Ok, I've managed to make the functions work, but now I'm having trouble getting the time stepper work. I am using
the direct-style script (so that it runs stand-alone, without
simple.py). This has worked out great so far, but I cannot find a
good way to run the time solver without a ProblemConf. Is there a
recommended way to solve time-dependent problems in the direct
I could go into a lot more specifics about things that I've tried,
so let me know if you need more information.
On 01/10/2014 07:02 AM, Robert Cimrman wrote:
On 01/10/2014 10:51 AM, David N. Mashburn wrote:
Hello again Robert,
I'm finally coming back around to this project.
I see that using a time stepper with gradual load increase is
the way to go for
a very large deformation solution; is there a recommended way to
go about this
in sfepy? Is there a way to implement an increasing variable
into the built-in
time solver, or is it better to run the simulation in a python
loop and modify
the inputs manually?
Have a look at the perfusion example  - there is a pressure
traction term with pressure depending on time (function
get_traction()). Ignore the variables and terms you do not need -
the traction is applied using dw_tl_surface_traction term. Let me
know if this helps.
I am also not clear on whether the
original mesh is suitable for every time
step or if it will need to be updated.
The total Lagrangian formulation integrates over the undeformed
domain, and it should work up to a pretty large deformation. Be
sure the mesh is fine enough, and that the load increments are
such that the nonlinear solver in each time step converges. When
you have your problem description written down, send me the
complete example in case of convergence problems.
On 02/23/2013 06:13 AM, Robert Cimrman
On 02/22/2013 06:40 PM, David Mashburn wrote:
Thanks Robert, that already helps a
lot. Glad to know it is a non-trivial
We are actually trying to cross-check some analytical
solutions, so I would
like to get this to work at least to some degree of
Do you think that those would be a good tests to add to sfepy
Ok, that makes sense now.
I've tried swapping out a simple
neohookean system with bulk penalty and all
that like in the example. A warp violation seems to be
causing an exception
after one iteration with a nominal amount of stress.
I've been digging through the nonlinear solver's parameters
and can't find a
way to shrink the initial step size. The other work-around I
can think of is
to use a time stepper to gradually increase the stress. Is
another/easier way to do this?
Yes, this is the way to do it - use time stepping to increase
gradually. I am not aware of other ways. In nonlinear analysis
Newton solver, a good initial guess is required.
Also, is it normal for a system with a
fairly large deformation to throw a
warp violation and then still recover afterwards (if so,
then maybe this
exception is a bug?)
How does it recover? I assume it just throws off the warped
solution and the
nonlinear iteration does not converge, right?