Abstract
Plastic deformation during the manufacture process of electric resistance welded (ERW) pipe determines the stress–strain relationship of the steel pipe, which affects the collapse pressure of offshore pipelines. To track the deformation history of the pipe, the entire process was simulated via finite element analysis using a solid element. A material model that considered both the Bauschinger effect and strain hardening was adopted. Various sizes of pipe cross-sections were simulated. As greater compression was applied during the sizing process, the strain hardening effect became more significant, so that the compressive yield strength was increased in the circumferential direction. The strain hardening effect was most prominent for a smaller diameter-to-thickness ratio (D/t), so that an increase in the collapse pressure could be obtained with a larger sizing ratio. Therefore, current design criteria for the collapse pressure recommended by Det Norske Verita (DNV) and API could be enhanced for a smaller D/t to consider the strain hardening effect during the sizing process.
Highlights
Electric resistance welded (ERW) pipes have excellent productivity and economic efficiency because they are manufactured in a single continuous process from beginning to end
Since ERW pipes are manufactured via a cold-forming process, variation in the material properties of the ERW pipes due to plastic deformation is an important factor for evaluating the collapse pressure
Han et al [3] conducted three-dimensional finite element analysis to simulate the actual manufacture of an ERW pipe and used the sizing portion of the process to evaluate the possibility of improving the collapse pressure
Summary
Electric resistance welded (ERW) pipes have excellent productivity and economic efficiency because they are manufactured in a single continuous process from beginning to end. Establishing the collapse pressure is essential for designing offshore pipelines, because this determines the buckling strength against external pressure, which is significantly influenced by the circumferential compressive stress–strain curve of the pipe [4]. Han et al [3] conducted three-dimensional finite element analysis to simulate the actual manufacture of an ERW pipe and used the sizing portion of the process to evaluate the possibility of improving the collapse pressure. Stress conditions and a deformed shape at the middle section of the shell model were mapped to the solid model This led to a conservative evaluation of the collapse pressure. The possibility of increasing the collapse strength of the ERW pipe by using the recommended current design standards was discussed
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