Microstructure-sensitive plasticity and fatigue modeling of extruded 6061 aluminum alloys

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dc.contributor Todd, Beth A.
dc.contributor Barkey, Mark E.
dc.contributor.advisor Jordon, J. Brian
dc.contributor.author McCullough, Robert Ross
dc.date.accessioned 2017-03-01T17:21:58Z
dc.date.available 2017-03-01T17:21:58Z
dc.date.issued 2014
dc.identifier.other u0015_0000001_0001796
dc.identifier.other McCullough_alatus_0004M_12140
dc.identifier.uri https://ir.ua.edu/handle/123456789/2240
dc.description Electronic Thesis or Dissertation
dc.description.abstract In this study, the development of fatigue failure and stress anisotropy in light weight ductile metal alloys, specifically Al-Mg-Si aluminum alloys, was investigated. The experiments were carried out on an extruded 6061 aluminum alloy. Reverse loading experiments were performed up to a prestrain of 5% in both tension-followed-by-compression and compression-followed-by-tension. The development of isotropic and kinematic hardening and subsequent anisotropy was indicated by the observation of the Bauschinger effect phenomenon. Experimental results show that 6061 aluminum alloy exhibited a slight increase in the kinematic hardening versus applied prestrain. However, the ratio of kinematic-to-isotropic hardening remained near unity. An internal state variable (ISV) plasticity and damage model was used to capture the evolution of the anisotropy for the as-received T6 and partially annealed conditions. Following the stress anisotropy experiments, the same extruded 6061 aluminum alloy was tested under fully reversing, strain-controlled low cycle fatigue at up to 2.5% strain amplitudes and two heat treatment conditions. Observations were made of the development of striation fields up to the point of nucleation at cracked and clustered precipitants and free surfaces through localized precipitant slip band development. A finite element enabled micro-mechanics study of fatigue damage development of local strain field in the presence of hard phases was conducted. Both the FEA and experimental data sets were utilized in the implementation of a multi-stage fatigue model in order to predict the microstructure response, including fatigue nucleation and propagation contributions on the total fatigue life in AA6061. Good correlation between experimental and predicted results in the number of cycles to final failure was observed. The AA6061 material maintained relatively consistent low cycle fatigue performance despite two different heat treatments.
dc.format.extent 71 p.
dc.format.medium electronic
dc.format.mimetype application/pdf
dc.language English
dc.language.iso en_US
dc.publisher University of Alabama Libraries
dc.relation.ispartof The University of Alabama Electronic Theses and Dissertations
dc.relation.ispartof The University of Alabama Libraries Digital Collections
dc.relation.hasversion born digital
dc.rights All rights reserved by the author unless otherwise indicated.
dc.subject.other Mechanical engineering
dc.subject.other Mechanics
dc.subject.other Materials Science
dc.title Microstructure-sensitive plasticity and fatigue modeling of extruded 6061 aluminum alloys
dc.type thesis
dc.type text
etdms.degree.department University of Alabama. Dept. of Mechanical Engineering
etdms.degree.discipline Mechanical Engineering
etdms.degree.grantor The University of Alabama
etdms.degree.level master's
etdms.degree.name M.S.

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