Files and Formats

Within this section supported file formats are discussed.

Input Files and Formats

The optimization preprocessor reads the ASCII input files *.bdf. The Bulk entries must be in fixed format and in either small or large field format. Parameter statements (PARAM) may be set as free format.

Result Files and Formats

SIMULIA Tosca Structure uses MSC Nastran® output OP2. The following parameters are automatically generated or changed by SIMULIA Tosca Structure:

PARAM,POST,-1
PARAM,POSTEXT,YES
PARAM,TINY,0.0
PARAM,DBALL,SCRATCH
PARAM,OUGCORD,BASIC

For sensitivity-based topology optimization PARAM, POST, -4 is set in the first iteration.

SIMULIA Tosca Structure 2018 adds any output (DISPLACEMENTS, STRESS, etc.) required by the optimization if no outputs are given.

Important:

Please let SIMULIA Tosca Structure add the output request for obtaining the lowest possible CPU-time of the optimization. In many cases output writing is the most CPU-time consuming task for MSC Nastran® and thus SIMULIA Tosca Structure adds only those output requests that are necessary for the optimization. Therefore, the user should set as few output requests as possible, if any.

Remarks

Important:

  • The validation input file is created based on the original input deck. Thus for an automatic validation all required outputs have to be added in the beginning to the original input deck or the validation input file has to be changed manually after generation before starting the validation run.
  • When MSC Nastran® is configured to run in mode=i8, you must set the following flag in your SIMULIA Tosca Structure configuration or the CONFIG section in your job parameter file:

    ${fem_modif_add_call} = ${fem_modif_add_call}."--mode i8";

    MSC Nastran® does not write the stiffness matrix to the output file when mode=i8 is set. The SIMULIA Tosca Structure control shell provides a simple workaround to overcome the problem, but it has no means to detect the current MSC Nastran® mode setting. The ${fem_modif_add_call} flag is used to indicate the correct mode setting. Since MSC Nastran® version 2014, the mode can be set during the installation process. The default is mode=i8. If this option is selected and it is used for all jobs, it is recommended to set the aforementioned fem_modif_add_call setting in the global SIMULIA Tosca Structure configuration (tosca_ctrl.cfg) file.
  • In topology optimization large changes are applied to the elements' density and thus Young's modulus. This may result in problems with the pivot ratio of the stiffness matrices during a Nastran run. This could be overcome by changing the MAXRATIO parameter in the bulk data section like, e.g.: PARAM,MAXRATIO,10.E10
  • All PARAM statements must be located in the Bulk Data section. Having PARAM statements in the Case Control section will cause generation of invalid modified input deck