NASTRAN Procedure

The fem_data_file can be generated using NASTRAN, by means of the ALTER cards provided in directory etc/modal.d/ of the distribution.

The steps of the procedure are as follows:

1. prepare a NASTRAN input card deck, made of bulk data, eigenanalysis properties data and/or static loads (details about this phase are currently missing and will be provided in future releases of the manual).

2. complete the NASTRAN input file by putting some specific ALTER cards. In detail:
   1. the file MBDyn_NASTRAN_alter_1.nas contains ALTER definitions for static solutions; appropriate loading subcases for each solution must be provided in the case control and in the bulk data sections of the input file;

      FIXME: I don't know how to use static shapes only.

   2. the file MBDyn_NASTRAN_alter_2.nas contains ALTER definitions for eigenanalysis solutions; an appropriate eigenanalysis method, with the related data card must be provided in the case control and in the bulk data sections of the input file;

      FIXME: I don't know how to use this together with static shapes; I only get the normal mode shapes, even if the matrices are complete.

   3. the file MBDyn_NASTRAN_alter_3.nas contains ALTER definitions for eigenanalysis solutions; an appropriate eigenanalysis method, with the related data card must be provided in the case control and in the bulk data sections of the input file;

      Note: this works; see tests/modal/beam.README.

   Exactly one of these files must be included at the very top of the NASTRAN input file; they already include the appropriate SOL statement, so the input file must begin with

   $ Replace '#' below with number that matches your needs
   INCLUDE 'MBDyn_NASTRAN_alter_#.nas'
   CEND
   $... any other executive control and bulk data card
   

   The static solution of case (a: SOL 101) and the eigensolution of case (b: SOL 103) need to be performed in sequence; if only the eigensolution is to be used, the ALTER file of case (c: SOL 103) must be used. The static solution of case (a) generates a binary file mbdyn.stm; the eigensolutions of cases (b-c) generate two binary files, mbdyn.mat and mbdyn.tab, which, in case (b), include the static solutions as well. The ALTER currently included in the MBDyn distribution work correctly only with the following PARAM data card:

   PARAM,POST,-1
   

3. Run NASTRAN.

4. Run the tool utils/femgen, which transforms the above binary files into the fem_data_file. The file name is currently requested as terminal input; this is the name of the file that will be used in the input model for mbdyn. Conventionally, the .fem extension is used.