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Research Papers

Experimental Characterization of Damage Processes in Aluminum AA2024-O

[+] Author and Article Information
S. Kweon

Aerospace Engineering, Texas A&M University, College Station, TX 77843-3141skweon2@tamu.edu

A. J. Beaudoin

Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801-2906abeaudoi@illinois.edu

R. J. McDonald

Mechanical Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801-2906rjmcdona@illinois.edu

J. Eng. Mater. Technol 132(3), 031008 (Jun 16, 2010) (9 pages) doi:10.1115/1.4001445 History: Received January 04, 2010; Revised March 03, 2010; Published June 16, 2010; Online June 16, 2010

Much of the damage mechanics literature has focused on void growth due to tensile hydrostatic stress. To clarify the effect of combined shear stress and hydrostatic stress on the development of damage, specimens of various geometries were employed in an experimental program to cover a wide range of triaxiality and shear stress. Digital image correlation (DIC) is utilized to measure the fracture strain of the 2D specimens. Experiments are paired with simulations utilizing J2 plasticity theory to complement the experiments and relate the fracture strain with combined hydrostatic and shear stresses. The results display accelerated damage for cases dominated by shear at low triaxiality. Crystal plasticity simulations were carried out using boundary conditions based on the DIC displacement field. These simulations indicate that tensile hydrostatic stress develops due to grain-to-grain interaction.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Specimens employed in this study

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Figure 2

Pictures of the simple shear specimen taken during the DIC test. The dotted area is the area of interest window for postcorrelation.

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Figure 3

Stress strain response and the fitting result

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Figure 4

The simple shear specimen at the onset of fracture. The leftmost figure displays effective plastic strain ε¯p from the simulation with the center one showing the DIC strain field.

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Figure 5

Comparison between the J2 and DIC equivalent strain fields for the shear-more-tension specimen. The leftmost figure displays effective plastic strain ε¯p from the simulation with the center one showing the DIC strain field.

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Figure 6

The thin plate with a hole at the onset of fracture. The leftmost figure displays effective plastic strain ε¯p from the simulation with the center one showing the DIC strain field.

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Figure 7

The oval cylinder of a center diameter 4.4 mm at the onset of fracture. (a) Edge cracked surface, (b) effective plastic strain ε¯p, and (c) ε¯Ψ+≡∑Δε¯p, when triaxiality is positive.

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Figure 8

The uniaxial tension specimen at the onset of fracture. The left figure displays effective plastic strain ε¯p.

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Figure 9

Fracture strain versus triaxiality. (a) 2024-O and 2024-T351. The dashed curves indicate trends for AA2024-O. (b) For 2024-O notched cylinder. Interpolated point is obtained by averaging instability starting point and fracture point with respect to both triaxiality and fracture strain.

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Figure 10

DIC results, (a) uy, (b) εxy at 0.4 mm pin displacement, and (c) normalized load versus displacement curves from the machine and the simulation

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Figure 11

Development of hydrostatic and shear stresses in a crystal plasticity simulation with boundary conditions from the DIC result

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