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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>>
>
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