FBD Plot

Use the Free Body Plot tool to create, edit, and display free-body section plots. Calculate the contribution of one or more elements to the force and moment equilibrium at desired nodes.

Display either force and moment or displacement and rotation on a collection of free-body sections.

Use the Free Body Plot tool to visualize the following:
  • Displacement and rotations on nodes of a collection of free-body sections
  • Force and moment of a collection of free-body sections:
    • As resultant on each section
    • As free-body force acting on nodes of each free-body section
    • Review the contribution of internal forces and applied forces

You can use the Plot workflow to create multiple FBD Plot entities with one active at a time.

  1. From the Post ribbon, select the Free Body Plot tool.


    Figure 1.
  2. From the guide bar, click and select a fbd plot.
  3. Optional: From the Post ribbon, select the Create FBD Plot controls satellite tool from the Plot group to define a new FBD plot.


    Figure 2.
  4. Optional: From the guide bar, click to review and edit the current plot definition.
    The fbdplot dialog opens.
    1. Define the plot definition.
      Parameter Action
      Section Type
      Force/Moment
      Calculate and plot forces and moments acting of each free-body section selected.
      Translation/Rotation
      Plot displacement and rotation arrows on each nodes of the selected free-body sections.
      Datatype
      Resultant
      Plot the summed force and moment at summation point.
      Free Body
      Plot internal forces on each interface nodes.
      Grid Point
      Plot grid point forces due to the selected contributions.
      Forces: Internal, Applied, SPC, and MPC.
      Resolve-in System to resolve plot in.
      Free Body System
      Honors the system selection on each free-body section entity.
      Global System
      Ignore settings at entity level and evaluate and plot values on global (basic) system.
      User System
      Ignore settings at entity level and evaluate and plot values on selected user cartesian system.

      Learn more about System Transformation.

    2. Click Close.
  5. Optional: Select a subset of free-body sections to apply the plot.
  6. Click Plot to display the plot.
  7. Select one of the following:
    • Click to clear the plot.
    • Click to exit the tool without saving changes.
Tip:
  • Plots are based on the current load case and step, which can be reviewed and updated from the status bar or the browser.
  • Existing plots can also be displayed or cleared using the plot icons in the Results Browser.
  • Editing the definition for a displayed plot will automatically update the graphics. For large models, editing the plot definition may be faster if the plot is not displayed.
  • When inside the Plot tool, displayed components can be controlled from legend: status and color.

System Transformation

Analysis System

If a plot is done with Resolve-in set to Free Body System and the free body section is a Mesh based section where user set system to Analysis system, then:
  • Results are extracted from file in global system.
  • Node output system is extracted from current session.
  • Transformation applies from global to current output system assigned on node.
This means that:
  • A provision is provided to assign new output systems to any node and post process results in that output system no matter what system was used in the run.
  • Analysis system will match the solver run analysis system if the current session systems assigned to nodes match with the solver deck used at run time.

Analysis system option generally does not make sense in the event of Resultant plot. Results are always plot along global system even if summation point is set to a Node ID with an output system.

Section Cut System

The default system for entities defined by plane is the system formed by:
  • Z-axis = Plane normal
  • Y-axis = (Plane normal)^(Orientation vector)
  • X-axis = (Y-axis)^(Z axis)

Usually x-axis directly matches with Orientation since the manipulator used to define and edit entity store orthogonal vectors.

Raw results are extracted from result files in global system then transformed to plane local system.

Known Limitations with H3D Files

OptiStruct native *.h3d file has a known limitation. Results are always saved in an *.h3d file as X,Y,Z components output in the node’s output system, but there is no information of such system in result file. All transformations mentioned above rely on a reader that can give raw results either in output system or global system. Hence, a further transformation may apply.

It is recommended to use the same model as the one that generated the result file and to not change system assignation when working with h3d results. This limitation does not apply to *.op2 and *.hdf5 files if model information is saved in file too.