#4982 Adding a spring boundary condition

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Helios113
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#4982 Adding a spring boundary condition

Post by Helios113 »

Hello,

This PR implements a spring boundary condition which will be used by MoFEM for dynamic problems. It can also be used by other solvers that deal with dynamic problems.

There is also one addition to stiffness units which is needed as well.

Here is link to the PR: https://github.com/FreeCAD/FreeCAD/pull/4982
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Pauvres_honteux
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Re: #4982 Adding a spring boundary condition

Post by Pauvres_honteux »

Helios113 wrote: Fri Aug 20, 2021 9:57 am ... boundary condition ...
Would that include the surface as well. It est, not only its boundary?
Helios113
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Re: #4982 Adding a spring boundary condition

Post by Helios113 »

Hi,

You can apply the condition only to surfaces. So you can do it on any surface you like :D .
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Pauvres_honteux
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Re: #4982 Adding a spring boundary condition

Post by Pauvres_honteux »

Helios113 wrote: Wed Sep 01, 2021 6:58 am ... only to surfaces.
That sounds a bit ominous. Reason being, when virtual elements gets implemented one would definitely want to apply stiffness to them as well.

I can also forsee stiffness being applied to solids, lines and curves in the case one want to apply/create different property to e.g. a screw, a spring(spiral/leaf), a pipe(simplified to a polyline with bends), a tube(simplified to a spline) and so on.

But maybe I'm interpreting this PR in wrong way?
Perhaps it shall be a drop-in solution for other programmers to utilize in their tools?
Or will your PR drop-in other programmers tools?

Hmm, maybe some explanatory pictures would clarify things? Any chance you can make a Picasso for us to admire?
Helios113
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Re: #4982 Adding a spring boundary condition

Post by Helios113 »

Hi,

So the reason I said only surfaces was because this spring BC is intended to be used by MoFEM, the FEM solver I am implementing. My team said that they don't really like applying springs to vertices or lines, so I disabled those options. If someone needs to add springs BCs to other elements, then it is just a simple change to make.

So to answer your question, the spring BC is a drop in solution for MoFEM , but it can also be a drop in solution for everyone else.

I am also working on another BC related thing called the Universal Boundary, I am just waiting on this to be merged for the next PR. Becuase MoFEM has a lot of BCs for different things, adding all of them would be impractical. Hence, the universal boundary allows users to load custom boundary conditions and apply them to everything. Maybe this can also help you out?

Regards,
Preslav
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Pauvres_honteux
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Re: #4982 Adding a spring boundary condition

Post by Pauvres_honteux »

Helios113 wrote: Thu Sep 02, 2021 11:09 am My team said that they don't really like applying springs to vertices or lines...
There you go. And me and my mates like it a lot. How different it can be around the world.

Helios113 wrote: Thu Sep 02, 2021 11:09 am ... the spring BC is a drop in solution for MoFEM , but it can also be a drop in solution for everyone else.
And by that crystal clear statement every programmer out there, having a FEM-itch to scratch, now know who to contact!

Helios113 wrote: Thu Sep 02, 2021 11:09 am ... the universal boundary allows users to load custom boundary conditions and apply them to everything.
Maybe this can also help you out?
It sure sounds like it could!
Provided it comes with an easy to understand + use GUI ? And a Wiki of course.
Helios113
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Re: #4982 Adding a spring boundary condition

Post by Helios113 »

You can have a look at the UI here: https://github.com/Helios113/FreeCAD/tr ... l_boundary
You can either get the new ui file or just build this. It's not fully baked because I need to compile MoFEM with static binaries but it's more difficult than I thought, so I disabled some features.
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Pauvres_honteux
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Re: #4982 Adding a spring boundary condition

Post by Pauvres_honteux »

Helios113 wrote: Thu Sep 02, 2021 2:21 pm You can either get the new ui file or just build this.
Hmm, I think I'm better off waiting then. Compiling is not my cup of tea.
NewJoker
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Re: #4982 Adding a spring boundary condition

Post by NewJoker »

Helios113 wrote: Thu Sep 02, 2021 2:21 pm
This PR was merged and thus the spring boundary condition is available now. However, it can' be used at the moment since MoFEM solver is not implemented yet, right ? What is the status of this implementation - is it still active ? If not and MoFEM won't be added in the near future then maybe the spring constraint could be adapted for CalculiX solver ? Or at least let's place it under the "Constraints without solver" tab to avoid the confusion.

Here's a recent thread in which a user asked about this constraint:
https://forum.freecadweb.org/viewtopic.php?f=18&t=66056
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