Characterization of Delamination in 2099-T861 Aluminum-Lithium

McDonald, Russell J.

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https://hdl.handle.net/2142/14561 Copy

Description

Title

Characterization of Delamination in 2099-T861 Aluminum-Lithium

Author(s)

McDonald, Russell J.

Issue Date

2010-01-06T16:12:22Z

Director of Research (if dissertation) or Advisor (if thesis)

Kurath, Peter

Doctoral Committee Chair(s)

Kurath, Peter

Committee Member(s)

• Beaudoin, Armand J.
• Tortorelli, Daniel A.
• Fressengeas, Claude
• Aravas, Nikolaos

Department of Study

Mechanical Sci & Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(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.

Graduation Semester

2009-12

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http://hdl.handle.net/2142/14561

Copyright and License Information

Copyright 2009 Russell J. McDonald

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