Dear Zhenghuai Guo,
If I understand correctly, you're trying to model creep with contact. If
so, then you can probably assume that your elastic properties are weakly
coupled with stress. In that case you can probably just update your elastic
properties every time step.
So, you need to write a loop where you change the properties every step.
Here are some ideas
1) Your elastic properties lambda and mu cannot be fixed sized constants,
as they will depend on stress values throughout the domain. The logical way
to handle this is
by setting them as a so-called im_data, which is a field defined on
Gauss points (on mesh_im class). Please look up documentation or source how
to add im_data.
2) Isotropic linearized elastic brick does not compute and store stress
field. You will need to define stress field as im_data too and compute it
from your solution
using probably high-level assembly syntax
<http://getfem.org/userdoc/interMM.html#interpolation-based-on-the-high-level-weak-form-language>
ga_interpolation_im_data(md, "lambda*Trace(Grad_u)*Id(qdim(u)) +
mu*(Grad_u+Grad_u'))" , im_data &imd_stress, base_vector
&stress_result_vector);
3) The whole calculation should look like this:
initialize the elastic properties as im_data
create im_data for the stress
add contact bricks
while(t < T)
{
md.solve();
compute the stresses from the displacement field using high-level
assembly syntax interpolations
compute the new values for the elastic properties with high-level
assembly syntax interpolations
post-process;
t = t + delta T;
}
Best regards,
Andriy
On Fri, 16 Nov 2018 at 04:42, Zhenghuai Guo <[email protected]>
wrote:
> Dear Andriy,
>
>
>
> I am planning to do a time dependent deformation with consideration of the
> contact and friction. I would like to apply the elasticity theory with
> Young’s modulus being a function of time and local stress value.
>
>
>
> Could you please advise about the following?
>
>
>
> 1. If I use *add_isotropic_linearized_elasticity_brick (mim, varname,
> dataname_lambda, dataname_mu, region=None), *how can I make the
> Young’s modulus time and stress dependent? In the test examples e.g. in
> demo_tripod.py, Young’s modulus is only added by the method
> *add_initialized_data* as a constant scalar value.
> 2. If I carry out elasticity formulation by a approach like the one in
> demo_tripod_alt.py using low level approach to building the linear system
> by hand, can I in the meantime apply together the bricks framework e.g.
> *add_master_contact_boundary_to_large_sliding_contact_brick(indbrick,
> mim, region, dispname, wname=None)?*
>
>
>
>
>
> Thank you very much
>
> Best regards
>
> Zhenghuai Guo
>
>
>
>
>
>
>
> *From:* Andriy Andreykiv <[email protected]>
> *Sent:* Thursday, November 8, 2018 8:56 PM
> *To:* Zhenghuai Guo <[email protected]>
> *Cc:* [email protected]
> *Subject:* Re: [Getfem-users] mesh_deformation
>
>
>
> Dear Zhenghuai Guo,
>
>
>
> You can build getfem and getfem based programs using either GCC c++
> compiler for Linux based systems
>
> (read Page 5 of the user doc:
> http://download-mirror.savannah.gnu.org/releases/getfem/doc/gmm_userdoc.pdf
> )
>
> or with Microsoft Visual Studio (you can use free Community edition). You
> can find MSVC solution in msvc directory of the distribution.
>
> Unfortunately, the solution for MSVC is not kept up-to-date and you would
> need to re-add all getfem sources to it to make it work.
>
>
>
> You can deform your mesh with a simple call:
>
> auto deformator = temporary_mesh_deformator(mf, U, true, false);
>
> //the first true means "deform on creation", the second false means
> "do not restore the mesh back when temporary_mesh_deformator reaches the
> end of life"
>
> mf - is the mesh_fem for your displacement field and U is the
> displacement vector with gmm::vect_size(U) = mf.nb_dof();
>
>
>
> Best regards,
>
> Andriy
>
>
>
>
>
> On Thu, 8 Nov 2018 at 01:15, Zhenghuai Guo <[email protected]>
> wrote:
>
> Dear Andriy,
>
>
>
> Thank you for your explanation.
>
>
>
> Regarding creep, at the moment I only use liner_elasticity_brick with
> young’s modulus being changed on each time-step. This is just to start
> with. I am new in Getfem in fact.
>
>
>
> Could you please advise about the follows?
>
>
>
> 1. Are you using c++ to run getfem? If so, can you give some hints
> how I can to it? I can’t see any instruction about setting up for c++.
> 2. If you don’t use c++, how do you normally use the
> *getfem::temporary_mesh_deformator
> (from getfem_deformable_mesh.h) or other C functions? *
>
>
>
> I was trying to see if it is possible to use this function in Python
> interface by using SWIG or Python.Boost. But it is far beyond my knowledge.
>
>
>
> Thank you very much
>
>
>
> Regards
>
> Zhenghuai Guo
>
>
>
> *From:* Andriy Andreykiv <[email protected]>
> *Sent:* Wednesday, November 7, 2018 8:32 PM
> *To:* Zhenghuai Guo <[email protected]>
> *Cc:* [email protected]
> *Subject:* Re: [Getfem-users] mesh_deformation
>
>
>
> Dear Zhenghuai Guo,
>
>
>
> I don't use Python interface much, but your assumption is correct,
> using getfem::temporary_mesh_deformator (from getfem_deformable_mesh.h)
> you can apply displacement field to the mesh.
>
> By default temporary_mesh_deformator will deform the mesh and un-deform
> it in the destructor, unless you build it with the argument
> to_be_restored=false.
>
> I only assume that you can do it with Python too.
>
>
>
> I'm not really experienced with creep, but intuitively I would assume that
> you can also use large deformation formulation to account for the change in
> geometry.
>
> Or it's not how you intend it?
>
>
>
> In your follow up email you are asking about the usage of mesh slices.
> From what I know it's used primarily for post-processing, not calculation.
> If you intend to use it solely for
>
> post-processing than you can easily achieve it nowadays with Paraview,
> were you import a vtk file, warp the result with a displacement field and
> take a desired slice.
>
>
>
> Best regards,
>
> Andriy
>
>
>
> On Sat, 3 Nov 2018 at 12:33, Zhenghuai Guo <[email protected]>
> wrote:
>
> Dear Sir or Madam,
>
>
>
> Could you please advise how I and deform a mesh according to a
> displacement field?
>
>
>
> I am trying to simulate a time dependent deformation of a cylinder like
> object using python-interface. After applying stress the object creeps with
> time.
>
>
>
> I think I can just go with many small time steps. In each time step, I
> would like to update and deform the mesh according to the displacement
> calculated as a function of time. And the deformed mesh will be an input
> for next time step.
>
>
>
> I can see there is some related information such as (1)
> ‘getfem_deformable_mesh.h’ in page 18 in
> https://download-mirror.savannah.gnu.org/releases/getfem/doc/getfem_project.pdf
> (2) ‘getfem::slicer_apply_deformation’ in
> http://getfem.org/userdoc/export.html#getfem::slicer_apply_deformation .
> But I can find details examples.
>
>
>
> Thank you very much
>
> Zhenghuai Guo
>
> *Tyree Xray CT network facility, School of Minerals and Energy Engineering
> Resources, UNSW Sydney*
>
>
>
>
>
>
>
>
