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In this paper, the deformability of line pipe with local metal loss was examined. A full-scale experiment and a finite element (FE) analysis were carried out for line pipe with local metal loss subjected to an axial compressive load. As a result, a good agreement was obtained between the analytical and experimental results. This indicated that the present analytical method was applicable to evaluate the deformability of line pipes with local metal loss subjected to a large ground movement. Parametric studies were then conducted to clarify the relationship between the geometry of the local metal loss and the deformability using the FE analytical method. Keywords: pipelines, compressive deformation, local metal loss, peak load strain, experiment, finite element analysis

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 pre-strained 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. [DOI: 10.111511.2746395]

In order to clarify the significant parameters to control the deformability of high-grade induction bend pipes, finite element analyses simulating the deformation behavior subjected to an internal pressure and bending moment were carried out. Parametric studies were conducted using the finite element models with various mechanical properties and geometric imperfections. The change in the integrity of the buried pipeline due to the quality of the induction bend pipe was then quantitatively examined. Consequently, this study indicated that the mechanical properties, the dimensions and tolerance and the properties of the 'transition' part should be appropriately designed in proportion to the ground deformation. [DOI: 10.1115/1.1839881]

In this study, the deformability of high-grade pipelines subjected to an axial compressive deformation was experimentally and analytically discussed. Six cases of axial compression experiments with high-grade line pipe were carried out. The pipe specimens had various material properties and wall thickness. Finite-element analyses were also carried out and verified the reliability. Then, a finite-element analysis method for evaluating the deformability of the line pipe was established. By using this method, parametric studies were carried out. The effects of the strain-hardening behavior and pipe geometry on the deformability of the high-grade pipelines were examined.

The behavior during the cold bending of pipelines was experimentally and analytically investigated. Full-scale cold bending experiments were performed on API X60 and X80 grade line pipes. Finite element (FE) analyses simulated the cold bending process by considering the contact interactions between a pipe and the components of the bending machine. The results of the simulation were in good agreement with the full-scale experiments. The stress-strain relationship and yield to tensile ratio (Y/T) had no obvious effect on the strain distribution after cold bending. The tensile tests quantitatively evaluated the decrease in the yield stress along the longitudinal direction on the cold bends due to the Bauschinger effect. [DOI: 10.1115/1.1554701]

This study investigated ductile crack initiation limit of pipeline girth welded joints with different strength mismatches. The ductile crack initiation limit for the girth welded joints was evaluated by conducting three-point bending fracture toughness tests and wide plate tensile tests with a surface notch. In addition, effect of heat input on the ductile crack initiation limit of weld metal (WM) was evaluated on the assumption that a welding condition would be varied in the field in the actual pipeline construction. As the results, the equivalent plastic strain at the notch tip for the ductile crack initiation of the three-point bending tests was consistent with those of the wide plate tests, and the heat input hardly affected the ductile crack initiation limit within the range of this study. This meant that the ductile crack initiation limit of the pipeline girth welded joints with strength mis-match was able to be estimated using the equivalent plastic strain obtained from the three-point bending tests. Based on these results, we proposed a procedure to determine the rational fracture toughness requirements which took into account the difference in the plastic constraint between standard fracture toughness test and pipeline girth welded joints. This procedure was also possible to determine the required strength matching level for a strain-based design for girth welded joint containing surface notch in the centre of the WM in terms of preventing the ductile crack initiation. [ABSTRACT FROM AUTHOR]