Dear Kosta,
In your equation below, could you explain me few things.
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))
1) Could you please explain the terms/variables mft, "t", "sigma".
Also, I believe your expression above is for a 2D case.
Thanks
Yours sincerely
Samyak Jain
On Thu, Jan 26, 2017 at 7:27 PM, samyak jain <[email protected]>
wrote:
> Dear Kosta,
>
> I will try the projection method you mentioned in your previous mail. I am
> using 'add_integral_large_sliding_contact_brick_raytracing' and then I am
> adding slave and master brick with boundary conditions for my contact
> problem. Actually I need to calculate pressure everywhere and not just the
> contact region. I just tried to calculate in on the contact surface. I will
> try the projection method you mentioned and will let you know how it goes.
>
> Thanks for your help.
>
> Yours sincerely
> Samyak
>
>
>
>
> On Thu, Jan 26, 2017 at 7:21 PM, Konstantinos Poulios <
> [email protected]> wrote:
>
>> Dear Samyak
>>
>> The projection method of my previous mail works also for large strains if
>> you simply replace the expression for the stress tensor with the
>> corresponding one. Of course, as you suggested you can also do an
>> interpolation instead of projection, but then you depend on the averaging
>> that the interpolation function of GetFEM++ will do behind the scene for
>> the discontinuous field that you are working with. I have never tried it on
>> a surface, so I cannot say how it works.
>>
>> But if you care only about the contact interface, why don't you simply
>> use the Lagrange multiplier which already describes the traction on this
>> surface? Which contact algorithm do you use?
>>
>> Best regards
>> Kosta
>>
>>
>>
>> On Thu, Jan 26, 2017 at 10:47 AM, samyak jain <[email protected]
>> > wrote:
>>
>>> 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 <samyakjainsamyak@gmail.
>>>> com> 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
>>>>>>
>>>>>> ---------
>>>>>>
>>>>>>
>>>>>> _______________________________________________
>>>>>> Getfem-users mailing list
>>>>>> [email protected]
>>>>>> https://mail.gna.org/listinfo/getfem-users
>>>>>>
>>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> Getfem-users mailing list
>>>>> [email protected]
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>>>>>
>>>>>
>>>>
>>>
>>
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