Robert
I'm having problems relating the model's output to the actual test output. One issue that is confusing is that if I reduce the displacement interval from 0.001 to 0.0001, say and the time during this interval to ensure a consistent loading rate, then the results change significantly, both the maximum load at failure and the displacement at maximum load. This is unexpected. I can't think what the problem can be - any ideas on your side?
On Wed, Jan 26, 2011 at 10:50 AM, Robert Cimrman <cimr...@ntc.zcu.cz>wrote:
Ok, interesting. Well, I cannot help you much at this point :)
You might want to try a finer mesh, just to compare with the current one...
r.
On Wed, 26 Jan 2011, Andre Smit wrote:
I think the iterations are indirectly sorting this out. In fact I found
that the initial stiffness(0) doesn't influence the results at all. I've attached results of compression (comp) and tension (tens) tests at rate of 1mm/sec as well as the script in its current state. Based on lab tests, comparative compression failure at this rate occurs at 6.6 N/mm2 whereas tension failure occurs at 3.0 N/mm2. So the script is accurately predicting compression failure but under-estimating tension failure. Still exploring ...
a
On Wed, Jan 26, 2011 at 10:19 AM, Robert Cimrman <cimr...@ntc.zcu.cz> wrote: Well, this flag is used essentially only in the generic solver used by simple.py. In the strain rate solver script we solve every time step regardless this flag.
The first time step is different, however, as strain equals strain0 (no previous strain defined), and so initial dstrain is zero. Maybe this causes some problems?r.
On Wed, 26 Jan 2011, Andre Smit wrote:
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.ebcs['Load'].dofs['u.2'] = disp pb.ts.is_quasistatic = True # <<<=========== Force quasistatic pb.time_update(ts) On Wed, Jan 26, 2011 at 9:57 AM, Robert Cimrman <cimr...@ntc.zcu.cz> wrote: So the problem is the single dot outside the linear curve, right? What if you add '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. -- You received this message because you are subscribed to the Google Groups "sfepy-devel" group. To post to this group, send email to sfepy...@googlegroups.com. To unsubscribe from this group, send email to sfepy-devel...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sfepy-devel?hl=en. -- Andre -- You received this message because you are subscribed to the Google Groups "sfepy-devel" group. To post to this group, send email to sfepy...@googlegroups.com. To unsubscribe from this group, send email to sfepy-devel...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sfepy-devel?hl=en. -- You received this message because you are subscribed to the Google Groups "sfepy-devel" group. To post to this group, send email to sfepy...@googlegroups.com. To unsubscribe from this group, send email to sfepy-devel...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sfepy-devel?hl=en. -- Andre -- You received this message because you are subscribed to the Google Groups "sfepy-devel" group. To post to this group, send email to sfepy...@googlegroups.com. To unsubscribe from this group, send email to sfepy-devel...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sfepy-devel?hl=en.-- You received this message because you are subscribed to the Google Groups "sfepy-devel" group. To post to this group, send email to sfepy...@googlegroups.com. To unsubscribe from this group, send email to sfepy-devel...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sfepy-devel?hl=en.
-- Andre
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-- Andre