Computation of the stress intensity factor KI for external longitudinal semi-elliptic cracks in the pipelines by FEM and XFEM methods

S El Fakkoussi,C I Pruncu,A Elkhalfi,H Moustabchir

doi:10.1007/s12008-018-0517-1

Abstract

Evaluation of structural integrity of a cracked structure has become an important matter in the industrial field since couples of decades. However, damage process occurred in a structural component is not yet fixed. The objective of this research was to compute the stress intensity factor KI, in mode I, using in the linear elastic domain, by the finite element method and the extended finite element method. The defect studied in this survey has a form of a longitudinal semi-elliptic crack, located on the outer surface of the tube. A summary of the paper contains a numerical convergence for each method in terms of accuracy and limitations. The proposed methodology and outcomes released from this study act as novel design tool for the industrial engineers when is required to generate a robust solution for product development working in critical conditions.

Highlights

In the field of oil industry, the pipelines are the most used means of transporting petroleum materials such as gas, oil and hydrogen
The numerical results obtained using the ABAQUS software were compared in terms of KI factor between the two finite element method (FEM) and XFEM methods
The two numerical methods (FEM and XFEM) used for calculation of the Stress Intensity Factor KI, in mode I, in the elastic linear domain prove a robust tool for assessment of structural components

Summary

Introduction

In the field of oil industry, the pipelines are the most used means of transporting petroleum materials such as gas, oil and hydrogen. The pipes installed above ground are of great issue During their operation, they can generate several unexpected damages that cause significant material and human damage as well as environmental damage, especially if they are in the oceanic environment. The research carried out by Lam [1] on the statistics of the accidents of the pipes, shows that the majority of the breaks are due to: pits of corrosion, the impact of a bullet lost if one is in a hunting zone (for piping install above ground), or at the impact of a bucket excavating machinery These defects are in the form of a crack or a scratch; they affect the pipeline resistance and cause a sudden break that can be catastrophic. Researchers are interested in evaluating the structural integrity of pressurized pipelines

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Conclusion