Details
| Original language | English |
|---|---|
| Qualification | Doctor of Engineering |
| Awarding Institution | |
| Supervised by |
|
| Date of Award | 16 Apr 2018 |
| Place of Publication | Hannover |
| Publication status | Published - 2018 |
Abstract
Sustainable Development Goals
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Hannover, 2018. 107 p.
Research output: Thesis › Doctoral thesis
}
TY - BOOK
T1 - Numerical investigation on hydrogen embrittlement of metallic pipeline structures
AU - Möhle, Milena
N1 - Doctoral thesis
PY - 2018
Y1 - 2018
N2 - Motivated by shifting to renewable energy sources, the utilization of hydrogen gas as an energy carrier is discussed to account for expected irregularities in supply. Here, the construction of a new hydrogen pipeline network would be rather expensive such that the usage of the existing natural gas pipeline system is in the focus of investigation. One major problem is that hydrogen embrittles the material and can cause fatal failure especially in case of pipelines which were already damaged during their service time. At the localized stress fields around pre-existing cracks, hydrogen accumulates and converts the material response from ductile to brittle failure. Based on experimental findings, the so-called Hydrogen Enhanced Localized Plasticity (HELP) mechanism is identified to govern hydrogen embrittlement in the prevalent case by reducing the yield stress in a continuum sense. To solve the highly coupled equations of the mechanical model and the transient hydrogen distribution model, an iterative finite element scheme is applied using a discontinuous Galerkin method for time discretisation. A continuum model of a natural gas pipeline with a radial crack is investigated. Therefore, a surrogate model using the boundary layer approach is adopted, whose results are in good agreement with a model of the full pipeline structure. Based on the idea of the local softening effect by the HELP mechanism, three different approaches to account for hydrogen embrittlement are discussed. Firstly, the steady state hydrogen distributions in front of the crack tip are evaluated while in a next step the effect of hydrogen on the mechanical properties is discussed. When investigating the impact of different crack lengths, a notably increasing amount of hydrogen embrittlement is identified. The results highlight the importance of carefully investigating the actual conditions in the specific pipelines and adequately accounting for hydrogen embrittlement in numerical simulations as a basis for ducting hydrogen through the existing pipeline system.
AB - Motivated by shifting to renewable energy sources, the utilization of hydrogen gas as an energy carrier is discussed to account for expected irregularities in supply. Here, the construction of a new hydrogen pipeline network would be rather expensive such that the usage of the existing natural gas pipeline system is in the focus of investigation. One major problem is that hydrogen embrittles the material and can cause fatal failure especially in case of pipelines which were already damaged during their service time. At the localized stress fields around pre-existing cracks, hydrogen accumulates and converts the material response from ductile to brittle failure. Based on experimental findings, the so-called Hydrogen Enhanced Localized Plasticity (HELP) mechanism is identified to govern hydrogen embrittlement in the prevalent case by reducing the yield stress in a continuum sense. To solve the highly coupled equations of the mechanical model and the transient hydrogen distribution model, an iterative finite element scheme is applied using a discontinuous Galerkin method for time discretisation. A continuum model of a natural gas pipeline with a radial crack is investigated. Therefore, a surrogate model using the boundary layer approach is adopted, whose results are in good agreement with a model of the full pipeline structure. Based on the idea of the local softening effect by the HELP mechanism, three different approaches to account for hydrogen embrittlement are discussed. Firstly, the steady state hydrogen distributions in front of the crack tip are evaluated while in a next step the effect of hydrogen on the mechanical properties is discussed. When investigating the impact of different crack lengths, a notably increasing amount of hydrogen embrittlement is identified. The results highlight the importance of carefully investigating the actual conditions in the specific pipelines and adequately accounting for hydrogen embrittlement in numerical simulations as a basis for ducting hydrogen through the existing pipeline system.
U2 - 10.15488/3689
DO - 10.15488/3689
M3 - Doctoral thesis
CY - Hannover
ER -