Hi Jean-Paul,
Another question which might be the reason why I am getting the
inconsistencies in my newton-raphson convergence. I just realised
this..
What I am doing is the following -
I am giving small compressive displacements to the
film+substrate. I am also calculating the eigenvalues of the
tangent_stiffness matrix (after the convergence of newton
method), to understand the stability of the system. The moment I
encounter a negative smallest eigenvalue, I want to go to a
previous time step and would like to solve for a small
compressive displacement. For instance, if the compression is 0.1
at this time step and the eigenvalue is negative, I go to the
previous time step and give a compressive displacement of 0.05.
Here is my concern, I have added a condition that, if I find a
negative eigenvalue during any time step, I update the
/solution_n = solution_n - solution_delta/; and then run the time
step again (with a smaller compressive displacement) after doing
/solution_delta = 0.0/. Since the next state is also dependent on
the updated quadrature point data (stresses etc.), I would also
need to update the quadrature point data to the previous step.
Could you please let me know, how am I supposed to do that?
In the documentation in code gallery
<https://dealii.org/developer/doxygen/deal.II/code_gallery_Quasi_static_Finite_strain_Compressible_Elasticity.html>,
it is written that -
"/The first function is used to create a material object and to
initialize all tensors correctly: The second one updates the
stored values and stresses based on the current deformation
measure //Grad//u//n/" (inside the Point History class). However,
I only find one function which is setup_lqp, and not the
update_lqp or something similar.
Thanks!
Animesh
On Tuesday, November 10, 2020 at 5:24:13 PM UTC+5:30 Animesh
Rastogi IIT Gandhinagar wrote:
Hi Jean-Paul,
There seem to be some inconsistencies in the simulations
results that I am getting, therefore I wanted to check if I
have applied the material laws properly accounting for the
heterogeneities. Below, I have addted the edited functions
that are responsible for that. Could you please let me know
if there is something wrong here? I have checked the material
properties (mu1, mu2 etc), and they are being read correctly
by the code from the parameters file. I have also checked
that the material ids (1 and 2) are correctly applied to the
cells where I need them.
--------------------------------------
void setup_lqp (const Parameters::AllParameters ¶meters,
const unsigned int &materialid)
{
//Material 1 - Thin Film
if (materialid == 1)
{
std::cout<<"1_id"<<std::endl<<parameters.mu1<<std::endl<<parameters.nu1<<std::endl;
material.reset(new
Material_Compressible_Neo_Hook_One_Field<dim,NumberType>(parameters.mu1,
parameters.nu1));
}
//Material 2 - Substrate
if (materialid ==2)
{
material.reset(new
Material_Compressible_Neo_Hook_One_Field<dim,NumberType>(parameters.mu2,
parameters.nu2));
}
}
-------------------------------------------
template <int dim,typename NumberType>
void Solid<dim,NumberType>::setup_qph()
{
std::cout << " Setting up quadrature point data..." <<
std::endl;
quadrature_point_history.initialize(triangulation.begin_active(),
triangulation.end(),
n_q_points);
for (typename Triangulation<dim>::active_cell_iterator cell =
triangulation.begin_active(); cell !=
triangulation.end(); ++cell)
{
const
std::vector<std::shared_ptr<PointHistory<dim,NumberType> > >
lqph =
quadrature_point_history.get_data(cell);
Assert(lqph.size() == n_q_points, ExcInternalError());
for (unsigned int q_point = 0; q_point < n_q_points;
++q_point)
lqph[q_point]->setup_lqp(parameters,
cell->material_id());
}
}
--------------------------------------
Thanks!
Animesh
On Tuesday, November 3, 2020 at 12:09:03 PM UTC+5:30 Animesh
Rastogi IIT Gandhinagar wrote:
Hi Jean,
Sorry for late response. Thank you for your detailed
answer. Using your suggestions I was able to assign the
material ids to different area of my domain of interest.
Thanks again!
Animesh
On Tuesday, October 27, 2020 at 3:05:39 AM UTC+5:30
Jean-Paul Pelteret wrote:
Dear Animesh,
Let me preface my suggestion by saying that you can
introduce some heterogeneity in more than one way.
That is, you're not bound to using a material ID
(which is what I'm going to suggest), but you could
use some geometric arguments to determine which class
or material properties should dictate the
constitutive response at a continuum point. You also
need not use the class-based structure that this code
galley example has. There are other tutorials (e.g.
step-8) that use Functions that return the material
coefficients at any point in space. So you should
keep that in mind as you read my suggestion.
In my opinion, the simplest approach would be the
following:
1. The PointHistory::setup_lqp() function
<https://github.com/dealii/code-gallery/blob/master/Quasi_static_Finite_strain_Compressible_Elasticity/cook_membrane.cc#L720-L724>
is the point at which the constitutive law at some
quadrature point is set. So you should extend this
function in some way to make a decision about which
material it is in, and what the material law at that
point is. The first thing that you might do is add an
argument for the material ID, and then choose
constiutitve parameters based on the material ID.
You'll note that the concrete constitutive law is
stored in a pointer. This makes it easy to extend to
support other constitutive laws, because you can for
example abstract the
Material_Compressible_Neo_Hook_One_Field class into
some base class and other classes (maybe a
Material_Compressible_Mooney_Rivlin_One_Field) and
then, based on the material ID, select which
constitutive law is applied at that quadrature point.
2. The PointHistory::setup_lqp() function is called
from Solid::setup_qph()
<https://github.com/dealii/code-gallery/blob/master/Quasi_static_Finite_strain_Compressible_Elasticity/cook_membrane.cc#L1203-L1211>
, and more specifically inside a loop over all cells.
Its possible to retrieve the cell->material_id() or
cell->center() (or, if you create a quadrature rule
to help you then you can get the actual position of
the quadrature point if you want such granularity).
You can then pass this information in to
PointHistory::setup_lqp() to help decide which
constitutive law / parameters to apply. If using the
material ID then you will, of course, want to set the
material ID when building or reading in your
triangulation.
That is, at least, how I typically do things when
using this code as a basis for extension. I hope that
this helps you introduce heterogeneities into your
problem!
Best,
Jean-Paul
On 26.10.20 08:15, Animesh Rastogi IIT Gandhinagar wrote:
Hello All,
I am trying to solve the wrinkling problem of a thin
stiff film attached to a soft substrate in dealii. I
am using the code - from the code gallery for this
purpose. For the simulations, I would have to
consider the film and the substrate with different
material properties.
I understand that I would have to do something
within the class Qudrature point history. However, I
am getting a little confused on how to approach it.
It would be great if someone could help me with this.
This is the code that I am using for this purpose -
https://dealii.org/developer/doxygen/deal.II/code_gallery_Quasi_static_Finite_strain_Compressible_Elasticity.html
<https://dealii.org/developer/doxygen/deal.II/code_gallery_Quasi_static_Finite_strain_Compressible_Elasticity.html>
Thanks!
Animesh
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