FEM CalculiX Cantilever 3D

Tutorial
Topic
Finite Element Analysis
Level
Beginner
Time to complete
10 minutes
Authors
Bernd
FreeCAD version
0.16.6377 or above
Example files
None
See also
None

Introduction

This example is meant to show how a simple Finite Element Analysis (FEA) in FreeCAD's FEM Workbench looks like in the FreeCAD interface and how the results can be visualized. It illustrates how to trigger a FEA and how to change the load value and load direction. Furthermore, since the example file is provided with any FreeCAD installation, it a useful and easy check to run for the purpose of ascertaining if the the FEM Workbench is set up properly.

Requirements

• A compatible version of FreeCAD designated in the tutorial overview.

  Use the Help → About FreeCAD to see the version of FreeCAD installed

• No external software is needed for loading the example file, viewing the mesh and geometry as well as for visualizing the results.
• For rerunning the FEA the solver software CalculiX has to be installed on your computer. Probably the solver has been installed together with FreeCAD already. If the solver CalculiX is not installed see FEM Install.

Set up the example file

Load the example file

• Start FreeCAD.
• If the Start Workbench is not activated, load it and open the start page.
• Open the example "FemCalculixCantilever3D.FcStd".

Activate the analysis container

• To work with an analysis the analysis has to be activated.
• In the tree view, double click on the Analysis,
• or right click on the Analysis and choose Activate analysis.

Analysis container and its objects

• If the analysis is activated, FreeCAD itself will change the current workbench to FEM.
• There are at least 5 objects needed to make a static mechanical analysis.
• analysis container

1. a solver
2. a material
3. a fixed boundary condition
4. a force load
5. a FEM mesh

• In this example, results are already included as well.

Visualizing Results

1. Be sure the analysis is activated.
2. Be sure the analysis still contains the result object, if not just reload the example file.
3. Double click the result object , or select it and click the Show result button in the FEM toolbar.
4. In the task window, choose z-Displacement. It shows -86.93 mm in negative z-direction. This makes sense since the force is in negative z-direction as well.
5. Activate the check box besides the bottom slider of displacement show.
6. The slider can be used to alter the mesh to view the deformation in a simplified manner.
7. Choose among the different Result types to view all in the GUI available result types.

Purging Results

1. Be sure the analysis is activated.
2. To remove the results: select in the icon toolbar the Purge results button.

Running the FEA

• In the tree view double click on the solver object .
• In the task panel of the solver object make sure static analysis is selected.
• Click on Write .inp file in the same task window. Watch the log window until it prints "write completed."
• Click on Run CalculiX. Since this is a very small analysis it should take less than a second to run.
• In the text window it should print in green letters "CalculiX done without error!" and in the next line "loading result sets ..."
• You just have finished your first FEA in FreeCAD if there has not been any error message.
• Click on Close in the task window.
• A new result object should be created. You know how to visualize the results already.
• If you get an error message no solver binary or similar when triggering the analysis check FEM Install.

Running the FEA the fast Way

• In tree view select the solver object of the analysis .
• In the icon toolbar click on Run solver calculations.
• The Calculix input file will be written, CalculiX will be triggered and the result object should be created.

Changing Load Direction and Load Value

• In the tree view expand CCX_Results and select the ResultMesh object and press the Space key.
  • Result: The visibility of the FEM mesh will be turned off. The geometrical model is still visible.
• In the tree view double click on the FEMConstraintForce object to open its task panel
• In the task window change the load value to 500000000 N = 500 MN (Note: force unit in task window has to be in N)
• On the geometrical model click on one of the long edges in x-direction.
• Click on the Direction button.
  • Result: The red arrows that illustrate force will change their direction in x-direction. They indicate the force direction.
• Since tension should be applied to the box the Reverse Direction needs to be triggered by clicking on it.
• The red arrows of the force will change their direction.
• Click on OK in task window.

• You know how to trigger an analysis and how to visualize results already.
• The deformation in x-direction should be 18.95 mm.

What next?

• We are now finished with the basic workflow for the FEM Workbench.
• You are now prepared to do the second FEM tutorial.
• We will create the CalculiX cantilever by ourselves and compare the results with the beam theory.