Date of Award

9-18-2019

Publication Type

Master Thesis

Degree Name

M.A.Sc.

Department

Civil and Environmental Engineering

Keywords

Cyclic Pressure Loading, Energy Pipelines, Fatigue Failure, Nonlinear FEA, Stress Concentration Factors, Wrinkle Defect

Supervisor

Das, S.

Rights

info:eu-repo/semantics/openAccess

Abstract

The development of a small wrinkle in a buried pipeline can be a challenging issue for pipeline operators to approach. Although a vast majority of research has been conducted, to evaluate the integrity of a pipeline showing signs of irregularities such as corrosion, pipe wall buckling and/or rippling; there is limited research data or guideline(s) available as to how to assess the severity of a small wrinkle defect. If not dealt with appropriately, these small wrinkle defects can lead to further damage of the pipe wall as a result of fatigue damage caused by internal pressure cycling. This research program was designed to investigate the behaviour and structural integrity of wrinkled pipelines subjected to severe pressure cyclic loading. This research program comprises of both lab-based experimental work, followed by a finite element analysis (FEA) based numerical approach. This study shows that a pipe with a wrinkle defect may lead to fatigue failure resulting in circumferential cracking at the wrinkle apex, due to localized stress concentration. Additionally, it was also found that the magnitude of the stress concentration is highly dependent on the geometry of the wrinkle profile. Analysis based on experimental and numerical results was undertaken to evaluate stress concentration factors, which could be used to establish the remaining fatigue life of a wrinkled pipe subjected to typical pressure fluctuations arising in oil and gas pipelines.

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