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Hi Hugo,
Yes, I checked the dimensions and they should be OK.
Indeed, the height of the model is about that. The final goal is complicated, but we don’t have to do it by tomorrow. 🙂Did you change some settings in the model? Your simulation looks far better than what I can do. I’ll try to do a video as well, so you can have a look (probably later this week).
In the meantime, I tried to set up some verification examples. A simple 3D beam with gravity acting on it. I compare the results (nodal reaction forces) with ANSYS (because that’s what we use normally). And it seems that for the same problem the difference between the two increases if I increase the mesh density. Normally I would expect an increased accuracy with more elements. So it’s a bit odd.
I will set up a few more test cases to see if this is a general behaviour or specific to the problem.Best regards,
ZsoltHi Hugo,
Well this just only part of the problem that I have built so far. There will be other components and then the component would be moved around on a given path so that it should not collide with other components. It may be even possible that there are more moving flexible bodies that will have to avoid collision of the stationary rigid bodies (or the other moving flexible bodies).
In this simple test I just move the component up and down, before setting up anything more complicated. My problem is that the object is not following the prescribed motion. Although it is a flexible body it’s quite rigid due to its properties, so nothing exciting should be happening really. But when the lifting happens only the top part seem to be moving, it stretches a lot while the bottom seems to be stuck in place. Later on there is a lot of movement happening everywhere, but it looks quite unrealistic for steel. That’s why I’m suspecting that something setting the plastic behaviour is wrong.
I tried other FEM forcefields (like fastTetrahedralCorotational), but then the max Young’s modulus is limited to 9e+10 (Aluminium has that kind of E). Actually that too produces a quite surprising result. I’d expect a stiffer behaviour for that too.Zsolt
Dear Hugo,
No I’m not monitoring stress and strain (I know how to get the Mises stress, but not the strain actually)
However, the component is made of steel. It can/should not behave like this (E=2e11, nu=0.3).
The only load is gravity really and the lifting is slow.
I did an ANSYS analysis and the total displacement is about 5 mm (while the length of this component is about 15m) for its own weight. So it should be really rigid.
So what I’m suspecting that maybe it’s one of those parameters (plasticMaxThreshold, plasticYieldThreshold and plasticCreep) that are not set properly and that’s why it looks so rubbery/jelly like. Is there a setting for pure elastic behaviour? For now, that would be a good enough approach. Or what their physical meaning is? Should plasticYieldThreshold be 0.002 (0.2%) for most metals? Or is it something completely different.
Cheers,Zsolt
Hi Hugo,
Changing the order did not help.
I uploaded the files, they’re here.
(I removed TPointModel as that is not needed yet)
Thanks.Zsolt
Hi,
I think I solved it.
The Cholesky solver didn’t work, it was complaining about the determinant.
However, increasing the number of iterations (to 100) for the CGLinearsover helped. The problem is not too big, so actually it still runs pretty quickly.
Cheers,Zs.
