Prepare the Analysis

Define a load step, modify nonlinear solution controls, and add the commands necessary for use with Helius PFA.

1. Click Analysis > Create > Analysis Deck.
2. Click the Solution Type button and select IMPLICIT NONLINEAR. Click OK.
3. Click the Direct Text Input button and click the Nastran System Cell Section radio button.
4. Type NASTRAN SYSTEM(444) = 1 on the first line and NASTRAN SYSTEM(151) = 1 on the second line.
5. Click the File Management Section radio button and type CONNECT SERVICE hpfa 'autodesk.hpfa'.
6. Click the Bulk Data Section radio button and copy or type the following:

   PARAM, POST, 1
   $
   NLSTEP, 1, 1.0
    , GENERAL, 1000,
    , FIXED, 100,
    , MECH, PV, , 0.005
   $
   NLOUT, 101
   , ESV, SV2
   $
   GENUDS, hpfa
   $
   UDSESV, , 8

7. Now check on the System Cell Write to Input Deck, FMS Write to Input Deck, and BULK Write to Input Deck boxes and specify write at Start for each.

   

8. Click OK and click Apply on the Analysis form.

Some important notes about the entries above:

• The CONNECT SERVICE and GENUDS entries collectively specify the use of the Helius PFA User Material Subroutine.
• The PARAM entry is required for post-processing results.
• The GENERAL field in the NLSTEP entry specifies the maximum number of iterations to perform before MSC Nastran determines the need to reduce the time incrementation (cut-back). Setting this number to 1000 ensures MSC Nastran is able to take full advantage of the improved convergence characteristics provided by Helius PFA.
• The FIXED field in the NLSTEP entry specifies that 100 substeps will be used for the total solution time, allowing us to examine the progression of failure. The number of substeps can vary depending on the problem.
• The MECH field in the NLSTEP entry modifies the convergence tolerance to 0.5%. The default tolerance (10%) is relatively loose and can result in unacceptable accuracy.
• The NLOUT entry specifies that state variables should be written to the results file. This is required to view results produced by Helius PFA.
• The UDSESV entry specifies the number of state variables. This number must be 8 or higher. Refer to the Request Output of the MCT State Variables page for additional reference.

For additional details on these entries, please refer to the MSC Nastran Quick Reference Guide. For more information on how these entries should be used in accordance with Helius PFA, refer to the User's Guide.