Characterization of Delamination in 2099-T861 Aluminum-Lithium

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2010

Author dc:creator

• McDonald, Russell J.

Contributors dc:contributor

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

• Aluminum-Lithium
• Material Behavior
• Material Experiments
• Delamination
• Grain Boundary Stresses
• Crystal Plasticity
• Cyclic Deformation

Statement dc:rights

• Copyright 2009 Russell J. McDonald

Language dc:language

en

Handle dc:identifier

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

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/14561