Free Open Source FEM Softwares

August 26, 2010 by Admin · 2 Comments
Filed under: CAD, FEM 
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Contents

Intro

This post shows a few interesting (and free) solutions structural engineers may find useful.

The common structural softwares for FEM analysis like Ansys, Abaqus, Nastran,etc.. have a license cost from 20′000 up to more than 100′000. If you are not a worker inside a great company or if you are not rich, you can not afford that.

Today on the web there are several free solutions, some of them have great potential, almost like commercial utilities. They are just a little harder to use, they are not the kind of user friendly softwares.

A complete list of the packages can be found here:  http://en.wikipedia.org/wiki/List_of_finite_element_software_packages

A first attempt to link all fem free utilities into a single operating system has been made by J, Cugnoni with his Caelinux. Caelinux is an ubuntu linux version that contains many free fem utilities. Unfortunately the current version is the old ubuntu 9 and it can gives drivers issues with modern machines. Anyway all the packages in Caelinux can be installed on most linux platforms.

I report here my review about the 3 softwares that I consider  a good trade-off between usability/perfomances and capabilities.

Code Aster

www.code-aster.org/

Code_Aster is an Open Source software package for Civil and Structural Engineering finite element analysis and numeric simulation in structural mechanics originally developed as an in-house application by the French company EDF. It was released as free software under the terms of the GNU General Public License, in October 2001.

Code aster can be compiled both on windows and linux, but since it can be integrated with the cad utility SALOME, it is better to use it on linux. A complete integrated package called SAlOME-MECA can be downloaded here: http://www.code-aster.org/V2/spip.php?article303

Code Aster is suitable for very complicated termo-mechanical analysis: it can take into account plasticity, non linear geometry, material state exchange, cracking and creep.

Unfortunately it take some time to learn how to use code aster. The solver takes as main input a python script that defines the kind of analysis , boundary conditions, time steps etc. To write this file is necessary a basic knowledge of FEM algorithms. A few samples for typical analysis are available on the web. The python library to write the input file is enormous and most of the doc is in french, this can be painful for someone. Two main utilities to simplify the Code_Aster input process are available: EFICAS that helps writing the input file and ASTK a job manager server.

ELMER

http://www.csc.fi/english/pages/elmer


Elmer is an open source multiphysical simulation software developed by CSC. Elmer development was started 1995 in collaboration with Finnish Universities, research institutes and industry.

Elmer includes physical models of fluid dynamics, structural mechanics, electromagnetics, heat transfer and acoustics, for example. These are described by partial differential equations which Elmer solves by the Finite Element Method (FEM)

Among the three elmer is simplest to use. A nice GUI guides the user trough all the fem model construction. It also has a mesh package even if it doesn’t allow for many editings. With elmer is just so easy to realize multiphisics anaisys. It also has a good built-in material library that turn out to be very useful. An interactive post-processing tools allows to visualize results.

Calculix

http://www.calculix.de/

CalculiX is a package designed to solve field problems. The method used is the finite element method.

With CalculiX Finite Element Models can be build, calculated and post-processed. The pre- and post-processor is an interactive 3D-tool using the openGL API. The solver is able to do linear and non-linear calculations. Static, dynamic and thermal solutions are available. Both programs can be used independently. Because the solver makes use of the abaqus input format it is possible to use commercial pre-processors as well. In turn the pre-processor is able to write mesh related data for nastran, abaqus, ansys, code-aster and for the free-cfd codes duns, ISAAC and OpenFOAM. A vda CAD interface is available. The program is designed to run on Unix platforms like Linux and Irix computers but also on MS-Windows.

The CalculiX package was developed by a team of enthusiasts in their raw spare time. They are employees of MTU Munich, an Aero Engine manufacturer in Germany which granted the publication.

Calculix is made by two console applications: CCX which handles the computation and CGX which handles the graphical operations. Calculix offers steady and dynamics structural and fluid analysis and has one main peculiarity: it has the same Abaqus input file syntax.

More

Do you use others utilities that should be included in the above list? just tell us in the comments.

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Structured Tedrahedral Mesh Generation

August 20, 2009 by Luigi Giaccari · 2 Comments
Filed under: Algorithms, Computational Geometry, FEM 
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MexImage

STRUCTTETRAMESH:
StructTetraMesh is a tool to build structured tetreaedral mesh on cuboid dataset. This is usefull in avoiding delaunay 3D triangulation that for  this kind of dataset are particularly slow and numerically unstable.
This tool allows a huge speed improvement against delaunayn for 3D points, the output triangulation will also be “slivers-less”, this is  particularly important for programs that need a conform triangulation like
fem analysis and search structure algorithms.

INPUT:
x,y,z must be vectors, they represent the axis of the cuboid. It is
also very important they need to be sorted. To improve performances there
is no check for sorted vectors so you have to check yourself.

OUTPUT:
The Cuboid points are stored in the p: N x 3 array, the tetraedral mesh
with points index is stored in tetr: Ntetr x 4 array. First point is
flagged with index one.

EXAMPLE

x=1:4;
y=1:6;
z=1:7;

[p,tetr]=StructTetraMesh(x,y,z);
figure(1)
axis equal
tetramesh(tetr,p);

Author: Giaccari Luigi
Created: 18/04/2009

For infos/questions/suggestions : giaccariluigi@msn.com

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Structured Triangular Mesh Generation

August 18, 2009 by Luigi Giaccari · Leave a Comment
Filed under: Computational Geometry 
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Structured triangular mesh

STRUCTTRIMESH:
StructTriMesh is a tool to build structured triangular mesh on rectangle
shaped dataset. This is useful in avoiding delaunay 2D triangulation in
order to improve speed performances.
It can be used for graphical purposes, fem analysis, sedata structures…

INPUT:
x,y must be vectors, they represent the axis of the rectangle. It is
also very important they need to be sorted. To improve performances, there
is no check for sorted vectors so you have to check yourself.

OUTPUT:
The mesh described as:

  • p: N x 2 array, points of the triangular mesh
  • t: Ntri x 3 array.  Triangles indexes referring to p array. First point is flagged with index one.

EXAMPLE:

x=1:4;
y=1:6;

[p,t]=StructTriMesh(x,y);
figure(1)
axis equal
hold on
title('Triangular Mesh','fontsize',14);
trimesh(t,p(:,1),p(:,2),'color','g');

Author: Giaccari Luigi
Created: 22/04/2009

For info/questions/suggestions : giaccariluigi@msn.com

Download Now

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