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Characterization of Delamination in 2099-T861 Aluminum-Lithium

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Title: Characterization of Delamination in 2099-T861 Aluminum-Lithium
Author(s): McDonald, Russell J.
Director of Research: Kurath, Peter
Doctoral Committee Chair(s): Kurath, Peter
Doctoral Committee Member(s): Beaudoin, Armand J.; Tortorelli, Daniel A.; Fressengeas, Claude; Aravas, Nikolaos
Department / Program: Mechanical Sci & Engineering
Discipline: Mechanical Engineering
Degree Granting Institution: University of Illinois at Urbana-Champaign
Degree: Ph.D.
Genre: Dissertation
Subject(s): Aluminum-Lithium Material Behavior Material Experiments Delamination Grain Boundary Stresses Crystal Plasticity Cyclic Deformation
Abstract: Aluminum-lithium alloys provide a lower density and higher stiffness alternative to other high strength aluminum alloys. However, many Al-Li alloys exhibit a non-traditional failure mechanism, delamination. Delamination refers to the failure along the grain boundary interface. The delamination phenomenon is often observed from fracture toughness testing as cracking along grain boundaries perpendicular to the mode I primary crack. In this investigation, delaminations were also observed after cyclic deformation of both uniaxial and torsion experiments. Many of the experimental observations, such as rate insensitivity and crystallographic orientation, were incorporated into a cyclically stable crystal plasticity framework with rate independent kinematic hardening. It was hypothesized that texture lead to interface stresses that could not be obtained by a continuum approach. Local grain boundary interface stresses were estimated using the uniform deformation and bi-crystal models. These models were computationally amenable to provide both orientation dependence and the statistical nature of the grain boundary stresses for a given bulk texture and nominal loading. A coupled shear-normal damage parameter was formulated to quantitatively characterize the nucleation of delamination. The damage estimated for a wide range of simulations (uniaxial, torsion, fracture) correlated well with the experimental trends.
Issue Date: 2010-01-06
URI: http://hdl.handle.net/2142/14561
Rights Information: Copyright 2009 Russell J. McDonald
Date Available in IDEALS: 2010-01-06
Date Deposited: December 2
 

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