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Using Substructuring

Command(s): SOLVE

GUI: Main Menu> Solution> Solve> Current LS

Results from the solution consist of the complete solution for nonsuperelements and the reduced solution - DOF solution at masters - for the superelements. The complete solution for nonsuperelements is written to the results file (Jobname.RST, RTH, or RMG), which you can postprocess using normal postprocessing procedures.

The reduced solution is written to the file Jobname.DSUB. You can review this file using one of these methods:

Command(s): SEDLIST

GUI: Main Menu> General Postproc> List Results> Superelem DOF Utility Menu> List> Results> Superelem DOF Solu

To expand the reduced solution to all elements within the superelement, you will need to perform the expansion pass, explained next.

7.Leave SOLUTION:

Command(s): FINISH GUI: Main Menu> Finish

10.2.3. Step 3: Expansion Pass (Expanding Results Within the Superelement)

The expansion pass is where you start with the reduced solution and calculate the results at all degrees of freedom in the superelement. If multiple superelements are used in the use pass, a separate expansion pass will be required for each superelement.

The procedure for the expansion pass assumes that the .EMAT, .ESAV, .SUB, .LN22, .DB, and .SELD files from the generation pass and the .DSUB file from the use pass are available. For larger substructures, the files .LN09 and .LN20 will also be required if they were created in the generation pass. The expansion pass logic automatically detects which, if any, factorized matrix files are available and chooses

the appropriate expansion pass method and solver accordingly. If an offset of node numbers was used in the use pass [SETRAN or SESYMM], it will automatically be taken into account in the expansion pass.

The backsubstitution method uses the reduced solution from the use pass and substitutes it back into the available factorized matrix file to calculate the complete solution. The full resolve solution reforms the element stiffness matrices originally used to create the superelement. The global stiffness matrix for these elements is then assembled. The reduced solution is applied to the model as displacement boundary conditions, and the complete solution within the superelement is solved.

Note

The displacement boundary conditions are automatically applied internally at the master degrees of freedom during the expansion pass solution and are automatically deleted when the solution completes.

The expansion pass logic for substructuring analyses first searches for the superelement .LN22 file and, if found, chooses the sparse solver to perform a backsubstitution (the EQSLV command is ignored). Otherwise, the program will stop the expansion pass and give a message suggesting an alternate expansion method.

If the .LN22 file is not detected for the specified superelement, the full resolve method is chosen. The PCG solver is chosen by default for the full resolve method. You can select the sparse solver using the

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EQSLV command to override the default. Other equation solvers cannot be used with the full resolve method.

1.Clear the database:

Command(s): /CLEAR

GUI: Utility Menu> File> Clear & Start New

This has the same effect as leaving and re-entering the program.

2.Change the jobname to what it was during the generation pass. This way, the program can easily identify the files required for the expansion pass:

Command(s): /FILNAME

GUI: Utility Menu> File> Change Jobname

3.Restore the generation pass database:

Command(s): RESUME

GUI: Utility Menu> File> Resume Jobname.db

4.Enter SOLUTION using one of these methods:

Command(s): /SOLU

GUI: Main Menu> Solution

5.Activate the expansion pass and its options:

Command(s): EXPASS

GUI: Main Menu> Solution> Load Step Opts> ExpansionPass

Expansion pass on or off - Choose "on."

Name of superelement to be expanded - Specify the name (Sename):

Command(s): SEEXP

GUI: Main Menu> Solution> Load Step Opts> ExpansionPass> Expand Superelem

(The complete name of the file is assumed to be Sename.SUB.)

Name of the reduced solution file from use pass - Specify the name (Usefil) using the SEEXP command (or the menu path shown above). The complete name of the file is assumed to be Usefil.DSUB.

Real or imaginary component of displacement - Applicable only if the use pass was a harmonic analysis. Use the Imagky key on the SEEXP command (or the menu path shown above). If all solutions are to be expanded (NUMEXP,ALL), Imagky is ignored and both the real and imaginary solutions are expanded.

6.Identify the use pass solution(s) to be expanded. You can either expand a single solution [EXPSOL] or a range of solutions (including all) [NUMEXP]:

Single Solution - use either the load step and substep numbers or the time (or frequency) to identify a solution:

Command(s): EXPSOL

GUI: Main Menu> Solution> Load Step Opts> ExpansionPass> Single Expand> By Load Step

 

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Using Substructuring

Main Menu> Solution> Load Step Opts> ExpansionPass> Single Expand> By Time/Freq

Note

If the load step being expanded contains nonzero DOF constraints, the database must have matching DOF values. If it does not, the DOF constraints must be respecified [D] in the expansion pass.

Range of Solutions - Identify the number of solution and time or frequency range:

Command(s): NUMEXP

GUI: Main Menu> Solution> Load Step Opts> ExpansionPass> Range of Solu's

7.Specify load step options. The only options valid for a substructure expansion pass are output controls:

Output Controls - These options control printed output, database and results file output, and extrapolation of results.

If you want to include any results data on the printed output file (Jobname.OUT):

Command(s): OUTPR

GUI: Main Menu> Solution> Load Step Opts> Output Ctrls> Solu Printout

If you want to control the data on the results file (Jobname.RST):

Command(s): OUTRES

GUI: Main Menu> Solution> Load Step Opts> Output Ctrls> DB/Results File

If you want to review element integration point results by copying them to the nodes instead of extrapolating them (default):

Command(s): ERESX

GUI: Main Menu> Solution> Load Step Opts> Output Ctrls> Integration Pt

8.Start expansion pass calculations:

Command(s): SOLVE

GUI: Main Menu> Solution> Solve> Current LS

9.Repeat steps 6 to 8 for additional use pass solutions to be expanded. If you need to expand the solution for a different superelement, you will need to leave and re-enter SOLUTION.

Note

If the superelement to be expanded contains contact elements and has multiple use passes, use separate expansions (repeating steps 1 through 7) or issue the NUMEXP command to expand multiple load steps together.

10.Finally, leave SOLUTION:

Command(s): FINISH GUI: Main Menu> Finish

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of ANSYS, Inc. and its subsidiaries and affiliates.

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