problem with Stress

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problem with Stress

Postby mohammmad » Thu Oct 11, 2018 1:25 am

Hi all,
I have an 2ِD element that in each section of the element there are three component: strainXX, strainYY, and strainXY. I use ND material, first plain-strain J2 Plasticity Material for steel section and second plain-strain Drucker Prager Material.
Because of the specific cross - section conditions, I set the variable (strainYY) in such a way that stressYY is 0.0. In order to set stressYY=0.0, I got the tangent stiffness matrix(getTangent) of the material each time and did this:

see th picture :
[URL=http://uupload.ir/view/kt8u_capture2.png][IMG]http://uupload.ir/files/kt8u_capture2_thumb.png[/IMG][/URL]
http://uupload.ir/files/kt8u_capture2.png
Code:
const Matrix& newK = theMat->getTangent();
strain(1) = -((strain(0)*newK(1, 0) + strain(2)*newK(1, 2)) / (newK(1, 1)));


But, the problem is when I set this new strain vector with "theMat->setTrialStrain(strain);" and after that, I call "theMat->getStress();", in the resultant stress vector stressYY (in vector is stress(1)) is not zero.
why?
mohammmad
 
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Joined: Tue Aug 21, 2018 4:10 am



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