Numerical Failure Pressure Prediction of Crack-in-Corrosion Defects in Natural Gas Transmission Pipelines

Modeling;crack in corrosion;ABAQUS;CIC;Mechanical Engineering

Bedairi, Badr

University of Waterloo

关键词: Modeling;    crack in corrosion;    ABAQUS;    CIC;    Mechanical Engineering;   

Others  :  https://uwspace.uwaterloo.ca/bitstream/10012/5368/1/MSc-Thesis-Badr-V-8-999.pdf

瑞士|英语

来源: UWSPACE Waterloo Institutional Repository

【 摘 要 】

The aim of this study was to use the finite element method to model crack, corrosion, and Crack-in-Corrosion defects in a pipeline.The pipe material under investigation for this study was API 5L X60, 508 mm diameter with a wall thickness of 5.7 mm.The pipe material was evaluated using Tensile, Charpy, and J testing in order to model the defects and to establish the numerical failure criteria.Corrosion defects were modeled as flat-bottomed grooves.The collapse pressure was predicted when the deepest point in the bottom of the defect reached a critical stress.Based on this criterion, the FE corrosion failure pressure predictions were conservative compared to the experimental failure pressures, conducted by Hosseini [9], with an average error of 10.13%.For crack modeling, the failure criteria were established considering the plastic collapse limit and the fracture limit.Both the Von Mises stress in the crack ligament and the J-integral values around the crack were monitored to predict the failure pressure of the model.The crack modeling was done based on two approaches, the uniform depth profile and the semi-elliptical profile.The crack with uniform depth profile was done because the uniform shape is the logical equivalent shape for a colony of cracks.The crack with the semi-elliptical profile was done to have a less conservative results and because the experiments were done with semi-elliptical cracks.The FE crack modeling results were conservative compared to the experimental collapse pressure with an average error of 19.64% for the uniform depth profile and 5.35% for the semi-elliptical profile.In crack-in-corrosion (CIC) defect modeling, the crack was modeled with uniform depth because it was very difficult to model the semi-elliptical crack profile when the crack defect is coincident with a corrosion defect.The results were conservative compared to the experimental results with an average error of 22.18%.In general, the FE modeling provides the least conservative failure pressure prediction over the existing analytical solutions for pipe with longitudinal corrosion, crack, and CIC defects.