Files and Formats

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) might be set as free format.

Result Files and Formats

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

To make FemToOnf skip the PARAM, POST, -1 check in the MSC Nastran® interface, you can add the following DRIVER block:


DRIVER
  driver.Modules[ ToscaModules.FEM_2_ONF ].AddCallArgs = [ r'--ignore_ppr 1' ]
END_

Tosca Structure 2023 adds any output (DISPLACEMENTS, STRESS, etc.) required by the optimization if no outputs are given.

Important:

Let 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 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 file or the validation input file must be changed manually after generation before starting the validation run.
When MSC Nastran® is configured to run in mode=i4, you must set the following flag in your Tosca Structure configuration or the CONFIG section in your job parameter file:
driver.Solver.AddCallArgs = ['--mode', 'i4']

The default mode used by Tosca Structure is i8.
In topology optimization, large changes are applied to the elements' density and, thus, Young's modulus. This might 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, for example: 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 files.