View Stress Concentration Heatmaps in FreeCAD FEM

Viewing stress concentration heatmaps in FreeCAD FEM involves running your finite element analysis, accessing the post-processing tools, and displaying the stress tensor fields—most commonly von Mises stress—on a color-mapped 3D gradient. This guide explains how to transition from a solved simulation to a clear visual heatmap, customize the stress range to highlight critical stress concentrations, and use post-processing pipelines for advanced data visualization.

Step 1: Run the Solver and Generate Results

  1. Switch to the FEM Workbench using the workbench dropdown menu.
  2. In the tree view, locate your analysis container.
  3. Select your solver object (such as SolverCalculiX) and click the Run Solver button (yellow icon with a green play arrow) in the toolbar.
  4. Click Write .inp file, then click Run CalculiX. Once finished, close the solver control dialog.
  5. A result object (typically named CCX_Results) will appear in the tree view under your analysis container.

Step 2: Display the Built-In Result Object

The quickest way to view a stress heatmap is through the standard result object:

  1. Double-click the CCX_Results object in the tree view to open the Result panel in the Tasks tab.
  2. Under the Display section, change the field to von Mises stress (or Tresca, depending on your criteria).
  3. Check the Show box to overlay the colored contour plot onto your mesh.
  4. Use the slider or input fields under Plot to manually define the minimum and maximum stress values. Clamping the maximum value lower can help highlight local stress concentrations that might otherwise blend into a single color band.

Step 3: Use the Post-Processing Pipeline for Advanced Heatmaps

For higher quality and more flexible heatmaps, use FreeCAD's VTK-based post-processing tools:

  1. Select the CCX_Results object in the tree view.
  2. Click the Post Pipeline from Result button in the toolbar (or navigate to FEM > Post Processing > Post Pipeline from Result).
  3. With the newly created Pipeline object selected, click the Scalar Clip Filter or Warp Filter if you wish to see deformation alongside stress.
  4. In the Property tab (Data tab) of the Pipeline object:
    • Set Field to von Mises.
    • Set Vector Mode to Magnitude (if applicable).
  5. In the View tab of the Pipeline object:
    • Set Display Mode to Surface.
    • Adjust Color Map to your preferred gradient (e.g., Rainbow, Cool to Warm, or Jet).

Step 4: Isolate Stress Concentrations

Stress concentrations around sharp corners, holes, or boundary conditions can create extreme peaks that skew the color scale across the rest of the model.

  • Limit the Scalar Range: In the pipeline's properties, switch the scalar range mode from automatic to custom. Set an upper limit slightly below peak singular values so subtle stress gradients become visible across the rest of the geometry.
  • Enable the Color Bar: Toggle the color legend display in the View properties to read exact numerical values corresponding to the heatmap colors.