Multiscale Modeling of Hydrogen Embrittlement for Multiphase Material

Handle URI:
http://hdl.handle.net/10754/316598
Title:
Multiscale Modeling of Hydrogen Embrittlement for Multiphase Material
Authors:
Al-Jabr, Khalid A.
Abstract:
ABSTRACT Hydrogen Embrittlement (HE) is a very common failure mechanism induced crack propagation in materials that are utilized in oil and gas industry structural components and equipment. Considering the prediction of HE behavior, which is suggested in this study, is one technique of monitoring HE of equipment in service. Therefore, multi-scale constitutive models that account for the failure in polycrystalline Body Centered Cubic (BCC) materials due to hydrogen embrittlement are developed. The polycrystalline material is modeled as two-phase materials consisting of a grain interior (GI) phase and a grain boundary (GB) phase. In the rst part of this work, the hydrogen concentration in the GI (Cgi) and the GB (Cgb) as well as the hydrogen distribution in each phase, were calculated and modeled by using kinetic regime-A and C, respectively. In the second part of this work, this dissertation captures the adverse e ects of hydrogen concentration, in each phase, in micro/meso and macro-scale models on the mechanical behavior of steel; e.g. tensile strength and critical porosity. The models predict the damage mechanisms and the reduction in the ultimate strength pro le of a notched, round bar under tension for di erent hydrogen concentrations as observed in the experimental data available in the literature for steels. Moreover, the study outcomes are supported by the experimental data of the Fractography and HE indices investigation. In addition to the aforementioned continuum model, this work employs the Molecular Dynamics (MD) simulations to provide information regarding 4 5 bond formulation and breaking. The MD analyses are conducted for both single grain and polycrystalline BCC iron with di erent amounts of hydrogen and di erent size of nano-voids. The simulations show that the hydrogen atoms could form the transmission in materials con guration from BCC to FCC (Face Centered Cubic) and HCP (Hexagonal Close Packed). They also suggest the preferred sites of hydrogen for each case. The connections between the results for di erent scales (nano, micro/meso and macro-scale) were suggested in this dissertation and show good agreements between them. We nally conclude that hydrogen-induced steel fracture and the change of fracture mode are caused by the suppression of dislocation emission at crack tip and changing in the material structure due to accumulation of hydrogen, which is driven by the stress elds. This causes the brittle fracture to occur as inter-granular in the GB and trans-granular in the GI.
Advisors:
Moran, Brian ( 0000-0002-6875-8630 )
Committee Member:
Alsaiari, Hamad; Bakr, Osman ( 0000-0002-3428-1002 ) ; Samtaney, Ravi ( 0000-0002-4702-6473 )
KAUST Department:
Physical Sciences and Engineering (PSE) Division
Program:
Mechanical Engineering
Issue Date:
May-2014
Type:
Dissertation
Appears in Collections:
Dissertations; Physical Sciences and Engineering (PSE) Division; Mechanical Engineering Program

Full metadata record

DC FieldValue Language
dc.contributor.advisorMoran, Brianen
dc.contributor.authorAl-Jabr, Khalid A.en
dc.date.accessioned2014-05-07T12:51:06Zen
dc.date.available2014-05-07T12:51:06Zen
dc.date.issued2014-05en
dc.identifier.urihttp://hdl.handle.net/10754/316598en
dc.description.abstractABSTRACT Hydrogen Embrittlement (HE) is a very common failure mechanism induced crack propagation in materials that are utilized in oil and gas industry structural components and equipment. Considering the prediction of HE behavior, which is suggested in this study, is one technique of monitoring HE of equipment in service. Therefore, multi-scale constitutive models that account for the failure in polycrystalline Body Centered Cubic (BCC) materials due to hydrogen embrittlement are developed. The polycrystalline material is modeled as two-phase materials consisting of a grain interior (GI) phase and a grain boundary (GB) phase. In the rst part of this work, the hydrogen concentration in the GI (Cgi) and the GB (Cgb) as well as the hydrogen distribution in each phase, were calculated and modeled by using kinetic regime-A and C, respectively. In the second part of this work, this dissertation captures the adverse e ects of hydrogen concentration, in each phase, in micro/meso and macro-scale models on the mechanical behavior of steel; e.g. tensile strength and critical porosity. The models predict the damage mechanisms and the reduction in the ultimate strength pro le of a notched, round bar under tension for di erent hydrogen concentrations as observed in the experimental data available in the literature for steels. Moreover, the study outcomes are supported by the experimental data of the Fractography and HE indices investigation. In addition to the aforementioned continuum model, this work employs the Molecular Dynamics (MD) simulations to provide information regarding 4 5 bond formulation and breaking. The MD analyses are conducted for both single grain and polycrystalline BCC iron with di erent amounts of hydrogen and di erent size of nano-voids. The simulations show that the hydrogen atoms could form the transmission in materials con guration from BCC to FCC (Face Centered Cubic) and HCP (Hexagonal Close Packed). They also suggest the preferred sites of hydrogen for each case. The connections between the results for di erent scales (nano, micro/meso and macro-scale) were suggested in this dissertation and show good agreements between them. We nally conclude that hydrogen-induced steel fracture and the change of fracture mode are caused by the suppression of dislocation emission at crack tip and changing in the material structure due to accumulation of hydrogen, which is driven by the stress elds. This causes the brittle fracture to occur as inter-granular in the GB and trans-granular in the GI.en
dc.language.isoenen
dc.subjectHydrogenen
dc.subjectSteelen
dc.subjectEmbrittlementen
dc.subjectPlasticityen
dc.subjectDuctilityen
dc.titleMultiscale Modeling of Hydrogen Embrittlement for Multiphase Materialen
dc.typeDissertationen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
thesis.degree.grantorKing Abdullah University of Science and Technologyen_GB
dc.contributor.committeememberAlsaiari, Hamaden
dc.contributor.committeememberBakr, Osmanen
dc.contributor.committeememberSamtaney, Ravien
thesis.degree.disciplineMechanical Engineeringen
thesis.degree.nameDoctor of Philosophyen
dc.person.id113722en
All Items in KAUST are protected by copyright, with all rights reserved, unless otherwise indicated.