Trim Elements Inside Boxes

Use the Box Trim tool trim the model, or selected subset, to fit any defined box volumes.

For example, a full car model can be trimmed along the Y=0 axis to obtain the left or right side of the car. A fixed boundary condition is applied at the trimmed edges. It also removes the FE entities outside of the box, and cleans the model so that it is a runnable deck. The axis directions and terminology are based on modeling standards in the automotive industry.

Restriction: This option is available in the LS-DYNA, Nastran, Abaqus, OptiStruct, and Radioss profiles.
Different scenarios for using the Box Trim tool include:
  • Analysing one-half (or quarter) of the model using symmetry boundary conditions.
  • Trimming a full car model into a quarter or half model for further analysis.
  • Trimming a model to significantly gain computational time.
  • Trimming a model to debug an analysis error in a particular location in order to understand the cause of the error.
The Box Trim tool is very useful when you are doing a system-level analysis, and when portions of a full vehicle model include few complete subsystems or partial subsystems.
Note: This tool can only be used for 1st order elements.
  1. From the Elements ribbon, click the Box Trim tool.


    Figure 1.
  2. In the fist microdialog, click to add a new box volume.
    A second microdialog appears.
  3. Select elements.
    A preview of the box is drawn.

    By default, the box type is set to custom (bounding box/enclosed box).

    You can change the box type so that it fits specific regions. If the type is modified, the box gets re-drawn accordingly based on your element selection.

  4. Optional: Resize and relocate the box.
    • Click to manipulate the box with the Move.


      Figure 2.
    • Drag a face or an edge.


      Figure 3.
  5. Use the drop-down menu in the microdialog to orient the box with the global axes or to a best fit.


    Figure 4.
  6. Click Add Box.
    You are taken back to the first microdialog.
  7. Repeat steps 2-6 if you want to trim the model using multiple boxes.
  8. Optional: Click on the guide bar to create Single Point Constraints (SPCs) for all of the nodes along the trimmed edges. You can also set options that help clean the trimmed edge elements in order to achieve a better quality mesh.
  9. Click Trim either in the microdialog or on the guide bar.
Tip: Click on the guide bar to clear all boxes and start over.

How Entities on a Cutting Plane are Treated

The entities on a cutting plane must be treated as follows:
0D Elements
Delete 0D elements that are defined on the nodes that were deleted.
There are some special cases where the entity set and part are referred in it as a pointer. In these cases alone retain them.
1D Elements
All elements and rigids are retained.
2D Elements
Trim the element on the cutting plane.
3D Elements
Remove the element on the cutting plane.
Connectors
Remove the connector and it's corresponding FE realized.
Equations
This is mapped to loads in HyperWorks. Delete the equations if one of the nodes are deleted as part of Box trim.