Generating external superelements for Pre/Post system models

To generate superelements, you perform a static condensation (SOL 101 Superelement) or component-mode synthesis (SOL 103 Superelement) reduction. For more information about performing superelement reductions, see Superelement analysis.

When you use these superelements in Pre/Post system models, the following considerations apply.

Use NX Nastran 8 or later, or any version of Simcenter Nastran

NX Nastran 8 includes a new GEOM describer for the EXTSEOUT card to support post-processing of superelement results alongside the residual in Pre/Post system models. Superelements generated with MSC Nastran or earlier versions of NX Nastran are not fully supported for post-processing.

Specify DMIGOP2 as the file format

Ensure that the Superelement Options modeling object for the reduction solution specifies DMIGOP2 as the output file format. (The software outputs DMIGOP2 by default unless you change it.)

To quickly check the Superelement Options output file type, in the Simulation Navigator, right-click the Solution node and choose Edit, then click the Preview button. Look for a line similar to the following:

EXTSEOUT(GEOM,DMIGOP2=20)

If necessary, to change the superelement output options, click the Case Control tab, and click Edit next to the Superelement Options list.

Include at least three non-collinear boundary nodes

Your external superelement must have at least three non-collinear boundary nodes. This is required to position the superelement within the assembly FEM.

If you need to select extra boundary nodes in order to satisfy this requirement, and if these nodes will not be used to connect the superelement to the assembly FEM, you should include these nodes in the free DOF set (CSET).

For more information about defining boundary nodes for a superelement analysis, see DOF sets and Fixed and free boundary degrees of freedom (Nastran, ANSYS, and Abaqus).

Output requests

You can improve the efficiency of your superelement reduction by removing unnecessary output requests from your solution. However, you must include at least those output requests for results you intend to recover in the system run solution. For example, disabling the STRESS request in a SOL 103 Superelement solution can dramatically improve performance. However, if you intend to use the component-mode synthesis reduction in a linear statics system run, you must enable the STRESS request the superelement solution output requests in order to recover stresses from your system model.

Accuracy versus Performance

For component-mode synthesis reductions, increasing the number of modes requested will improve accuracy. However, you need to balance this improved accuracy against the correspondingly longer solve times and larger superelement file size. As a general rule, solve for modes which are two to four times the largest dynamic load frequency.

How do I

Replace Base FEM components with superelements

Load and display superelement results

Update a system model

Learn more

Superelement analysis

Using superelements in an assembly FEM

System modeling workflow

Replacing a component FEM with a superelement

Superelement mapping considerations

Connecting superelement boundary nodes to the residual

Superelement displays

Controlling the display of base FEM approximations

Solving the system model

Example: Assigning external superelements in the bulk data file

Example: Defining superelement connections and orientation

Post-processing system models

Creating a Simcenter Samcef superelement for Pre/Post system models

Supported system model solutions for Simcenter Samcef superelements

Look up more details

Supported system model solutions

Quick links

Command reference

Pre/Post video examples

Bulk Entry Descriptions

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Generating external superelements for Pre/Post system models, Simcenter 3D 2021.1 Series

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