Creating external superelement, but retain non-boundary nodes for plotting/visualization

mlevett3 · Mar 10, 2023

I have a cantilevered column type structure that I'm looking to reduce. I know I want the fixed boundary to be placed into the BSET, and to have enough spoints in the QSET, but I am confused on how to retain a select number of interior nodes and corner nodes (on the free end) that I can use to build up a plotel stick model for visualization purposes. This would be really useful when attaching it to other structure later on. If I select to output their displacements then I get a MUG1 matrix that I'm not used to seeing from other external superelements I have used which have plotels connecting interior nodes. So should these internal and corner nodes be CSET nodes even if that's no longer Craig-Bampton?

If so, and I have BSET and CSET, should I make the ASET the combination of the two? It looks like FEMAP makes me pick an ASET.

estring1 · Mar 16, 2023

The MUG1 matrix is part of the Output Transformation Matrix (OTM). This will be used later to process superelement interior nodes output requests (displacements, accelerations). Unless you want the interior nodes to be a part of the superelement reduction and retained as exterior nodes, there is no need to include them in ASET. The ASET is a combinationI suggest reading the Superelements User's Guide for the solver you are using (MSC/NX NASTRAN) to get more info on OTMs.

OTMs may be generated automatically when Nastran™ is used to create an external superelement using
the EXTSEOUT case control command. One or more types of OTM may be generated according to the
data recovery requests in the case control section of the external superelement generation input file.
When an input file is being prepared for the generation of an external superelement, the user decides which
GRID points in the input file will be used to attach the superelement to the assembly level analysis. These
GRID points define the boundary, or exterior points of the superelement and are explicitly defined to be in
the A set of the superelement. If component mode synthesis (CMS) is to be performed, at the users’
discretion, these boundary points may be held fixed or left free during the computation of the component
modes. By placing these boundary points on ASET/ASET1 or BSET/BSET1 or BNDFIX/BNDFIX1
entries, these points would be held fixed. If any points are to remain free during the computation of the
component modes, they are placed on CSET/CSET1 or BNDFREE/BNDFRE1 entries. By inference,
points not appearing on any of these entries are in the interior domain (the O set). By default, a displacement
OTM is always generated for the boundary points (the A set) of the external superelement and is used during
data recovery of the superelement. If PLOTEL elements are used to connect parts of the exterior and/or
interior points, displacement OTMs will also be generated for the points attached to the PLOTEL elements.
Any other OTMs need the definition of data recovery requests to initiate OTM generation for these items.
For example, if element force OTMs are required for elements 56 and 92 and elements stress OTMs are
required for elements 29 and 66, then the following data recovery requests will be needed.

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Creating external superelement, but retain non-boundary nodes for plotting/visualization

mlevett3

Automotive

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estring1

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