Fatigue crack growth in hydrogen pipeline steels

Che, Ziwei

Permalink

https://hdl.handle.net/2142/101584 Copy

Description

Title

Fatigue crack growth in hydrogen pipeline steels

Author(s)

Che, Ziwei

Issue Date

2018-07-17

Director of Research (if dissertation) or Advisor (if thesis)

• Sofronis, Petros
• Dadfarnia, Mohsen

Department of Study

Mechanical Sci & Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

fatigue, API steel, stress intensity factor

Abstract

Pipeline hydrogen transport and distribution are contemplated for hydrogen applications. Hydrogen introduction in the natural gas pipeline systems is also considered in the power to gas (P2G) approach to utilizing excess renewable energy when the supply exceeds the demand. It is well known that hydrogen embrittles all carbon steels used to manufacture pipelines and hence, safety and reliability of hydrogen transport requires that pipelines be assessed and tested against hydrogen embrittlement. The most severe embrittlement mechanism is hydrogen accelerated fatigue crack growth since it is well known that hydrogen can enhance fatigue crack growth rates by a factor of 10. In this thesis, the fatigue life of a line pipe manufactured with API steel is calculated by investigating the growth of a semi-elliptical crack on the inner diameter surface due to hydrogen pressure fluctuation. This behavior is compared with the life of the line pipe in an inert environment (e.g. natural gas or N2) under the same pressure fluctuations. The hydrogen or the inert environment pressure history is analyzed with the rainflow counting method and the crack depth calculations are carried out for a variety of API steels at load ratios for a given initial crack depth. The load ratio R equals where and are respectively the minimum and maximum stress intensity factors in a pressure cycle the crack experiences due to the pressure fluctuations. In particular for API X42 steel for which experimental data are available for calculations with greater load ratio, the fatigue life is calculated at load ratios and . The calculation of the stress intensity factor was done by using the closed form solution of Zahoor for which the validity range with regard to the crack and line pipe dimensions was established through comparisons with numerical calculations. The results demonstrate that hydrogen markedly accelerates crack growth and the initial crack depth has significant effect on the pipeline life.

Graduation Semester

2018-08

Type of Resource

text

Permalink

http://hdl.handle.net/2142/101584

Copyright and License Information

Copyright 2018 Ziwei Che

Owning Collections