Defining Surface-Based Contact in Implicit Steps

You can apply surface-based contact to define the interaction behavior between two discrete surface regions in the model. The contact options available depend on your analysis case context.

This task shows you how to:

See Also
About Surface-Based Contact
In Other Guides
About Step-dependent Actions

Define the Main and Secondary Surfaces

  1. From the Interactions section of the action bar, click Surface-based Contact .
  2. Optional: Enter a descriptive Name.
  3. Select Let system determine main/secondary assignment to allow the app to specify the main surface and secondary surface assignments automatically.
    The dialog box indicates the two faces as Surface 1 and Surface 2 and disables the swap option.
  4. Select the geometry supports in the model.

    You must apply surface-based contact must be applied between one or more faces or analytical rigid surfaces as the Main support and one or more faces as the Secondary support.

    Tip: When the contacting surfaces are difficult to discern, you can render all parts translucent except for parts associated with the contacting surfaces.
    • Click green to render all parts translucent except for contacting parts associated with the main surfaces.
    • Click magenta to render all parts translucent except for contacting parts associated with the secondary surfaces.

  5. Optional: If the geometry supports include surface (shell) geometry, click to change the side of the surface to be considered in the contact interaction.
  6. Optional: If necessary, click to swap the Main and Secondary supports.
  7. Continue to the next task, Define the Contact Property and Tie the Surfaces Together.

Define the Contact Property and Tie the Surfaces Together

Before you begin: Complete the previous task, Define the Main and Secondary Surfaces.
  1. From the Contact property options, select the name of a predefined contact property to be associated with this surface contact feature.

    If you do not choose a specific property, the app applies a default penalty contact. The default penalty contact provides a basic type of contact in which the penalty stiffness is constant, so the pressure-overclosure relationship is linear. The penalty stiffness is set to 10 times a representative underlying element stiffness.

    Note: The default penalty contact is different from having no contact property selected at all.

  2. From the Tie surfaces options, select one of the following:
    OptionDescription
    Within specified tolerance Ties together surfaces that are within the tolerance that you specify for the duration of the simulation; that is, no relative motion between the surfaces occurs at contacting interfaces. The app does not tie together surfaces outside of the tolerance.

    The default tolerance value is 5% of the characteristic element length.
    Compute tolerance from geometry Ties together surfaces regardless of the separation distance.

    A sufficiently large tolerance is computed automatically and used in the Abaqus solvers.
  3. Continue to the next task, Define the Discretization Method and Sliding and Clearance Behaviors.

Define the Discretization Method and Sliding and Clearance Behaviors

Before you begin: Complete the previous task, Define the Contact Property and Tie the Surfaces Together.
  1. Expand the Advanced section.
  2. From the Discretization method options, select one of the following:
    OptionDescription
    Surface-to-Surface Enforces contact conditions in an average sense over regions nearby secondary nodes rather than only at individual secondary nodes.
    Node-to-Surface Constrains secondary nodes not to penetrate into the main surface; however, the nodes of the main surface can penetrate into the secondary surface.
  3. Select Use small-sliding approximation to assume that although two bodies might undergo large motions, there will be relatively little sliding of one surface along the other.

    If you clear this option, the default behavior is finite sliding, which allows any arbitrary motion of the surfaces.

  4. If you chose Use small-sliding approximation, select Specify initial clearance to define an initial clearance that imposes an artificial uniform distance between two surfaces in surface-based contact.

    The specified clearance overrides the separation distance determined by the spatial coordinates of the surfaces and is used in all contact calculations for the simulation.

  5. If you chose Use small-sliding approximation or Node-to-Surface, enter a value for the Critical penetration.

    The critical penetration is the distance by which a point on the secondary surface must penetrate the main surface before the Abaqus solvers abandon the current increment and try again with a smaller increment.

  6. If you chose Node-to-Surface discretization, enter a value for the Extension zone.

    The extension zone is the fraction of the end segment or facet edge length by which the main surface is to be extended to avoid numerical roundoff errors associated with contact modeling. This value must be between 0.0 and 0.2.

  7. Continue to the next task, Define the Adjustment Behaviors.

Define the Adjustment Behaviors

Before you begin: Complete the previous task, Define the Discretization Method and Sliding and Clearance Behaviors.
  1. Expand the Advanced section.
  2. From the Adjust Options options, select one of the following:
    OptionDescription
    Capture offsets Prevents the overclosed nodes on the secondary surface from being moved (adjusted) back to the main surface.

    The app records the offset distances for the underclosed secondary surface nodes and acts as if they are in contact during the simulation.

    This option is available only when you have selected Use small-sliding approximation.
    Make strain-free adjustments Moves regions of the secondary surface within a specified adjustment zone so that they precisely contact the main surface; the adjustments do not create any strain in the model.

    You can choose the tolerance within which secondary surfaces are adjusted by changing the Gap capture zone.
    Resolve overclosures during analysis Prevents the adjustment of any secondary surfaces before the analysis starts.
  3. If you chose Make strain-free adjustments, enter a value for the Gap capture zone, which is the depth of the adjustment zone, as measured from the main surface.
  4. Click OK.