Alright, that fixes it! Now I understand the reason for quasistatic! In the non-linear analyses, the time stepper is set programatically - is is possible to force solving for the first time step here as well as in:

for ii, disp in ds:
#my_output(dformat % (ii + 1, ds.n_step, disp))

force0 = 0.0

pb.ts.is_quasistatic = True  # <<<=========== Force quasistatic
pb.time_update(ts)

On Wed, Jan 26, 2011 at 9:57 AM, Robert Cimrman wrote:

So the problem is the single dot outside the linear curve, right?

'quasistatic' : True,

to the time-stepper options? As it is now, the first time step is not solved but taken from the initial conditions (unspecified = zero) and boundary conditions (nonzero!), so it is not in equlibrium!

r.

On Wed, 26 Jan 2011, Andre Smit wrote:

Sorry - forgot to attach the figure - your point is taken re the nodal
residual. Forces are calculated and summed on each of the nodes in the
Top region. I checked this a while back and plotted in Paraview - the
forces are zero at the other nodes within the model but equal and
opposite in direction to the Top at the corresponding Bottom nodes of the
model (as you'd expect).

a

On Wed, Jan 26, 2011 at 9:26 AM, Robert Cimrman <cimr...@ntc.zcu.cz>
wrote:
Where can I see the line? maybe you forgot to attach a
figure?

As for the forces, it might be better to compute them using a
(inner) surface integral of stress instead of the nodal
rezidual. Btw. you look at the nodal force in the first node
of the Top region only, right? What are the values in the
other nodes?

r.

On Wed, 26 Jan 2011, Andre Smit wrote:

Thanks Robert!

I've attached a modification that shows the
strain/stress output for the
elastic case of the cylinder under compression.
The slope of the line is
Young's modulus as you'd expect. As with our
non-linear analyses, the
forces calculated after the first time step
appear to be too high - not
sure what the reason for this is.

On Wed, Jan 26, 2011 at 2:25 AM, Robert Cimrman
<cimr...@ntc.zcu.cz>
wrote:
There was some old code in the
stress_strain() function. The
exception was caused by putting directly the
traction
function into the EBC definition, instead of
its name. The
attached file should work.

r.

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