Modifying contact pair definitions

The contact pair candidates table presents all of the identified contact pair candidates in a format that allows you to easily review and modify the parameters of each contact pair definition. Abaqus/CAE supplies default values for each parameter of the contact pair definition (see Default interaction and constraint parameters).

You can customize some of the default parameter settings to suit your modeling needs by using the Rules tabbed page (see Defining default contact pair parameters). However, you may still need to modify some parameters manually before creating interactions and constraints. The Rules options cannot account for such modeling issues as the appropriateness of small-sliding contact or assignment of varying frictional contact properties. You also may need to swap the assignment of main and secondary roles in contact pairs to ensure continuity and robustness.

See Also
Understanding contact and constraint detection
Using contact and constraint detection

Context:

To modify a parameter, change the value that is displayed in the corresponding cell of the contact pair candidates table. You modify cell values in one of four ways:

  • To change a name parameter, click on the cell and type a new name. The old name is overwritten as you type.

  • For cells that accept specific values, first click the cell to activate it. Then click the arrow next to the cell and select the desired value from the list that appears.

  • For cells that require more detailed information to define the parameter, double-click the cell and enter the appropriate information in the dialog box that appears.

  • For all cells other than name parameters, click mouse button 3 on the cell and select Edit Cells from the menu that appears. You can also click the cell and then click the button above the contact pair candidates table. Enter the appropriate information in the dialog box that appears.

You cannot modify values for the following parameters:

  • Separation

  • Main Instance

  • Secondary Instance

Each row of the contact pair candidates table represents a single contact pair candidate. The following instructions apply to a single row. Repeat them as often as necessary for each row in the table. For instructions on editing parameters for multiple contact pair candidates simultaneously, see Miscellaneous review procedures.

  1. In the Name column, change the name of the contact pair, if desired.
  2. In the Main Surface or Secondary Surface column, change the name of the generated main surface or secondary surface, if desired.

    The Main Surface and Secondary Surface columns are not displayed in the contact pair candidates table by default. See Configuring the layout of the contact pair candidates table, for instructions on adding these columns to the table.

  3. Click mouse button 3 on any cell in the row, and select Switch Surfaces from the menu that appears to reverse the role of the main and secondary surfaces for the selected contact pair. You can also click the row and then click the button above the contact pair candidates table. (To determine the role assignments in a contact pair, see Confirming search results in the viewport.)
  4. To indicate whether a contact interaction or a tie constraint is created for the contact pair candidate, select Interaction or Tie in the Type column.

    You cannot change the Type for previously created tie constraints or interactions that include node-based regions.

  5. To specify the tracking approach that will be used in an Abaqus/Standard contact formulation, select a value in the Sliding column:

    • Select Finite to use the finite-sliding tracking approach.

    • Select Small to use the small-sliding tracking approach.

    Abaqus/CAE ignores the Sliding column when creating tie constraints and for Abaqus/Explicit analyses. For more information on the tracking approach, see Contact Formulations in Abaqus/Standard.

  6. To specify the surface discretization that will be used in a contact or tie formulation, select a value in the Discretization column:

    • Select Node-Surf to use node-to-surface discretization.

    • Select Surf-Surf to use surface-to-surface discretization.

    For more information on surface discretization, see Mesh Tie Constraints; Contact Formulations in Abaqus/Standard; and Contact Formulations for Contact Pairs in Abaqus/Explicit.

  7. For contact interactions, select the interaction property in the Property column.

    If the appropriate contact property is not available, you can create a new one:

    1. Click mouse button 3 anywhere in the contact pair candidates table, and select Create Property from the menu that appears.
    2. Create a contact interaction property as described in Defining a contact interaction property.

      When you have finished using the interaction property editor, the property you created will be available under the Property column in the contact pair candidates table.

    Abaqus/CAE ignores the Property column when creating tie constraints.

  8. For contact interactions, select the contact controls in the Contact Controls column.

    The Contact Controls column is not displayed in the contact pair candidates table by default. See Configuring the layout of the contact pair candidates table for instructions on adding this column to the table.

    If the appropriate contact controls are not available, you can create them:

    1. Click mouse button 3 anywhere in the contact pair candidates table, and select Create Contact Controls from the menu that appears.
    2. Create the contact controls as described in Customizing contact controls.

      When you have finished specifying the contact controls, the controls you created will be available under the Contact Controls column in the contact pair candidates table.

    Abaqus/CAE ignores the Contact Controls column when creating tie constraints.

  9. Use the adjustment options to reposition a secondary surface (or portions of a secondary surface) precisely onto the main surface at the beginning of an analysis:
    1. Double-click the cell in the Adjust column.

      The Secondary Node/Surface Adjustment Options dialog box appears.

    2. The options available in the Secondary Node/Surface Adjustment Options dialog box depend on the value in the Type column for the associated contact pair candidate:

      • If you are creating a contact interaction, select one of the following options:

        No adjustment

        Abaqus/CAE will not reposition any nodes or surfaces.

        Adjust only to remove overclosure

        Abaqus/CAE will reposition any initially overclosed secondary nodes or constraint points precisely onto the main surface.

        Specify tolerance for adjustment zone

        Abaqus/CAE will reposition any secondary nodes or constraint points located within the specified distance from the main surface precisely onto the main surface.

        Adjust secondary nodes in set

        Abaqus/CAE will adjust the secondary nodes or constraint points included in the specified geometry set precisely onto the main surface.

        Abaqus/CAE ignores the Adjust column for contact interactions in an Abaqus/Explicit analysis. For more information about adjustment options for contact interactions, see Contact Initialization for Contact Pairs in Abaqus/Standard.

      • If you are creating a tie constraint, you can modify both the adjustment options and the tie position tolerance in the Secondary Node/Surface Adjustment Options dialog box:

        • By default, Abaqus adjusts all tied secondary nodes so they lie precisely on the main surface. To prevent adjustment of the secondary nodes (but still tie the secondary node degrees of freedom to the main surface), toggle off Adjust secondary surface initial position.

        • Abaqus ties only those secondary nodes that lie within a specific distance from the main surface. To let Abaqus calculate a reasonable distance automatically, select Use computed default. To specify a distance directly, select Specify distance, and enter the distance in the field provided.

        For more information about adjustment options and position tolerances for tie constraints, see Mesh Tie Constraints.

    3. Click OK.
  10. To change the analysis step in which the contact pair is activated, select a step name in the Create Step column.

    The Create Step column is not displayed in the contact pair candidates table by default. See Configuring the layout of the contact pair candidates table, for instructions on adding this column to the table.

  11. For contact interactions using surface-to-surface discretization, select whether or not contact smoothing will be applied in the Surface Smoothing column:

    • Select Automatic to let Abaqus/CAE identify any surfaces (or portions of surfaces) in the contact pair that are axisymmetric or spherical. If the Highlight in viewport option is enabled, Abaqus/CAE displays the axis of symmetry or spherical center for any identified surfaces in the viewport. Abaqus smooths these surfaces during contact calculations to minimize inaccuracies caused by mesh discretization. The Automatic option is available only for geometry models.

    • Select None to prevent contact smoothing from being applied to any surfaces in the contact pair.

    Abaqus/CAE ignores the Surface Smoothing column for tie constraints and for contact interactions in an Abaqus/Explicit analysis. For more information about contact surface smoothing, see Smoothing Contact Surfaces in Abaqus/Standard.