iMechanica - Comments for "Working with 4th order tensors - UMAT?"
https://imechanica.org/node/19634
Comments for "Working with 4th order tensors - UMAT?"enYou can use as it is!
https://imechanica.org/comment/28506#comment-28506
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<p><em>In reply to <a href="https://imechanica.org/node/19634">Working with 4th order tensors - UMAT?</a></em></p>
<div class="field field-name-comment-body field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p>Even I use 4th order tensors in my UMAT, there are two options - </p>
<p>1) Use it as such, mostly you would be computing the stiffness tensor with respect to another coordinate system .i.e. C'_ijkl = R_ip R_jq R_kr R_ls C_pqrs</p>
<p>Calculate the rotation matrix (R ) and you may use 4 for loops to do this transformation, after the transformation you can convert it to voigt notation </p>
<p>2) Instead of doing the tranformation using the fourth order tensor, you may also do it on voigt's notation. But the transformation matrix carries the factors of 2 and sqrt(2) terms, IF I remember correctly. I best believe, you can find this in the Micromechanics of defects by T.Mura</p>
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</ul>Thu, 04 Aug 2016 15:04:50 +0000rajan_prithivicomment 28506 at https://imechanica.orgAvoid 4th order tensors if you can
https://imechanica.org/comment/28195#comment-28195
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<p><em>In reply to <a href="https://imechanica.org/node/19634">Working with 4th order tensors - UMAT?</a></em></p>
<div class="field field-name-comment-body field-type-text-long field-label-hidden"><div class="field-items"><div class="field-item even"><p>It is much better to avoid explicitly representing 4th order tensors if you can. When starting to write my own UMAT, I wrote up a little tutorial on formatting the tangent stiffness matrix. You can find it at the following</p>
<p><a href="https://drive.google.com/file/d/0BzO5SDANDZyjQUVScDRTRnRleVk/view">https://drive.google.com/file/d/0BzO5SDANDZyjQUVScDRTRnRleVk/view</a></p>
<p>That should answer all your questions. Any additional questions should be answered in Abaqus' documentation.</p>
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</ul>Wed, 30 Mar 2016 10:58:31 +0000mswancomment 28195 at https://imechanica.org