iMechanica - Comments for "Constitutive models for rubber"
https://imechanica.org/node/13783
Comments for "Constitutive models for rubber"enDear Matt,
thank you
https://imechanica.org/comment/22715#comment-22715
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<p><em>In reply to <a href="https://imechanica.org/node/13783">Constitutive models for rubber</a></em></p>
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Dear Matt,
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thank you so much. You were able to clarify me this little doubts about these argouments.</p>
<p>Now I understand.
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Italo
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</ul>Thu, 06 Dec 2012 23:53:21 +0000Italo Persechinocomment 22715 at https://imechanica.orgQuick answers
https://imechanica.org/comment/22623#comment-22623
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<p><em>In reply to <a href="https://imechanica.org/node/13783">Constitutive models for rubber</a></em></p>
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HI Italo,
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The first equation is correct for the Cauchy stress in an incompressible material. The second equation is for the first Piola-Kirchoff stress, which some refer to as the nominal stress. This all has to do with stress measures.
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The problem with the pressure is that in an incompressible material it is not solely a function of the deformation. The stress calculated from the deformation for an incompressible material will only be a deviatoric stress. The pressure field consistent with a deviatoric stress field must satisfy boundary conditions and equations of equilibrium (or of motion if the problem is dynamic).
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To get a real understanding of this, I suggest you delve a little deeper into Ogden or into Holzapfel's Nonlinear Solid Mechanics. <img src="http://www.imechanica.org/modules/tinymce/includes/jscripts/tiny_mce/plugins/emotions/images/smiley-cool.gif" border="0" alt="Cool" title="Cool" /></p>
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Matt Lewis<br />
Los Alamos, New Mexico
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</ul>Wed, 05 Dec 2012 17:52:06 +0000Matt Lewiscomment 22623 at https://imechanica.orgError | iMechanica