Modifying the nodes that define an element

[miguel...@gmail.com]

Hi

I'm trying to modify the nodes that define an element using pyNastran, for example If I have a 'CONROD' element in my model between nodes '5' and '6':

conrod = model.elements[1]

print(cornod)

CONROD         1       5       6      10    .001      .2

how can I modify the nodes that define the rod, so the element is beteewn '5' and '7'?

If I do :

conrod.nodes_ids[1] = 7

the nodes of the element remain the same.

Thanks

[Steven Doyle]

I didn't realize that was that even allowed.  That's a property and accesses different data depending on if the card is cross-referenced or not.  It's for informational purposes.

If the element is cross-referenced:

conrod.nodes_ref[1].nid = 7

and if it's not:

conrod.nodes[1] = 7

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[miguel...@gmail.com]

That doesn't work either, I attach a .bdf file and .py for testing.

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[Steven Doyle]

You have a cross-referenced model, which is why your script doesn't work.  Cross-referencing is opt-out as an option in read_bdf.

So nominally, I'd do it like this:

from pyNastran.bdf.bdf import BDF

model = BDF()

model.read_bdf('test.bdf')

conrod = model.elements[1]

conrod.nodes_ref[1].nid = 7

model.write_bdf('test2.bdf')

but that would give you two node 7s with different locations.  I thought you were trying to remap/renumber the node while keeping connectivity the same.

To do that, you could do that with cross-referencing as:

conrod.nodes_ref[1] = model.Node(7)

or:uncross-reference it (with or without re-cross-referencing)

conrod.uncross_reference()

conrod.nodes[1] = 7

conrod.cross_reference(model)

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[miguel...@gmail.com]

Thanks, that clarified the issue