Editorial Board Members’ Collection Series: Metal Crystal/Polycrystal Plastic Strain Hardening

A special issue of Metals (ISSN 2075-4701). This special issue belongs to the section "Crystallography and Applications of Metallic Materials".

Deadline for manuscript submissions: 30 September 2024 | Viewed by 8108

Special Issue Editors


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Guest Editor
DEVCOM Army Research Laboratory, Aberdeen Proving Ground, Adelphi, MD 21005, USA
Interests: mechanics; physics; materials science; applied mathematics; differential geometry
*
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Guest Editor
Department of Mechanical Engineering, A. James Clark School of Engineering, University of Maryland, College Park, MD 20742, USA
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
* passed away on May 2023
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Special Issue Information

Dear Colleagues,

Pronouncements in recent years about the lack of progress in understanding metal plastic strain hardening that occurs between yielding and fracturing do not fully correspond with subsequent research reports made on the subject.  The stated lack of progress after Taylor’s model description of a parabolic stress–strain curve will be refuted in the present Special Issue update on “Metal Crystal/Polycrystal Plastic Strain Hardening”.  Post-Taylor considerations of interest include but are not limited to the nature of deformation-induced point defect production, a role for partial dislocation/stacking fault characterizations, dislocation intersections/reactions, dislocation group dynamics, and dislocation pile-up/grain boundary obstacle associations.  Strain hardening roles in stress–strain, fatigue, and hardness tests, in the latter case especially involving nano-indentation hardness testing, are to be characterized and correlated with corresponding constitutive modeling of plasticity/hardening and computational simulations of metal behaviors. Particular attention is given to the several sub-topics of metal processing via severe plastic deformation, the evolution of micro- and nano-scale structures and strength levels, and to additive metal manufacturing methods.

Contributions describing experiments, theory, and/or numerical simulations are all welcome. Techniques can involve one or more length/time scales. For example, modeling can include DFT, molecular dynamics, discrete dislocation dynamics, phase field methods, continuum dislocation theory, anisotropic single/polycrystal crystal plasticity, strain gradient theory, and/or macroscopic continuum plasticity. Time scales can range from very long (e.g., quasi-static indentation, fatigue) to very short (e.g., shockwaves and impact). Regarding constitutive modeling, classical analytical and emerging machine learning-driven approaches are of interest. In any case, papers will include some aspects related to the keywords, most notably plastic yielding and strain hardening in crystalline solids, as evidenced by the title of this Special Issue.

Dr. John D. Clayton
Prof. Dr. Ronald W. Armstrong
Guest Editors

Manuscript Submission Information

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Keywords

  • strain hardening
  • dislocations
  • crystals
  • polycrystals
  • plastic yielding
  • dislocation intersections/reactions
  • stress–strain
  • fatigue
  • hardness
  • fracture

Published Papers (5 papers)

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Editorial

Jump to: Research, Review

7 pages, 1812 KiB  
Editorial
Metal Crystal/Polycrystal Plasticity and Strengths
by Ronald W. Armstrong
Metals 2022, 12(12), 2070; https://doi.org/10.3390/met12122070 - 01 Dec 2022
Cited by 1 | Viewed by 1304
Abstract
A brief historical sketch is given of Taylor’s dislocation density-based model description, leading to the prediction of a parabolic, tensile, stress–strain curve for the plastic deformation of aluminum. The present focus is on additional results or analyses obtained on the subject for crystal/polycrystal [...] Read more.
A brief historical sketch is given of Taylor’s dislocation density-based model description, leading to the prediction of a parabolic, tensile, stress–strain curve for the plastic deformation of aluminum. The present focus is on additional results or analyses obtained on the subject for crystal/polycrystal strain hardening. Our current understanding of such material behavior is attributed to post-Taylor descriptions of sequential deformation stages in stress–strain measurements that are closely tied to specific dislocation interaction and reaction mechanisms. A schematic comparison is given for individual face-centered cubic (fcc), body-centered cubic (bcc), and hexagonal close-packed (hcp) crystal curves and to related strength properties determined for individual crystals and polycrystalline material. For the fcc case, an example sessile dislocation reaction is described based on a stereographic projection. Then, quantitative constitutive-relation-based assessments are presented for the tensile strain hardening leading to the plastic instability behaviors of copper and tantalum materials. Full article
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Research

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13 pages, 1493 KiB  
Article
Hall–Petch Description of the Necking Point Stress
by Alexey Vinogradov and Yuri Estrin
Metals 2023, 13(4), 690; https://doi.org/10.3390/met13040690 - 31 Mar 2023
Viewed by 1367
Abstract
We posited that the grain size dependence of the tensile necking stress, as determined by the Considère criterion for plastic instability, is a more meaningful characteristic of the Hall–Petch (H–P) effect than that of the yield stress or the 0.2% proof stress. An [...] Read more.
We posited that the grain size dependence of the tensile necking stress, as determined by the Considère criterion for plastic instability, is a more meaningful characteristic of the Hall–Petch (H–P) effect than that of the yield stress or the 0.2% proof stress. An inverse square-root dependence of the necking stress on the grain size was derived from a dislocation dynamics-based constitutive model. In this model, the grain size effect enters the stress indirectly via the evolution of the dislocation density. Model predictions were confirmed by the experimental data for nickel and titanium. Full article
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17 pages, 1940 KiB  
Article
Atomistic-Continuum Constitutive Modeling Connection for Gold Foams under Compression at High Strain Rates: The Dislocation Density Effect
by Mohammed H. Saffarini and George Z. Voyiadjis
Metals 2023, 13(4), 652; https://doi.org/10.3390/met13040652 - 25 Mar 2023
Cited by 3 | Viewed by 1246
Abstract
Constitutive description of the plastic flow in metallic foams has been rarely explored in the literature. Even though the material is of great interest to researchers, its plasticity remains a topic that has a much room for exploration. With the help of the [...] Read more.
Constitutive description of the plastic flow in metallic foams has been rarely explored in the literature. Even though the material is of great interest to researchers, its plasticity remains a topic that has a much room for exploration. With the help of the rich literature that explored the material deformation mechanism, it is possible to introduce a connection between the results of the atomistic simulations and the well-established continuum constitutive models that were developed for various loading scenarios. In this work, we perform large-scale atomistic simulations of metallic gold foams of two different sizes at a wide range of strain rates (107109 s1) under uniaxial compression. By utilizing the results of those simulations, as well as the results we reported in our previous works, a physical atomistic-continuum dislocations-based constitutive modeling connection is proposed to capture the compressive plastic flow in gold foams for a wide range of sizes, strain rates, temperatures, and porosities. The results reported in this work present curated datasets that can be of extreme usefulness for the data-driven AI design of metallic foams with tunable nanoscale properties. Eventually, we aim to produce an optimal physical description to improve integrated physics-based and AI-enabled design, manufacture, and validation of hierarchical architected metallic foams that deliver tailored mechanical responses and precision failure patterns at different scales. Full article
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16 pages, 1573 KiB  
Article
Yield Surfaces and Plastic Potentials for Metals, with Analysis of Plastic Dilatation and Strength Asymmetry in BCC Crystals
by Aleksander Zubelewicz and John D. Clayton
Metals 2023, 13(3), 523; https://doi.org/10.3390/met13030523 - 05 Mar 2023
Cited by 1 | Viewed by 1517
Abstract
Since the 1980s, constitutive modeling has steadily migrated from phenomenological descriptions toward approaches that are based on micromechanics considerations. Despite significant efforts, crystal plasticity remains an open field of research. Among the unresolved issues are the anomalous behavior of metals at low temperatures [...] Read more.
Since the 1980s, constitutive modeling has steadily migrated from phenomenological descriptions toward approaches that are based on micromechanics considerations. Despite significant efforts, crystal plasticity remains an open field of research. Among the unresolved issues are the anomalous behavior of metals at low temperatures and the stress upturn at extreme dynamics. This work is focused on the low-temperature responses of body-centered-cubic (bcc) metals, among them, molybdenum (Mo). At these conditions, the plastic flow strength is governed by the motion of screw dislocations. The resultant non-planarity of core structures and slip causes the following: the shear stress includes non-glide components, the Schmid law is violated, there is a tension-compression asymmetry, and the yield surface and plastic potential are clearly decoupled. We find that the behavioral complexities can be explained by atomistically resolved friction coefficients in macroscopic yield and flow. The plastic flow mechanisms establish the departure point into the follow-up analysis of yield surfaces. For example, we know that while the von Mises stress is explained based on energy considerations, we will also show that the stress has a clear geometric interpretation. Moreover, the von Mises stress is just one case within a much broader class of equivalent stresses. Possible correlations among non-Schmid effects (as represented macroscopically by friction coefficients), volume change (i.e., residual elastic dilatation) from dislocation lines, and elastic anisotropy are investigated. Extensions to the shock regime are also established. Full article
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Review

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32 pages, 1155 KiB  
Review
Toward Material Property Extraction from Dynamic Spherical Indentation Experiments on Hardening Polycrystalline Metals
by John D. Clayton, Daniel T. Casem, Jeffrey T. Lloyd and Emily H. Retzlaff
Metals 2023, 13(2), 276; https://doi.org/10.3390/met13020276 - 30 Jan 2023
Cited by 3 | Viewed by 1641
Abstract
Static indentation and dynamic indentation are reviewed, with a focus on extraction of material properties of isotropic strain-hardening polycrystalline metals that may be rate- and temperature-sensitive. Static indentation is reviewed first, followed by dynamic indentation, since the former is regarded as a specialization [...] Read more.
Static indentation and dynamic indentation are reviewed, with a focus on extraction of material properties of isotropic strain-hardening polycrystalline metals that may be rate- and temperature-sensitive. Static indentation is reviewed first, followed by dynamic indentation, since the former is regarded as a specialization of the latter with inertia, rate dependence, and adiabatic heating excluded. Extending concepts from the literature review, a treatment of dynamic indentation using dimensional analysis is forwarded, and a general framework for extraction of material property information (i.e., constitutive model parameters) from instrumented dynamic spherical indentation experiments is set forth. In an example application of the methodology, experimental data obtained from instrumented spherical indentation in a miniature Kolsky bar apparatus are evaluated via dimensional analysis. The substrate material is aluminum alloy Al 6061-T6. Several definitions of indentation strain proposed for static indentation are assessed for dynamic indentation, as are indentation strain rates. While the fidelity of the experimental method and inertial effects could inhibit extraction of elastic properties, extraction of certain plastic constitutive properties may be feasible. Current data are insufficient to enable determination of a complete and unique set of all physical properties. Motivated by the present review and analysis, new experiments and simulations are proposed that would identify influences of material properties, facilitating their extraction from data. Full article
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