Create, Review, and Edit MPC Equations

Create MPCs

MPCs are used to create a simple linear equation that relates the displacements of the included nodes and degrees of freedom. MPCs are activated in the case control similar to other boundary conditions.

Restriction: Currently only OptiStruct and Nastran interfaces are supported.
  1. From the Analyze ribbon, click the BCs > MPCs tool.

    Figure 1.
  2. Select the independent node(s).

    At least one independent node is required.

  3. Select a dependent node.

    The MPC is automatically created upon selecting the dependent node.

    A degree of freedom that is specified as dependent may not be specified as dependent for any other entity in the model (for example, RBE, MPC, SPC).

  4. Optional: Click and on the microdialog to adjust the degrees of freedom of the dependent and independent nodes to be included in the MPC.

    Only one DOF is allowed for the dependent node.

  5. Optional: Click on the microdialog to specify a uniform weighting factor or automatically calculate the weighting factors of the independent nodes based on their respective distance from the dependent node.
  6. Optional: Click on the microdialog to enter node-based editing mode.
    1. Select one or more independent nodes.
    2. Choose whether to update their DOF or weighting factors using the drop-down menu.
    3. Enter a new value for the selected nodes.

      DOFs are specified as a combination of the numerals 1-6 (for example., 123, 123456, 124).

  7. Optional: Click on the microdialog to reposition the dependent node using the Move tool.

    If the dependent node is attached to other elements, a new node will be created and moved to the new location.

  8. On the guide bar, click to create another MPC or click to exit the tool.

Review and Edit MPCs

  1. To open the MPC context in edit mode, do one of the following from idle:
    • Double-click on an MPC.
    • Select an MPC, then select Edit from the right-click menu.
    • Select an MPC, then access the tool via the ribbon icon.
  2. Utilize any of the actions noted above to review or modify the MPC connectivity, DOF, and/or independent node location.
  3. On the guide bar, click to create another MPC or click to exit the tool.
  • Refer to the entity status icon on the guide bar for status and feedback. Clicking the icon will fit the view to the current MPC.
  • Changes made in the MPC context are automatically committed to the database. If a change is made that invalidates the MPC (for example, clearing the independent node selection), the MPC will turn grey and the database will not be updated until the MPC is made valid again. The entity status icon and error flags on the selectors help identify required inputs.
  • Hold Ctrl (add) or Shift (remove) in to select individual nodes in quick succession. The MPC will be updated upon releasing Ctrl/Shift.