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Victor
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That's the normal way unconstrained rigid body rotation works in FEA (and in real life!). You sometimes get a random rotation or solver failure. It's still a correct solution but there isn't a unique solution.
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@disla. I'll try with 2.19 and get back to you. Seems OK on 2.17 with the 3 node rotations suppressed except the solution doesn't complete all the way to 100%. @prop_design. You can download by clicking the rectangle bar that shows the filename ins…
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I think that distortion is really just very large rigid body rotations. If you reduce the deformation scale factor, it looks more like rotation. I can't easily tell where the axis of rotation is and if it's correctly rotating about the reference nod…
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You example appears to work correctly for me. I don't get any rotations, and only the (500, 500, 500) mm displacement. This is with CCX 2.17 so I wonder if something has become incompatible in later versions. Bear in mind that *RIGID BODY isn't k…
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Yes but not in a wrong way. Displacement constraints and forces on the Reference node end up on the REF NODE for CCX while rotations and moments on the same Reference node end up as DOF 1-3 constraints and loads on on the hidden ROT NODE. I'm start…
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Thanks for the investigation, disla. You're right that there's a lot of strange-seeming interdependencies between different kinds of constraints, but I don't think what you've found here solves the problems. A displacement like (500,500,0) doesn't …
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Oh, sorry, I didn't notice you were talking about *DISTRIBUTING COUPLING. Yea, they're certainly different. I found something was strange about that and never really used it. Doesn't explain why it won't solve properly for you though.
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Distributing displacement not responding.liml works for me with CCX 2.17 and the offset loads in Distributing.liml don't seem to cause any moments. The displacement also works there. Maybe this is that issue of the latest version of CCX not being co…
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Maybe it's changed in the latest version but I didn't think there could be a moment due to an offset reference node. Is that really *DISTRIBUTING, not *RIGID BODY? From what I understand, the position of the reference node is ignored by *DISTRIBUTIN…
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This might be too simple to help but here's a test case with Ramberg Osgood which converges. Apparently the YY strain is supposed to be 0.01192736 according to the formula and the solution agrees with that.
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You can copy and paste the list from the error message into Edit -> Select nodes by number. In case of the CCX solver, there are buttons Select nodes and Select elements in the Details window to do that.
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As @disla said, use Gmsh. It solves a lot of mysterious meshing failures. The only reason it's not the default or even the only mesher is that it's free software with a capital "f" so it doesn't want Mecway peeing in its sandpit.
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@disla, could you elaborate a bit on how you'd use this proposed feature? I imagine something like: * Select some faces * Add the node at the centroid * Put node-surface coupling on them * Then what? I don't thing there's much you can do wi…
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@Sergio, I feel that having a lot of specific pre-defined shapes could become a bit of an anti-feature if it gets big enough that it's hard to know if it contains what you want or not. The existing plate meshes are actually generated by a general pu…
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Inner radius is for the central hole and those shapes don't have a hole. You can make a hole by using Mesh tools -> Hole on the central node afterwards. Plate mesh is a legacy feature that I've maintained mainly to not lose functionality, but ha…
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@disla, not sure if Gmsh identifies the separate parts. If it does, perhaps I can get Mecway to read that information. But I wonder if that code Sergio posted merges it all into one homogeneous thing?
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Thanks @disla, that's impressive, especially confirming very large rotations which are often a problem. Took me a long time to work it out too but seems like the core principle is exploiting the fact that CCX uses translational DOFs to represent rot…
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Happy to have passively helped
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Hello Ken I think the easiest way for axial symmetry and nonlinear through Mecway is the thin wedge. Enforce symmetry using elastic support with a high normal stiffness and zero tangential stiffness so it behaves like frictionless support which is …
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I don't know an accurate way to model tightening torque. I would imagine applying a fixed rotation angle to the bolt and constraining the nut against rotation after it is tensioned but not sure how valid that is. Other than torque, put contacts bet…
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Thanks for reporting this bug. It happens on big models with a high ratio of external to internal element faces because Mecway uses the total number of faces to estimate what texture resolution to use and it assumes that most of them will be invisib…
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Use the CCX solver (Analysis settings -> Solver). With the internal solver, bonded contact is always rigid in the thickness direction.
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I'm not sure. It looks like a problem reading a file, maybe the solution data from CCX. Does it happens at the end of a CCX solve? Is there any other information in the error message? Also, is this Mecway version 14 and if CCX, what version of that?
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I think it's the longest dimension of the element, or something close to that. I usually pick a value around 1-10 times the minimum wall thickness to prevent extremely flat elements which seem to cause meshing failures. You're right that for the bes…
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Not something to worry about. When CCX expands shells to solids, it sometimes joins them together with shared nodes as you'd expect but sometimes it separates them and connects them with MPCs so they're disconnected in the mesh but still connected m…
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It meshes OK if you set Maximum element size to 10 mm. This seems to be necessary with thin-walled parts sometimes.
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I had a look at section 4.5.1/2/3 and it seems to really depend on the the element formulation being no better or worse than what they expect. Perhaps this is why only approved software is allowed? I was going to suggest refining the mesh to create …
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Not sure if this would help, but are you aware of OUTPUT=2D on *NODE FILE or *EL FILE? It causes shells remain as 2D elements in the solution and CCX averages the stresses from the 3D nodes into 2D, which loses information like bending stress but sh…
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Thanks John. Fantastic idea.
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No, sorry. The file format is defined by the code that generates it which is not organized to make generating a complete definition easy.
