Merging Bodies

The Merge option available in the Project browser context menu allows you to merge two or more rigid bodies. This feature is particularly useful during the initial set-up phase of model building, generally following a CAD import. Two or more bodies that may be represented as a single rigid body, can now be merged into one body using this feature. The following will also take place whenever there is a merge of bodies:
  • Calculation of combined mass/inertia and CG.
  • Changing other entity references (graphics, joints, etc.) from bodies being merged to the new bodies.

To use the Merge option, you must select two (or more) rigid bodies that you would like to merge. Multiple bodies can be selected in the Project browser or in the graphics area using the Shift key + left click method.

Once the bodies have been selected, right-click to bring up the context menu and select the Merge option.

Figure 1.

The right-click context menu provides options to merge the selected bodies to a new body or to a Ground Body.

If Merge Bodies is selected, the Merge Bodies dialog is displayed which allows you to enter in a new Label and Varname for the merged bodies. After clicking OK to close the dialog:
  • A new Body entity is created with the given label, varname, and the effective mass and inertia values.
  • A new CG point is created and used by the new body at the effective location of the CG of the bodies being merged.
The following operations are also performed (in addition to those listed above) when merging as a new body or merging with Ground:
  • All references to other entities (graphics, joints, bushings, forces, etc.) to the bodies being merged, if any, now refer to the newly created body/Ground Body.
  • The merged bodies are deleted from the model.
An example outlining this process is shown below:

Figure 2. Merge Bodies Example

To learn how to use this feature in more detail please refer to tutorial MV-1035: Importing CAD or FE into MotionView.

Important Notes

  • The Merge option cannot be used on a pair body, Point Mass body, or a deformable body (Flexible Body and NLFE Body).
  • This feature works only on bodies within the same parent system/Assembly. Merging bodies which belong to different parent containers are not supported.
  • References of bodies being merged in expressions (parametric expressions) will not change. Such expressions needs to be corrected to refer to the newly created body.
  • The CG points related to the bodies being merged are retained in the model.