FreeCAD Memo

Stress analysis (1)

9/21/2015
Version 0.15
FreeCAD has a FEM solver "CalculiX" and a tetra mesher "NetGen" as components and you can perform stress analysis on FreeCAD.
This feature is currently under development and not enough functionality, but we try to perform simple stress analysis in this example.
A shape to be calculated A shape to be calculated
Analysis result Analysis result

Creating a shape

At first we create a shpe to be calculated.
A shape to be calculated A shape to be calculated

Creating new analysis

Switch workbench to FEM workbenchFEM workbench and create new analysis case.
  1. Select a shape to be calculated in model tree and select AnalysisFem_Analysis.
    Set parameters for meshing in a displayed diaolg.
    Analysis creation dialog Analysis creation dialog
    Each parameter meaning is as follows.
    Parameter
    Max. SizeMax size of an element
    Second orderWhether second order elements will be generated
    FinenessFineness of mesh. You can select one of "VeryCoarse", "Coarse", "Moderate", "Fine", "VeryFine" and "UserDefined".
    Nbr Segs per EdgeNumber of segments per edge
    Nbr Segs per RadiusNumber of segments per radius
    OptimizeWhether optimize will be performed
  2. Click Apply to generate meshes. Confirm created meshes and click OK to exit meshing.
    Meshes that was created Meshes that was created
  3. When meshes are displayed, you cannot set condition settings. So hide the meshes and show original shape in model tree.
    The item's visibility can be switch by selecting item in model tree and pushing space key.
    Model tree after meshing Model tree after meshing
    Hide meshes and show an original shape Hide meshes and show an original shape

Analysis condition settings

  1. Selelct Constraint FixedFem_Analysis to set fixed faces. Click Add reference on a dialog and select faces on 3D view to set fixed faces condition.
    Click [OK] to the dialog after settings.
    Setting of fixed faces Setting of fixed faces
  2. Selelct Constraint ForceFem_Analysis to set faces for applying a force. Click Add reference on a dialog and select faces on 3D view to set applying a force condition.
    Setting of faces for applying a force Setting of faces for applying a force
  3. If you click Direction and select a line on 3D view, the force direction will be set to the line direction. Check Reverse direction to reverse the force direction.
    Setting of a force direction Setting of a force direction
  4. Input a load of the force to Area load. In this exmaple we set 100.0 as a load.
    Setting of a load Setting of a load
    Click OK to close the dialog after settings.
  5. Model tree becomes as following after the settings.
    Model tree after condition settings Model tree after condition settings
  6. Select MatrialFem_Material to set a material of the shape. Prepared materials are as follow.
    Prepared materials
    Material nameYoung modulus [MPa]Poisson ratio
    ABS2.32e+30.350
    CalculiX2.1e+50.300
    Concrete3.2e+40.170
    PLA3.64e+30.360
    Steel2.0e+50.300
    Wood1.2e+40.050
    And you can click MatWeb database... to access database on web and take a material properties and set them to FreeCAD.
    Material item will be added to the model tree by this settings.
    Material setting dialog Material setting dialog
    Model tree after material settings Model tree after material settings
  7. Show meshes and hide a original shape in model tree after analysis condition settings.
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