3-D fatigue crack study in offshore pipelines

• Main Author: Soh, Wei Jian
• Other Authors: Xiao Zhongmin
• Format: Final Year Project
• Language: English
• Published: 2017
• Subjects: DRNTU::Engineering::Mechanical engineering::Mechanics and dynamics
• Online Access: http://hdl.handle.net/10356/72003
• Institution: Nanyang Technological University

Structural flaws and defects involving multiple cracks has been a concern over the years. The presences of multiple cracks can result in much worse outcomes compared to a single crack due to faster crack propagation when multiple cracks are coalesced. A lot of studies had been made in investigating the stress intensity factor of multiple cracks but little mentioned on the fatigue behaviour of multiple interacting cracks. In our current study, numerical simulations on the fatigue behaviours of offshore pipelines with multiple interacting cracks were carried out, in view of the high cost of the full-scale experiment setup and sufficient validation of numerical simulations accuracy from the open literature. ABAQUS ver6.14 was used for performing Extended Finite Element Method (XFEM) to simulate the fatigue behaviour of 34 cases of two interacting cracks (a surface crack and an embedded crack) in a pipe under various configurations, in terms of crack sizes, crack aspect ratio, crack relative distance and stress ratio, etc. The trend of each varying initial parameters and the fatigue crack propagation profile was investigated and compared to relevant studies. Comparison was made with BS7910 and reveal that the BS7910 procedure in assessing multiple cracks is over conservative.