FEM tutorial
| Topic |
|---|
| Finite Element Analysis |
| Level |
| Beginner |
| Time to complete |
| 10 minutes + Solver time |
| Authors |
| Drei |
| FreeCAD version |
| 0.17 or above |
| Example files |
| None |
| See also |
| None |
Introduction
This tutorial is meant to introduce the reader to the basic workflow of the FEM Workbench, as well as most of the tools that are available to perform a static analysis.
Requirements
- FreeCAD version 0.17 or above.
- Netgen and/or GMSH is installed on the system (included in the FreeCAD installation).
- Calculix is installed on the system (included in the FreeCAD installation).
- The reader has the basic knowledge to use the Part and PartDesign Workbenches.
Procedure
Modeling
In this example a Cube is used as the study object, but any model created in the Part or PartDesign Workbenches can be used instead.
- Press the
Std New button to create a new document.
- Activate the
Part Workbench.
- Create a Cube.
- Change its Dimensions to the following:
- Length: 8.000 m.
- Width: 1.000 m.
- Height: 1.000 m.
Now we have a model to work with.
Creating the Analysis
- Activate the
FEM Workbench.
- Select the Model →
Analysis container option from the menu.
Constraints and Forces
- Hide the mesh from the Tree View.
- Show the original model.
- Select
Create FEM fixed constraint.
- Click Add, select the back face of the Cube object (face on the YZ axis) and click OK.
- Select
Create FEM force constraint.
- Click Add, select the front face of the Cube object (the face parallel to the back face) and set the Force [N] value to 9000000.
- Set the Direction to -Z by selecting one of the face edges parallel to that direction.
- Click OK.
We now have established the restrictions and forces for our static study.
Material
- Select
Material for solid and choose Calculix-Steel as the material.
- Click OK.
Meshing
It is recommended to make a mesh as the last step in the analysis preparations due to association to a geometry in FreeCAD. Depending on FreeCAD installation, there can be Netgen or GMSH meshers, you can use any of them.
Netgen
- Select the model.
FEM mesh from shape by Netgen: Generates a finite element mesh for a model using Netgen.
- In the meshing dialog, click Apply and OK.
You can also drag and drop a mesh to a Mechanical Analysis that does not have a mesh within the Tree View.
GMSH
- Select the model
FEM mesh from shape by Gmsh: Generates a finite element mesh for a model using Gmsh.
- In the meshing dialog, click Apply and OK.
We have now meshed our object and are ready to add constraints and forces.
Running the Solver
Standard Procedure
- Select the solver object
contained in the Analysis container.
- Select
Solver job control from the menu.
- Select Write .inp File.
- Select Run CalculiX.
- Click OK.
Quick Procedure
- Select the solver object
contained in the Analysis container.
- Click on
Run solver calculations.
Analyzing Results
- From the Object Tree, select the CCX_Results object.
- Select
Show result.
- Choose among the different Result types to view the results.
- The slider at the bottom can be used to alter the mesh visualization. This allows us to visualize the deformation experienced by the object, keep in mind that this is an approximation.
- To remove the results select
Purge results.
If you select the Z displacement result type, you can see that the obtained value is almost identical to the test example provided by FreeCAD. Differences may occur due to the quality of the mesh and the number of nodes it possesses.
We are now finished with the basic workflow for the FEM Workbench.
Notes
- For a video tutorial based on this written tutorial watch: FEM MaterialReinforced tutorial.
- Materials: Solid Material, Fluid Material, Non-Linear Mechanical Material, Reinforced Material (Concrete); Material Editor
- Element Geometry: Beam Cross Section, Beam Rotation, Shell Plate Thickness, Fluid Section for 1D Flow
- Electromagnetic Boundary Conditions: Electrostatic Potential Boundary Condition, Current Density Boundary Condition, Magnetization Boundary Condition, Electric Charge Density
- Fluid Boundary Conditions: Initial Flow Velocity Condition, Initial Pressure Condition, Flow Velocity Boundary Condition
- Geometrical Analysis Features: Plane Multi-Point Constraint, Section Print Feature, Local Coordinate System
- Mechanical Boundary Conditions and Loads: Fixed Boundary Condition, Rigid Body Constraint, Displacement Boundary Condition, Contact Constraint, Tie Constraint, Spring Boundary Condition, Force Load, Pressure Load, Centrifugal Load, Gravity Load
- Thermal Boundary Conditions and Loads: Initial Temperature, Heat Flux Load, Temperature Boundary Condition, Body Heat Source
- Overwrite Constants: Constant Vacuum Permittivity
- Mesh: Mesh From Shape by Netgen, Mesh From Shape by Gmsh, Mesh Boundary Layer, Mesh Refinement, Mesh Group, Erase Elements, FEM Mesh to Mesh
- Solve: Solver CalculiX, Solver Elmer, Solver Mystran, Solver Z88; Mechanical Equations: Elasticity Equation, Deformation Equation; Electromagnetic Equations: Electrostatic Equation, Electricforce Equation, Magnetodynamic Equation, Magnetodynamic 2D Equation, Static Current Equation; Flow Equation, Flux Equation, Heat Equation, Solver Job Control, Run Solver
- Results: Purge Results, Show Result, Apply Changes to Pipeline, Post Pipeline From Result, Pipeline Branch, Warp Filter, Scalar Clip Filter, Function Cut Filter, Region Clip Filter, Contours Filter, Glyph Filter, Line Clip Filter, Stress Linearization Plot, Data at Point Clip Filter, Calculator Filter; Filter Functions: Plane, Sphere, Cylinder, Box; Data Visualizations: Create Lineplot, Create Histogram, Create Table
- Utilities: Clipping Plane on Face, Remove All Clipping Planes, FEM Examples; Clear FEM Mesh, Display Mesh Info
- Additional: Preferences; FEM Install, FEM Mesh, FEM Solver, FEM CalculiX, FEM Concrete; FEM Element Types
- Getting started
- Installation: Download, Windows, Linux, Mac, Additional components, Docker, AppImage, Ubuntu Snap
- Basics: About FreeCAD, Interface, Mouse navigation, Selection methods, Object name, Preferences, Workbenches, Document structure, Properties, Help FreeCAD, Donate
- Help: Tutorials, Video tutorials
- Workbenches: Std Base, Assembly, BIM, CAM, Draft, FEM, Inspection, Material, Mesh, OpenSCAD, Part, PartDesign, Points, Reverse Engineering, Robot, Sketcher, Spreadsheet, Surface, TechDraw, Test Framework
- Hubs: User hub, Power users hub, Developer hub