On Mon, Jan 24, 2011 at 9:08 AM, Robert Cimrman <cimr...@ntc.zcu.cz> wrote:

On Mon, 24 Jan 2011, Andre Smit wrote:

Thanks

works like a charm! Two comments:

1) Since the model is 1/8 of actual the deformation rate is half of
actual test. So the strain rate in the Fc, Ft and Ec functions should be
doubled:
e *= 2 # With 1/8 model the applied deformation rate is half of actual
test

Yes, modify it as needed :)

2) Don't you think failed elements (smin) should only be assigned at the
end of an iteration run and not during sub-iterations.

I do not know - if you do not change the stiffness in sub-iterations, then nothing changes after the first one, and there is no need for them, right?

r.

On Mon, Jan 24, 2011 at 2:05 AM, Robert Cimrman <cimr...@ntc.zcu.cz>
wrote:
ok, so the patch is in... the script should work
out-of-the-box.

r.

On Sat, 22 Jan 2011, Robert Cimrman wrote:

I have overhauled the script, so that there are no
globals, subiterations
can be ended as needed etc. The traction() function is
removed, the
loading displacement is given simply by value. I hope
it does what you
intended.

It needs a patch to TimeStepper, that I will be able to
upload first on
Monday, so either just look at it, or fix it
yourself... :)

r.

----- Reply message -----
From: "Andre Smit" <freev...@gmail.com>
To: <sfepy...@googlegroups.com>
Subject: Conference
Date: Fri, Jan 21, 2011 02:47

Robert

I believe I've sorted out the oscillation problem,
which was a bug in the
code. I've pasted the latest version at [1] that now
converges tightly
after 3 or 4 iterations. I have a few comments.

As you will see:

a) I'm runnng the solver repeatedly with increasing
displacements. This
was mainly because I'm unable to change the
displacement variable (disp)
in traction() outside of the function. Globals and
lists didn't work for
me here.
b) To overcome this obstacle, the displacement for each
solver/displacement cycle is saved to file and read
from disk in
traction().
c) I iterate the problem until the force converges and
then increment the
displacement.
d) The element stiffness matrix (Ele) is saved to file
and loaded at the
start of the subsequent displacement interval.

Comments:
1) I considered adding a variable to ts, say ts.disp
and adding the
displacement to that, making it available in traction.
I'm sure there is
a better way though.
2) I also cannot terminate the ts loop and am forced to
run through all
ts.n_steps. This is a problem since the forces converge
at different
number of steps at which point I would like the loop to
end.

[1] http://paste.pocoo.org/show/324169/

Andre

On Wed, Jan 19, 2011 at 10:22 AM, Robert Cimrman
<cimr...@ntc.zcu.cz>
wrote:
   On Wed, 19 Jan 2011, Andre Smit wrote:

   Robert - I'm trying to change the displacement
(disp)
   in the traction
   function when the force stabilizes but for some
reason
   the scope of disp
   within traction() appears different to that within
   calc_force(), even
   though disp is defined as global. Any ideas?

   old_force = 0
   def calc_force(pb, ts, state):
        global disp,old_force
        d = state()
        pb.remove_bcs()
        f = pb.evaluator.eval_residual(d)
        pb.time_update()
        f.shape = (pb.domain.mesh.n_nod, 3)
        p = []
        for n in pb.domain.regions['Top'].vertices[0]:
            p.append(f[n][2])
        p = nm.array(p)
        if abs(old_force-p.sum()) < fvar:
            my_output(disp,",",p.sum())
            disp -= ddisp
        old_force=p.sum()

   def traction(ts, coors, bc=None):
        global disp
        #disp = -(ts.dt*(ts.step+1))
        print "traction disp: ", disp
        val = nm.empty_like(coors[:,0])
        val.fill(disp)
        return val

I would use brute force:

globals()['disp'] = ...

You cannot really change value of a global that is
immutable
(IMHO)...
A common idiom is to use list instead, like:

disp = [0]

def traction(ts, coors, bc=None):
   disp[0] = ...

      What is the meaning of 'smix' stiffness, for
   strain rate
      zero?

   I'm not sure.

That might be the problem causing the oscillations...

r.

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