On the observations of autowaves and avalanches in an aluminum magnesium alloy

Mudrock, Rebecca N.

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https://hdl.handle.net/2142/24188 Copy

Description

Title

On the observations of autowaves and avalanches in an aluminum magnesium alloy

Author(s)

Mudrock, Rebecca N.

Issue Date

2011-05-25T14:57:16Z

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

Beaudoin, Armand J.

Department of Study

Mechanical Sci & Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Plasticity
• Dynamic Phenomena
• Dynamic Strain Aging
• Aluminum Alloys
• Image Analysis

Abstract

The present study attempts to answer the question of what the local deformation characteristics look like in a dynamically strain aging material before the onset of macroscopic instability. A solution strengthened aluminum magnesium alloy was tested in a work hardened condition in uniaxial tension under a constant applied displacement rate. In situ digital image correlation captured the 2D spatial strain field which was differentiated to find the local strain rate field. Propagating waves in the local strain rate were observed in an extended elastoplastic transition during macroscopically uniform deformation before the onset of the Portevin-Le Chatelier effect. The formation of the synchronous oscillations suggests a reduction in dimensionality in the system. These waves eventually transition into intermittent plastic behavior which is attributed to dislocation avalanches. The strain magnitudes for these autowaves and dislocation avalanches are much lower than would be observed for a plastic burst developed from the Portevin-Le Chatelier effect. Fourier analysis on the global load signal confirms the observed intermittency spans multiple scales, which is consistent with the behavior of various materials. Also, wavelet analysis provided a method of quantifying transitions in the deformation behavior in both the time and frequency domains and reveals a period doubling transition in both the global and local signal.

Graduation Semester

2011-05

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http://hdl.handle.net/2142/24188

Copyright and License Information

Copyright 2011 Rebecca N. Mudrock

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