FEM CalculiX Cantilever 3D

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Introducción

Este ejemplo pretende mostrar cómo se ve un simple Análisis de elementos finitos (FEA) en FreeCADs FEM Module y cómo se pueden visualizar los resultados. Se muestra cómo activar un FEA y cómo cambiar el valor de la carga y la dirección de la carga. Además, dado que el archivo de ejemplo se proporciona con cualquier instalación de FreeCAD, es fácil verificar si el módulo FEM está configurado correctamente.

FEM example01 pic00.jpg

Requisitos

  • Versión de FreeCAD = 0.16.6377 o superior.
  • Esto se puede verificar en el menú Ayuda -> acerca de FreeCAD. El número de Revisión tiene que ser superior a 6377
  • No se necesita software externo para cargar el archivo de ejemplo, ver la malla y la geometría, así como para visualizar los resultados.
  • Para volver a ejecutar el FEA, el software de resolución de problemas CalculiX debe estar instalado en su computadora. Probablemente el solucionador ya se haya instalado junto con FreeCAD. Si el solucionador CalculiX no está instalado, consulte FEM Install.

Set up the example file

Load Start Workbench

  • Start FreeCAD
  • The Start Workbench should be loaded

Load the example file

  • Go to the example projects and click on "Load an FEM analysis example"
  • If due to further operations some geometry, constraints or the results are broken or deleted just repeat the steps above.

FEM example01 pic01.jpg


Activate the analysis container

  • To work with an analysis the analysis has to be activated.
  • In tree view right click on the FEM Analysis.png MechanicalAnalysis → Activate analysis

FEM example01 pic02.jpg

Analysis container and its objects

  • If the analysis is activated FreeCAD itself will change the current workbench to FEM.
  • There are at least the 5 objects needed to make a static mechanical analysis.
  • FEM Analysis.png analysis container
  1. FEM Solver.png a solver
  2. FEM Material.png a material
  3. FEM FixedConstraint.png a fixed constraint
  4. FEM ForceConstraint.png a force constraint
  5. FEM Create.png a FEM mesh
  • Since in the example here the results are included as well there is a sixth object, the results FEM ShowResult.png.

Visualizing Results

  • Be sure the analysis is activated.
  • Be sure the analysis still contains the result object, if not just reload the example file.
  • Click in icon toolbar on FEM ShowResult.png Show result
  • In task window choose z-Displacement. It shows -88.443 mm in negative z-direction.
  • This makes sense since the force is in negative z-direction as well.
  • Activate the check box besides the bottom slider of displacement show.
  • The slider can be used to alter the mesh to view the deformation in a simplified manner.
  • Choose among the different Result types to view all in the GUI available result types.

FEM example01 pic03.jpg


Purging Results

  • Be sure the analysis is activated.
  • To remove the results select in the icon toolbar FEM PurgeResults.png Purge results

Running the FEA

  • In Tree view double click on the solver object FEM Solver.png.
  • In 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!" 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.

FEM example01 pic04.jpg

Running the FEA the fast Way

  • In tree view select the solver object FEM Solver.png of the analysis FEM Analysis.png.
  • In the icon toolbar click on FEM RunCalculiXccx.png Quick Analysis.
  • 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 tree view select the FEM mesh object FEM Create.png and press the Space key.
    • Result: The visibility of the FEM mesh will be turned off. The geometrical model is still visible.
  • In tree view double click on the force constraint 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)
  • Click on the Direction button.
  • On the geometrical model click on one of the long edges in x-direction.
    • Result: The red arrowsnthat illustrate force will change their direction in x-direction. They indicate the fixed 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.

FEM example01 pic05.jpg

  • Turn the visibility of the FEM mesh FEM Create.png on by selecting it in tree view and pressing the Space key.
  • You know how to trigger an analysis and how to visualize results already.
  • The deformation in x-direction should be 19.05 mm.

FEM example01 pic06.jpg

¿Qué sigue?

  • Ahora hemos terminado con el flujo de trabajo básico para el Módulo FEM.
  • Ahora está preparado para hacer el segundo FEM tutorial.
  • Crearemos el cantilever CalculiX por nosotros mismos y compararemos los resultados con la teoría del haz.

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