Hi Navneet,
I agree with Wolfgang's advice. Specifically, I suggest you start by
double-checking the formulation you implemented in deal.ii. Surely, your Jc
tangent tensor can't be zero! Also, shouldn't the volumetric part of your
strain energy density be a function of the bulk modulus kappa, not of p?
Something like:
\Psi = c_1\left(I_1 - 3\right) + \frac{1}{2} \kappa \left( J - 1\right)^2
and then the pressure appears in the stress tensor because
p = - \frac{\partial \Psi_{vol}}{\partial J}
I implemented a mixed u/p quasi-incompressible hyperelastic formulation in
a Fortran code during my PhD. I think it is similar to what you're trying
to implement. You'll find all the analytical derivations for tangent
tensors and the outline of the algorithm I used in my dissertation on
ResearchGate. I really recommend the following references, if you haven't
checked them already:
Crisfield (1991), Non-linear finite element analysis of solids and
structures. John Wiley & Sons.
Bonet and Wood (2008), Nonlinear Continuum Mechanics for Finite Element
Analysis. Cambridge University Press.
Hope this helps!
Ester
El dijous, 14 maig de 2020 12:38:56 UTC-4, Wolfgang Bangerth va escriure:
>
> On 5/14/20 10:28 AM, navneet roshan wrote:
> >
> > Thank you for the response, Sorry, I did't put the precise question.
> > My geometry is not deforming after first loading step,
> > Is it locking behaviour? Do I need to give some special treatment to the
> > incompressibility constraint? as
> > some references suggests using augmented lagrangian and using
> selectively
> > reduced integration.
>
> It may be that others can speak with more knowledge about the question.
>
> But what have you done already to debug the problem? Have you simplified
> the
> material law by setting certain parameters to zero? Have you considered
> uniaxial tests for which you can derive an exact solution, and compared
> your
> code to that exact solution?
>
> From your question, I infer that you have derived a complicated code
> whose
> results you don't understand. That may be because you don't understand the
> underlying mathematics (is it locking? do I need a different formulation?)
> or
> because the code has a bug. You need to develop the mental tools to deal
> with
> this kind of question -- you will be in this situation many more times in
> the
> future. My approach is generally to make the problem simpler (like in the
> examples above) so that I can derive what I expect theoretically and
> compare
> with what I get practically.
>
> Best
> W.
>
> --
> ------------------------------------------------------------------------
> Wolfgang Bangerth email: bang...@colostate.edu
> <javascript:>
> www: http://www.math.colostate.edu/~bangerth/
>
>
--
The deal.II project is located at http://www.dealii.org/
For mailing list/forum options, see
https://groups.google.com/d/forum/dealii?hl=en
---
You received this message because you are subscribed to the Google Groups
"deal.II User Group" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to dealii+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/dealii/584c0f04-1de7-4ba3-aa76-e4bb83364ce7%40googlegroups.com.
