MV-3030: Load Export

In this tutorial you will learn how to use the Load Export utility to bridge the gap between Multi-Body Dynamics (MBD) analysis and Finite Element (FE) analysis in MotionSolve.

The utility allows you to bridge this gap by doing the following:
  • Identifying and summarizing all loads acting on one/multiple body(ies) for any given time step(s) in a tabular format.
  • Identifying and transferring all the forces and moments for one component at any given time step(s) to a Nastran input deck that contains GRID, CORD, FORCE, and MOMENT cards
Using Load Export
To use this utility, specify the components in the MotionSolve model for which loads are to be processed. You can do this by doing one of the following:
  • Use the MotionView interface.
  • Edit the MDL model fle to add force output requests on body(ies).

When performing the MS/ADAMS solver run on the MotionView model, you will get a metadata file (an ASCII file written out from MotionView that contains information about force output on a body).

This file along with the solver output files viz. MS (*.plt) or ADAMS (*.req) become the input files for this utility. The application scope of this utility is shown in Figure 1:


Figure 1. Interaction diagram

Create Metadata File and Launch Load Export

In this step you will create a metadata file and launch the Load Export utility.

Before you begin, copy the load_export.mdl file, located in the mbd_modeling\externalcodes folder, to your <working directory>.

  1. Start a new MotionView session.
  2. Load the front vehicle model file load_export.mdl, located in <working directory>.
  3. In the Project Browser, right-click on Model and select Add > General MDL Entity > Output.
    Tip: You can also add an Output if you right-click on the (Outputs) icon on the Model-General toolbar.
  4. In the Add Outputs dialog, accept the default selections and click OK.
  5. In the Output panel, use the drop-down menu to change the Output type from Displacement to Force.
  6. Double-click the collector.
  7. In the Select a Body dialog, expand the folders Frnt macpherson susp > Bodies and choose Lwr control arm - left.
    Tip: You can also select the Lwr control arm - left directly from the modeling window by clicking the Body collector once.


    Figure 2.
  8. Repeat steps 3 through 7 to create an output force request for Lwr control arm - right.
  9. Click the (Run) panel button.
  10. From the Main tab in the panel, specify an End time of 2 seconds.
  11. Save the solver input file as load_export.xml, to the <working directory>.
  12. Click the Run button to invoke MotionSolve and solve the model.
    MotionView creates a metadata file named load_export.meta in the <working directory>.

Use Load Export Utility and Generate Nastran Input Deck

In this step you will use the Load Export Utility and generate a Nastran Input Deck.

  1. From the menu bar, click Flex Tools > Load Export.


    Figure 3. Launching the Load Export Utility


    Figure 4. The Load Export Utility
  2. From the Load Export panel, open the file load_export.meta from your <working directory>.
    All bodies for which force outputs are requested are displayed in a tree structure in the Body Selection panel. You can select one or multiple bodies from the tree.
  3. Expand the sys_frnt_susp folder and select the Lwr control arm-left body.


    Figure 5. Body Selection panel
    All the forces acting on the lwr control arm - left will display in the Force Selection panel.
  4. In the Force Selection panel, choose all three forces acting on Lwr control arm - left.


    Figure 6. Force Selection Panel
  5. In the Time Selection panel, click the Range button.
  6. Specify a Minimum Time Step Value of 1 and a Maximum Time Step Value of 2.


    Figure 7. Activating the Export Panel
  7. In the Time Selection panel, click Apply.


    Figure 8.
    Note: You must click the Apply button to verify the validity of the time steps. If a time step you entered is not present in the ADAMS request file, an error message is generated and you must make corrections.
  8. In the Export panel, click the OptiStruct/Nastran radio button.


    Figure 9. Nastran options
  9. Click the Nastran Options button to launch the Nastran Export Panel.
    This dialog allows you to enter the Nastran node ID numbers, as well as specifying the following options:
    • Nastran deck format (Large/Small)
    • The reference frame (LPRF/Global) in which the GRID cards are written
    • Whether or not to explicitly output the CORD1R card in the input deck (Yes/No)


    Figure 10.
  10. Accept the default selections in the dialog. Then specify the Node ID's as follows:
    • Lwr ball joint - 1
    • LCA rear bush - 2
    • LCA frnt bush - 3
  11. Click Apply.
  12. On the Load Export panel, click Export.
  13. Specify a file name and click Save.
    This creates a subcase file, in addition to the Nastran input deck, in the same directory as the .dat file.
  14. Repeat steps 3 through 13 to export loads on the Lwr control arm - right.
    Note: If you select multiple bodies, the Nastran Export Panel will look as show in Figure 11:


    Figure 11. Nastran Export Panel for multiple body selection