Fatigue study on interacting 3-D crack problem in offshore pipeline

• Main Author: Pan, Zi Jiao
• Other Authors: Xiao Zhongmin
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Mechanical engineering
• Online Access: https://hdl.handle.net/10356/150288
• Institution: Nanyang Technological University

Various types of defects occur during the installation and operation of subsea pipelines. Recent statistics on subsea pipelines incidents shows that cracking caused failure is the most critical one. Crack defects greatly increase the probability of leakage and fracture of the offshore pipelines. In the current project, the existing software package ANSYS is employed to analyze the fatigue failure in pipelines caused by crack defects. The influence of crack length and crack depth to the fatigue life of pipelines has been investigated. Data from our simulations are summarized in order to analyze the most critical cause for those incidents. Results from our simulations show that the fatigue life of subsea pipelines is sensitive to all the factors mentioned above. Especially the crack depth plays a very important role in fatigue failure. The conclusions drawn from our study may provide reference for ocean engineering practices. In the current study, the ANSYS workbench 2021R1 structural static analysis module is used to perform fatigue analysis on the cracks of the submarine pipeline with cracks. One of the half-pipes contains one semi elliptical embedded crack at one end of the pipe. The other one consists of a semi elliptical surface crack placed inside the surface of the pipe. In the structural static analysis module, the elliptical cracks are added to the pipeline through the fracture command, and the fatigue tool is used to analyze the length, depth and pressure range of the cracks.