FEMFAT®

Within this section the durability solver FEMFAT® is discussed.

General

For a shape optimization with SIMULIA Tosca Structure in combination with FEMFAT®, special results have to be requested in the FEMFAT® preprocessing. The requested result files may be read by SIMULIA Tosca Structure and allow the correct interfacing of the two software packages.

The following result formats for SIMULIA Tosca Structure may be requested in FEMFAT®:

  • ONF 600 SIMULIA Tosca Structure optimization neutral file This data block contains a node list and a damage value for each node.
  • ONF 601 SIMULIA Tosca Structure optimization neutral file with load case information. This additionally data block contains load case information. This allows several FEMFAT® Basic calculations which may later be combined in SIMULIA Tosca Structure.
Important:

The type of DRESP determines the result format! Use:

TYPE = DAMAGE          ! For ONF 600
TYPE = DAMAGE_LC       ! For ONF 601

It is important that the result from the life analysis has the same name as the life-solver input deck except for the file extension.

For example:

<life_input_file>.ffj

must produce a result file called:

<life_input_file>_600.onf  (or <life_input_­file>_601.onf)
Important:

If the latter file does not exist in the working directory of the SIMULIA Tosca Structure Job, the optimization will stop due to missing results. A corresponding error message will be output to the user.
Important:

For all design nodes that are used for shape optimization a damage value has to be provided. So the area for damage calculation may be reduced to the design area in order to save calculation time.

Changes in the FEMFAT® FFJ file

During the fatigue life simulation preprocessing, the user selects the finite element solver result file interactively in FEMFAT®. While exporting the ffj file, the absolute path settings for the stress input file(s) are stored to the control file. 

setValue {0 {{setValue {} {} StressFileDatasetNumber 0}}} {0 ok}  StressInputFile C:\scratch\holeplate_dam.op2

If FEMFAT® is called inside the SIMULIA Tosca Structure optimization loop, it has to be ensured, that FEMFAT® is reading the modified stress data in each design cycle. The new result file(s) are always generated in the SIMULIA Tosca Structure optimization working directory. So SIMULIA Tosca Structure is automatically modifying the ffj file and adapting the path of the stress input(s) to a relative path into the actual working directory. This is admissible as during the optimization procedure, FEMFAT® is always running in the SIMULIA Tosca Structure working directory.

setValue {0 {{setValue {} {} StressFileDatasetNumber 0}}} {0 ok}  StressInputFile ./holeplate_dam.op2
Important:

Be careful: if a FEMFAT® analysis should be executed outside SIMULIA Tosca Structure based upon a SIMULIA Tosca Structure-modified FEMFAT® input file. If FEMFAT® is not running in the directory where the ffj file is located, the stress result files may not be found and FEMFAT® will stop with an appropriate error message.

Start of FEMFAT® in BATCH mode

For the optimization, FEMFAT® has to run in batch mode. The following files must exist

  • Solver Input file(s) (*.bdf, *.inp, *.cdb, ...)
  • FEMFAT® Jobfile *.ffj

    The FEMFAT jobfile name and the FE-input deck name are not required to be the same.

At the end of the job file, the FEMFAT® calculation must be started. The following entry must exist in the jobfile:

setValue {} {} StartAnalysisLoop

This can be realized easily by exporting the ffj file from the FEMFAT® application after the execution of the analysis.

The FEMFAT® batch run should be tested before the complete optimization is started. The command line for a FEMFAT® batch run is the following:

Windows:

<femfat_install>\lib\dll\femfat4exe  <femfat_install>\bin\bin\femfat.tbc -job=<jobname>.ffj

Linux:

<femfat_install>\bin\bin\femfat4 -job=<jobname>.ffj