add_card for 'GRID' or 'CTRIA3'

[Thomas Brooks]

I'm trying to add a node to the model and I'm using the code shown below.

new_node=['GRID',next_node,None,new_node_loc[0],new_node_loc[1],new_node_loc[2]]
#where next_node is an int and the rest are floats
model.add_card(new_node,'GRID')

when I try to get position of the new node with

model.nodes[new_node].get_position()

I get an error that implies that there is no coordinate system defined so I've added a line so that the code looks like:

new_node=['GRID',next_node,None,new_node_loc[0],new_node_loc[1],new_node_loc[2]]
model.add_card(new_node,'GRID')
model.nodes[new_node].cp=model.coords[0]

Then when I try to create a new element with this node I use:

new_element=['CTRIA3',next_element,break_element.Pid(),next_node,break_element.nodes[node_num].Nid(),break_element.nodes[0].Nid()]

model.add_card(new_element,'CTRIA3')

This seems to also not properly create the element because the code below gives an error:

model.elements[next_element].Normal()

The error is:

"    positions[i, :] = node.get_position()

AttributeError: 'int' object has no attribute 'get_position'"

And sure enough, when I check model.elements[next_element].nodes I see a list of integers rather than node objects.

I have tried to use node objects in place of the node IDs, but I get a different error shown below:

RuntimeError: field='GRID        1691          -.2475.4286823   -.045\n' is not 16 characters long...rawValue=GRID        1691          -.2475.4286823   -.045

What am I doing wrong?

Thomas

[Steven Doyle]

Tom,

You need to cross reference your model after using the `add_card` method by calling:

    model.cross_reference()

The code builds that call into the read_bdf method.

https://github.com/SteveDoyle2/pyNastran/wiki/Cross-Referencing

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[Thomas Brooks]

Is there a way to cross reference a model multiple times? Can I cross reference a single element or node with the rest of the model?

[Steven Doyle]

You can call:

node = model.nodes[nid]

node.cross_reference(model)

to cross reference a single node/element/etc.

I wouldn't call model.cross_reference() twice though that's on the list (as well as an uncross_reference option).

The general recommendation though is to load everything, cross reference, and then use it.