Strain-based CTOD estimation formulations for fracture assessment of offshore pipelines subjected to large plastic deformation

• Published in: Ocean engineering 2014-11, Vol.91, p.64-72
• Main Authors: Zhang, Y.M., Xiao, Z.M., Zhang, W.G., Huang, Z.H.
• Format: Article
• Language: English
• Subjects: Applied sciences; Buildings. Public works; Crack opening displacement; Crack tip opening displacement; Exact sciences and technology; Formulations; Fracture mechanics; Hydraulic constructions; Internal pressure; Large plastic bending; Marine; Offshore; Offshore engineering; Offshore pipeline; Offshore structure (platforms, tanks, etc.); Pipelines; Plastic deformation; Strain-based estimation formulation
• ISSN: 0029-8018; 1873-5258
• DOI: 10.1016/j.oceaneng.2014.08.020

The extreme loading conditions, i.e. the large plastic bending combined with high internal pressure, and the potential cracks or flaws in the welds pose tremendous challenges to the structural integrity for offshore pipelines. In this paper, the fracture response of offshore pipeline with semi-elliptical surface crack under large plastic deformation is analyzed through 3-dimensional finite element simulations. Extensive parametric studies are performed to investigate the influences of the crack geometry, strain hardening coefficient and internal pressure on the evolutions of crack tip opening displacement (CTOD). Furthermore, by virtue of response surface methodology, the new strain-based CTOD estimation formulations are proposed to assess the fracture behavior of flawed pipelines subjected to pure bending load as well as biaxial load, respectively. •Fracture responses of offshore pipelines are investigated numerically.•Various combined loadings are considered.•Extensive parametric studies are performed for CTOD evolutions.•New strain-based CTOD estimation formulations are proposed for fracture assessment.