The Effect of Pre-Strain on Ductile Fracture Toughness of Reeled Pipeline Steels

The reel-lay method is a cost efficient alternative to the S-lay and J-lay methods for small to medium size steel offshore pipelines. The quality of the pipeline construction is enhanced by on-shore welding and inspection under controlled conditions. However, reeled pipelines are subject to at least two symmetrical plastic strain cycles during installation. The plastic straining associated with reeled installation modifies the axial tensile response of the pipe material. Also, it has been suggested that plastic straining may reduce the fracture toughness. In this work small scale tests, representative of conditions experienced under reeling of steel pipelines, have been carried out. The fracture resistance curves obtained for the material in the as-received and strained conditions have been compared. No significant effect of the reeling strain cycle on the fracture toughness during subsequent straining was observed.