Dear Kostas,
Thanks for the reply. I am using large strain law and using python language.
I have a 3D-mesh and mfu1 is the displacement fem for mesh1. CONTACT_BOUND
is the region where I am trying to calculate the stress tensor.
I am trying something of this sort below. Could you please check and tell
me if what I am doing is correct or not. I reshape the stress tensor into
9*(no. of dof /3) as 3-dimension tensor will have 9 components and md is
model object.
stress = np.reshape(md.interpolation("lambda*Trace(Grad_u1 +
Grad_u1')*Id(3) + mu*(Grad_u1 + Grad_u1')", mfu1,
CONTACT_BOUND),(9,mfu1.nbdof()/3),'F')
Thanking You
Yours sincerely
Samyak Jain
On Thu, Jan 26, 2017 at 5:07 PM, Konstantinos Poulios <
[email protected]> wrote:
> Dear Samyak
>
> It would be helpful to know which material law you use (small or large
> strains?) and which programming language (python, matlab, scilab, C++?).
>
> E.g for small strains elasticity in python, something like this should
> work:
>
> mass_mat_t = gf.asm_mass_matrix(mim, mft)
> for i,j in [[1,1],[2,2],[1,2]]:
> sigmaij = gf.asm_generic(mim, 1, "({Lambda}*Div_u*Id(qdim(u)) +
> {Mu}*(Grad_u+Grad_u'))({i},{j})*Test_t".format(Lambda=Lambda, Mu=Mu, i=i,
> j=j), -1,
> "u", False, mfu, md.variable("u"),
> "t", True, mft, np.zeros(mft.nbdof()))
> sigmaij = np.transpose(gf.linsolve_mumps(mass_mat_t, sigma))
>
> Then sigmaij has the ij component of the stress tensor projected on the
> finite element space defined in mft. If mft is a Lagrangian FEM the values
> of sigmaij will correspond to the nodes of mft. The projection from gauss
> points to the finite element space is as Yves mentioned some kind of
> averaging.
>
> I hope this helps.
>
> Best regards
> Kostas
>
>
>
> On Thu, Jan 26, 2017 at 2:48 AM, samyak jain <[email protected]>
> wrote:
>
>> Dear Yves,
>>
>> Thanks a lot for your reply. I am not sure what you mean there. I have
>> gone through the example and they calculate Von Mises Stress but there is
>> already a function for that. Could you please tell me which physical
>> quantity or expression is being interpolated in that example so that I can
>> use it as a basis for my pressure calculation. It would be really helpful
>> if you would elaborate a bit on the usage and the example for calculating
>> any expression as I am quite new to fem and getfem. Thanks a lot.
>>
>> Yours sincerely
>> Samyak
>>
>> On Wed, Jan 25, 2017 at 6:44 PM, Yves Renard <[email protected]>
>> wrote:
>>
>>>
>>> Dear Samyak,
>>>
>>> There is no specific function for that, but you can use the
>>> interpolation facilities of the model object. You can see an example of use
>>> for instance in the demo_thermo_elasticity_electrical_coupling example
>>> which has a python, Matlab, Scilab and C++ version. You can interpolate
>>> any expression. Be aware that the stress being discontinuous across the
>>> element edges/faces, the value will be averaged.
>>>
>>> Regards,
>>>
>>> Yves
>>>
>>>
>>> Le 25/01/2017 à 06:08, samyak jain a écrit :
>>>
>>> Dear getfem-users,
>>>
>>> I have started using getfem recently to work on few contact problems
>>> between elastic bodies.
>>>
>>> I am able to solve few simple cases and I am able to compute
>>> displacement (u) and Von-Mises/Tresca values on my mesh nodes.
>>>
>>> The problem I am facing is that I have to calculate pressure at the mesh
>>> points and for that I believe I need the stress tensor values at these
>>> discrete mesh points. Could someone please guide me or tell me how to get
>>> the value of these variables. I went through the documentation and checked
>>> everywhere but I couldn't find a way to calculate stress tensor/pressure.
>>>
>>> Thanks a lot.
>>>
>>> Samyak
>>>
>>>
>>>
>>> _______________________________________________
>>> Getfem-users mailing
>>> [email protected]https://mail.gna.org/listinfo/getfem-users
>>>
>>>
>>>
>>> --
>>>
>>> Yves Renard ([email protected]) tel : (33) 04.72.43.87.08
>>> Pole de Mathematiques, INSA-Lyon fax : (33) 04.72.43.85.29
>>> 20, rue Albert Einstein
>>> 69621 Villeurbanne Cedex, FRANCE
>>> http://math.univ-lyon1.fr/~renard
>>>
>>> ---------
>>>
>>>
>>> _______________________________________________
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>>> https://mail.gna.org/listinfo/getfem-users
>>>
>>>
>>
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>>
>
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