Transfer MSC Apex Model to Patran

MSC Apex offers significant time savings in geometry clean-up and meshing in comparison to most commercial pre-processors. Though tailored to designers and engineers looking to quickly obtain answers for design changes MSC Apex can be used alongside MSC Patran and MSC Nastran to speed up the process of model building.

 

The goal of this article is to highlight some possible complications when of moving out of Apex and to offer suggestions on overcoming these difficulties.

 

The Apex development team has been releasing an updated version of Apex roughly every six months and this article is only current up to the Fossa release. Many reasons that may lead an analyst to export their FEM out of Apex in Fossa may be features in future releases.

 

It is possible that an Apex user may want export their model to continue preprocessing in Patran or to solve in MSC Nastran. A few possible reasons are:

  • The Apex Structures module was not purchased”

  • Design iterations are unlikely and the model can be solved faster in MSC Nastran”

  • The model is large and may require more control over memory to solve more efficiently”

  • Pre/post-processing tools are currently unavailable that are accessible in Patran/MSC Nastran”

  • Solvers or solver features are currently not accessible through Apex”

There are a few caveats to exporting your model out of Apex that should be considered:

  • Geometry and mesh will need to be reassociated depending on the analyst’s needs.

    • Some features may not be properly associated if the “Suppress/Unsuppress” tool was used within Apex as these changes are not made on the geometry level.

  • Importing result files (.h5, .op2, .xdb, .MASTER/.DBALL) is not supported and not all cards are supported when importing a .bdf or .dat file into Apex such as RBE2 and RBE3.

  • Node and element numbering are not available to the user within Apex and manually grouping components in Patran could be time consuming.

  • Element and node numbering may change between exports meaning that any previously created files such as spreadsheets or Patran databases that depend on numbering may be out-of-date.

When exporting out of Apex follow the steps below. The process should remain the same no matter how the analyst would like to use the model afterward.

 

1) In MSC Apex

  1. File -> Export or Ctrl + E
  2. Change ‘Save as type:’ to Nastran Export (*.bdf) and enter your filename
  3. Export Window:
    • Select your model units from the dropdown
    • Recommended:
      1. Check the checkbox for ‘Wide Field’
      2. Check the radio button for ‘Hierarchical’ (if multiple parts)
  4. Export cleaned geometry as Parasolid (*.x_t)

At ESA we have had the most success using the parasolid format when importing into Patran

 

Two possible paths once outside of MSC Apex are:

  • solve the model using MSC Nastran or
  • import into Patran to perform addition work prior to solving.

2) In MSC Patran

 

The following steps assume some familiarity with Patran

  1. Create a new .db
  2. File -> Import
    • Select exported geometry
      • Use default settings
  3. Before importing the FEM (.bdf) add the following edited line under property sets to ensure that Patran imports named properties. A similar line can be used for loads and boundary conditions.
    • e.g – $ Pset: “Main_Housing_6061” will be imported as: “Main_Housing_6061”
  1. Select exported .bdf file
    • Click ‘MSC.Nastran Input Options…’
    • Check ‘Create Prop. & Matl. Groups’
      • Tip: If different material properties are assigned to each part in Apex this option can save a significant amount of time when creating groups for components.
    • Import FEM
  1. Check working directory for a file with the extension .bdf.rej
    • This file contains lines/cards that were rejected when importing. All lines begin with ‘$’, however lines that begin with ‘$>’ are These lines are shown to provide context. This can be confirmed by finding these lines within the Patran database.
  2. Meshing Tab -> Action: Associate -> Select specific element type and geometry you would like to associate (1D,2D,3D)
    • Association is dependent on global tolerance which can be changed by the following:
      • Preferences -> Global -> Global Model Tolerance
      • Global tolerance affects many operations throughout Patran and the default (or smaller) value should be used.

3) MSC Nastran

At this time running the exported .bdf from MSC Apex requires some manual manipulation on the user’s part as case control cards are not exported. We have created sample decks for SOL101 and 103 with typical cards included, though some additional work will still be required for many cases. Examples decks can be found here.