Special Issue "Dislocation Mechanics of Metal Plasticity and Fracturing"

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: 10 February 2020

Special Issue Editor

Guest Editor
Prof. Dr. Ronald W. Armstrong

Department of Mechanical Engineering, A. James Clark School of Engineering, University of Maryland, College Park, MD 20742, USA
Website | E-Mail
Interests: dislocation mechanics; constitutive equations; Hall-Petch relations; Zerilli-Armstrong equations; microstructural stereology; high rate metal deformations; ductile-brittle transition behaviors; x-ray diffraction imaging

Special Issue Information

Dear Colleagues,

The modern understanding of metal plasticity and fracturing began in the 1920s with the pioneering work, first, on crack-induced fracturing by Griffith and, secondly, on dislocation-enhanced crystal plasticity by Taylor, Orowan, and Polanyi. Modern counterparts of this work are fracture mechanics as invented by Irwin and dislocation mechanics initiated in large part by Cottrell. No less important was the breakthrough development of optical characterization of sectioned polycrystalline metal microstructures begun by Sorby in the late 19th century, leading eventually to modern x-ray and electron microscopy methods of assessing crystal fracture surfaces, via fractography, and internal dislocation behaviors. A major current effort is to match computational simulations of metal deformation/fracturing behaviors with experimental measurements made over extended ranges of metal microstructures and over varying external conditions of stress-state, temperature, and loading rate.  The relationship between such simulations and the development of constitutive equations for a hoped-for predictive description of material deformation/fracturing behaviors is an active topic of research. The purpose of the present Special Issue is to offer a publication venue for current reports on the two subjects of understanding metal failures and understanding corresponding deformation strengths relating to metal processing.

Prof. Dr. Ronald W. Armstrong
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1500 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • crystal plasticity
  • metal fracturing
  • dislocation mechanics
  • fracture mechanics
  • crystal/polycrystal microstructures
  • crystal deformation/fracturing simulations
  • constitutive equations

Published Papers (3 papers)

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Editorial

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Open AccessEditorial
Dislocation Mechanics Pile-Up and Thermal Activation Roles in Metal Plasticity and Fracturing
Metals 2019, 9(2), 154; https://doi.org/10.3390/met9020154
Received: 14 January 2019 / Accepted: 27 January 2019 / Published: 31 January 2019
Cited by 1 | PDF Full-text (1407 KB) | HTML Full-text | XML Full-text
Abstract
Dislocation pile-up and thermal activation influences on the deformation and fracturing behaviors of polycrystalline metals are briefly reviewed, as examples of dislocation mechanics applications to understanding mechanical properties. To start, a reciprocal square root of grain size dependence was demonstrated for historical hardness [...] Read more.
Dislocation pile-up and thermal activation influences on the deformation and fracturing behaviors of polycrystalline metals are briefly reviewed, as examples of dislocation mechanics applications to understanding mechanical properties. To start, a reciprocal square root of grain size dependence was demonstrated for historical hardness measurements reported for cartridge brass, in line with a similar Hall-Petch grain size characterization of stress-strain measurements made on conventional grain size and nano-polycrystalline copper, nickel, and aluminum materials. Additional influences of loading rate (and temperature) were shown to be included in a dislocation model thermal activation basis, for calculated deformation shapes of impacted solid cylinders of copper and Armco iron materials. Connection was established for such grain size, temperature, and strain rate influences on the brittle fracturing transition exhibited by steel and other related metals. Lastly, for AISI 1040 steel material, a fracture mechanics based failure stress dependence on the inverse square root of crack size was shown to approach the yield stress at a very small crack size, also in line with a Hall-Petch dependence of the stress intensity on polycrystal grain size. Full article
(This article belongs to the Special Issue Dislocation Mechanics of Metal Plasticity and Fracturing)
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Research

Jump to: Editorial

Open AccessArticle
Influence of Size on the Fractal Dimension of Dislocation Microstructure
Metals 2019, 9(4), 478; https://doi.org/10.3390/met9040478
Received: 29 March 2019 / Revised: 19 April 2019 / Accepted: 20 April 2019 / Published: 25 April 2019
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Abstract
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 (n2) is found to be [...] Read more.
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. Full article
(This article belongs to the Special Issue Dislocation Mechanics of Metal Plasticity and Fracturing)
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Open AccessFeature PaperArticle
Size Effects of High Strength Steel Wires
Metals 2019, 9(2), 240; https://doi.org/10.3390/met9020240
Received: 6 February 2019 / Revised: 13 February 2019 / Accepted: 14 February 2019 / Published: 17 February 2019
Cited by 1 | PDF Full-text (4116 KB) | HTML Full-text | XML Full-text
Abstract
This study examines the effects of size on the strength of materials, especially on high strength pearlitic steel wires. These wires play a central role in many long span suspension bridges and their design, construction, and maintenance are important for global public safety. [...] Read more.
This study examines the effects of size on the strength of materials, especially on high strength pearlitic steel wires. These wires play a central role in many long span suspension bridges and their design, construction, and maintenance are important for global public safety. In particular, two relationships have been considered to represent strength variation with respect to length parameters: (i) the strength versus inverse square-root and (ii) inverse length equations. In this study, existing data for the strength of high strength pearlitic steel wires is evaluated for the coefficient of determination (R2 values). It is concluded that the data fits into two equations equally well. Thus, the choice between two groups of theories that predict respective relationships must rely on the merit of theoretical developments and assumptions made. Full article
(This article belongs to the Special Issue Dislocation Mechanics of Metal Plasticity and Fracturing)
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