Create, Review, and Edit RBE3 Elements

Create RBE3s

RBE3 elements are commonly used to connect parts, attach nonstructural concentrated masses, apply loads and boundary conditions, and in other places where a distributed connection is needed. In contrast to RBE2s and contrary to the name, RBE3s do not behave as rigid bodies. An RBE3 creates a flexible connection between the constituent nodes and degrees of freedom where the displacement of the center node is equated to the weighted average of the displacement of the other nodes. This tool may be used to quickly create and modify RBE3s directly when the use of Connectors technology is not necessary/desired.

Restriction: Currently only OptiStruct and Nastran interfaces are supported.
  1. From the Model ribbon, click the RBE3 tool.
    Figure 1.


    Note: The RBE3 tool is part of a drop down action group that also includes RBE2 and Rigid Body. If RBE3 is not visible, click the drop-down arrow next to the icon.
  2. Select the independent nodes.
    At least one independent node is required. As soon as two or more nodes are selected, the RBE3 is created with an automatic dependent node at the centroid of the independent nodes.
    Tip: Use the edge or face selectors to quickly create RBE3s in holes
  3. Optional: Select a dependent node.

    If only one independent node was selected, the RBE3 will automatically be 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).

    Clearing the dependent node selection will revert to an automatic center node if the RBE3 includes two or mode independent nodes.

  4. Optional: Click and on the microdialog to adjust the degrees of freedom of the dependent and independent nodes to be included in the RBE3.
  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.
    Distance-based weighting is calculated by:
    w i = d i −1 ∑ j n d j −1 MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4DamaaBa aaleaacaWGPbaabeaakiabg2da9maalaaabaGaamizamaaDaaaleaa caWGPbaabaGaeyOeI0IaaGymaaaaaOqaamaaqadabaGaamizamaaDa aaleaacaWGQbaabaGaeyOeI0IaaGymaaaaaeaacaWGQbaabaGaamOB aaqdcqGHris5aaaaaaa@4468@
  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 RBE3 or click to exit the tool.

Review and Edit RBE3s

  1. To open the RBE3 tool in edit mode, do one of the following from idle:
    • Double-click on an RBE3.
    • Select an RBE3, then select Edit from the right-click menu.
    • Select an RBE3, then access the tool via the ribbon icon.
  2. Utilize any of the actions noted above to review or modify the RBE3 connectivity, DOF, weighting factors, and/or dependent node location.
  3. On the guide bar, click to create another RBE3 or click to exit the tool.
Tip:
  • Refer to the entity status icon on the guide bar for status and feedback. Clicking the icon will fit the view to the current RBE3.
  • Changes made in the RBE tool are automatically committed to the database. If a change is made that invalidates the RBE (for example, clearing the independent node selection), the RBE will turn grey and the database will not be updated until the RBE 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 RBE will be updated upon releasing Ctrl/Shift.