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Problem Reprt

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asked Oct 11, 2016 by MarcoTar (770 points)
Hi Vaclav.

I'm here to tell you one thing about the F.E.M Membrane creation which I aske you in the quesiton 'Soil Settlement'.

Yesterday, me and my Professor changed the length of the membrane from 3.4*3.4 to 2.8*2.8, same thickness and 11 nodes for each side (x,y axis). In addition, we didn't change anything else. Same Engine as before, maybe the critical time step is small but it do work.

Here offers you this Information, hope it's useful to you in order to provide the Membrane creation in the future.

Best Regards

Feixiang Xuan
commented Oct 11, 2016 by eudoxos (43,490 points)

Hi, sorry I have not replied to the previous question yet. I am not sure what you say -- did you change dimensions and now the result is correct? Or why you changed the size? v (PS if you are reporting a bug, use https://github.com/woodem/woo/issues)

commented Oct 11, 2016 by MarcoTar (770 points)

Hi Vaclav.

To be honest, there are too many thanks I need to express to you. So you don't need to say sorry to me. :) Everyone got the job, individual life, difficulties even rest to do. I can understand.

Well, as for this problem report. Frankly speaking, I don't know if it's a bug or sth else. Because we only change the dimension of the membrane. It works for the small sphere (small diameter). When I try to make the spheres larger, the membrane will become unstable. Perhaps you know it will show the membrane is destroyed.

The good news is that the membrane deflection is right now. And due to the sphere's diameter of mine simulation is very small, so the membrane unstable phenomena doesn't appear to me now but if you use the big diameter sphere, it will occur.

In conclusion:

We only change the following 1 point of the membrane creation:
1) From 3.43.4 to 2.82.8. Thickness and the rest thing including Engines remain the same.

Question still exist: (In the code not my question :) )
If you put the larger diameter of the sphere, the membrane will become unstable.

Thanks a lot. Vaclav.
Take your time.

And if you have time please give me some information about the question I added to the data plotting about how to access the Reaction, stress, displacement plotting question.

Cheers

Best Regards

Feixiang Xuan

commented Oct 11, 2016 by eudoxos (43,490 points)

The first thing to try is to go down with Scene.dtSafety parameter; the estimate is not exact (it considers only the diagonal elements of the stiffness matrix -- instead of computing its eigenvalues), so especially with multinodal elements, you may need to go down. Try setting it to 0.1 or even less and see what happens.

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