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Open AccessArticle

Influence of Size on the Fractal Dimension of Dislocation Microstructure

Department of Mechanical and Aerospace Engineering, University of California Los Angeles, Los Angeles, CA 90095, USA
Author to whom correspondence should be addressed.
Metals 2019, 9(4), 478;
Received: 29 March 2019 / Revised: 19 April 2019 / Accepted: 20 April 2019 / Published: 25 April 2019
(This article belongs to the Special Issue Dislocation Mechanics of Metal Plasticity and Fracturing)
Three-dimensional (3D) discrete dislocation dynamics simulations are used to analyze the size effect on the fractal dimension of two-dimensional (2D) and 3D dislocation microstructure. 2D dislocation structures are analyzed first, and the calculated fractal dimension ( n 2 ) is found to be consistent with experimental results gleaned from transmission electron microscopy images. The value of n 2 is found to be close to unity for sizes smaller than 300 nm, and increases to a saturation value of ≈1.8 for sizes above approximately 10 microns. It is discovered that reducing the sample size leads to a decrease in the fractal dimension because of the decrease in the likelihood of forming strong tangles at small scales. Dislocation ensembles are found to exist in a more isolated way at the nano- and micro-scales. Fractal analysis is carried out on 3D dislocation structures and the 3D fractal dimension ( n 3 ) is determined. The analysis here shows that ( n 3 ) is significantly smaller than ( n 2 + 1 ) of 2D projected dislocations in all considered sizes. View Full-Text
Keywords: dislocation microstructure; fractal analysis; size effect dislocation microstructure; fractal analysis; size effect
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Cui, Y.; Ghoniem, N. Influence of Size on the Fractal Dimension of Dislocation Microstructure. Metals 2019, 9, 478.

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