FEM CalculiX: Difference between revisions

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This page collects all informations about the solver used by FreeCAD's FEM Module. The interface between the solver and FreeCAD in pre- as well as post processing is also described. At the moment (Mid 2015 and FreeCAD 0.16dev) the only supported solver by the FEM Module is [[http://www.calculix.de/ CalculiX]].
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== Introduction == <!--T:19-->
== CalculiX ==
Depending on the operating system you are working with you need to install CalculiX first. Check out [FEM Install].


<!--T:2-->
=== Interface ===
This page collects information on the [http://www.calculix.de/ CalculiX] finite element solver, the default solver in the [[Image:Workbench_FEM.svg|24px]] [[FEM_Workbench|FEM Workbench]] for structural and thermo-mechanical analysis. Depending on the operating system you are working with, you'll need to install CalculiX before running your first simulation. Please see [[FEM_Install|FEM Install]].
Interaction between FEM Module and CalculiX is done by text files. The FEM Module writes a CalculiX input file, starts CalculiX, logs the output of CalculiX and read the output files of CalculiX if they are available. The
[[FEM_Calculation]] tool manages the whole process. User interaction in the process is possible.


<!--T:12-->
==== Preprocessing interface ====
The solver is able to do linear and non-linear calculations, for static, dynamic, and thermal problems. The solver operates on an Abaqus input file ({{incode|.inp}}), which means it can be used with different pre-processors that support this format. The program includes its own graphical preprocessor which, however, is not used by FreeCAD, only the solver itself.
CalculiX uses abaqus input file format. The input file could be edited before the solver is started. The units used in the CalculiX input file are independet from the units used in FreeCAD. They will be mm and N. (ToDo: check this. What happens with the mesh if inch is used in FreeCAD. Density was introduced. With this we have kg and s and no longer N?! how about this !?!)


<!--T:13-->
The FEM Module - CalculiX interface supports the following objects:
CalculiX is designed to run on Unix platforms like Linux and Irix computers but also on MS-Windows. CalculiX was developed by engineers from MTU Aero Engines, Munich, Germany, to assist them in designing machinery such as jet turbines. The software is currently released to the public on the terms of the GPL version 2.
===== FEM Elements =====
* Tet4 and Tet10 --> [[FEM_Mesh#Tetrahedron_element Tetrahedron]]
* S3 and S6 as well as B31 and B32 are in development


== Integration with FreeCAD == <!--T:20-->
===== Analysis =====
* linear static analysis


<!--T:3-->
===== Materials =====
Interaction between the [[FEM_Workbench|FEM Workbench]] and CalculiX is done through writing and reading text files. The sequence of operations is as follows:
* one linear elastic isotropic (uniformity in all directions) material
* multiple material is in development


<!--T:10-->
# A CalculiX input file is created with details required to run the simulation
# The CalculiX solver is started with this input file
# The output from the solver is logged
# The output files from the solver are read, if they are available


<!--T:11-->
[[FEM Module]]
The [[FEM_SolverControl|FEM Control Solver]] tool manages the whole process. User interaction in the process is possible.

== Preprocessing interface == <!--T:21-->

<!--T:4-->
The input file that CalculiX uses can be prepared and edited before the solver is started. The units used in the input file are independent of the units set in FreeCAD; they will always be millimeters (mm) and Newton (N).

<!--T:14-->
{{Emphasis|(ToDo: check this. What happens with the mesh if inch is used in FreeCAD? As density was introduced, with this we have kg and s and no longer N?! how about this?!)}}

<!--T:15-->
The CalculiX interface supports the following objects:

=== FEM Elements === <!--T:22-->

<!--T:5-->
* Tet4 and Tet10
* S3 and S6
* B31 and B32
* and those described in [[FEM_Mesh_CalculiX|FEM Mesh CalculiX]]

=== Analysis === <!--T:23-->

<!--T:6-->
* Linear and nonlinear static analysis
* Frequency analysis
* Linear buckling analysis
* Coupled thermal-structural analysis

=== Materials === <!--T:24-->

<!--T:7-->
* Linear elastic isotropic materials (uniformity in all directions)
* Plasticity with isotropic hardening

== Postprocessing interface == <!--T:25-->

<!--T:8-->
The FEM Workbench loads CalculiX results into a [[FEM_ResultShow|result object]] which will contain:
* Displacements
* Stresses
* Strains
* Equivalent plastic strain (PEEQ) – if nonlinear material was used
* Temperature – for thermomechanical analysis
FreeCAD reads results from *.frd file which was created by CalculiX. If these results contain multiple time steps, each time step is imported to FreeCAD as a new result object. Same behavior applies for Frequency or Buckling analysis with multiple eigenvalues.

<!--T:18-->
Reaction forces can be found in ccx_dat_file which contains reaction force components (fx, fy, fz) for each fixed boundary condition and for each displacement boundary condition which constrains translation degrees of freedom.

== Related == <!--T:16-->

<!--T:17-->
* [[FEM_Mesh_CalculiX|FEM Mesh CalculiX]]
* [[FEM_Preferences#CalculiX|CalculiX preferences]] dialog menu in the FEM Workbench preferences menu


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[[Category:Developer{{#translation:}}]]

Latest revision as of 18:46, 7 December 2023

Introduction

This page collects information on the CalculiX finite element solver, the default solver in the FEM Workbench for structural and thermo-mechanical analysis. Depending on the operating system you are working with, you'll need to install CalculiX before running your first simulation. Please see FEM Install.

The solver is able to do linear and non-linear calculations, for static, dynamic, and thermal problems. The solver operates on an Abaqus input file (.inp), which means it can be used with different pre-processors that support this format. The program includes its own graphical preprocessor which, however, is not used by FreeCAD, only the solver itself.

CalculiX is designed to run on Unix platforms like Linux and Irix computers but also on MS-Windows. CalculiX was developed by engineers from MTU Aero Engines, Munich, Germany, to assist them in designing machinery such as jet turbines. The software is currently released to the public on the terms of the GPL version 2.

Integration with FreeCAD

Interaction between the FEM Workbench and CalculiX is done through writing and reading text files. The sequence of operations is as follows:

  1. A CalculiX input file is created with details required to run the simulation
  2. The CalculiX solver is started with this input file
  3. The output from the solver is logged
  4. The output files from the solver are read, if they are available

The FEM Control Solver tool manages the whole process. User interaction in the process is possible.

Preprocessing interface

The input file that CalculiX uses can be prepared and edited before the solver is started. The units used in the input file are independent of the units set in FreeCAD; they will always be millimeters (mm) and Newton (N).

(ToDo: check this. What happens with the mesh if inch is used in FreeCAD? As density was introduced, with this we have kg and s and no longer N?! how about this?!)

The CalculiX interface supports the following objects:

FEM Elements

Analysis

  • Linear and nonlinear static analysis
  • Frequency analysis
  • Linear buckling analysis
  • Coupled thermal-structural analysis

Materials

  • Linear elastic isotropic materials (uniformity in all directions)
  • Plasticity with isotropic hardening

Postprocessing interface

The FEM Workbench loads CalculiX results into a result object which will contain:

  • Displacements
  • Stresses
  • Strains
  • Equivalent plastic strain (PEEQ) – if nonlinear material was used
  • Temperature – for thermomechanical analysis

FreeCAD reads results from *.frd file which was created by CalculiX. If these results contain multiple time steps, each time step is imported to FreeCAD as a new result object. Same behavior applies for Frequency or Buckling analysis with multiple eigenvalues.

Reaction forces can be found in ccx_dat_file which contains reaction force components (fx, fy, fz) for each fixed boundary condition and for each displacement boundary condition which constrains translation degrees of freedom.

Related