Identify the User Subroutine

Helius PFA interacts with MSC Nastran and the SOL 400 code via a user-material subroutine. We must define this user subroutine in the bulk data file to run an analysis with Helius PFA.

Below the NASTRAN SYSTEM entries, add the following line:
```
CONNECT SERVICE hpfa 'autodesk.hpfa'
```

After the PARAM, POST, 1 entry, add the following:

GENUDS, hpfa
$
MATUSR, 9025, 1, 23
MATUDS, 9025, MATUSR, hpfa, UMAT
, REAL, 3, 1, 1, 0, 0, 0, 0,
,     , 0, 0, 0, 0, 0.1, 1E-06
$
UDSESV, , 8

These lines identify the hpfa user defined service and tell MSC Nastran to use this subroutine to evaluate the user material (MATUSR, MATUDS). The final line identifies the number of state variables to pass to the subroutine. Refer to the Helius PFA User's Guide for further detail regarding these entries.

An example bulk data file with these specifications is shown below:

NASTRAN SYSTEM(444) = 1
NASTRAN SYSTEM(151) = 1
$
CONNECT SERVICE hpfa 'autodesk.hpfa'
$
SOL 400
CEND
SUBCASE 1
   SUBTITLE=Default
   NLSTEP = 1
   SPC = 2
   LOAD = 1
   NLSTRESS (PLOT,NLOUT=101) = ALL
$
BEGIN BULK
$
NLSTEP, 1, 1.0
 , GENERAL, 1000
 , FIXED, 100,
 , MECH, PV, , 0.005
$
NLOUT, 101
, ESV, SV2, SV3, SV4
$
PARAM, POST, 1
$
GENUDS, hpfa
$
MATUSR, 9025, 1, 23
MATUDS, 9025, MATUSR, hpfa, UMAT
, REAL, 3, 1, 1, 0, 0, 0, 0,
,     , 0, 0, 0, 0, 0.1, 1E-06
$
UDSESV, , 8

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