Tutorial: Analyzing a Model with Contacts

Tutorial Level: Beginner Analyze a model with contacts to understand the difference between sliding and separating.

In this lesson you will learn how to:
  • Create nuts and bolts in aligned and single holes
  • Run an analysis
  • View contacts
  • Redefine contacts
  • Run sliding and separating analyses


Open the Sway Bar Model

Before you begin, copy the file(s) used in this tutorial to your working directory.
  1. Double-click the Analysis_Contacts.stmod file to load it in the modeling window.
  2. Make sure the display units in the Unit System Selector are set to MPA (mm t N s).
    Important: Setting display units to MPA (mm t N s) will be important for comparing analysis results.
  3. Notice that the model already has a load case defined. Our objective for this load case is to accurately simulate the transfer of loads from the torque applied at the inside end of the bar to the bracket designated as the design space.


Create Nuts and Bolts in Aligned Holes

  1. On the Structure ribbon, select the Fasteners tool.
    Tip: To find and open a tool, press Ctrl+F. For more information, see Find and Search for Tools.
    The tool finds two locations with aligned holes.
  2. Click Apply on the guide bar to create fasteners.


  3. Observe as Inspire creates nuts and bolts in both locations.


Create a Nut and Bolt in a Single Hole

  1. While the Fasteners guide bar is still active, click Aligned Holes and select Single Holes.


  2. Inspire finds multiple locations with single holes. Click the single-hole location shown below to insert a grounded bolt.


  3. Right-click and mouse through the check mark to exit, or double-right-click.

Redefine the Contact

Redefine the contacts in the model before you run an analysis to permit or restrict their movement.

  1. On the Structure ribbon, select the Contacts tool.
    Tip: To find and open a tool, press Ctrl+F. For more information, see Find and Search for Tools.
    All of the contacts in this model are currently defined as bonded contacts (default) and are shown in blue.


  2. Click the contact where the bar touches the L bracket.
    A microdialog appears.


  3. Choose a contact Type from the dropdown list on the microdialog to change the contact type.
    • Select Bonded if parts are bonded or glued together.
    • Select Sliding if there is relative sliding between the parts.
    • Select Separating if the relative parts can separate.
    • Select No Contact if parts are close but you don't want them to have contact.

Run the Analysis with Sliding Contact

  1. While the Contacts guide bar is still active, click the contact where the bar touches the L bracket and select Sliding in the microdialog.
  2. Right-click and mouse through the check mark to exit, or double-right-click.
  3. On the Structure ribbon, click the Run Analysis button in the Analyze tool group.


  4. Run the analysis using the following settings.
    1. Add Sliding to the run name.
    2. Select OptiStruct as the solver.
    3. Change the Element Size to 3.0 mm.
    4. Set Speed to More Accurate.
    5. Click Run.


  5. When the run is complete, select it in the Run Status window and click View Now to view the results.


    Tip: You can also double-click the Results icon in the Model Browser to view results for a load case.

  6. In the Analysis Explorer, select Factor of Safety from the Result Types dropdown.


  7. In the Analysis Explorer, select Show/Hide Deformed State to show the deformed state of the model.
  8. Select Show/Hide Elements in the View Controls to show the finite element mesh.
  9. Click the button on the animation toolbar to review the analysis. Click the button to pause the animation.
    Notice that the L-bracket and the sway bar are acting as if they are tied radially. This leads to an unrealistic stress in the L-bracket as the sway bar should be allowed to open a gap.

  10. Right-click and mouse through the check mark to exit, or double-right-click.
    Note: With Sliding contact types, you can run the model faster, but the results will not be as accurate.

Rerun the Analysis with Separating Contact

  1. On the Structure ribbon, select the Contacts tool.
    Tip: To find and open a tool, press Ctrl+F. For more information, see Find and Search for Tools.
  2. Click the contact where the bar touches the L bracket and select Separating in the microdialog.
  3. Right-click and mouse through the check mark to exit, or double-right-click.
  4. On the Structure ribbon, click the Run Analysis button in the Analyze tool group.


  5. Run the analysis using the following settings.
    1. Add Separating to the run name.
    2. Select OptiStruct as the solver.
    3. Change the Element Size to 3 mm.
    4. Set Speed to Faster.
    5. Click Run.


  6. When the run is complete, select it in the Run Status window and click View Now to view the results.


    Tip: You can also double-click the Results icon in the Model Browser to view results for a load case.

  7. In the Analysis Explorer, select Factor of Safety from the Result Types dropdown.


  8. Select Show/Hide Elements in the View Controls to show the finite element mesh and improve visibility of relative displacements.
  9. Click the button on the animation toolbar to review the analysis. Click the button to pause the animation.
    Notice that the sway bar correctly separates from the top of the L-bracket without introducing an unrealistic stress.

  10. Right-click and mouse through the check mark to exit, or double-right-click.
Note: With Separating contact, a nonlinear contact solution is used. This increases the run time but is a better representation of the actual physics.

Contact Status Results

  1. In the Analysis Explorer, select Contact from the Result Types dropdown.
  2. Select Gap from the Contact dropdown.
  3. Select the Create, Show, and Hide Callouts button.
  4. Hover the mouse over the result contour to see the calculated gap. Notice that the gap is closed on the bottom and open on the top.
  5. Select Status from the Contact dropdown.
    Notice the state of the different contacting areas.