FreeCAD FEM Workbench Stress Analysis Guide

This guide provides a comprehensive walkthrough for performing a linear static stress analysis on a solid mechanical component using FreeCAD's built-in Finite Element Method (FEM) workbench. You will learn how to initialize an analysis container, assign material properties, apply boundary constraints and mechanical forces, generate a finite element mesh, run the CalculiX solver, and interpret von Mises stress distributions to validate your mechanical design.

1. Prepare the Geometry and Activate FEM

Ensure your 3D mechanical part is completely modeled as a single solid body using the Part Design or Part workbench. Switch to the FEM workbench using the workbench dropdown selector located in the top toolbar.

2. Create the Analysis Container

Click the Analysis container button (represented by a yellow capital 'A' icon) in the toolbar. This container acts as the root directory for your simulation, holding your material definitions, boundary conditions, mesh, and solver settings.

3. Assign Material Properties

  1. Select your solid part in the tree view.
  2. Click the Material for solid button in the FEM toolbar.
  3. In the task panel, choose a standard engineering material from the drop-down list (such as Steel-Generic or Aluminum-Generic), or manually enter the Young's Modulus and Poisson's Ratio.
  4. Verify that the correct solid object is linked to the material, then click OK.

4. Apply Boundary Constraints

  1. Click the Constraint fixed button to define where the component is anchored.
  2. Click Add in the task panel and select the face, edge, or vertex where the part is held rigid.
  3. Click OK to apply the zero-displacement constraint.

5. Apply External Loads

  1. Click the Constraint force button to simulate the mechanical load.
  2. Click Add and select the surface where the load acts.
  3. Specify the load magnitude in Newtons (N).
  4. Define the load direction by selecting an edge parallel to the desired force vector, or toggle the Reverse direction checkbox if the direction arrow points the wrong way.
  5. Click OK.

6. Generate the Mesh

FreeCAD provides tools like Netgen and Gmsh to discretize the geometry.

  1. Select the main solid body in the model tree.
  2. Click FEM mesh from shape by Netgen (or Gmsh).
  3. In the task panel, choose the element order (use Second order / quadratic elements for accurate stress calculations).
  4. Set the Max size to an appropriate element dimension relative to the part features (smaller values yield more accurate results but increase computation time).
  5. Click Apply to generate the tetrahedral mesh, then click OK.

7. Run the CalculiX Solver

  1. Double-click the CalculiX solver object inside the Analysis container in the tree view.
  2. In the task panel, select the analysis type as Static.
  3. Click Write .inp file to generate the input deck for the solver.
  4. Click Run CalculiX to begin the computation.
  5. Once the solver outputs indicate success with no errors, click OK to close the task panel.

8. Inspect the Stress Results

A results pipeline object (e.g., CCX_Results) will appear inside the Analysis container.

  1. Double-click the results object to activate the post-processing panel.
  2. Select Von Mises stress from the result type dropdown menu.
  3. Adjust the color scale and visibility settings to identify stress concentrations (hot spots).
  4. Compare the peak von Mises stress against the yield strength of your chosen material to determine your factor of safety and verify structural integrity.