Session: MF-02-09 Materials for Hydrogen Service (Joint with C&S)-9

Paper Number: 154853

154853 - Fully-Coupled Cohesive Element Model for Simulating Hydrogen Embrittlement in Pipeline Steels 

Abstract: 

Hydrogen degrades the mechanical properties of steels reducing their ductility, fatigue resistance and their fracture toughness. This phenomenon is known as hydrogen embrittlement (HE), it is directly applicable to hydrogen pipelines and has motivated significant research in the pipeline community. The numerical simulation of hydrogen embrittlement can be considered as a cost-efficient way of studying the effects of this multiparameter phenomenon and characterizing the effects of hydrogen in the mechanical properties of steels. Those simulations require the implementation of both hydrogen diffusion and hydrogen induced material degradation. The present study presents a fully coupled model that takes into account the effect of hydrogen diffusion and the hydrogen induced material degradation as proposed by the hydrogen enhanced localized plasticity (HELP) and the hydrogen enhanced decohesion (HEDE) mechanisms proposed in the literature over the years. The proposed mechanisms are coupled in a von Mises plasticity model using cohesive elements to simulate the reduced cohesive strength in the presence of hydrogen. The constitutive model is employed to simulate fracture toughness tests and small-strain tensile tests and the numerical results are compared with actual experimental data. In this context, the material parameters are calibrated and compared with the experimentally measured CTOD-R curves results of C(T) specimens and the stress-strain results of coupon specimens subjected to tension in hydrogen environment.

Presenting Author: Spyros Karamanos University of Thessaly

Presenting Author Biography: Spyros A. Karamanos, is Professor of Computational Structural Mechanics, at the University of Thessaly, Greece, Department of Mechanical Engineering. He teaches courses in Structural Mechanics and Finite Element Methods. From 2016-2019 he was Chair of Structural Engineering, at the School of Engineering, The University of Edinburgh.
Spyros specializes in structural mechanics and integrity of energy infrastructure systems, with emphasis on steel structures. His research interests focus on buckling and fatigue of pipelines and offshore structures, mainly tubular components and systems, using computational (finite element) methods, and experimental testing. His research has been funded primarily by European research projects, with the participation of European steel and pipeline industry. He has published more than 180 papers in refereed journals and conference proceedings.
Spyros has a 5-year Diploma in Civil Engineering from the National Technical University of Athens, Greece (1989), and received his PhD in Structural Engineering from The University of Texas at Austin, USA (1993).

Authors:

Aris Stamou University of Thessaly
Spyros Karamanos University of Thessaly