cold Bends for Line Pipes

Abstract

To comprehensively investigate the tensile properties of cold bends, full-scale cold bending experiments, tensile tests using prestrained small-scale specimens, and finite element (FE) analyses of the cold bending processes were conducted on API 5L X60 and X80 grade line pipes. The tensile tests revealed that the tensile properties of the cold bends were comparable to the uniaxially prestrained specimens machined from the straight part of the pipes. A FE model simulating the cold bending process was verified with the full-scale experimental results in terms of the distributions of residual strains. These results supported a procedure for estimating the tensile properties of the cold bends with a combination of the FE model and the tensile tests using the prestrained specimens; the residual strains obtained from the FE model are transformed into the tensile properties based on the relationship between the residual strains and the tensile properties. This study clarified that the tensile properties come close to being uniformly distributed by reducing the distance between the bending locations; the distance between the bending locations has a significant influence on the overlap of adjacent deformed areas, which governs the distribution of the tensile properties of the cold bends.

The effect of hot bending and thermal ageing on creep and microstructure evolution in thick-walled P92 steel pipe

“…By contrast, a very limited knowledge has been established about the changes in the creep strength and high-temperature behaviour of hot bent thick-walled pipes [13][14][15][16][17][18]. The common basic topics in the analyses of bending characteristics have been addressed such as wrinkling instability, over thinning, cross-section deformation and springback phenomenon.…”

“…The tungsten-modified 9%Cr steel P92 (ASTM Grade P92) was introduced in plants in 2001 [3]. Much effort has been applied to investigating the effects of cold bending on thin-walled pipes for line pipe applications [12][13][14]. It was reported that the tensile properties of the cold bends are different from those of the straight pipes due to work hardening and the Bauschinger effect [12].…”