oofem-wiki

The unv2oofem convertor translates SRDC's I-DEAS (Integrated Design and Engineering Analysis Software) unv-mesh file format to native OOFEM input file. Unv file-type is an open ASCII datafile, which is used by several finite element codes. The CAD/mesh generating open-source software SALOME is intended to create such unv files. Unv2oofem convertor handles

• mesh geometry
• material assignment
• assignment of boundary conditions and conditions in nodes

The unv2oofem is a part of the svn OOFEM distribution, which is also downloadable by files. It is possible, but not recommended due to simultaneous updates, to download older release unv2oofem 1.0. The unv2oofem convertor consists from three files:

• unv2oofem.py - python script reading unv input files and creating OOFEM input file
• oofemctrlreader.py - general manipulation classes related to OOFEM data format.
• unv2x.py - the base class written by J.Cugnoni. This file creates an internal FEM object structure in memory.

The unv2oofem operates on two files

• unv file - defines topology (elements, nodes, edges, faces). Each entity transporting to OOFEM must be included in a group, which is also defined with unv file. For example in Salome can be the groups easily defined by clicking to the icon “create group” in the menu bar.
• control file - describes mapping of unv groups to OOFEM entities. These include material description, loads, supports, type of problem (solid mechanics, transports), solver parameters, outputs etc. The mapping relies on an element ID in unv-file, which shows the following table. Each ID can be mapped to corresponding OOFEM olement, e.g. ID 11 can represent Truss1D or Beam3D OOFEM elements.

The minimal working example simulates a plane-stress problem. The geometry is meshed using linear quadrilateral finite elements. Two materials are included, one edge is supported and the opposite edge is loaded by tractions.

This section demonstrates how to create the mesh in Salome and how to build the necessary groups:

1. The geometry is created in the Geometry module as a rectangle. Then go to Mesh module and hit Mesh→Create mesh. In the dialog, select the rectangle as a Geometry, assign 1D algorithm (Wire discretization) and 1D hypothesis (Maximal size), assign 2D algorithm (Quadrangle mapping). Select Mesh_1 in the left panel and by right-clicking invoke Compute.
   
2. At this moment, finite elements are created. The resulting mesh is shown on the screen with the mesh info label.
   
3. Click Mesh→Create group, choose face and select finite elements of the first material group with the help of Shift key. Two groups material_1 and material_2 of finite elements are created, on which material properties will be mapped.
   
   Both materials can be colored.
   
4. Define groups for supports and loads in the same way, by selecting appropriate edges and nodes. Create two groups support_nodes and load_edge.
   
   
5. The unv file is exported using File/Export while the mesh is selected. The Salome native file hdf, unv output file and control file is downloadable as a zip file..

We need to define information about materials, tractions and boundary conditions. The control file looks like

unv2oofem_example.out
This example shows how to convert unv file to OOFEM input file.
linearstatic nsteps 1 nmodules 1
vtkxml tstep_all domain_all primvars 1 1 vars 2 4 1 stype 1
domain 2dplanestress
OutputManager tstep_all dofman_all element_all
ncrosssect 1 nmat 2 nbc 2 nic 0 nltf 1
SimpleCS 1 thick 1.0 width 1.0
isole 1 d 0.0 e 15.0 n 0.25 tAlpha 0.0
isole 2 d 0.0 e 20.0 n 0.25 tAlpha 0.0
BoundaryCondition 1 loadTimeFunction 1 prescribedvalue 0.0
ConstantEdgeLoad 2 loadTimeFunction 1 Components 2 10.0 0.0 loadType 3 ndofs 2
ConstantFunction 1 f(t) 1.0
#Comment may be inserted anywhere
#Data for extractor, if necessary
#%BEGIN_CHECK% tolerance 1.e-8
## check reactions
#REACTION tStep 1 number 1 dof 1
#NODE tStep 1 number 5 dof 1 unknown d
#%END_CHECK%
 
group load_edge
elemprop BoundaryLoads 2
etype[11] BoundaryLoads
 
group support_nodes
nodeprop bc 2 1 1
 
group material_1
elemprop mat 1 crosssect 1
etype[44] PlaneStress2d
 
group material_2
elemprop mat 2 crosssect 1
etype[44] PlaneStress2d

The unv2oofem convertor creates the OOFEM input file unv2oofem_example.in executing a python command:

$ unv2oofem.py unv2oofem_example.unv unv2oofem_example.ctrl unv2oofem_example.in

All the files can be downloaded as a ZIP file.