Issue #6093 - FEM constraints not on object when using placement (part design workbench)

About the development of the FEM module/workbench.

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bernd
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Re: FEM constraints not on object when using placement (part design workbench)

Post by bernd »

LSoltmann wrote: Fri Jul 24, 2020 4:49 pm I found a workaround for this issue until it can be fixed. Export the part design object to a STEP file, import the STEP file, apply the constraints to the newly imported object. Now the constraints follow the object as it's moved using placement.
ohh there is a much better one because export and import of step could cause tolerance problems because they might changes.

Use part workbench to create a simple copy of your body. The copy will be a Part on the changed placement. This works flawless with FEM.

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Re: FEM constraints not on object when using placement (part design workbench)

Post by jnxd »

LSoltmann wrote: Fri Jul 24, 2020 4:49 pm I found a workaround for this issue until it can be fixed. Export the part design object to a STEP file, import the STEP file, apply the constraints to the newly imported object. Now the constraints follow the object as it's moved using placement.
I would not advice that. That is one more step to take for every minor change in the part design object.
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Re: FEM constraints not on object when using placement (part design workbench)

Post by jnxd »

I will take a look at this. Apologies if I'm missing anything, but is the "placement" used here the same as "transform" that can be used on PD bodies?
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Re: FEM constraints not on object when using placement (part design workbench)

Post by jnxd »

So I debugged and observed a couple of differences between using part and part design features (refer to the example files attached):
  1. When placement is changed for a PD body (there is no placement option in the feature itself), Fem::Constraint::execute() is not called. This is called in [Part].
  2. Even after a forced recompute (with PD), the TopoShape that is being used does not have any transformation applied. For part this transformation is applied.
This suggests that the following is happening: any placement changes are stored in the body, but the FEM constraint stores references from the feature (the box in the examples) and uses the feature's transformation.

So our task is to make sure these transformations can be accessed from each other: on the one side pd feature should be "touched" when the body's placement is changed, and on the other side when we use the feature's geometric data, the body's placement is taken in account.
Attachments
fem-on-part.FCStd
(6.03 KiB) Downloaded 36 times
fem-on-partdesign.FCStd
(9.92 KiB) Downloaded 39 times
Last edited by jnxd on Tue Apr 19, 2022 5:21 pm, edited 1 time in total.
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Re: FEM constraints not on object when using placement (part design workbench)

Post by Kunda1 »

Thanks @jnxd for following up. I've updated the issue #6093 to reflect your research
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