RaminBabaei's blog
https://imechanica.org/blog/4462
enA crystal plasticity continuum theory with length scale dependent internal residual stress and free surface effect
https://imechanica.org/node/13113
<div class="field field-name-taxonomy-vocabulary-6 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/76">research</a></div></div></div><div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/1040">Crystal plasticity</a></div><div class="field-item odd"><a href="/taxonomy/term/6200">Geometrically Necessary Dislocation Density</a></div><div class="field-item even"><a href="/taxonomy/term/7928">Nonlocal continuum theory</a></div><div class="field-item odd"><a href="/taxonomy/term/7929">Internal stress</a></div><div class="field-item even"><a href="/taxonomy/term/7936">Free surface</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p class="MsoNormal" align="justify">
<span>The long range elastic interaction between dislocations is naturally accounted in<br />
discrete dislocation plasticity through stress field of individual dislocation.<br />
In addition, the dislocation boundaries elastic interaction is considered via<br />
image stress superposition approach in the finite element framework. In current<br />
study these interaction terms are considered in crystal plasticity framework<br />
through length scale dependent internal residual stresses which are arise from<br />
two sources: (I) long-range elastic interaction between geometrically necessary<br />
dislocations (GNDs) in an infinite medium and (II) their interaction with<br />
boundaries appearing as image effects.</span>
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<p class="MsoNormal">
<span>The formulation is applied to the case of a long, thin specimen subjected to uniform curvature<br />
which mimics the micro beam under pure bending. The analysis shows that even<br />
under nominally uniform GND density distribution, internal stresses present due<br />
to the finite spatial extent of the GND density field and free surfaces effects<br />
which were not captured in the previous developed strain gradient theories. A<br />
comparison with experimental results suggests that the length-scale for<br />
internal stresses, described as a correlation length-scale, should increase<br />
with decreasing specimen thickness (Motz et al, 2005). This observation is rationalized by<br />
associating the internal length-scale with the average slip-plane spacing,<br />
which may increase with decreasing specimen size due to paucity of dislocation<br />
sources. Finally, we also discuss the length-scale dependent image stress in<br />
terms of the Peach-Koehler force density proposed by Gurtin (2002). </span></p>
<p>1) <a href="http://www.sciencedirect.com/science/article/pii/S0022509612001391">http://www.sciencedirect.com/science/article/pii/S0022509612001391</a> </p>
<p>2) <a href="http://www.sciencedirect.com/science/article/pii/S0022509610002371">http://www.sciencedirect.com/science/article/pii/S0022509610002371</a>
</p>
</div></div></div>Wed, 12 Sep 2012 02:53:56 +0000RaminBabaei13113 at https://imechanica.orghttps://imechanica.org/node/13113#commentshttps://imechanica.org/crss/node/13113Need help about nanocomposite materials
https://imechanica.org/node/2322
<div class="field field-name-taxonomy-vocabulary-8 field-type-taxonomy-term-reference field-label-hidden"><div class="field-items"><div class="field-item even"><a href="/taxonomy/term/447">Finite Element Method</a></div><div class="field-item odd"><a href="/taxonomy/term/1498">modeling</a></div><div class="field-item even"><a href="/taxonomy/term/1549">nanocomposite</a></div></div></div><div class="field field-name-body field-type-text-with-summary field-label-hidden"><div class="field-items"><div class="field-item even"><p><span>I am Ramin Aghababaei , new PhD student at Mechanical Department of National University of Singapore. My thesis is about finite element modelling of nanocomposites. </span><span> </span><span>Because I am at the first way of my research, I want to know more about my research topic and know exactly why I want to do or what is the problem and how can I solve it? </span><span> </span><span>So I have some questions and your experience is invaluable for me in this way.</span><span> </span><span>1-what are the important parameters in the modelling of nanostructures which must be considered?</span><span> </span><span>2-what is the main problem of current finite element method to model the nanostructure, especially nanocomposite materials(for example in traditional methods or in ABAQUS program)?</span><span> </span><span>3-Can we expand traditional methods like as Rayleigh-Ritz or Least square methods to model and analysis of nanocomposites? </span><span> </span><span>Thank you very much .</span><span> </span><span>Regards,</span><span> </span><span>Ramin</span><span> </span></p>
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</div></div></div>Tue, 20 Nov 2007 07:38:30 +0000RaminBabaei2322 at https://imechanica.orghttps://imechanica.org/node/2322#commentshttps://imechanica.org/crss/node/2322