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API Data Surface to create Load on Nodes - Follower Forces

Hello,

I have some node forces and moments in a .txt file and I wanted to transfer them to my FEMAP model. I've already created the API script to prepare the data structures.

Now, I wanted to apply the loads on the nodes but in an automated way. Manually, I can choose "Nodal Load", and then on "Entity Selection" I can choose "method: On Curve", and on the "Create Loads on Nodes" menu, I can choose "Direction Vector" and assign the correspondent "Data Surface". This way, the loads are directly applied to the nodes and I can visualize it.

 

I've checked that there is another post with a similar question but the loads are applied on the geometry instead of nodes. I wanted the forces to be applied directly on the nodes, because I will deform the structure quite a lot and I want the load to "follow" the nodes. I'm not sure if this will happen when assigning it to a line (geometry). 

 

Any ideas on how can I do this using the API?

 

Thanks in advance!
Tiago

 

Note: The .txt forces and moments nodes don't coincide directly with the FEMAP nodes. That is why I wanted to use the data structure, to interpolate results in between.

1 REPLY

Re: API Data Surface to create Load on Nodes - Follower Forces

Hello,

 

In NASTRAN pressure loads (applied to elements or their faces) are follower forces in many cases. FEMAP can write varying pressure fields with data surfaces as shown in the help section related to data surface (Help > Commands > 7.2.6.1 > "Arbitrary 3-D Data Surface")

 

Also in NASTRAN you can define follower nodal forces (FORCE1 or 2 cards), I think FEMAP reads these cards but does not write them. If you are set on nodal forces you'll have to write a complete script which computes them then writes them out in bulk format.

 

For other solvers I do not know unfortunately...

 

I'm guessing FEMAP's arbitrary 3D data surface uses inverse distance weighting, which is explained here:

https://en.wikipedia.org/wiki/Inverse_distance_weighting

 

Note that this might not be the behaviour you're looking for, especially if you need extrapolation at certain points. I would suggest doing what is shown in the example: know your value at the corners f your load application domain.

There are many means for data interpolation, all fairly easy to code in FEMAP:

https://en.wikipedia.org/wiki/Multivariate_interpolation

 

AP