Simulate a thread/cord of fabric/nylon?

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a.l
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Simulate a thread/cord of fabric/nylon?

Post by a.l »

Does something as exotic as a workbench/simulator of a thread/cord (of e.g. fabric or nylon etc.) exist?

Meaning does some tool exist where it is possible to draw a thread/cord and simulate whether it is tense, loose or somewhere in between in an elastic state?
If yes, is it possible to draw that inside an existing FreeCAD model e.g. drawn in Part Design?

Thanks :)
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NewJoker
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Re: Simulate a thread/cord of fabric/nylon?

Post by NewJoker »

The closest you can get to that is with the FEM workbench where you can simulate the behavior of any part under almost (torsion is not yet properly implemented) any type of load. The difficulty lies in the fact that you need proper material properties. For highly elastic materials you should use a hyperelastic model but it's not supported by FreeCAD at the moment (however, the CalculiX solver itself supports it so you could export the input file and change a few lines manually outside of FreeCAD). As a result, you can get the stresses, strains and displacements in the part being analyzed.
KAKM
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Re: Simulate a thread/cord of fabric/nylon?

Post by KAKM »

You might also consider using this: https://forum.freecad.org/viewtopic.php?f=18&t=39165

If you use MBDyn to model the things the thread/cord is attached to, you should be able to determine the length of the cord (distance between the two attachment points), which will in turn tell you whether it's loose or stretched. (You would have to set your own threshold to determine whether a cord is partially or fully tense–there isn't a formal distinction between them).

Whether it would make more sense to try this direction or what NewJoker recommended would depend on exactly what your goals are for this simulation.
drmacro
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Re: Simulate a thread/cord of fabric/nylon?

Post by drmacro »

It can be modeled. See this thread: https://forum.freecadweb.org/viewtopic. ... st#p382991

Simulation might be difficult. Or are just talking about animation?
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hammax
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Re: Simulate a thread/cord of fabric/nylon?

Post by hammax »

... twisted or braided rope?
"ParametricCurve" could be used. => https://forum.freecadweb.org/viewtopic. ... 07#p528425

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a.l
Posts: 86
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Re: Simulate a thread/cord of fabric/nylon?

Post by a.l »

I am really impressed by all your answers!
Regardless I can see I have a lot of reading and understanding those various concepts (and the math...)

Well, basically I would like to simulate a thread of fabric (e.g. cotton) or nylon that is hold/guided along a path (but not restrained/locked from moving).
The thread is then supposed to be pulled either in one or another direction a long the path (guided by some holders that change the direction of the thread a bit by some degrees of angle) and then finally I would like to simulate the pull on the thread and the object that the thread is attached to in its other end.

Yeah, I know it might sound a bit complicated, but imagine a ring (the path) on which the thread is pulled in either one way or the other. At a certain point a long that path an object is attached and because of the pull on the thread that object is moved as well. Depending on the direction of the thread the object is then pulled into a different position.
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