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==1 Title, abstract and keywords==
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== Abstract ==
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Plastic flow in crystal at micron-nano scales involves many new interesting issues. Some results are
 +
obtained for uniaxial compression experiments conducted on FCC single crystal micro-pillars, e.g.
 +
size effect and strain burst, etc. [<span id='cite-1'></span>[[#1|1]]]. In these experiments, the surfaces are transmissible and loading
 +
gradients are absent. Therefore, the strain gradient theory could not well explain these new
 +
mechanical behaviors. This in turn has led to several hypotheses based on intuitive insights, classical
 +
theory and dislocation plasticity in order to study the size effect at submicron scale. In the model
 +
proposed [<span id='cite-2'></span>[[#2|2]]], mobile dislocations may escape from the free surface leading to the state of dislocation
 +
starved whereby an increase in the applied stress is necessary to nucleate or activate new dislocation
 +
sources. By performing in-situ TEM [<span id='cite-3'></span>[[#3|3]]], the dislocation motion affected the material properties is
 +
observed. However, the atypical plastic behavior at submicron scales cannot be effectively
 +
investigated by either traditional crystal plastic theory or large-scale molecule dynamics simulation.
  
−
Your paper should start with a concise and informative title. Titles are often used in information-retrieval systems. Avoid abbreviations and formulae where possible. Capitalize the first word of the title.
+
Accordingly, the discrete dislocation dynamics (DDD) coupling with finite element method (FEM)
 +
[<span id='cite-4'></span>[[#4|4]]], so a discrete-continuous crystal plastic model (DCM) is developed. Three kinds of plastic
 +
deformation mechanisms for the single crystal pillar at submicron scale are investigated. (1) Single
 +
arm dislocation source (SAS) controlled plastic flow. It is found that strain hardening is virtually
 +
absent due to continuous operation of stable SAS and weak dislocation interactions. When the
 +
dislocation density finally reaches stable value, a ratio between the stable SAS length and pillar
 +
diameter obeys a constant value. A theoretical model is developed to predict DDD simulation results
 +
and experimental data [<span id='cite-5'></span>[[#5|5]]]. (2) Confined plasticity in coated micropillars. Based on the simulation
 +
results and stochastic distribution of SAS, a theoretical model is established to predict the upper and
 +
lower bounds of stress-strain curve in the coated micropillars [<span id='cite-6'></span>[[#6|6]]]. (3) Dislocation starvation under
 +
low amplitude cyclic loading. This work argued that the dislocation junctions can be gradually
 +
destroyed during cyclic deformation, even when the cyclic peak stress is much lower than that
 +
required to break them under monotonic deformation. The cumulative irreversible slip is found to be
 +
the key factor of leading to junction destruction and promoting dislocation starvation under low
 +
amplitude cyclic loadings. Based on this mechanism, a proposed theoretical model successfully
 +
reproduces dislocation annihilation behavior observed experimentally for small pillar and dislocation
 +
accumulation behavior for large pillar. The predicted critical conditions of dislocation starvation
 +
agree well with the experimental data.
  
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Provide a maximum of 6 keywords, and avoiding general and plural terms and multiple concepts (avoid, for example, 'and', 'of'). Be sparing with abbreviations: only abbreviations firmly established in the field should be used. These keywords will be used for indexing purposes.
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== Recording of the presentation ==
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{| style="font-size:120%; color: #222222; border: 1px solid darkgray; background: #f3f3f3; table-layout: fixed; width:100%;"
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An abstract is required for every paper; it should succinctly summarize the reason for the work, the main findings, and the conclusions of the study. Abstract is often presented separately from the article, so it must be able to stand alone. For this reason, references and hyperlinks should be avoided. If references are essential, then cite the author(s) and year(s). Also, non-standard or uncommon abbreviations should be avoided, but if essential they must be defined at their first mention in the abstract itself.
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| {{#evt:service=youtube|id=https://youtu.be/_C15ed4MIE8|alignment=center}}
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==2 The main text==
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|- style="text-align: center;"  
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| Location: Technical University of Catalonia (UPC), Vertex Building.  
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You can enter and format the text of this document by selecting the ‘Edit’ option in the menu at the top of this frame or next to the title of every section of the document. This will give access to the visual editor. Alternatively, you can edit the source of this document (Wiki markup format) by selecting the ‘Edit source’ option.
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|- style="text-align: center;"
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| Date: 1 - 3 September 2015, Barcelona, Spain.
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Most of the papers in Scipedia are written in English (write your manuscript in American or British English, but not a mixture of these). Anyhow, specific journals in other languages can be published in Scipedia. In any case, the documents published in other languages must have an abstract written in English.
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===2.1 Subsections===
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Divide your article into clearly defined and numbered sections. Subsections should be numbered 1.1, 1.2, etc. and then 1.1.1, 1.1.2, ... Use this numbering also for internal cross-referencing: do not just refer to 'the text'. Any subsection may be given a brief heading. Capitalize the first word of the headings.
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===2.2 General guidelines===
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Some general guidelines that should be followed in your manuscripts are:
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:*  Follow internationally accepted rules and conventions. In particular use the international system of units (SI). If other quantities are mentioned, give their equivalent in SI.
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Please insert tables as editable text and not as images. Tables should be placed next to the relevant text in the article. Number tables consecutively in accordance with their appearance in the text (<span id='cite-_Ref382560620'></span>[[#_Ref382560620|table 1]], table 2, etc.) and place any table notes below the table body. Be sparing in the use of tables and ensure that the data presented in them do not duplicate results described elsewhere in the article.
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<span id='_Ref382560620'></span>
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{| style="margin: 1em auto 1em auto;border: 1pt solid black;border-collapse: collapse;"
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|-
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| style="text-align: center;"|Thickness
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| style="text-align: center;"|3.175 mm
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| style="text-align: center;"|Young Modulus
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| style="text-align: center;"|12.74 MPa
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| style="text-align: center;"|Poisson coefficient
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| style="text-align: center;"|0.25
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| style="text-align: center;"|Density
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| style="text-align: center;"|1107 kg/m<sup>3</sup>
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<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
 
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<span style="text-align: center; font-size: 75%;">Table 1: Material properties</span></div>
 
  
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Graphics may be inserted directly in the document and positioned as they should appear in the final manuscript.
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== General Information ==
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* Location: Technical University of Catalonia (UPC), Barcelona, Spain.
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* Date: 1 - 3 September 2015
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* Secretariat: [//www.cimne.com/ International Center for Numerical Methods in Engineering (CIMNE)].
  
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<span id='_Ref448852946'></span>
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== External Links ==
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<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
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* [//congress.cimne.com/complas2015/frontal/default.asp Complas XIII] Official Website of the Conference.
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[[Image:Scipedia.gif|center|480px]]
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* [//www.cimnemultimediachannel.com/ CIMNE Multimedia Channel]
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</div>
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<div class="center" style="width: auto; margin-left: auto; margin-right: auto;">
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<span style="text-align: center; font-size: 75%;">Figure 1. Scipedia logo.</span></div>
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Number the figures according to their sequence in the text (<span id='cite-_Ref448852946'></span>[[#_Ref448852946|figure 1]], figure 2, etc.). Ensure that each illustration has a caption. A caption should comprise a brief title. Keep text in the illustrations themselves to a minimum but explain all symbols and abbreviations used. Try to keep the resolution of the figures to a minimum of 300 dpi. If a finer resolution is required, the figure can be inserted as supplementary material
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==References==
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For tabular summations that do not deserve to be presented as a table, lists are often used. Lists may be either numbered or bulleted. Below you see examples of both.
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1. The first entry in this list
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2.1. A subentry
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You may choose to number equations for easy referencing. In that case they must be numbered consecutively with Arabic numerals in parentheses on the right hand side of the page. Below is an example of formulae that should be referenced as eq. <span id='cite-_Ref424030152'></span>[[#_Ref424030152|(1)]].
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| style="vertical-align: top;"| <math>{\nabla }^{2}\phi =0</math>
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(1)
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|}
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===2.4 Supplementary material===
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Supplementary material can be inserted to support and enhance your article. This includes video material, animation sequences, background datasets, computational models, sound clips and more. In order to ensure that your material is directly usable, please provide the files with a preferred maximum size of 50 MB. Please supply a concise and descriptive caption for each file.
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==3 Bibliography==
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<span id='_Ref449344604'></span>
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Citations in text will follow a citation-sequence system (i.e. sources are numbered by order of reference so that the first reference cited in the paper is [<span id='cite-1'></span>[[#1|1]]], the second [<span id='cite-2'></span>[[#2|2]]], and so on) with the number of the reference in square brackets. Once a source has been cited, the same number is used in all subsequent references. If the numbers are not in a continuous sequence, use commas (with no spaces) between numbers. If you have more than two numbers in a continuous sequence, use the first and last number of the sequence joined by a hyphen (e.g. [<span id='cite-1'></span>[[#1|1]], <span id='cite-3'></span>[[#3|3]]] or [<span id='cite-2'></span>[[#2|2]]-<span id='cite-2'></span>[[#4|4]]]).
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<span id='_Ref449084254'></span>
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You should ensure that all references are cited in the text and that the reference list. References should preferably refer to papers published in Scipedia. Unpublished results should not be included in the reference list, but can be mentioned in the text. The reference data must be updated once publication is ready. Complete bibliographic information for all cited references must be given following the standards in the field (IEEE and ISO 690 standards are recommended). If possible, a hyperlink to the referenced publication should be given. See examples for Scipedia’s articles [<span id='cite-1'></span>[[#1|1]]], other journal articles [<span id='cite-2'></span>[[#2|2]]], books [<span id='cite-3'></span>[[#3|3]]], book chapter [<span id='cite-4'></span>[[#4|4]]], conference proceedings [<span id='cite-5'></span>[[#5|5]]], and online documents [<span id='cite-6'></span>[[#6|6]]], shown in references section below.
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==4 Acknowledgments==
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Acknowledgments should be inserted at the end of the paper, before the references section.
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==5 References==
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[[#cite-1|[1]]] Author, A. and Author, B. (Year) Title of the article. Title of the Journal. Article code. Available: [http://www.scipedia.com/ucode. http://www.scipedia.com/ucode.]
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[[#cite-1|[1]]] MD. Uchic, DM. Dimiduk, JN. Florando, WD. Nix, Sample dimensions influence strength and
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crystal plasticity, Science, 305(2004), 986-989.
 
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[[#cite-2|[2]]] Author, A. and Author, B. (Year) Title of the article. Title of the Journal. Volume number, first page-last page.
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[[#cite-2|[2]]] JR. Greer, WC. Oliver, WD. Nix, Size dependence of mechanical properties of gold at the
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micron scale in the absence of strain gradients, Acta Mater, 53(2005), 1821-1830
 
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<div id="3"></div>
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[[#cite-3|[3]]] Author, C. (Year). Title of work: Subtitle (edition.). Volume(s). Place of publication: Publisher.
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[[#cite-3|[3]]] ZW. Shan, RK. Mishra, SAS. ASIF, et al., Mechanical annealing and source-limited
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deformation in submicrometre-diameter Ni crystals, Nat Mater, 7(2008), 115-119
 
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<div id="4"></div>
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[[#cite-4|[4]]] Author of Part, D. (Year). Title of chapter or part. In A. Editor & B. Editor (Eds.), Title: Subtitle of book (edition, inclusive page numbers). Place of publication: Publisher.
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[[#cite-4|[4]]] ZL. Liu, XM. Liu, Z. Zhuang, XC. You, A multi-scale computational model of crystal plasticity
−
 
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at submicron-to-nanometer scales, Int. J. Plasticity, 25(2009), 1436-1455
 
<div id="5"></div>
 
<div id="5"></div>
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[[#cite-5|[5]]] Author, E. (Year, Month date). Title of the article. In A. Editor, B. Editor, and C. Editor. Title of published proceedings. Paper presented at title of conference, Volume number, first page-last page. Place of publication.
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[[#cite-5|[5]]] YN. Cui, P. Lin, ZL. Liu, Z. Zhuang, Theoretical and numerical investigations of single arm
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dislocation source controlled plastic flow in FCC micropillars, Int. J. Plasticity, 55(2014), 279-
 +
292
 
<div id="6"></div>
 
<div id="6"></div>
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[[#cite-6|[6]]] Institution or author. Title of the document. Year. [Online] (Date consulted: day, month and year). Available: [http://www.scipedia.com/document.pdf http://www.scipedia.com/document.pdf]. [Accessed day, month and year].
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[[#cite-6|[6]]] YN. Cui, ZL. Liu, Z. Zhuang, Theoretical and numerical investigations on confined plasticity in
 +
coated pillars at microscale, J. Mech. Phys. Solids, 76(2015), 127-143

Latest revision as of 11:29, 19 July 2016

Abstract

Plastic flow in crystal at micron-nano scales involves many new interesting issues. Some results are obtained for uniaxial compression experiments conducted on FCC single crystal micro-pillars, e.g. size effect and strain burst, etc. [1]. In these experiments, the surfaces are transmissible and loading gradients are absent. Therefore, the strain gradient theory could not well explain these new mechanical behaviors. This in turn has led to several hypotheses based on intuitive insights, classical theory and dislocation plasticity in order to study the size effect at submicron scale. In the model proposed [2], mobile dislocations may escape from the free surface leading to the state of dislocation starved whereby an increase in the applied stress is necessary to nucleate or activate new dislocation sources. By performing in-situ TEM [3], the dislocation motion affected the material properties is observed. However, the atypical plastic behavior at submicron scales cannot be effectively investigated by either traditional crystal plastic theory or large-scale molecule dynamics simulation.

Accordingly, the discrete dislocation dynamics (DDD) coupling with finite element method (FEM) [4], so a discrete-continuous crystal plastic model (DCM) is developed. Three kinds of plastic deformation mechanisms for the single crystal pillar at submicron scale are investigated. (1) Single arm dislocation source (SAS) controlled plastic flow. It is found that strain hardening is virtually absent due to continuous operation of stable SAS and weak dislocation interactions. When the dislocation density finally reaches stable value, a ratio between the stable SAS length and pillar diameter obeys a constant value. A theoretical model is developed to predict DDD simulation results and experimental data [5]. (2) Confined plasticity in coated micropillars. Based on the simulation results and stochastic distribution of SAS, a theoretical model is established to predict the upper and lower bounds of stress-strain curve in the coated micropillars [6]. (3) Dislocation starvation under low amplitude cyclic loading. This work argued that the dislocation junctions can be gradually destroyed during cyclic deformation, even when the cyclic peak stress is much lower than that required to break them under monotonic deformation. The cumulative irreversible slip is found to be the key factor of leading to junction destruction and promoting dislocation starvation under low amplitude cyclic loadings. Based on this mechanism, a proposed theoretical model successfully reproduces dislocation annihilation behavior observed experimentally for small pillar and dislocation accumulation behavior for large pillar. The predicted critical conditions of dislocation starvation agree well with the experimental data.

Recording of the presentation

Location: Technical University of Catalonia (UPC), Vertex Building.
Date: 1 - 3 September 2015, Barcelona, Spain.

General Information

External Links

References

[1] MD. Uchic, DM. Dimiduk, JN. Florando, WD. Nix, Sample dimensions influence strength and crystal plasticity, Science, 305(2004), 986-989.

[2] JR. Greer, WC. Oliver, WD. Nix, Size dependence of mechanical properties of gold at the micron scale in the absence of strain gradients, Acta Mater, 53(2005), 1821-1830

[3] ZW. Shan, RK. Mishra, SAS. ASIF, et al., Mechanical annealing and source-limited deformation in submicrometre-diameter Ni crystals, Nat Mater, 7(2008), 115-119

[4] ZL. Liu, XM. Liu, Z. Zhuang, XC. You, A multi-scale computational model of crystal plasticity at submicron-to-nanometer scales, Int. J. Plasticity, 25(2009), 1436-1455

[5] YN. Cui, P. Lin, ZL. Liu, Z. Zhuang, Theoretical and numerical investigations of single arm dislocation source controlled plastic flow in FCC micropillars, Int. J. Plasticity, 55(2014), 279- 292

[6] YN. Cui, ZL. Liu, Z. Zhuang, Theoretical and numerical investigations on confined plasticity in coated pillars at microscale, J. Mech. Phys. Solids, 76(2015), 127-143

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