Rigid body constraint

About the development of the FEM module/workbench.

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Pauvres_honteux
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Re: Rigid body constraint

Post by Pauvres_honteux »

What do you guys say about separating what to be connected from the connection properties?

That way it opens up for one connection and multiple properties. Where only one property is active per calculation session, i.e. it speeds up the process. Especially good for showing your collegues different scenarios in a short time frame.

Hmm, perhaps it also opens up for time based calculations where the properties change over time?
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NewJoker
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Re: Rigid body constraint

Post by NewJoker »

What properties are you talking about ? Rigid body comstraints don’t have any, their definition is just setting which nodes should be connected to which reference point. Couplings are a bit more complex as you can also define weight for the connection and choose DOFs to be constrained but that’s it when it comes to settings.

Or do you have something different in mind than those constraints ?
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bernd
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Re: Rigid body constraint

Post by bernd »

NewJoker wrote: Wed Aug 11, 2021 11:31 am What properties are you talking about ? Rigid body comstraints don’t have any, their definition is just setting which nodes should be connected to which reference point. Couplings are a bit more complex as you can also define weight for the connection and choose DOFs to be constrained but that’s it when it comes to settings.

Or do you have something different in mind than those constraints ?
From user point of view yes, but from developer point of view:

- we create a new FEM constraint object
- this object will have some attributes (properties)
- reference face
- reference point
- depending if existing constraints are used or not some more properties to held the force and fix

These properties will be attached to the object. The object will be passed to the writer and the writer will write the input file.

Attached a example of the last whole new object implementation: https://github.com/FreeCAD/FreeCAD/comp ... 282db7c8c6
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bernd
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Re: Rigid body constraint

Post by bernd »

bernd wrote: Wed Aug 11, 2021 11:43 am Attached a example of the last whole new object implementation: https://github.com/FreeCAD/FreeCAD/comp ... 282db7c8c6
after the first commit the object runs, there is just no gui tool to ceate (python need to be used) it and no task panel and no unit test. Eventually for a real object for sure they are needed too.
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Re: Rigid body constraint

Post by jnxd »

@NewJoker I'm working on this right now but it's been a while using INP files. Could you attach a sample file with how it should all work? Doesn't have to be too complicated (in fact better if it isn't): say an 8- element cube with rigid body constraint applied on one face.
My latest (or last) project: B-spline Construction Project.
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NewJoker
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Re: Rigid body constraint

Post by NewJoker »

jnxd wrote: Thu Oct 27, 2022 5:00 pm @NewJoker I'm working on this right now but it's been a while using INP files. Could you attach a sample file with how it should all work? Doesn't have to be too complicated (in fact better if it isn't): say an 8- element cube with rigid body constraint applied on one face.
Sure, I attached the file. Thank you for your interest in this topic. Please let me know if you need any help with CalculiX's syntax or other issues regarding the implementation.

RB.zip
(486 Bytes) Downloaded 54 times

P.S. The example involves torsion so the load is applied to ROT NODE of rigid body constraint.
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bernd
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Re: Rigid body constraint

Post by bernd »

very cool, If the obeject is implemented it would be great just to include such simple example to the FEM python examples. I even did it before I started wich such object implementation to have something to test with.

If you have any question come up ...

bernd
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ebrahim raeyat
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Re: Rigid body constraint

Post by ebrahim raeyat »

NewJoker wrote: Fri Aug 06, 2021 5:35 pm Loads (force/torque) and boundary conditions (displacement/rotation) can be applied to it, so their codes may require some changes too.
Hi. I thinks this is what calculix must be done, am I wrong?
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NewJoker
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Re: Rigid body constraint

Post by NewJoker »

ebrahim raeyat wrote: Mon Oct 31, 2022 10:50 am Hi. I thinks this is what calculix must be done, am I wrong?
From CalculiX's side, it's just a matter of applying *BOUNDARY or *CLOAD to a node used as a REF NODE (for translational DOFs) or ROT NODE (for rotational DOFs). So, in the attached example, you can find:

Code: Select all

*CLOAD
22, 1, 1000
where 22 is a number of a node used as ROT NODE in rigid body definition. Degree of freedom 1 is selected which corresponds to the first rotational DOF (rotation about X axis).
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Re: Rigid body constraint

Post by jnxd »

bernd wrote: Fri Oct 28, 2022 9:40 pm If you have any question come up ...

bernd
Thanks for the offer. A question came up: this particular constraint requires a new node to be created; (how) can this be done within write_constraint_rigidbody.py? This node will need to have a number different than existing nodes, and there could be multiple rigid bodies, which would need different nodes to be added.
My latest (or last) project: B-spline Construction Project.
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